5311_2001_equipmentarrangement
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t c v n v i e t n a m e s e s t a n d a r d
tcvn 5311:2001
mobile offshore units
rules for classification and construction
equipment arrangement
Hanoi - 2001
TCVN 5311:2001
2
Foreword
TCVN 5311:2001 replaces to TCVN 5311:1991.
TCVN 5311:2001 is edited by Vietnam Register and TCVN/TC8 ''Shipbuilding and Offshore'' Technical
Standard Board, is proposed by Ministry of Transportation and Standard - Measure - Quality General
Department, is promulgated by Ministry of Science, Technology and Environmental
TCVN 5311:2001
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table of content
1. General............................................................................................................................................. 13
1.1. Application.............................................................................................................................................13
1.2. Reference standard...............................................................................................................................13
1.3. Definitions and explanations ...............................................................................................................14
1.4. Materials.................................................................................................................................................16
2. Rudder and steering gear............................................................................................................... 16
2.1. General ...................................................................................................................................................16
3. Mooring Equipment for Temporary Mooring ................................................................................ 16
3.1. General ...................................................................................................................................................16
3.2. Equipment number................................................................................................................................17
3.3. Equivalent Mooring Equipment ...........................................................................................................17
3.4. Windlasses.............................................................................................................................................18
3.5. Offshore mooring Chains.....................................................................................................................18
3.5.1. Application ......................................................................................................................................18
3.5.2. General ...........................................................................................................................................18
3.5.3. Kinds of offshore chains .................................................................................................................18
3.5.4. Materials .........................................................................................................................................18
3.5.5. Processes of manufacture..............................................................................................................19
3.5.6. Offshore chain manufacturers ........................................................................................................20
3.5.7. Heat treatmen.................................................................................................................................20
3.5.8. Dimensions and forms....................................................................................................................20
3.5.9. Dimensional tolerances ..................................................................................................................20
3.5.10. Mass ...............................................................................................................................................23
TCVN 5311:2001
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3.5.11. Breaking tests ................................................................................................................................ 24
3.5.12. Proof tests...................................................................................................................................... 25
3.5.13. Mechanical tests ............................................................................................................................ 26
3.5.14. Non-destructive test....................................................................................................................... 28
3.5.15. Repair of defects............................................................................................................................ 29
3.5.16. Markings ........................................................................................................................................ 29
3.5.17. Painting .......................................................................................................................................... 30
3.5.18. Record ........................................................................................................................................... 30
4. Mooring equipment..........................................................................................................................30
4.1. General .................................................................................................................................................. 30
5. Positioning Systems........................................................................................................................30
5.1. General .................................................................................................................................................. 30
5.1.1. Application ..................................................................................................................................... 30
5.1.2. General .......................................................................................................................................... 31
5.2. Classification of Positioning Systems ............................................................................................... 31
5.2.1. General .......................................................................................................................................... 31
5.2.2. Classification of Mooring System................................................................................................... 31
5.2.3. Dynamic Positioning System ......................................................................................................... 32
5.3. Anchor Mooring System...................................................................................................................... 33
5.3.1. General .......................................................................................................................................... 33
5.3.2. Calculating the Tension of Mooring Line ....................................................................................... 34
5.3.3. Equipment for Anchor Mooring System......................................................................................... 35
5.4. Tension Mooring System..................................................................................................................... 36
5.4.1. General .......................................................................................................................................... 36
5.4.2. Tension mooring systems.............................................................................................................. 37
5.4.3. Equipment for Tension Mooring Systems...................................................................................... 38
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5.5. Single-point Mooring Systems ............................................................................................................38
5.5.1. General ...........................................................................................................................................38
5.5.2. Single-point Mooring Systems........................................................................................................38
5.6. Dolphin Mooring Systems....................................................................................................................38
5.6.1. General ...........................................................................................................................................38
5.6.2. Dolphin Mooring Systems...............................................................................................................39
5.7. Dynamic Positioning System (DPS) ....................................................................................................39
5.7.1. General ...........................................................................................................................................39
5.7.2. installation comprising the DPS......................................................................................................40
5.7.3. Power system................................................................................................................................41
5.7.4. Thruster system.............................................................................................................................41
5.7.5. DP-control system.........................................................................................................................42
5.7.6. Computer system ...........................................................................................................................43
5.7.7. Position reference systems ..........................................................................................................44
5.7.8. Vessels sensors ............................................................................................................................44
5.7.9. Cables and piping systems ..........................................................................................................45
6. Towing arrangement....................................................................................................................... 45
6.1. Tow line ..................................................................................................................................................45
6.2. Chain cables ..........................................................................................................................................46
6.3. Towage ...................................................................................................................................................46
6.4. Line throwing appliances .....................................................................................................................46
7. Signal Masts .................................................................................................................................... 46
7.1. General ...................................................................................................................................................46
7.1.1. Specifications..................................................................................................................................46
8. Watertight bulkheads and closing appliances ............................................................................. 47
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8.1. Watertight bulkheads........................................................................................................................... 47
8.1.1. General .......................................................................................................................................... 47
8.1.2. Boundary Penetrations .................................................................................................................. 48
8.2. Closing Appliances .............................................................................................................................. 48
8.2.1. General .......................................................................................................................................... 48
8.2.2. Internal Openings used during Operation...................................................................................... 49
8.2.3. External Openings used during Operation .................................................................................... 49
8.2.4. Internal and External Openings kept permanently closed while Afloat ......................................... 50
9. Jacking machinery...........................................................................................................................51
9.1. General .................................................................................................................................................. 51
9.1.1. Application ..................................................................................................................................... 51
9.1.2. Documentation............................................................................................................................... 51
9.2. Design and construction ..................................................................................................................... 51
9.2.1. General .......................................................................................................................................... 51
9.2.2. Design loads .................................................................................................................................. 52
9.2.3. Electric motor capacity................................................................................................................... 53
9.2.4. Gearing .......................................................................................................................................... 53
9.2.5. Shafts and shaft connections......................................................................................................... 53
9.2.6. Gear casings.................................................................................................................................. 54
9.2.7. Bearings......................................................................................................................................... 54
9.3. Load control........................................................................................................................................ 54
10. Accident prevention Provision .......................................................................................................55
10.1. General .............................................................................................................................................. 55
11. Drilling plant ( Drill)..........................................................................................................................55
11.1. General .............................................................................................................................................. 55
TCVN 5311:2001
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11.1.1. Application ......................................................................................................................................55
11.2. Supervision/certification and categories .......................................................................................55
11.2.1. Categories ......................................................................................................................................55
11.2.2. Supervision.....................................................................................................................................56
11.3. Documentation..................................................................................................................................56
11.3.1. Design documentation....................................................................................................................56
11.3.2. Fabrication record...........................................................................................................................57
11.4. Materials.............................................................................................................................................58
11.4.1. General ...........................................................................................................................................58
11.4.2. Bolting material ...............................................................................................................................58
11.4.3. Corrosion ........................................................................................................................................58
11.4.4. Material certificates.........................................................................................................................59
11.5. Design principles ..............................................................................................................................59
11.5.1. General ...........................................................................................................................................59
11.5.2. Arrangement ...................................................................................................................................60
11.5.3. Environmental conditions ...............................................................................................................60
11.5.4. Loads ..............................................................................................................................................61
11.5.5. Design pressure and temperature..................................................................................................61
11.5.6. Well fluid composition.....................................................................................................................61
11.5.7. Design safety factors ......................................................................................................................61
11.5.8. Spare parts .....................................................................................................................................62
11.6. Systems .............................................................................................................................................62
11.6.1. General ...........................................................................................................................................62
11.6.2. Blowout prevention system.............................................................................................................62
11.6.3. Marine riser system ........................................................................................................................65
11.6.4. Heave compensation and tensioning system.................................................................................65
11.6.5. Hoisting, Rotating and Pipe Handling System................................................................................66
11.6.6. Bulk Storage, Drilling Fluid Circulation and Cementing system.....................................................66
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11.6.7. Well Test and Flare System........................................................................................................... 67
11.7. Structural and mechanical components........................................................................................ 68
11.7.1. General .......................................................................................................................................... 68
11.7.2. Blowout preventer system ............................................................................................................. 68
11.7.3. Marine riser system........................................................................................................................ 69
11.7.4. Heave compensation system......................................................................................................... 69
11.7.5. Hoisting, Rotating and Pipe Handling System............................................................................... 69
11.7.6. Bulk Storage, Drilling Fluid Circulation and Cementing system .................................................... 70
11.7.7. BOP handling system .................................................................................................................... 70
11.7.8. Well test and flare system.............................................................................................................. 70
11.8. Piping ................................................................................................................................................ 70
11.8.1. General .......................................................................................................................................... 70
11.8.2. Hard piping design......................................................................................................................... 71
11.8.3. Flexible piping ................................................................................................................................ 73
11.8.4. Valves and other piping parts ........................................................................................................ 73
11.8.5. Piping connections......................................................................................................................... 74
11.8.6. Supporting elements...................................................................................................................... 74
12. Oil production plant .........................................................................................................................75
12.1. Application........................................................................................................................................ 75
12.2. Supervision and Equipment certification ...................................................................................... 76
12.2.1. System design review.................................................................................................................... 76
12.2.2. Equipment certification .................................................................................................................. 76
12.3. Documentation ................................................................................................................................. 77
12.3.1. Design documentation for production systems and arrangement ................................................. 77
12.3.2. Design documentation for equipment packages ........................................................................... 78
12.3.3. Design documentation for category I equipment ........................................................................... 78
12.3.4. Design documentation for category I piping .................................................................................. 79
TCVN 5311:2001
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12.3.5. Documentation for structures .........................................................................................................80
12.3.6. Documentation on corrosion protection..........................................................................................80
12.3.7. Fabrication documentation .............................................................................................................80
12.4. Materials and corrosion protection.................................................................................................81
12.4.1. General ...........................................................................................................................................81
12.4.2. Corrosion Protection.......................................................................................................................81
12.4.3. Erosion............................................................................................................................................83
12.5. Design principles ..............................................................................................................................83
12.5.1. General ...........................................................................................................................................83
12.5.2. Definitions and explanations...........................................................................................................83
12.5.3. Design loads, general.....................................................................................................................84
12.5.4. Environmental conditions ...............................................................................................................84
12.5.5. Design pressure and temperature..................................................................................................85
12.5.6. Design safety factors ......................................................................................................................85
12.6. Systems .............................................................................................................................................85
12.6.1. General ...........................................................................................................................................85
12.6.2. Control and monitoring ...................................................................................................................86
12.6.3. Shut down.......................................................................................................................................86
12.6.4. Equipment for safety control...........................................................................................................87
12.7. Production, injection and utility systems.......................................................................................87
12.7.1. General ...........................................................................................................................................87
12.7.2. Definitions and explanation ............................................................................................................87
12.7.3. Safety systems interconnections with emergency shutdown (ESD) system..................................89
12.7.4. Process shutdown ( PSD ) system.................................................................................................89
12.7.5. Relief, depressurising and disposal system - Design principles ....................................................90
12.7.6. Pressure relief system ....................................................................................................................90
12.7.7. Depressurising system ...................................................................................................................91
12.7.8. Gas disposal system . ....................................................................................................................91
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12.7.9. Flare............................................................................................................................................... 91
12.7.10. Cold vents.................................................................................................................................. 92
12.7.11. Drainage system and facilties for produced water .................................................................... 92
12.7.12. Separator system ...................................................................................................................... 93
12.7.13. Water injection system .............................................................................................................. 93
12.8. Piping ................................................................................................................................................ 93
12.8.1. General .......................................................................................................................................... 93
12.8.2. Definitions and explanation............................................................................................................ 93
12.8.3. Design requirements - General...................................................................................................... 94
12.8.4. Wall thickness................................................................................................................................ 95
12.8.5. Expansion joints and flexible hoses............................................................................................... 99
12.8.6. Plastic pipes ( GRP or GRE pipes )............................................................................................. 100
12.8.7. Valves and special items ............................................................................................................. 101
12.8.8. Piping connections....................................................................................................................... 102
12.8.9. Supporting elements.................................................................................................................... 103
12.9. Equipment....................................................................................................................................... 103
12.9.1. General ........................................................................................................................................ 103
12.9.2. Definitions and explanations........................................................................................................ 104
12.9.3. design documentation.................................................................................................................. 105
12.9.4. Design requirements.................................................................................................................... 105
12.10. Riser systems................................................................................................................................. 105
12.10.1. General.................................................................................................................................... 105
12.10.2. Definitions and explanations ................................................................................................... 106
12.10.3. Documentation for approval .................................................................................................... 106
12.10.4. Design requirements - General ............................................................................................... 107
12.10.5. Design requirements- Monitoring and control ......................................................................... 108
12.11. Structures ....................................................................................................................................... 109
12.11.1. General.................................................................................................................................... 109
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12.11.2. Documentations for approval ...................................................................................................109
12.11.3. Design requirements ................................................................................................................109
12.12. Electrical installations....................................................................................................................110
12.12.1. General.....................................................................................................................................110
12.12.2. Documentation .........................................................................................................................110
12.13. Instrumentation and control systems...........................................................................................110
12.13.1. General.....................................................................................................................................110
12.13.2. Documentation .........................................................................................................................110
12.14. Fire protection and extinction .......................................................................................................111
12.14.1. General.....................................................................................................................................111
13. Helicopter deck.............................................................................................................................. 111
13.1. General.............................................................................................................................................111
13.1.1. Application ....................................................................................................................................111
13.2. Arrangement....................................................................................................................................111
13.3. Equipment........................................................................................................................................112
TCVN 5311:2001
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Introduction
Mobile Offshore Units - Rules for classification and construction include:
TCVN 5309 : 2001 Classification
TCVN 5310 : 2001 Hull
TCVN 5311 : 2001 Equipment Arrangement
TCVN 5312 : 2001 Stability
TCVN 5313 : 2001 Subdivision
TCVN 5314 : 2001 Fire protection, detection and extinction
TCVN 5315 : 2001 Machinery Installations
TCVN 5316 : 2001 Electrical Installations
TCVN 5317 : 2001 Materials
TCVN 5318 : 2001 Welding
TCVN 5319 : 2001 Safety Equipment
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TCVN 5311:2001 Vietnamese standard TCVN 5311:2001
Mobile Offshore Units - Rules for classification and construction
Equipment Arrangement
. General
.1. Application
The Standard for the Equipment arrangement are to be applied to manufacture and survey of the
equipment of the Mobile offshore Units (hereimafter referred to as ''Units'') mentioned in 1.1-1 TCVN
5309:2001, technical supervised and classed by the Vietnam Register (hereimafter referred to as VR) .
The equipments on board of the unit are to be complied with the relative requirements of the Part 2, Hull
construction and Equipment of Ships TCVN 6259-7:1997 and part 7B .
The equipment other than those prescribed in this Part may be used where specially approved in
connection with the design and usage. In such cases, the detailed data relating to the process of
manufacture, construction, etc. of the equipment are to be submitted for approval.
Technical inspection of equipment is to comply with requirements in TCVN 5309:2001.
.2. Reference standard
From TCVN 6259-1:1997 to TCVN 6259-11:1997 Rules for the Classification and Construction of sea-
going Steel ships .
TCVN 6809:2001 rules for the classification and construction of single point moorings
Mobile Offshore Units - Rules for classification and construction include :
TCVN 5309 : 2001 Classification
TCVN 5310 : 2001 Hull
TCVN 5311 : 2001 Equipment Arrangement
TCVN 5312 : 2001 Stability
TCVN 5313 : 2001 Subdivision
13
TCVN 5311:2001
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TCVN 5314 : 2001 Fire protection, detection and extinction
TCVN 5315 : 2001 Machinery Installations
TCVN 5316 : 2001 Electrical Installations
TCVN 5317 : 2001 Materials
TCVN 5318 : 2001 Welding
TCVN 5319 : 2001 Safety Equipment
1.3. Definitions and explanations
1 Beside definitions and explanations below, other definitions and explanations in 1.3 TCVN 5309:2001
and Part 2 Hull construction and equipment TCVN 6259-2:1997 are also used.
2 The following definitions are only valid within the scope of this TCVN .
(1) Traveling block an arrangement of pulleys, or sheaves, through which drilling line is reeved and
that moves up and down the derrick or mast .
(2) Crown block : an assembly of sheaves mounted on beams at the top of the derrick or mast over
which the drilling line is reeved.
(3) Drill collar : a heavy, thick-walled tube, usually steel, placed between the drill pipe and the bit in
the drill sterm to provide a pendulum effect to the drill sterm and weight to the bit.
(4) Draw works : the hoisting mechanism on a driiling rig. It is essentially a large winch that spools
off or takes in the drilling line and thrus raises or lowers the drill stem and bit.
(5) String : the entire length of casing, tubing, sucker rods, or drill pipe run into a hole.
(6) Diverter: equipment attached to the top of casing which can be closed to prevent the vertical
flow of the fluid and to divert the flow .
(7) Safety disk : a thin disk placed on piping or pressure vessels which can be broken through at a
certain minimum pressure.
(8) Production system: system necessary tfor delivery of hydrocarbon of specified quality and
quantity. The production system may include separation processe, compression, storage,
hydrocarbon disposal, etc.
(9) Utility system : system providing the installations with supporting functions, typical systems are
cooling water, glycol regeneration, hot oil for heating, chemical system for injection, instrument
TCVN 5311:2001
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air and power generation system.
(10) Riser tensioner: hydraulic system which maintain tension of the risers.
(11) Pit : Tanks which are used for holding mud pit, salt water, settling of mud sediments, and
storage of reserve mud and other disposed substances.
(12) Swivel : a rotary tool that is hung from the rotary hook and the traveling block to suspend the drill
stem and to permot it to rotate freely. It also provides a connection for the rotary hose and a
passageway for the flow of drilling fluid into the drill stem.
(13) Tongs : the large wrenches used to make up or break out drill pipe, casing, tubing, or other pipe;
variously called casing tongs, pipe tongs, and so forth, according to the specific use.
(14) Shear ram : the component in a blowout preventer that cuts, or shears, through drill pipe and
forms a seal against well pressure.
(15) Minimum Design Temperature: minimum design operating or ambient start-up temperature. The
lowest predictable metal temperature occuring during normal operation including start-up and
shut-down situations is to be used. If no thermal insulation is fitted, then ambient temperature is
tobe used if thi s is lower tham the temperature of the content.
(16) Casing : steel pipe placed in an oil or gas well as drilling progresses to prevent the wall of the
hole from caving in, to prevent seepage of fluids, and to provide a means of extracting
petroleum if the well is productive.
(17) Kill line : pipe attached to the blowout preventer stack, into which mud or cement can be
pumped to overcome the pressure of a kick.
(18) Manifold : an accessory system of piping to a main piping system ( or another conductor) that
serves to divide a flow into several parts, to combine several flows into one, or to reroute a flow
to any one of several possible destinations.
(19) Choke manifold: an arrangement of piping and special valves, called chokes. In drilling, mud is
circulated through a choke manifold when the blowout preventers are closed in on a kick .
(20) Tubing : small-diameter pipe that is run into a well to serve as a conduit for the passage of oil
and gas to the surface.
(21) Bellow : component sensative to pressure of compressed air controlled valve. When bellow is
extended the valve is moved.
(22) Rod : Rod which is marked for purpose of measurement.
TCVN 5311:2001
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(23) Equipment all mechanical and structural components which the drilling systems in 13.1.1-3
consists of.
(24) Degasser : the device used to remove gas from drilling fluid .
(25) Drilling Plant: equipment and systems necesssary for safe drilling operations, but not limited to
systems given in 13.1.1-3.
(26) Control stations in ''oil production plant part'' : are those spaces in which the unit's radio or main
navigating equipment or emergency source of power is located or where the fire recording or fire
control equipment or dynamical positioning control system is centralized or where a fire-
extinguishing system serving various locations is situated.
(27) Rotary hose : a reinforced flexible tube on a rotary drilling rig that conducts the drilling fluid from
the standpipe to the swivel and kelly.
1.4. Materials
1 Material used for manufacturing equipment is to comply with requirements of this TCVN as well as
Section 7-A Material, TCVN6259-7:1997.
2 Specimens and test procedures is to comply with requirements of this TCVN as well as Section 7-A VËt
liÖu, TCVN6259-7:1997,.
2. Rudder and steering gear
2.1. General
1 Each mobile offshore unit shall be provided with a reliable system ensuring its ateering and course-
keeing qualities with due regard for the operating conditions of the unit and in compliance with the
requirements of Chater 25 Part 2A TCVN 6259-2:1997, .
2 In non-self-propellered units the VR may allow to omit the steering gear or to provide only stabilizers;
however, this omission is subject to special consideration by the VR .
3. Mooring Equipment for Temporary Mooring
3.1. General
TCVN 5311:2001
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1 All units are to be provided with the mooring equipment for temporary mooring .
2 Anchors, chain cables and ropes necessary for temporary mooring are to be provided on units in
accordance with the requirements in this part and in Chapter 25 Part 2-A and Chapter 21 Part 2-B
TCVN6259-2:1997,according to their equipment number specified in 3.2 . Where, however, deemed
appropriate by VR, the requirements in Chapter 19, Part 8-A , TCVN6259-8:1997, may be applied to the
mooring equipment of units having no propelling machinery .
3 Permanent or semipermanet mooring systems cau be used as temporary mooring if satisfying
requirements of -2 .
3.2. Equipment number
1 The equipment number is to be determined according to the requirements in Chapter 25 Part 2-A,
Chapter 21 Part 2-B TCVN 6259-2:1997 for ship type units and Chapter 19, Part 8-A TCVN 6259-8:1997
for barge type units,.
2 The equipment number of shelf-elevating units and column stabilized units is to be obtained from the
following formula :
N = W2/3 + 2A1 + 0,1A2
Where:
W : Displacement of the unit in temporary mooring condition (t).
A1 : Projected areas except that of legs of self-elevating units, above the water line on planes
perpendicular to the centre line of the unit, respectively (m2 ).
A2 : Projected areas except that of legs of self-elevating units, above the water line on planes parallel to
the centre line of the unit, respectively (m2 ) .
3.3. Equivalent Mooring Equipment
1 If the VR recognizes that the effect of mooring equipment for operating condition is equivalent to that of
the temporary mooring quipment specified in 3.2 , such mooring equipment for operating condition is
regarded as the temporary mooring equipment specified in this part .
2 Where approved by the Society, wire ropes may be used in lieu of chain cables. In this case, however,
the wire ropes are to satisfy the requirements in Chapter 4, Part 7B TCVN 6259-7:1997, and their
breaking load is not to be less than the breaking test load for Grade 1 chain cables specified according to
the equipment number .
TCVN 5311:2001
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3.4. Windlasses
1 Units, except the mobile offshore drilling units and for those moored for a long period of time or semi-
permanently, are to be provide with windlasses having a sufficient hoisting capacity .
3.5. Offshore mooring Chains
3.5.1. Application
1 Offshore mooring Chains (hereinafter referred to as '' offshore chain''), shackles and swivels which are
connected to the offshpre chain (hereinafter referred to as ''accessories for offshore chain'') are to comply
with the requipments in 3.5 or to be of equivalent quality .
3.5.2. General
1 Offshore chains are to be manufactured in continuous lengths by flash butt welding and are to be heat
treated in a continuous furnace .
2 The connecting common links may be used in order to replace defective links which does not comply
with tests and examinations required by 3.5. However, the use of connecting common links is restricted to
3 links in each 100 m of offshore chain .
3 Notwithstanding the requirement of -2, the joining shackles may be used in order to replace defective
links which does not comply with tests and examinations required by 3.5. In this case, Number and type
of joining shackles used are to be subject to the approval of VR .
3.5.3. Kinds of offshore chains
Offshore chains are to be subdivided into three grades that are , :
- Grade R3 offshore chain
- Grade R3S offshore chain
- Grade R4 offshore chain
3.5.4. Materials
1 Offshore chains are to be made of the materials given in Table 3.5.4-1 according to their grades and
manufacturing processes, respectively .
2 The studs are to be made of steel whose the carbon content is in general less than 0.25% if the studs
are welded in place however, the studs may be made of steel bars corresponding to that of the offshore
TCVN 5311:2001
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chain or of equivalent thereto considered by VR .
3 Accessories for offshore chains are to be made of the materials given in Table 3.5.4-2 corresponding to
the grades of the connected offshore chain .
Table 3.5.4-1 Materials for offshore chain link
Grades of offshore chain Materials Grade of material
Grade R3 offshore chain Grade R3 offshore chain bar KSBCR3
Grade R3S offshore chain Grade R3S offshore chain bar KSBCR3S
Grade R4 offshore chain Grade R4 offshore chain bar KSBCR4
Table 3.5.4-2 Materials for accessories for offshore chain
Kind of
connected
Manufacturing process
offshore chain Casting Grade of
material Forging Grade of
material
Grade R3
offshore chain
Grade R3 steel casting for
offshore chain
KSCCR3 Grade R3 steel casting for
offshore chain
KSFCR3
Grade R3S
offshore chain
Grade R3S steel casting for
offshore chain
KSCCR3S Grade R3S steel casting for
offshore chain
KSFC3S
Grade R4
offshore chain
Grade R4 steel casting for
offshore chain
KSCCR4 Grade R4 steel casting for
offshore chain
KSFCR4
3.5.5. Processes of manufacture
1 The manufacturers of offshore chains including connecting common links are to obtain approval of VR in
advance concerning their manufacturing methods .
2 Where the studs are welded to offshore chain excluding Grade R4 offshore chain, are to be complied
with following (1) to (3) :
(1) Both ends of the stud are to be a good fit into the link and are not to be fitted on the flash butt
weld of the link as far as practicable, and the full periphery of the stud end is to be welded.
Welding of both ends of the stud is not permitted unless specially approved by VR .
(2) Welding position is to be flat as possible ;
(3) All welds are to be carried out before the final heat treatment of offshore chains .
TCVN 5311:2001
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3 Welding of studs in Grade R4 offshore chain is not permitted unless specially approved by VR .
4 Accessories of offshore chains are to be made by casting or forging. Their manufacturers are to obtain
approval by VR in advance concerning their manufacturing methods .
5 Machining of Kenter shackles is to result in fillet radius minimum 3% of nominal diameter .
6 Connecting common links are to be substituted for defective common links of offshore chain without
necessity for re-heat treatment of the whole length and with the method of heat treatment which is not to
affect the properties of the adjoining links whose temperature is nowhere exceed 2500C. However, an
alternative procedure may be applied to this joining method where specially approved by VR .
3.5.6. Offshore chain manufacturers
Manufactures which manufacture the offshore chains and accessories of them are to obtain approval by
VR .
3.5.7. Heat treatmen
1 Offshore chains are to be heat treated as normalized, normalized and tempered or quenched and
tempered in a continuous furnace. In principle, batch heat treatment is not permitted .
2 Accessories of offshore chain are to be heat treated as normalized, normalized and tempered or
quenched and tempered .
3.5.8. Dimensions and forms
1 The standard dimensions and forms of each kind of link and accessory are to be as given in Fig. 3.5.8-1
2 The nominal diameter of offshore chains is to be denoted by the diameter at the crown of the common
link .
3 Every kind of links and accessories are to be of uniform shape and their bent portions are to be sufficient
to allow each link to work smoothly .
3.5.9. Dimensional tolerances
1 The dimensions of offshore chains are to be measured at least 5% of all links after the execution of a
proof test .
2 The tolerances of offshore chains are to comply with the following requirements :
(1) The negative tolerance at the crown part of each kind of link is to comply with the requirements
TCVN 5311:2001
21
in accordance with the nominal diameter as given in Table 3.5.9-1 and the plus tolerance may
be up to 5% of its nominal diameter. However, no negative tolerances of the cross sectional
area of the crown part of the link is permitted .
Table 3.5.9-1 Negative tolerance of diameters
Nominal (mm) Negative tolerances (mm)
d ≤ 40 1
40< d ≤ 84 2
84 < d ≤ 122 3
d > 122 4
(2) The tolerances other than the crown part of each kind of link are to be up to +5%, but is not to
be negative .
TCVN 5311:2001
3,1 d ...
Common link Enlarged link
1,2 d
4 d
Swivel End linkElectr. welded
1,55d
1,125d0,67 d
5,7d
1,36
d
3,2 d ... cast
1,65
d 1,0 d-1,1 d
2,7 d
4,7 d
3,2 d
1,63 d
2,2 d 2 d
1,25 d ... forged
1,45 d ... cast
6,75
d
4 d
6,5d
1,1 d
6d
d
3,6 d
Joining shacklei Kenter shackle Anchor shackle
(2) Stud link chain and shackle
0,67 d
0,73 d
1,83 d 0,67 d
0,106 × d
0,36 d
d
4,4 d
1,4 d
1,4 d
3 d0,3 d
1,4 d 1,4 d
0,
9d
5,05 d
Tapered pin (Stainless steel)
0,8d
0,4d
2,1d
0,8d
4,2 d
6 d
1,52d d
0,73 d
Tapered pin (Stainless steel)
1,3 d
0,7d
1,3 d 1,3 d
1,2 d
2,8 d
d 0,2 d
1,6d
0,8d
7,1d
4 d
0,3d
1,1 d
1,1 d
d
Anchor shackle
2,82 d
d’
4,9d
3,5 d
1,1 d’
6d
3,8 d
Common link Joining shackle
d 1,2 d 0,19 d
1,5d
0,71
d
6,1d
3,8 d
1,13d
1,2 d
0,94 d
d 0,
710,
28
Tapered pin (Stainless steel)
1,2 d2,55 d
End link
1,32 d 1,32 d
Tapered pin(Stainless steel)
1,9d
8,5d
0,19 d
0,75
d
1,32 d
1,32 d
0,75
d 0,
37d
4,75 d
(1) Studless short link chain and shackle
Fig 3.5.8-1 Dimentions and forms of chain link, shackle and swivel
22
TCVN 5311:2001
23
(3) The tolerances with regard to the location of stud set are to be left to the discretion of VR .
(4) All other dimention are subjected to a manufacturing tolerances of ± 2,5%.
3 For all offshore chain, a length of 5 common links, which are connected is to be measured. The
measurement of a length of 5 links are to be carried out in accordance with the following procedures
while the offshore chain is loaded to 5 - 10% of the minimum proof load :
(1) The first five links is to be measured ;
(2) The next set of five links, at least two links from the previous five links are to be included, is to
be measured ;
(3) The measurement procedure specified in (2) is to be followed for the entire offshore chain
length;
(4) The links held in the end blocks may be excluded from this measurement .
4 The allowable manufacturing tolerance on a length of five links by measuring procedure specified in -3 is
to comply with the requirements as given in Table 3.5.11-1.
5 If a length of five links is shorter than allowable value, offshore chain may be stretched by tensile
loading. In this case, however, tensile load is not to exceed 110% of minimum proof load required .
6 If links are found to be defective or not to meet the dimensional tolerance requirement specified in -1,
defective links may be cut off and a connecting common link or joining shackle inserted in their place. In
this case, proof tests are to be carried out again after insertion of a connecting common link or a joining
shackle, and dimensions of a connecting common link or a joining shackle are to measure .
7 At least one accessories (of the same type, size and nominal strength) out of 25 is to be measured for
dimensions after proof load testing. Dimensions are subjected to a manufacturing tolerances of the
following (1) and (2 ) :
(1) The tolerances of the diameter at the bent portions of Kenter shackles are to be equal + 5%, but
may not be negative ;
(2) All other dimentions are subjected to a manufacturing tolerances of 2.5%.
3.5.10. Mass
1 The mass of offshore chains is to comply with the standard mass given in Table 3.5.11-1, in accordance
TCVN 5311:2001
24
with their kind, and to be measured after the execution of proof tests .
3.5.11. Breaking tests
1 The breaking test for offshore chain is to be carried out by the following procedures after final heat
treatment :
(1) A breaking test specimen consisting of at least 3 links is to be either taken from the offshore
chain or produced at the same time and in the same manner as the offshore chain ;
(2) The breaking test frequency is to be based on tests at sampling intervals according to Table
3.5.11-2 corresponding to its nominal diameter provided that every cast is represented .
(3) Each specimen is to be capable of withstanding the break load specified in Table 3.5.11-1
without fracture maintained at that load for 30 seconds .
(4) Where the capacity of the testing machine does not reach the breaking test loads specified in
Table 3.5.11-1, the breaking test may be substituted by a method approved by VR .
(5) If a breaking test fails, a thorough examination is to be carried out to identify the cause of failure.
(6) If a breaking test fails, two additional breaking test specimens representing the same sampling
length of offshore chain are to be subjected to the breaking test. If two additional breaking test
result satisfactorily, it will be decided what lengths of offshore chain can be accepted based
upon the results of the failure investigation specified in (5).
(7) If either or both results of the additional test and failure investigation specified in (5) and (6) fail,
the sampling length of offshore chain represented will be rejected. If a single link is found to be
defective or not to meet the requirement of breaking test, defective links may be cut out and
connecting common link or joining shackle inserted in its place and retest of breaking test may
be carried out. If the result of the retest is found satisfactory, the sampling length of offshore
chain represented may be passed.
2 The breaking test for accessories of offshore chain and connecting common link is to be carried out by
the following procedures after final heat treatment :
(1) For accessories of offshore chain, the breaking test is to be carried out for the following
frequency which is the least. However, for connecting common link and individually produced
accessories or accessories produced in small batches, the frequency of the breaking test is at
the discretion of VR .
(a) One accessory from each manufacturing lot, which have the same grade, size, and heat
TCVN 5311:2001
25
treatment, of 25 units or less of accessories .
(b) One accessory out of every batch .
(2) Each specimen of accessories of offshore chain and connecting common link is to be capable of
withstanding the break load specified for the grade and size of offshore chain for which they are
intended without fracture maintained at that load for 30 seconds .
(3) Where the breaking test is not satisfactory, the accessories may be retested by taking out two
units from the same lot specified in (1). If one such test fails to meet the requirements, the entire
unit of the same lot is rejected .
(4) Accessories and connecting common links used for the breaking test are generally not to be put
into use in service.
Table 3.5.11-1 Breaking and proof test loads, mass and length over 5 link for offshore chains
Kind of offshore chain
Item
Offshore chain
Grade R3
Offshore chain
Grade R3S
Offshore chain
Grade R4
Proof test load (kN) 0,0148d2(44-0,08d) 0,0180d2(44-0,08d) 0,0216d2(44-0,08d)
Breaking test load (kN) 0,0223d2(44-0,08d) 0,0249d2(44-0,08d) 0,0274d2(44-0,08d)
Mass of offshore chain (kg/m) 0,0219d2
Length over 5 links (mm) 22d min. ÷ 22,55d max.
Table 3.5.11-2 Number of breaking test
Unit: mm
Nominal diameter of
offshore chain d (mm)
Maximum sampling
interval (m)
Nominal diameter of
offshore chain d (mm)
Maximum sampling
interval (m)
d ≤ 48 91 111 < d ≤ 124 222
48 < d ≤ 60 110 124 < d ≤ 137 250
60 < d ≤ 73 131 137 < d ≤ 149 274
73 < d ≤ 85 152 149 < d ≤ 162 297
85 < d ≤ 98 175 162 < d ≤ 175 322
98 < d ≤ 111 198 175 < d 322
3.5.12. Proof tests
1 The proof test is to be carried out for the entire length of offshore chain by the following procedures after
final heat treatment :
TCVN 5311:2001
26
(1) Offshore chains are to withstand the proof test loads specified in Table 3.5.11-1 without crack,
breakage or any other defects .
(2) Notwithstanding the requirements of (1) above, where plastic straining is used to set studs, the
applied proof load is not to be greater than that in approval tests for manufacturing .
(3) If a link fails during proof load testing, a thorough examination is to be carried out to identify the
probable cause of failure of the proof test from the manufacturing records. Where the cause of
failure is identified and the presence in other lengths of factors or conditions thought to be
causal to failure is not found from the above failure investigation, this length of chain except a
failure link may be accepted .
(4) In the event that two or more links in the proof loaded length fail, that length of offshore chain is
to be rejected. An investigation and retest are to be carried out in accordance with the following
(a) to (c) and where these results are found satisfactorily, this length of offshore chain may be
accepted .
(a) A thorough examination is to be carried out to identify the probable cause of failure of the
proof test from the manufacturing records. The tests in order to identify the cause of
failure may be required where deemed necessary by VR .
(b) A breaking test specimen is to be taken from each side of the one failed link according to
3.5.11-1 (1), and subjected to the breaking test .
(c) Defective links may be cut out and connecting common link or joining shackle inserted in
its place and retest of proof load test is to be carried out .
2 All kinds of accessories and connecting common links are to be tested to the proof test loads specified in
Table 3.5.11-1, in accordance with the kinds and diameters of the offshore chains to be connected
therewith, and they are to be withstand the tests without crack, breakage or any other defects. This test
may be carried out simultaneously with the proof test for the offshore chains or together with any offshore
chains of the same diameter with which accessories are connected .
3.5.13. Mechanical tests
1 Mechanical tests for offshore chains are to be carried out in accordance with following manner after final
heat treatment :
(1) One tensile test specimen and 3 sets (9 pieces) impact test specimens are to be taken from the
maximum sampling interval corresponding to the nominal diameter of offshore chain specified in
Table 3.5.11-2. Test specimens are to be taken from the location given in Fig. 3.5.13-1 of the
part specified in the followings :
TCVN 5311:2001
27
(a) The tensile test specimen is to be taken in the side opposite the flash weld ;
(b) One set (3 pieces) impact test specimens are to be taken across the flash butt weld with
the notch centered in the middle, one set are to be taken across the unwelded side and
one set are to be taken from the bent region .
(2) Test procedures and form of test specimen are to comply with the requirements in Chapter 2
Part 7-A TCVN6259-1997 - ;
(3) Mechanical properties are to comply with the requirements specified in Table 3.5.13-1.
Table 3.5.13-1 Mechanical properties
Kind of Tensile test Impact(1)
offshore
chain
Yield point or proof
test (2)
Tensile
strength
(2)
Elongation
(L=5d)
Reduct
-ion of
area
Testing
temper-
ature
Minimum mean
obsorbed energy (J)
(N/mm2) (N/mm2) (%) (%) (0C) Except
welded part
Welded
part
Grade R3 ≥ 410 ≥ 690 ≥ 17 ≥ 50 -20 (3) ≥ 40 (3) ≥ 30 (3)
Grade R3S ≥ 490 ≥ 770 ≥ 15 ≥ 50 -20 (3) ≥ 45 (3) ≥ 33 (3)
Grade R4 ≥ 580 ≥ 860 ≥ 12 ≥ 50 -20 ≥ 50 ≥ 36
Note :
(1) When the absorbed energy of two or more test specimens among a set of test specimens is less in value
than the specified minimum mean absorbed energy or when the absorbed energy of a single test
specimen is less in value 70% of the specified minimum mean absorbed energy, the test is considered to
have failed .
(2) Aim value of yield to tensile ration is maximum 0.92 T.
(3) Impact test of Grade R3 and R 3S offshore chains may be carried out at the temperature of 00C where
approved by VR. In this case, minimum mean absorbed energy is not to be less than following :
Kind of offshore chain Except welded part Welded part
(a) Grade R3 offshore chain 60J 50J
(b) Grade R3S offshore chain 65J 53J
TCVN 5311:2001
28
(4) If the tensile test result does not conform to the requirements, a retest of two further specimens
selected from the same sample may be carried out. Where both additional tensile tests show
satisfactory results, the sampling length of offshore chain is considered acceptable .
(5) If the impact test results does not conform to the requirements, a retest of three further 1 set (3
pieces) specimens selected from the same sample may be carried out. The results of a retest are to
be added to those previously obtained to form a new average. If the results of a retest comply with
the requirements specified in Table 3.5.13-1 and the new average comply with the requirements
specified in Table 3.5.13-1, the sampling length of offshore chain is considered acceptable .
2 Mechanical tests for accessories of offshore chains and connecting common links are to be carried out
in accordance with following manner after final heat treatment :
(1) One tensile test specimen and one set (3 pieces) impact test specimen are to be taken at the
frequency specified in 3.5.11-2 (1) of accessories of offshore chains and connecting common
links and mechanical tests are to be carried out. Mechanical properties are to comply with the
requirements specified in Table 3.5.13-1 ;
(2) Where the test results specified in (1) above do not conform to the requirements, additional tests
may be carried out by the two tensile test specimens and 2 sets impact test specimens taken
from the same lot specified in (1) above. The results of the retest of impact test specimens are
to be added to those previously obtained to form a new average. Where one tensile test does
not conform to the requirement specified in Table 3.5.13-1, the sampling rot represented is to be
subjected to rejection and where the new average value does not comply with the requirements
specified in Table 3.5.13-1, the sampling rot represented is to be subjected to rejection .
Tensile test pecimen
r 3
Tensile test pecimen
r 3
Tensile test spcimen
Fig 3.5.13-1 Location for sampling test specimens for links of offshore chain
3.5.14. Non-destructive test
1 Offshore chains and accessories of offshore chains are to be free from harmful defects in use such as of
TCVN 5311:2001
29
pipe, cracks, notches, cuts, flakes and lack of fusion .
2 All offshore chains are to be subjected to the non-destructive test specified in the following (1) and (2)
after proof tests :
(1) Magnetic particles test or dye penetrant test
(a) Magnetic particles test or dye penetrant test for every link, is to be employed to examine
the flash butt welded area including the area gripped by the clamping dies;
(b) At least 10% of all studs welds within each length of offshore chains are to be examined
by magnetic particles test or dye penetrant test where studs are set to link by welding. If
cracks or lack of fusion are found, all welded parts are to be examined .
(2) Ultrasonic test
Ultrasonic test for all links is to be employed to examine the flash weld fusion .
3 Magnetic particles test or dye penetrant test for every accessories of offshore chain and connecting
common link, is to be employed to examine after proof test .
3.5.15. Repair of defects
1 Where insignificant defects are found from non-destructive test specified in 3.5.14, they are to be
repaired by grinding down no more than 5% of the link diameter in depth and streamlined to provide no
sharp contours, and where their final dimensions are to be within the dimensional tolerances required by
3.5.9, those offshore chains and their accessories are considered acceptable .
2 Where harmful defects are found from non-destructive test specified if 3.5.14-2, a defective link may be
cut out and connecting common link or joining shackle inserted in its place. Retests specified in 3.5.11 to
3.5.13 are to be carried out, and where the results comply with the requirements, these offshore chains
and their accessories are considered acceptable .
3.5.16. Markings
Where offshore chains and accessories of offshore chains have satisfactorily passed the tests and
inspections required by 3.5, they are to be marked as follows :
(1) Places of markings
- At stud of each end of offshore chains ;
- At stud of each end at intervals not exceeding 100 m ;
- On connecting common link;
TCVN 5311:2001
30
- On stud of common links next to connecting common links or joining shackles ;
- All kind of accessories of offshore chains.
(2) Kinds of markings
- VR's stamp ;
- The grade of offshore chains and accessories of offshore chains (e.g. VR-R3, VR-3S and VR-
R4);
- The nominal diameter of offshore chains and accessories of offshore chains ;
- Manufacturer's number .
3.5.17. Painting
Offshore chains and accessories of offshore chains are not to be painted until the tests and inspections
are finished .
3.5.18. Record
Manufacturers producing offshore chains and accessories of offshore chains are to make records with
regard to the manufacturing processes tests and inspections required to offshore chains and accessories of
offshore chains, and the results of them, and such records are to readily available to the surrey or when
requested .
4. Mooring equipment
4.1. General
1 Each unit is to be provided with mooring equipment as required in TCVN 6259-2:1997 Hull construction
and equipment of ship.
5. Positioning Systems
5.1. General
5.1.1. Application
1 The requirements in this Part apply to positioning systems to be provided with units. The positioning
system referred to here includes a mooring system or a dynamic positioning system for positioning a unit
TCVN 5311:2001
31
a specific location for a long period or semi-permanentty, or a mooring system or a dynamic positioning
system for positioning a unit engaged in specific work at a specific location for a long period or semi-
permanently.
5.1.2. General
1 The mobile offshore drilling units, whose type is a column stabilized type, a ship type or barge type, are
to be provided with the positioning system satisfied with the requiremenls in this Chapter .
2 The self-elevating units, notwithstanding the purpose of units, need not to be provided with the
positioning system .
3 Positioning systems are to be sufficiently capable of positioning the units safety at a specific position of
all design condition for positioning .
5.2. Classification of Positioning Systems
5.2.1. General
1 Positioning system means a proper system provided on board and is to be classified into two types
corresponding to its type :
(1) Mooring system
Mooring system means the positioning system excluding the dynamic positioning system
(2) Dynamic positioning system
Dynamic positioning system means the positioning system which the unit is kept a specific position
by automatically control of thruster systems such as thruster or propeller provided with the unit and
its system consists of the following systems specified in (a) to (c):
(a) Power system
(b) thruster systems such as thruster or propeller
(c) Dynamic positioning control system .
5.2.2. Classification of Mooring System
1 Mooring systems are to be classified into the following categories corresponding to the type :
(1) Anchor Morring system
TCVN 5311:2001
32
Anchor mooring systems are defined as those comprising anchors and sinkers laid to the sea
bottom, fairleaders, windlasses, winches and other mooring equipment provided at several parts of
the hull, and mooring lines connecting them, and obtaining a mooring force mainly from the net
weight of the catenary mooring lines (for those provided with intermediate buoys or intermediate
sinkers, their net weight or buoyancy). Here. The term mooring line means an integration of chains,
wire ropes, fabric ropes or their combination, connecting means such as shackles, or intermediate
buoys or intermediate sinkers
(2) Tension mooring systems
Tension mooring systems are defined as those comprising supporting members such as piles and
sinkers laid to the sea bottom, tension lines arranged upright direction, and connecting means to fix
the tension mooring lines to the hull structure, and confining the unit's heaves, rolls and pitches by
the increased buoyancy created by pulling the unit downward and the tension in the mooring line.
Here, tension mooring lines include steel pipes, chains, steel wire ropes and fibre ropes, and they
ara arranged straight in a high ten sile force which is mainly obtained from elastic elongation of
these lines .
(3) Single-point mooring sytems
In this system. mooring force is obtained only from a single point of a hull. The system comprises
mooring equipmemt installed in the hull, connecting systems, one or more mooring lines, mooring
construction instead of mooring lines, and supporting members laid to the sea bottom or provided
in the fixtures in the vicinity .
(4) Dolphin mooring systems
Dolphin mooring systems are those comprising dolphins such as fixed piles or concrete caissons
arranded adjacent the unit, fenders and fender beams arranged between the unit and dolphins, or
fenders provided in the unit as necessary. Positioning in this case is obtained from the reaction
force of the fixed dolphins.
(5) Other mooring systems
Mooring systems are other than (1) through (4) above .
5.2.3. Dynamic Positioning System
1 Dynamic positioning system ( hereinafter referred to as DPS ) is to be classified into the following three
categories specified in (1) to (3) :
(1) Class A DPS
TCVN 5311:2001
33
(2) Class B DPS
(3) Class C DPS
2 Categories of the DPS is defined in the following assumptions specified in (1) to (3) of the worst failure
conditions of each component consisting of DPS. Where the worst failure condition of each component
includes a miss-operation or a malfunction of this system .
(1) Class A DPS means a DPS that a loss of position keeping capability may occur in the event of a
single failure in a single component specified 5.2.1.1 (2) (a) to (c) is failed.
(2) Class B DPS means a DPS that a loss of position keeping capability is not to occur in the event
of a single failure in any active component or system such as generators, thrusters, remote
controlled valves, switchboards, etc. specified in 5.2.1.1(2) (a) to (c). Normally, static
components such as cables, pipes, manual valves, etc., however, will not be considered to fail
where adequate protection is demonstrated, and reliability is to be the satisfaction of the Society
(3) Class C DPS means a DPS that a loss of position keeping capability is not to occur in the event
of a single failure in all components or systems specified in 5.2.1.1(2) (a) to (c). This failure is to
include the following conditions specified in (a) and (b) :
(a) Where the component consisting of the system is in any one watertight compartment, all
components in this compartment are to be assumed to be failure due to flooding.
(b) Where the component consisting of the system is in any one fire sub-division duvided by
''A-60'' class,all components in this sub-division are to be assumed to be failure due to fire
3 Considering the requirements in -2(2) and (3) above, failure mode and effects analysis or fault tree
analysis deemed appropriately by the Society is to be carred out in order to demonstrate not to loss a
position keeping capability in the assumed worst failure conditions of each component .
5.3. Anchor Mooring System
5.3.1. General
1 The requirements in 10.3 apply to the units having the anchor mooring system as its sole positioning
means .
2 In the case where chains are used as the mooring line, these chains are not to comply with the
requirements in 3.5. Where chains of Grade R4 are used, special attention is to be paid that repair works
for any defects, loosen stud and corrosion by welding is in principle, prohibited for such chains .
3 The individual system components consisting on anchor mooring systems are to be designed using a
TCVN 5311:2001
34
design procedure capable of verifying the most severe loading conditions, having a safety factor
coefficients deemed appropriate by the Society .
4 It is desirable that the maximum value of motions of the unit in waves is determined by model
experiments. However, its value may be calculated by an analytical method verified through model
experiments which are deemed appropriate by the Society .
5 For assessing motions of the unit in waves at shallow waters, the shallow water effects are to be taken
into account. Where changes in tidal levplg in shallow waters are relatively large, the tidal difference
affecting unit motions is to be considered.
6 Corrosioll control and fatigue strength of mooring lines are to be considered .
7 The mooring lines with anchor are to have a sufficient length so that undue pulling up of anchors can be
prevented .
8 When multiple mooring system is adopted as mooring systems, all mooring lines, in principle, are to be
of the same elastic coefficient .
9 The parts of hull structure where windlassed are installed are to be capable of withstanding the break
load of the mooring lines .
10 Fairleads and sheaves are to be so desinged that excessive bending and wearing of mooring lines can
be prevented. Their fixtures connecting the hull structure are to be capable of withstanding the breaking
load of the mooring lines .
11 Suitable anchor storage arrangements are to be provided to prevent from moving the anchors in a
seaway. For units moored semi-permanently at a specific location, however, storage arrangements may
be dispensed with .
12 The design of anchor mooring systems, where anchor mooring systems are used in combination with
propulsion system, such as thrusters, for positioning, is to be as deemed appropriate by the Society .
5.3.2. Calculating the Tension of Mooring Line
1 For calculating the maximum tension acting on the mooring lines, the most severe combination of wind,
waves and current (generally, this condition corresponds to a case when all the directions of wind, wave
and current are consistent) is to be considered together with a sufficient number of angle of incidence.
For specific sea areas, combinations of wind, wave and current in different directions, which are likely to
create a higher tension are to taken into account as necessary .
2 In calculating the tension acting on the mooring lines, at least ite items (1) to (3) mentioned below are to
TCVN 5311:2001
35
be considered. Item (4) may be assessed as necessary. This analytical procedure is called the quasi-
static analytical procedure, the calculating procedure of tension acthing on the mooring lines are adopted
as standard. The maximum tension of mooring lines calculated by the quasi-static analytical procedure
has to have a suitable safety factor deemed appropriate by Society against thier breaking tension.
(1) Static tension of mooring lines due to its net weight and buoyancy .
(2) Steady tension of mooring lines due to steady horizontal displacements of the unit induced to
wind, waves and current .
(3) Quasi-static varying tension of mooring lines due to the unit's motions induced to waves .
(4) Tension of mooring lines considering their elastic elongation when they are used with a
moderate taut condition (generally in shallow waters), or when mooring lines with a low rigidity
such as fibre ropes are used .
3 For the mobile offshore drilling units, the anchor mooring system is to be so designed that a failure of
anyone mooring line does not cause progressive failure of the remaining mooring lines. For units ,other
than the mobile offshore units, the anchor mooring systems are to be as deemed appropriate by the
Society. In this case, a calculaling procedure of tension acting to mooring lines may also be adopted to
the quasi-static analytical procedure specified in -2. The period of recurrence of the environmental loads
such as wind and wave loads, however, may be taken as one year. The maximum tension of mooring
lines calculated by the quasistatic analytical method is to have a suitable safety factor deemed
appropriate by the Society against their breaking tension .
4 In addition to -2 above, when the following items (1) and (2) are taken into account, the safety factor
required where the quasi-static analytical procedure is adopted may be reduced to a value deemed
appropriate by the Society.
(1) Dynamic tension in mooring lines due to the damping force and the inertial force aclion on each
mooring line when they are generally used in deep waters.
(2) Quasi-static low-frequency varying tension of mooring lines due to low-frequency molions of the
unit in irregular waves when they are used in a sufficiently slack condition. (when the natural
period of the motions of the unit in a horizontal plane is sufficiently longer than the period of
ordinary waves) .
5.3.3. Equipment for Anchor Mooring System
1 Individual equipment for anchor mooring system is to be apporvedby the Society, in principle.
2 Windlasses used for anchor mooring system of unit are to comply with the following requirements
TCVN 5311:2001
36
specified in (1) to (3).
(1) Each windlass is to be provided with two independent power-operated breakes. Each brake is to
be capable of holding against a static load in the anchor cable of at least 50% of its breaking
strength. When deemed appropriate by the Society, one of the breaks may be replaced by
manually operated break.
(2) The windlass is to have a sufficient dynamic braking capacity to control normal combination of
loads from anchor, mooring cable and anchor handling vessel during the deployment of the
anchors at the maximum design pay-out speed of the windlass .
(3) When a power source for windlasses is lost, the power-operated breaking system is to be
automatically applied to and be capable of holding against 50 % of the total static braking
capacity of the windlass .
3 The measn specified in (1) through (4) below are to be provided for controlJing anchor mooring systems:
(1) Each windlass is to be capable of being controlled from a position which provides a good view of
the operation.
(2) Means are to be provided at the windlass control position to monitor the mooring line tension
and windlass power load and to indicate the amount of mooring line paid out .
(3) Mooring line tension indicator, wind velocity and wind direction indicators at the control station of
each windlass are to be provided at the manned control position.
(4) Measn of communication are to be provided between essential place for mooring operations (for
example: operating position, wheel house, control room, etc.)
4 Means are to be so provided that mooring lines can be released from the unit after the loss of the main
power supply .
5.4. Tension Mooring System
5.4.1. General
1 Tension mooring systems are to have a safety equivalent to the anchor mooring systems approved by
the Society .
2 The tension mooring systems may be desinged in accordance with the requirements of 5.3 for anchor
mooring sysytems. However, the items specified in 5.4.2 are to be taken into account .
TCVN 5311:2001
37
5.4.2. Tension mooring systems
1 It is to designed so that no slackening is caused in any tension mooring line due to changes in line
lension .
2 For mobile offshore drilling units, tension mooring lines are to be designed so that a failure of any one
tension mooring line does not cause a progressive failure of the remaining tension mooring lines.
3 The possible effects of a partial loss of buoyancy due to damage of the extent specified in 4.(Stability)
upon the mooring system are also to be assessed.
4 For mobile offshore drilling units, where the tension mooring system of the buoyancy type such a steel
pipe having a large-bore and thin-thickness is used. the possible effects of a partial loss of buoyancy due
to damage to anyone tension mooring line upon the mooring system are to be assessed .
5 In the case of tension mooring systems which are connected upright, the effects of sinkage of the unit
due to its motions in a horizontal plane are to be assessed .
6 The difference in tension of the tension mooring line due to tidal difference including astronomical tide
and meteorological tide is to be considered .
7 The effects of changes in the weight and the displacements of heavy items carried on board upon
tension of tension mooring lines are to be sufficiently taken into account .
8 Special consideration is to be given to the fatigue strength of the connections between the lension
mooring lines and the hull. Where steel pipe joints are used for tension mooring lines. the fatigue strength
at the stress concentrated areas is to be thoroughly assessed .
9 Consideration is to be given to wear of the connecitons between tension mooring lines and the hull
10 Where the effects of the non-linear behavior of tension mooring lines upon their tension are not
negligible, tension due to non-linear behavior is to be considered .
11 The effects of the high order vibrations of tension mooring lines upon fatigue strength, in particular, are
to be carefully assessed. In this case. the safety factor against the breaking load may be reduced to be
value deemed appropriate by the Society.
12 When mooring lines of the thin-thickness cylinder type are used. special consideration is to be given to
buckling due to combined axial and hoop .
13 The permissible stress when steel pipes are used for mooring lines is to be accordance with 4.2.2. .
14 When used in sea areas where currents are significanl.means are to be provided to suppress vibrations
TCVN 5311:2001
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of tension mooring lines due to vortex shedding as necessary .
5.4.3. Equipment for Tension Mooring Systems
1 For laying tension mooring lines, the initial tension in all mooring lines is to be coordinated to achieve
approximimate uniformity. Power equipment capable of adjusting the tension mooring lines is to be
provided as necessary .
2 A tension monitoring system is to be provided for each tension mooring line .
3 Plans and documents showing that, the supporting members laid to the sea bottom are designed so that
they cannot be pulled up under any design load condition are to be submitted to the Society for
rerference.
5.5. Single-point Mooring Systems
5.5.1. General
1 Single-point mooring systems are to have a safety equivalent to the anchor mooring systems approved
by the Society .
2 Single-point mooring systems may be designed in accordance with the requirements of 5.3, for anchor
mooring systems or TCVN 6809:2001. However, the specified in 5.5.2 are to be taken into account .
5.5.2. Single-point Mooring Systems
1 Predictions of unit mortions in waves and tension of mooring lines area, as a rule, to be based upon the
results of model experiments and non-linear time history domained calculations. However, if non-linear
time history domained, calculations are carried out using the analytical method and analysis programs
that have been sufficiently validated by model experiments, model experiments may be omitted subject to
approval by the Society.
2 Irregularities of waves and variances of wind are to be considered.
3 In calculating motions, the low frequency varying wave drifting forces of waves due to irregular waves
are to be considered .
5.6. Dolphin Mooring Systems
5.6.1. General
TCVN 5311:2001
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1 The mooring lines directly connecting units with dolphins among the dolphin mooring systems and their
connections to a unit's hull are to have a safety equivalent to the anchor mooring systems approved by
the Society .
5.6.2. Dolphin Mooring Systems
1 If dolphins such as fender beams having non-linear reaction characteristics are used in combination,
mooring lines are, as a rule, to be taken into account the requirements of 5.5.2.
2 The pressure bearing parts of unit's hull relating to fenders are to be capable of sufficiently withstanding
the maximum reaction of the doIphin system. In this case, the scope of the pressure bearing parts is to be
the widest predictable considering the changes in draught, tidal levels and ship motions .
5.7. Dynamic Positioning System (DPS)
5.7.1. General
1 The requirements in 5.7 apply to the units which are provided with the DPS as a solely positioning
system .
2 The DPS consists of the following system specified in (1) to (3)
(1) Power system
Power system means all components and systems necessary to supply the DPS with power. The
power system includes the followings (a) to (d).
(a) Prime movers with necessary auxiliary systems including piping .
(b) Generators.
(c) Switchboards
(d) Distributing system (cabling and cable routing).
(2) Thruster System
Thruster system means all components and systems necessary to supply the DPS with thrust force
and direction. The thruster system includes the followings (a) to (e) :
(a) Thrusters with drive units and necessary auxiliary systems including piping .
(b) Main propellers and rudders if these are under the control of the DPS .
(c) Thruster control electronics
(d) Manual thruster controls, and
TCVN 5311:2001
40
(e) Associated cabling specified in (a) to (d) above and distributing system (cabling and cable
routing ).
(3) Dynamic Positioning Control System
Dynamic positioning control system (hereinafter referred to as ''DP-control system".) means all control
components and systems, hardware and software necessary to dynamically position the vessel.The
DP-control system consists of the followings (a) to (c).
(a) Operating systems such as computer system/ joystick systems
(b) Sensor system including position reference system and display systems which indicate
the position and operating mode including operator panels
(c) associated cabling specified in (a) to (d) above and distributing system (cabling and cable
routing).
Where computer system means a system consisting of one or several computen including
software, their interfaces and display system .
3 Redundancy of systems required in 5.7 means ability of a component or system to maintain or restore its
function, when a single failure has occurred. Redundancy can be achieved, in general, by installation of
multiple components, systems or alternative means of performing a function .
4 Installations comprising dynamic positioning system are to be designed, manufactured, and tested in
accordance with the standard deemed appropriate by the Society .
5.7.2. installation comprising the DPS
1 Each installation comprising the DPS specified in 10.7.1-2. is to be immediately available and with such
capacity that the dynamic positionhtg operation (hereinafter referred to as -DP-operation-,) can be
continued for such a period that the work in progress can be terminated safely .
2 For Class A DPS, each installation need not be of redundancy system .
3 For Class B DPS, generators, thrusters, switchboards, remote controlled valves, etc.. are to be of
redundancy system .
4 For Class B DPS. the transfer to the others from one component or system is to be smooth and within
acceptable limitations of the operation and to be capable automatically as far as possible or operator
intervention is to be kept to a minimum.
5 For Class B DPS, a component or system not related to the DPS and which will cause a failure of the
DPS due to failure of this component or system is to comply with the relevant requirements in 5.7.
TCVN 5311:2001
41
6 For Class C DPS. each component comprising the DPS is lo be arranged in lhe compartment separately
by watertight and A-60 class sub-division. and cabling and piping system, in addition to comply with
the requirements in -3 to -5 above. Where each component complies with the fllowing requirements in (1)
to (3), However, each component need not be or redundant system.
(1) For connectors between one system and separated system such as a change over system from
the main computer system to the back-up computer systems, where the system is clearly safety
advantages to satisraction or the Society if the ru nction or this connector is lost.
(2) Non-redundant system is to be kept to absolute minimum and made to rail to the safest
condition. when a railure in this system is occur .
(3) Failure in one system is to in no case be transrerred to the other redundant systems .
5.7.3. Power system
1 The power system for the DPS is to comply with the requirements of Chapter 12 and is to have an
adequate response time to power demand changes in the worst failure condition specified in 5.2.3.
2 For Class A DPS. the power system need not be redundant .
3 For Class B DPS. the power system is to be divisible into two or more systems such that in the event of
failure of one system at least one other system will remain in operation. The power system may be run as
one system during DP-operation, but should be arranged by bus-tie breakers to separate automatically
upon failures which could be transferred from one system to another. including overloading and short-
circuits.
4 For Class C DPS, the power system and arrangements of this system are to comply with the followings :
(1) Each power system is to located in different spaces separated by '' A-60'' class sub-division.
(2) Where the power systems are located below the load waterline required by Chapte 8, each
power system is to be located in different spaces separated by watertight compartment .
(3) Bus-tie breakers are to be open during Class C DPS operations unless equivalent integrity of
power operation can be accepted according to 5.7.3-3 .
5.7.4. Thruster system
1 The thruster system is to provide thrust in longitudinal and lateral directions, and provide yawing moment
for heading control. The values of thruster force used are to be corrected for interference between
thrusters and other effects which may feduce the effective force.
TCVN 5311:2001
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2 Failure of thruster system including pitch, azimuth or speed control, is not to make the thruster rotate or
go to uncontrolled full pitch and speed.
3 The thruster system for Class A DPS need not comply with the requirements specifie-d in -1 after failure
of the power system is occurred.
4 The thruster system for Class B DPS and Class C DPS is to be connected to the power system in such a
way that the requirements in -1 can be complied with even after failure of one of the constituent power
systems and the thrusters connected to that system .
5.7.5. DP-control system
1 The design and arrangement of the DP-control system is to comply with the following requirements
specified in (1) to (4).
(1) The DP-control station is to be located in the space where the operator has a good view of the
vessel's exterior limits and the surrounding area .
(2) The DP-control station is to display information from the power systems, thruster systems, and
DP-control systems to ensure that these systems are functioning correctly. Information
necessary to operate the DPS safely is to be visible at all times .
(3) Display systems and the DP-control station in particular, are to be based on sound ergonometric
principles. The DP-control system is to provide for easy selection of control mode i.e. manual,
joystick, or computer control of thrusters, and the active mode is to be clearly displayed .
(4) Alarms and warnings for failures in systems interfaced to and/or controlled by the DPcontrol
system are lo be audible and visual. A permanent record of their occurrence and of status
changes is to be provided together with any necessary explanations .
2 The DP-control system for Class B DPS is to comply with the followings in addition to comply with the
requirements in -1.
(1) Operator controls are to be so designed that no single inadvertent act on the operators panel
can lead to a critical condition.
(2) The DP-control system is to prevent failures being transferred from one system to another .
(3) The redundant components are to be so arranged that a failure of one component, should be
isolated, and the other component activated .
(4) It is to be possible to control the thrusters manually, by individual joysticks and by a common
TCVN 5311:2001
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joysticks and by a common joystick, in the event of failure of the DP control system .
3 The DPcontrol system for Class C DPS is to comply with the requirements in -1 and -2, in addition, the
DP-control system is to be located in different spaces separated by ''A-60" class sub-division .
5.7.6. Computer system
1 Computer systems whose systems are of one system provicled with as the DP-control system for Class
A DPS need not be redundant.
2 Computer systems whose systems are of one system provided with as the DP-control system fof Class
B DPS are to comply with the following requirements specified in (1) to (5).
(1) The DPS is to consist of at least two independent computer systems. One computer system
which is being used during the DP-operation is the main computer system and the other
systems which are not being used during the DP-operation is the back-up computes.
(2) The back-up computer systems are to be arranged with automatic transfer of control after a
detected failure in the main computer systems. The automatic transfer of control from the main
computer system to the back-up computer systems is to be smooth, and within the acceptable
limitations of The DP-operation.
(3) An uninterruptable power supply (UPS) is bo be provided for each computer system to ensure
that any power failure will not affect more than one computer. An UPS battery capacity is to
provide a minimum of 30 minutes operation after the main supply system is failure.
(4) Computer systems are to include an appropriate software function approved by the Society to
be able to continuously verity that capability of positioning the unit remains after the worst failure
condition is occur.
(5) Common facilities such as self-checking routines, dala transfer arrangements, and plant
interfaces which are provided with the computer system, are not to be capable of causing the
failure of both/all computer systems.
3 Computer systems whose systems are of one system provided with as the DP control systems for Class
B DPS are to comply with the following requirements specified in (1) to (4), in addition that they are to
comply with the requirements in -2.
(1) The computer systems are to consist of the facilities of self-checking and alignment function .
(2) An alarm is to be initiated if any computer system fails or is not ready to take control.
TCVN 5311:2001
44
(3) During the DP-operation. this back-up computer systems are to be continuously updated by
input from the sensors, position reference system. thruster feedback, etc.. and be ready to take
over control .
(4) The switch-over of control to the back-up systems from the main computer system is to be
manual. situated on the back-up computer systems, and is not to be affected by failure of the
main computer system.
5.7.7. Position reference systems
1 For all classes of the DPS, position reference systems which are selected with due consideration to
operational requirements, both with regard to restrictions caused by the manner of deployment and
expected performance in working situation are to be provided with .
2 Position reference systems whose systems are of one system provided with as the DP-control system
for Class B DPS are to comply with the following requirements specified in (1) to (3) :
(1) At least three position reference systems are to be installed and simultaneously available to the
DP control system during operation. And they are not to be all be of the same type, but based
on different principles and suitable for the DP-operating conditions .
(2) The position reference systems are to produce data with adequate accuracy for the intended
DP- operation .
(3) The performance of position reference systems is to be monitored and warnings provided when
the signals from the position reference systems are either incorrect or substantially degraded .
3 Position reference systems whose systems are of one system provided with as the DP-control system
for Class C DPS are to be connected directly to the back-up computer systems and separated by '' A-60''
class subdivision from the other position reference systems, in addition that are to comply with the
requirements in -2.
5.7.8. Vessels sensors
1 Vessels sensors which are to at least measure vessel heading, vessel motions, and wind wpeed and
direction are to be installed to all calsses of DPS .
2 Vessels sensors whose systems are of one system provided with as the DP-control system for Class B
DPS are to comply with the following requirements specified in (1) and (2).
(1) When the DP-control system is fully dependent on correct signals from vessel sensors, these
signals are to be based of three systems serving the same purpose. This will result in at least
TCVN 5311:2001
45
three gyro compasses being installed where the direction of the unit is measured by the gyro
compass .
(2) Sensors for the same purpose, connected to redundant systems are to be arranged
independently so that failure of one will not affect the others .
3 Vessels sensors whose systems are of one system provided with as the DP-control system for Class C
DPS are to comply with the requirements in 2, in addition, one of each type of sensors is to be
connected directly to the back-up computer system and separated by A-60" class sub-division from the
other sensors .
5.7.9. Cables and piping systems
1 Cables and piping systems such as fuel oil pipes, lubricating oil pipes, hydraulic oil pipes, cooling water
pipes, etc., for Class B DPS, are to be located with due regard to fire hazards and mechanical damage.
2 Cables and piping systems such as fuel oil pipes, lubricating oil pipes, hydraulic oil pipes, cooling water
pipes, etc., for Class C DPS are to comply with the following requirements specified in (1) and (2).
(1) Cables for redundant equipment or systems are not to be routed together through the same
compartments .
(2) Where the requirement in (1) is not complied with or is unavoidable, such cables are to run
together in cable ducts of A-60 class sub-division, the termination of the ducts included,
which are effectively protected from all fire hazards, except that represented by the cables
themselves. Cable connection boxes are nut allowed in such ducts .
6. Towing arrangement
6.1. Tow line
1 Each non-self-propelled unit shall be supplied with two line according to the requirements of Part B
TCVN 6259-7:1997,. The breaking strength, in N, of the tow line shall be determined from the model tests
and not be less than that obtained from the formula :
F®øt = 73.Sn. Vk2 ( 6-1)
Where:
Sn - Area of the head resistance of the submerged part, in m2.
TCVN 5311:2001
46
Vk -Towing speed specified in the certificate, in knots
2 For non-self-propelled units the length of the tow line, in m, shall be determined from the formula :
l = 350 + 0,045 Nc (m) ( 6-2)
6.2. Chain cables
1 When chain cables are used as a part of the tow line, the breaking strength of these chain cables shall
not be less than the design breaking strength of the wire rope .
6.3. Towage
1 When the unit is being towed by several tugs, the breaking strength, in kN, of each tow line shall not be
less than that determined form the formula :
F = k4.n
Fdøt ( 6-3)
Where:
k4 = 1,15 when tow by two tugs
= 1,30 when tow by three tugs or more
n - number of tow lines
6.4. Line throwing appliances
1 Each unit is to be provided with one set of line-throwing appliances.
7. Signal Masts
7.1. General
7.1.1. Specifications
1 The outside diameter of steel masts which are not equipped with cargo derricks and are stayed with
shrouds as specified in -4 is not to be less than that obtained from the following formula: :
3,3 H (cm) : Outside diameter at the uppermost deck at which the mast is supported (hereinafter
TCVN 5311:2001
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referred to as 'base' ).
2,5 H (cm) : Outside diameter at the outrigger or at the part to which the upper end of shrouds is
connected (hereinafter referred to as 'top' ).
Where :
H : Height of mast from the base to the top (m).
2 The thickness of plating of masts at each part is not to be less than that obtained from the following
formula or 5 mm, whichever is greater :
2,5 + 0,1 Dm (mm) ( 7-1)
Where :
Dm : Outside diameter of masts at each part (m).
3 The base and top of masts are to be properly strengthened .
4 The rigging for masts is not to be less effective than would be obtained from two steel wire shrouds on
each side of the ship, of the size given in Table 7.1.1-1, so placed that each distance from the forward
and after chain plates to the base is not less than one-fourth of height of mast from base to top or B/4,
whichever is greater .
Table 7.1.1-1 Diameter of steel wire riggings
Height of masts from base to top (m) 9 12 15 18
Diameter of steel wire (mm) 20 22 24 26
Note :
(1) The wire rope is to be No.1 or No.3 wire rope specified in Chapter 4 Part 7-B.,TCVN 6259:1997.
8. Watertight bulkheads and closing appliances
8.1. Watertight bulkheads
8.1.1. General
1 Watertight bulkheads of ship-type and barge-type units are to be in accordance with the requirements in
Chapter 11, Part 2A TCVN 6259:1997 or Chapter 11, Part 2B, TCVN 6259:1997 and Chapter 10, Part 8A
TCVN 5311:2001
48
, TCVN 6259:1997. However, the arrangement of watertight bulkheads of the units to be provided in a
specified sea area and in a restricted area for a long period of time or semi-permanently or in case where
the arrangements of watertight bulkheads are approved by the VR is to be at the discretion of the VR .
2 The arrangement of watertight bulkheads in setf-elevating units and column stabilized units is to be at
the discretion of the VR .
3 The arrangements and scantlings of watertight decks and bulkheads in column stabilized unit are to be
effective to that point necessary to meet the requirements of damage stability .
4 Where openings are provided on watertight bulkheads, the requirements in 11.3. Part 2A, TCVN
6259:1997 and 13.2.5. Part 3 TCVN 6259:1997 are to be applied .
5 Tanks for fresh water or fuel oil, or any other tanks which are not intended to be kept entirely filled in
service, are to be in accordance with the requiremnts in Chapter 14, Part 2A TCVN 6259:1997.
8.1.2. Boundary Penetrations
1 Where watertight boundaries are required for damage stability, they are to be made watertight, including
piping,ventilation, shafting, electrical penetrations, and so on. Piping sys[ems and ventilation ducts within
the extent of damage are to be provided with valves which are capable of being remotely operated from
the weather deck, pump room, or other normally manned, space, and are to be satisfactorily arranged to
preclude the possibility of progressive flooding through the system to other spaces, in the event of
damage. Valve position indicators are to be provided at the remotely operating positions .
2 Notwithstanding the requirements in -1 non-watertight ventilalion ducts are to be provided with watertight
valves at the subdivision boundaries and the valves are to be capable of being operated from a remote
location,with position indicators on the weather deck, or in a normally manned space .
3 In the case of self-elevating units, ventilating systems which are not used during the transit condition
may be secured by alternative methods approvetl by the VR. In this case, necessary ventilation for closed
spaces and closing methods are to be arranged at the discretion of the VR .
4 In the case of column stabilized units, valve operating devices are to be in the central ballast control
station. And valve position indicators are to be provided at the remote control station .
8.2. Closing Appliances
8.2.1. General
1 The construction and closing appliances of openings through which the sea water is likely to flow in are
TCVN 5311:2001
49
to be in accordance with the requirements in Part 2A or 2B, TCVN 6259:1997.
2 Closing appliances provided in column stabilized units, which are not locate-d within areas of calculated
immersion and for which special considerations are given, are to be at the discretion of the VR.
8.2.2. Internal Openings used during Operation
1 Internal openings fitted with appliances to ensure watertight integrity, which are used during operation of
the unit while afloat, are to comply with the following :
(1) Doors are to be capable of being remotely operated from a control position (ballast control room)
which is above the final waterline after flooding as well as being operable locally from both
sides of the bulkhead. Indicators are to be provided at the control position to indicate whether
the doors are open or closed .
(2) The requirements regarding remote control in (1) may be dispensed with provided an alarm
system (e.g. light signals) is arranged showing personnel, both locally and at a control position,
whether the doors in question are open or closed. Hatch covers required for watertight integrity
are to have similar alarms .
(3) A signboard to the effect that the closing appliance is to be closed while afloat and is only to be
used temporarily, is to be fitted locally .
(4) The closing appliance to have strength, packing and means for securing which are sufficient to
maintain watertightness under the design water pressure or the watertight boundary under
consideration .
8.2.3. External Openings used during Operation
1 External openings fitted with appliances to ensure watertight integrity, which are used during operation of
the units while afloat, are to comply with the foIlowing :
(1) The waterline in the final condition of equilibrium after flooding, taking into account the effect of
wind, is to be below the lower edge of any opening through which progressive flooding may take
place .
(2) Openings under (1) include air pipes (regardless of closing appliances), ventilators, ventilation,
intakes and outlets, non-watertight hatches and weathertight doors.
(3) External openings for column stabilized unit are to be weather tight within the range necessary
to comply with the requirement of damage stability criteria and within a zone measured 4.0 m or
7 degree perpendicularly above the final waterline shown in FigFig 8.2.3-1.
TCVN 5311:2001
50
7o
B
A - 4m Zone of wB - 7
eathertightness thertightness o Zone of wea
G
A
4 m
Initial waterline
Final damage waterline
Fig 8.2.3-1 Minimum weathertight integrity Requirements for Column stabilized Unit
(4) Openings, fitted with appliances to ensure watertight integrity, such as non-opening side
scuttles, manholes and smaIl hatches, may be submerged .
(5) SmaIl hatches above (4) are those which are nor-maIly used for access by personnel. Such
openings, which may be submerged in case of damage, are to comply with the foIlowing :
(a) Openings are to be closed by approved quickacting watertight covers of steel or
equivalent material .
(b) An alarm system (e.g. light signals) is to be arranged showing personnel. both locaIly and
at a control position, whether the hatch covers in question are open or closed.
(c) A signboard to the effect that the closing appliance is to be closed while the unil is afloat,
and is only to be used temporarily, is to be titted locaIly .
(d) Such hatches are not to be regarded as emergency exits .
(6) Where flooding of chain lockers or other buoyant volume may occur, the openings to these
spaces are to be considered as downflooding points .
8.2.4. Internal and External Openings kept permanently closed while Afloat
1 Internal and external openings fitted with appliances to ensure watertight integrity, which are to be kept
permanently closed while afloat, are to comply with the following :
(1) A signboard to the effect that the opening is always to be kept closed while afloat is to be fitted
on the closing appliances in question .
(2) Manholes fitted with bolted covers need not e dealt with as under (1) .
TCVN 5311:2001
51
(3) The closing appliances are to have strength, packing and means for securing which are
sufficient to maintain watertightness under the design water pressure of the watertight boundary
under consideration .
9. Jacking machinery
9.1. General
9.1.1. Application
The requirements in this section are applicable to lifting machinery for self elevating units of the pinion-
rack type (herein after refered to as jacking machinery). All other types will be specially considered.
9.1.2. Documentation
The following plans and particulars are to be submited for approval:
- Jacking machinery arrangement .
- Assembly arrangement (cross sections) of jacking unit .
- Pinions and gear wheels
- All other power transmitting parts .
- Bearing specifications
- Casings, in particular the parts subjected to significant reaction forces.
- Remote control system
- Monitoring system ( if applicable)
- Electric motor incl. Brake
The following calculations are to be submitted for approval
- Calculation of load distribution beetween the jacking units on one leg during the various load
conditions such as storm load and soil penetration during preload .
9.2. Design and construction
9.2.1. General
1 The systemshould be designed so that over loading of components is avoided during all kinds of
operations . Items to be considered in this respect are :
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- Flexible mounting of jacking units .
- Characteristics of electric motors.
- Brake torque
- Interlock between electricmotors and fixation rack system( if any )
- Other ...
2 The brakes are to engage automatically in case of power supply failure to the lifting machinery .
3 Active components and systems are in general to be arranged with redundancy so that a single failure
does not cause loss of jacking funtion.
9.2.2. Design loads
1 Dynamic loads
A relevant load-time spectrum for the fatigue life is to be specified. This spectrum is at least to contain the
estimated necessary time load for:
(a) Lifting of the legs
(b) Descending of the legs
(c) Lifting of the platform
(d) Descending of the platform
(e) Variable load during holding ( if no fixation rack system )
(f) Exceptional use, such as working with one or more units out of service
(g) Compensating leg penetration during preloading by lifting with full or part preload, if
applicable .
The influence of friction is to be included for all mentioned conditions .
2 Static loads
The preload of the legs is to be defined. For self elevating units not equipped with a fixation rack system,
the maximum load is defined as the maximum reation between a leg and the jacking machinery in a storm
condition ( maximum weight + storm reaction )
For self elevating units equipped with a fixation rack system, the maximum load is defined as the preload.
3 Electric motors lifting capacity is the max. continuos output power which the motor can deliver in the
working period with specified temperature rise for the motor temperature class .
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4 For self elevating units without a fixation rack system, the required holding capacity is to be based on the
maximum load. The brake capacity (static friction torque ) is not to be less than 1,3 times the maximum
load, considering the mechanical efficiency of the drive gear .
5 For self elevating units with a fixation rack system, the required holding capacity is to be based on the
preload. The brake capacity (static friction torque ) is not to be less than 1,2 times the preload,
mechanical efficiency considered .
9.2.3. Electric motor capacity
1 The capacity of the electric motor is to be sufficient for the lifting requirements such as :
(1) Fifting platform with uneven leg load( but within approved tolerances ) for the specified duration .
(2) Lifting in preload, if specified, with a specified duration .
The friction between legs and guies as well as the efficiency of the gear transmissions are to be
considered .
9.2.4. Gearing
1 Details on calculation of gearing contains information on calculation of tooth root strength ( frctures ) and
flank surface durability ( pitting, spalling and case-crushing ) for for enclosed gear units .
2 The gearing safety factors SF against tooth fractures and SH against pitting, spalling and case-crushing
are to be at least
Table 9.2.4-1 Safety factors SF and SH
SF SH
Storm holding load ( applies to rigs without fixation rack system ) 1,5 1,0
Preload holding (applies to rigs with fixation rack system) 1,4 1,0
Accumulated lifting loads 1,5 1,0
For the main pinions and the rack the requirement to SF also applies. The contact stresses for
pinion-rack are subject to special consideration .
9.2.5. Shafts and shaft connections
1 Shafts are to fulfil the criteria in recognized by VR .
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2 Shrinkfit connections are to have a minimum friction torque of twice the torque corresponding to the
maximum load .
9.2.6. Gear casings
1 Welded gear casings are to be stress relieved
2 The casings are to be designed to prevent deflections which may be harmful for the gear meshings .
3 If practical, inspection openings are to be provided .
9.2.7. Bearings
1 Rolling bearings are to have a lifetime ( with 90% survival probability) of 5 times the specified lifetime of
the jacking unit The entire load spectrum is to be considered, as well as the influence of the lubricant .
The static load carrying capacity ( corresponding to a deformation of appr. 0,1%o of the roller diameter ) is
to be at least 1,5 times the load due to the max. applicable load .
2 The surface pressure in plain bearings is not to exceed 50% of the yield strength (0,2% proof stress) of
the bearing material when the maximum load is applied .
The plain bearings are to be designed in such a way that the dynamic loads do not result in any signficant
wear which may be harmful for the gear meshings .
9.3. Load control
1 For the purpose of load equalization between the jacking units, the unit torque ( at electric motor ) should
be checked and adjusted if necessary. This should be made after lifting of the platform, and after being
subjected to weather conditions which may have altered the distribution. This requirement does not apply
if an automatic load control device is used .
2 An alarm system for overheating of the electric motors is to be provided .
3 The power supply to each electric motor is to have protection against harmful effects of a possible short
circuit .
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10. Accident prevention Provision
10.1. General
1 Each unit is to be provided with accident prevention provision satisfying VR requirements.
11. Drilling plant ( Drill)
11.1. General
11.1.1. Application
1 The Rules in this part apply to drilling plants, including drilling related systems and equipment on board
of the drilling units .
2 The Rules are made to cover the safety of the drilling unit/installation and those onboard. Reliability and
operational aspects are not covered except where considered to be of significance for safety .
3 The following drilling systems with equipment are covered by the VR's clasification of drilling plants :
(1) Blow-out prevention with control systems
(2) Marine riser
(3) Heave compensation
(4) Hoisting, rotation and pipe handling
(5) Bulk storage, drilling fluid circulation and cementing
(6) Blow-out preventor handling
(7) Well testing .
4 All systems listed in -3 whether permanently or temporarily mounted onboard, are subject to approval by
the VR.
11.2. Supervision/certification and categories
11.2.1. Categories
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1 Equipment, including pipes and fittings, is to be categorized as follows :
(1) IA : Equipment of primary importance to safety, for which the approval of design and survey
during fabrication are considered essential .
(2) IB : Equipment of primary importance to safety, for which the approval of design and witnessing
the product quality are considered essential .
(3) II : Equipment related to safety which is normally manufactured according to recognized codes
and standards, and has proven industrial record .
11.2.2. Supervision
1 Equipment of category IA is to be certified by the VR according to the following principles :
(1) Design approval
(2) Survey during fabrication
(3) Final inspection with witnessing of functional, pressure and/or load testing
(4) Review of fabrication documentation with the issuance of component Certificate
2 Equipment of category IB is to be certified by the VR according to the following principles :
(1) Design approval
(2) Final inspection with witnessing of functional, pressure and/or load testing
(3) Review of fabrication documentation with the issuance of component Certificate
3 Equipment of category II will be accepted on the basis of a works certificate prepared by the
manufacturer. The certificate is to contain the following data as a minimum :
(1) Equipment specification
(2) Limitation w.r.t. operation of the equipment .
(3) Statement from the manufacturer to confirm that the equipment has been constructed and
manufactured according to recognized methods, codes and standards .
11.3. Documentation
11.3.1. Design documentation
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1 The following design documentation for the systems stated in 11.1.1-3 is to be submitted to the VR in
triplicate for approval :
(1) Arrangement with description and specification
(2) Piping and instrumentation diagram
(3) Control and monitoring system
(4) Lists with information of different equipment in the systems and their category
2 The following documents are to be submitted to the VR for information :
(1) Heat intensity calculations for the flare system
3 The following documents are to be submitted to the VR in triplicate for category IA and IB equipment for
approval :
(1) Design specifications, including specifications of work medium, pressure ratings, minimum
temperatures, corrosion control, environmental and functional loads, etc.
(2) Heat intensity calculations for the flare system
(3) Drawings, including sufficient details and dimentions to evaluate the design
(4) Strength calculations
(5) Bill of materials including material specifications as necessary
(6) Fabrication specifications including welding, heat treatment, type and extent of NDT, testing,
fabrication method, etc. .
11.3.2. Fabrication record
1 Fabrication record is to be maintained by the manufacturer in a traceable manner, so that relevalt
information regarding design specifications, materials, fabrication processes, inspection, heat treatment,
testing etc. can be checked .
2 Fabrication record for category IA and IB equipment is to be made available for acceptance by the
surveyor of the VR . The following particulars are to be included, as applicable:
(1) Manufacturer's statement of compliance.
(2) Reference to design specifications and drawings
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(3) Location of materials and indication of respective material certificates
(4) Welding procedure specifications and qualification test records.
(5) Location of weldings indicating where the particular welding procedures have been used
(6) Heat treatment records
(7) Location of non-destructive examination (NDE) indicating where the particular NDE method has
been used and its record
(8) Load pressure funtional test reports .
11.4. Materials
11.4.1. General
1 The materials are generally to be in accordance with TCVN 5317:2001 as well as the VR requirements
and are to be suitable for the purpose and have adequate properties of strength and ductility. Materials
incorporated in any portion of the installation designated critical as to the integrity and safety of the
installation are to have an appropriate atandard of notch toughness. In addition, materials to be welded
are to have good weldability properties .
2 For selection of acceptable materials suitable for H2S contaminated products ( sour service ) reference is
made to recognised standard by VR .
11.4.2. Bolting material
1 Bolts and nuts considered as essential for structural and operational safety are to conform to a
recognized standard by VR.
2 Major pressure retaining or structural bolts and nuts with min. yield strength above 490 N/mm2 are to be
manufactured of low alloy or alloyed steel i.e. (%Cr + %Mo + %Ni) ≥ 0,50 and supplied in quenched and
tempered condition .
11.4.3. Corrosion
1 All materials are to have appropriate resistance to corrosion and are to be chosen to avoid corrosion
problems. Alternatively materials are to be adequately protected from the effects of corrosion or suitable
extra material is to be provided to allow for its effects .
2 Corrosion allowance (c) for steel pipes in Table
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Table 11.4.3-1 Corrosion allowance (c) for steel pipes
Unit: mm
Piping service c
Compressed air 1,0
Hydraulic oil 0,3
Lubricating oil 0,3
Fresh water 0,8
Sea water in general 3
Hydrocarbon service 2
Mud/ Cement 3
1) For pipes passing through tanks, an additional allowance for external corrosion is to be
considered according to the figures given in the Table, depending on the external medium .
2) For pipes efficiently protected against corrosion, the corrosion allowance may be reduced up to
50%.
3) C-steel and staimless steel materials are not to be used for sea service unless the materials
contain high molybdenium .
11.4.4. Material certificates
1 All materials for major load bearing and pressure containing components are to be furnished with
documentation stating process of manufacture and heat treatment ( metallic materials) together with
results of relevant properties obtained through appropriate tests carried out in accordance with
recognized standards .
2 Materials for pressure containing and major load bearing components of equipment categorized as IA or
IB are as a minimum to be furnished with a works certificate . For equipment of category II a Test Report
is acceptable .
11.5. Design principles
11.5.1. General
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1 Systems including equipment are to be designed according to this part and applied codes/standards .
2 When it is essential for the safety of the drilling plant that the function of a component is maintained as
long as possible in the event of fire, materials with high heat resistance are to be used and rating is to be
verified .
3 System and equipment are to be protected against excessive loads and pressure .
11.5.2. Arrangement
1 All equipment and parts which are to be operated or subject to inspection and maintenance on board are
to be installed and arranged for easy access .
2 The drillfloor is to be arranged with at least two exits free from obstructions and protruding
arrangements.
3 All equipment is to be located to ensure safe operation and, if located in hazardous areas, is to be
suitably protected for installation in such areas. Equipment in hazardous areas are to be so protected that
maximum surface temperature does not exceed 80% of the autoignition temperature of the explosive
gas/air mixture. Where autoignition temperature is unknown, max. temperature of 200oC is to be applied.
4 The systems are to be so arranged that one single maloperation or malfuntion will not lead to a critical
situation for the unit. Safety systems are to provide two independent levels of protection to prevent or
minimize the effects of a single malfunction or fault in process equipment and piping system including
their controls. The two levels of protection are to be provided by functionally different types of safety
devices to reduce the probability for common cause failures.
5 All equipment is to be equipped with indicating instruments considered necessary for safe operation .
11.5.3. Environmental conditions
1 The environmental criteria and motion characteristics of the unit, for the design conditions; operation,
survival and transit are to be approved by VR .
2 Test results or other relevant documentation confirming the components' or systems' suitability for their
intended purpose may be required.
3 Where applicable, the following aspects are to be taken into consideration when establishing the
environmental loads :
(1) The unit's motions
(2) Win forces
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(3) Air and sea temperatures
(4) Waves
(5) Current
(6) Loads from possible snow and ice accretion
(7) Earthquake
11.5.4. Loads
1 Each part of the drilling plant is to be designed for the most unfavourable load condition, for which it is
intended to be used.
2 For each loading condition, and for each item to be considered, the most unfavourable combination,
position and direction of loads which may act simultaneously, are to be used in the analysis.
3 All external loads which may impair theproper function of the drilling plant and have significant influence
or cause a reduction of the safety, strength and reliability, are to be considered .
11.5.5. Design pressure and temperature
1 Due to internal or external conditions, the design temperature for which the component may be allowed
to operate with the corresponding design pressure is to be specified with adequate margins to cover
uncertainties in the prediction .
2 The consideration is to include start-up, shutdown and those abnormal conditions which are considered
likely to occur .
3 When deemed necessary, studies, calculations, etc. to establish particular operational limitations .
11.5.6. Well fluid composition
1 Due consideration is to be given to well fluid composition with regard to such phenomena as corrosion,
stress corrosion cracking, erosion, fouling, etc. .
11.5.7. Design safety factors
1 The safety factors to be used in determination of an acceptable stress level for the various load
conditions are to be established by the designer, and included in the design documentation .
2 Safety factors are to be in accordance with relevant code, standard or recommended practice for each
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particular component if not specified in this part .
3 The yield strength used in calculations is not to exceed 0,85 of the specified minimum tensile strength .
11.5.8. Spare parts
1 Any spare part is to be subject to the equivalent certification as the original parts .
11.6. Systems
11.6.1. General
1 The drilling system is to be designed to operate safely under the maximum load conditions anticipated
during drilling operations, and limit the risk of any danger .
2 All components in a system, and co-operating systems, are to be satisfactorily matched with regard to
function capacity and strength .
3 Relative motion between different parts of a system is to be allowed for to the extent necessary without
including detrimental stresses .
11.6.2. Blowout prevention system
1 The blowout prevention system is normally to consist of at least the following :
(1) A diverter with a securing element for closing around the drilling equipment in the hole.
Normally, two diverter lines, each sufficient to take the predicted flow are to be provided. The
lines are preferably to lead to opposite sides of the unit .
(2) One bag-type/ annular preventer
(3) One blind/ shear ram preventer equipped with mechanical locking device.
(4) Two pipe ram preventers equipped with mechanical locking devices .
(5) Necessary control equipment as stated in -3 and -4 below
2 Blowout preventer stack Côm thiÕt bÞ chèng phun ph¶i tho¶ m·n c¸c yªu cÇu sau:
(1) The blowout preventer stack is to be designed so that fluid and gas can be conducted out of the
system, and so that fluid can be pumped in .
(2) Two valves are to be installed close to the blowout preventer stack for each of the kill and choke
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lines. These valves are to allow for remote control. Where blowout preventers are installed on
the sea-bed these valves are to be of the fail-safe type. The valves are to be located so that they
are protected against damage from falling equipment etc. .
3 Blowout preventer control Bé ®iÒu khiÓn thiÕt bÞ chèng phun ph¶i tho¶ m·n c¸c yªu cÇu sau:
(1) The blowout preventers are to be connecte to at least two control panels, one operated at the
driller's stand. The control panels are to be connected directly to the main unit of the control
system, and are not to be connected in series .
(2) The second control panel is to be located at a suitable distance from the driller's stand, and is to
be arranged for easy access, also when the control panel at the driller's stand is not functioning
or is out of reach .
(3) The control panels are to give clear indication whether the blowout preventers are open or
closed. Furthermore, the panel are to indicate pressure and volume for the various functions/
operations .
(4) The control panels are to be fitted with visual and audible alarm signals for low accumulator
pressure, for loss of energy supply, as well as for low levels in the control fluid storage tanks .
(5) The main unit of the control system, including the pilot valves, is to be situated so that it is
shielded from the drillfloor/ cellar deck. It is, however, to be easily accessible from the drillfoor,
In addition, it is to be possible to reach the unit from the outside without having to go via the
drillfloor or the cellar deck .
(6) The closing unit accumulators for surface BOP's are to have sufficient volumetric capacity to
provide the usable fluid volume ( with pumps inoperative ) to close one pipe ram and the annular
preventer in stack plus the volume to open the hydraulic choke line valve .
(7) The closing unit accumulators for subsea BOP's are to have sufficient volumetric capacity to
provide the usable fluid volume ( with pumps inoperative ) to close and open the ram preventers
and one annular preventer .
(8) The control system of the blowout preventer is to be designed in such a way that each of the
blowout preventers, except the annular preventer(s), can be closed within 30 seconds. The
annular preventer(s) are to be capable within 45 seconds of closing .
(9) The BOP stack is to be provied with two independent pods for the BOP control lines from the
main control unit .
4 Diverter control:
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(1) The diverter control system is to be connected to a control panel which can be operated
manually from a place near the driller's stand .
(2) The diverter control system is to be equipped with an interlock so that the valve in the diverter
pipe which leads out to the leeward side is opened before the diverter closes around the drilling
equipment .
5 Choke manifold :
(1) The high pressure side of the choke manifold is to have at least the same working pressure as
the rated working pressure of the blowout preventer stack.
(2) It is to be possible to pump mud through the choke and kill manifold up to the rated pressure of
the blowout preventer stack .
(3) It shall be possible to lead the returns from the choke manifold through an installed mud/gas
separator .
(4) The choke and kill manIfold and choke/kill lines are to be arranged so that pumping through one
line and simultaneous flow return over the chokes through the opposite line is possible .
(5) The choke manifold is to be equipped with the following :
(a) At leas 3 chokes, of which one is to allow for remote control, and one for manual
adjustment. It shall be possible to isolate and change eachchoke, if necessary, while the
manifold is in use .
(b) One valve for each of the outlet/inlet lines, so that lines to and from the manifold can be
isolated. Where high pressure/low pressure zones meet in the manifold system, 2 valves
arranged in series are to be used. Manifolds for 345bar or higher pressures are to be
equipped with minimum 2 valves before each of the chokes. The working pressure of the
valves are to refer to maximum working pressure of the choke manifold .
(6) The following indications are to be easily visible to the operator of the remotely controlled
chokes: drill pipe pressure, the choke manifold pressure and drilling fluid pump rate. At the place
of operation of the manually adjustable choke(s), only the drill pipe pressure and the choke
manifold pressure are to be displayed .
6 Valves in drill string :
(1) Means are to be provided to prevent back flow in the drill string during all drilling conditions, both
disconnected and connected if not provided as specified in (2) to (6) .
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(2) An upper kelly cock is to be installed below the swivel, and a lower kelly cock at the bottom of
the kelly .
(3) The upper/lower kelly cocks are to be designed for 5000 psi.
(4) The kelly cocks are to be maintained in a serviceable condition and are to be tested concurrently
with the blowout preventers.
(5) The wrench or other tool used to close the kelly cock is to be kept in a readily accessible place,
and its purpose and use made known to all employees who may be expected to use it .
(6) An open/close driUstring safety valve is to be located in open position on the drillfloor for
immediate use. The valves are to be of proper size and thread configuration to fit the pipe in use
at the time. This valve is to be capable of withstanding the same well surface pressures as the
blowout preventers that are used.
11.6.3. Marine riser system
1 Kill and choke lines :
(1) Kill and choke lines are to be provided from the blowout preventer stack and are to be
connected to a choke manifold .
(2) Kill and choke lines with connections, valves, etc., are to have at least the same working
pressure as the rated working pressure of the blowout preventer stack .
2 Riser wellhead connector :
(1) Emergency operation of the riser wellhead connector is to be possibIe from another location
than the place of normal operation The location of the control is to be so chosen so that at least
one control point is likely to be accessible in tht event of an emergency .
11.6.4. Heave compensation and tensioning system
1 Restricted flow in both directions of compensators are to be arranged to safeguard against loss of
pressure fluid .
2 Air control panels and accurnmulators are to be fitted wIth safety valves .
3 Air relief lines from safety valves are to be self draining .
4 Compresssed air is to be used only with noncombustible fluids .
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5 One failure of a component of the riser tensioners is not to lead to overall failure of the system .
11.6.5. Hoisting, Rotating and Pipe Handling System
1 Equipment installed in the derrick and above the drilling floor is to be properly fastened .
2 Hoisting ThiÕt bÞ n©ng ph¶i tho¶ m·n c¸c yªu cÇu sau:
(1) A safety device is to be arranged prevent the travelling block from being run into the crown block
(2) In the event of main brake failure, the drawwork is to be equipped with an emergency stop
device which is to be readily identified and easily accessible. The emergency stop device is to
have the capability to stop and lower the load safely in the event of main brake faiure .
(3) The maximum permissible working load for a system of interdependent equipment is to refer to
the weakest component of tile system, e,g. winches, wire, hooks, pulleys, etc .
3 Piping handling :
(1) There are to be provisions for securing of drill pipecollars, tubing, rods and casing which may be
racked in the derrick .
(2) Storage racks are to be designed or other means provided to prevent drill collars, pipe and
other tubular material from accIdentally rolling/skiddmg off or being re leased from the rack .
(3) All tongs are to be securely attached to the derrick mast or a back-up post and anchored by a
wire rope or stiff arm having a minimum breaking strength greater than the breaking strength of
the pulling cable or chain .
(4) Tongs are to be arranged with safety lines and the lines working on the side opposite the safety
line are to have a minimum strength greater than the force of the make-up torque .
(5) All fittings and connections are to have at least the breaking strength of the cable, wire rope or
stiff arm they are attached to, and knots are not to be used to fasten cable or wire rope lines .
(6) Power tong pressure systems are to be equipped with a safety relief valve.
11.6.6. Bulk Storage, Drilling Fluid Circulation and Cementing system
1 The mud mixing facIlities are to be suffIcient for the intended drilling program .
2 Bulk storage :
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(1) Hydraulic/pneumatic equipment is to be fitted with safety valves .
(2) For bulk storage tanks in enclosed areas testable safety valves are to be used, which can be
vented out of the area. Such enclosed areas are to be ventilated so that a pressure build-up will
not occur in the event of a break or a leak in the air supply system .
3 Drilling fluid circulation :
(1) Degasser and mud/gas separator are to be vented in a safe manner .
(2) High pressure mud pumps are to be fitted with pulsation dampeners and safety relief valves set
at the maximum allowable pressure of the systems
(3) Mud relief line from the safety valve is to be self draining .
(4) The following parameters are to be indicated at the drilling console:
(a) Mud pump discharge pressure and rate
(b) Weight of mud entering and leaving the borehole
(c) Pit volume, indicating the increase or decrease in drilling fluid volume .
(d) Drilling fluid return indicator, showing the difference in volume between the drilling fluid
discharged and returned to the platform. The flowmeter is to be capable of compensating
for rig movements .
(e) Gas content in the mud .
(f) Weight of the drill string
(g) Rate of penetration and drilling depth .
(5) An audio-visual alarm is to be installed to indicate abnormal conditions in pit mud volume .
11.6.7. Well Test and Flare System
1 Two valves in series are to be fitted in possible by passes of pressure reducing devices (as for example
chokes).
2 Heat exctlsnger is to be equipped with safety valves
3 The swivel and kelly hose (rotary hose) are not to be a part of the test line .
4 At least two complete flare lines or other devices through which any flow from the well may be directed
to different sides of the drilling unit are to be arranged .
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5 Any flare line or any other line downstream of the choke manifold is to have an inside diameter not less
than the inside diameter of the largest line in the choke manifold .
6 Possibilities for cooling of flare burners are to be available .
7 The flare burners are to be located at a safe distance from the unit. This is normally to be documented
by heat intensity calculation .
8 Where compressed air systems are used to supply burner assemtlies, means are to be provided to
prevent contamination of the compressed air systems by hydrocarbons .
11.7. Structural and mechanical components
11.7.1. General
1 Components are to be designed in accordance with these Rules and recognized codes, standards or
guidelines ®−îc §¨ng kiÓm c«ng nhËn.
2 Components are to be designed with regard to their intended use, their interaction with or near other
components and their safe use under all known operating conditions,including overload if anticipated .
3 Where flanges and clamp/hub connections are used consideration is to be given to external loading in
addition to internal pressure .
4 Skids and components that need to be lifted for maintenance/installation are to have properly designed
lifting lugs
5 For structures such as derrick, flare boom, BOP frames etc. the charpy V-notch requirements given in
Rules ®· ®−îc §¨ng kiÓm c«ng nhËn.
11.7.2. Blowout preventer system
1 The shear rams are to be capable of shearing the thickest section of the heaviest drillpipe specified for
use with the blowout preventers .
2 Pipe rams are to be designed for any hang-off loads to which they may be subjected .
3 Surface hydraulic control lines and fittings are to be capable of withstanding a fire for a period of time
sufficient for necessary operation of the BOPs .
4 The lower kelly cock is to be of such a design that it can be run through the BOP stack where the BOPs
are not installed on the sea bed .
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5 Design of diverter system is to take account of possible erosion during operation
6 Valves in the diverter system are to be capable of operation under worst predictable conditions .
11.7.3. Marine riser system
1 Hydraulically operated wellhead, riser, and choke/kill line connectors are to have redundant mechanisms
for unlock and disconnect. The secondary unlock mechanism may be hydraulic or mechanical but is to
operate independently of the primary unlocking mechanism.
11.7.4. Heave compensation system
1 Hydraulic cylinders and accumulators are to be designed for both internal pressure loads and loads as a
result of their functicn as structural members .
11.7.5. Hoisting, Rotating and Pipe Handling System
1 Wire clamps are to be of approved type with 2 gripping areas. The number of clamps is to be in
accordance with VR however, not less than 3 .
2 Where plastic covered wire is used special consideration is to be given to the number and type of
clamps used .
3 Individual components such as sheaves, hooks, shackles, wire slings, permanent attachments, etc. are
to be marked with the maximum permissible working load .
4 All air winches in the derrick, on drillfloor, cellar deck and catwalk are to be shielded and marked with the
maximum pernlissible working load .
5 Winches are to have an automatic brake which when the power supply fails. The brake is to be able to
stop the winch at full speed when lowering the maximum load .
6 Winches are to be fitted with an operating handle which will return automatically to the stop position
when not being operated. The stop position is to be clearly marked .
7 Winches used for the hoisting of personnel are to be designed with fixed operation up and down (no free
fall with brakes)
8 Racking foundations and storage racks are to be designed to withstand the maxin:um anticipated load of
racked pipe, drill collars and other intended loads .
9 Design of casing stabbing arrangement is to provide for the following safety features :
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(1) automatic stop when raising/lowering handle is released .
(2) an emergen:y stop device to be activated in the event of failure of the hoisting mechanism
(3) where a stabbing board arrangement is fitted an additional mechanical locking device is to be
provided .
11.7.6. Bulk Storage, Drilling Fluid Circulation and Cementing system
1 All bulk storage tanks are to be equipped with safety valves/rupture discs to prevent damage due to
overpressure. Rupture discs are only to be used for bulk storage tanks in open areas or if fitted with a
relief line to an open area .
2 The design of atmospheric vessels is to take account of the static pressure developed by vent pipes or
similar connections where such are fitted .
11.7.7. BOP handling system
1 Design of the BOP-carrier is to take account of loads resulting from transportation and stowing of the
BOP ®Æt.
11.7.8. Well test and flare system
1 The flarf boom structure is to be designed for both operating and stowed condition
2 In desigring the flare/burner boom structure due consideration is to be given to thermal loads during
flaring .
11.8. Piping
11.8.1. General
1 Piping includes pipes, flexible piping such as expansion elements and flexible hoses, other parts such as
valves and fittings, piping connections such as welded connections bolted flanges, clamps, couplings,
gaskets etc. and hangers and support brackets .
2 For piping not covered by the applied recognized codes or standards a combined stress calculation
may be used .
3 Relevant factors and combination of factors are to be taken into account during design when evaluating
possible failure modes such as, but not limited to :
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)
(1) corrosion/erosion types
(2) vibration, hydraulic hammer
(3) pressure pulsations
(4) abnormal temperature extremes
(5) impact forces
(6) leakages.
11.8.2. Hard piping design
1 Pipe calculations are to ensure that the pipes have the necessary strength (i.e. strength thickness)
during their life of operation .
2 If a combined st;ess calculation according to Von-Mises theory is applied, the equivalent combined
stress is at no point of the piping wall to exceed 60% of the minimum specified yield strength of the
material .
The minimum yield strength (σf ) of any material is to be taken as the smaller of :
(1) minimum upper yield strength ;
(2) yield strength at 0,2% offset;
(3) 0,8 x minimum tensile strength of the material (σb);
The equivalent combined stress as defined by Von-Mises is:
( ) ( ) ( 20r
2rl
2l0e σσσσσσ0,70σ −+−+−= (11-1)
Where:
σ0 : circumferential or hoop stress
σl : longitudinal or axial stress
σ0 : radial stress
The calculations for σ0 ,σl ,σ0 may be based on Lame's equations for thick cylinders .
3 The minimum design wall thickness (t) of all piping is to account for :
(1) bending allowances
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(2) allowances for threads
(3) corrosion allowances
(4) erosion allowances.
The minimum wall thickness of a straight or bent pipe is not to be less than :
t= to + allowance
If pipes are to be bent, the minimum wall thickness before bending is not to be less than
to + b
Where :
to - Strength thickness
b - bending allowance
4 When the allowance for bending b is not determined by a more accurate procedure, or when the bending
is not carried out by a bending procedure ensuring a control of the wall thickness, the allowance for
bending is not to be less than :
b = otRD
2,51
Where:
D - outer diameter of pipe
R - radius of the bend
to - strength thickness
If the bending ratio D/R is not given this ratio is to be taken equal 1/3.
5 The caIculated minimum strength thickneSs of piping which is to be threaded is to be increased by an
allowance equal to thread depth. For machined surfaces or grooves,where the to;erance is not specified,
the tolerance is to be 0.5mm in addition to the specified depth of cut .
6 For steel materials the corrosion allowance is to be as specified Table 13.5.3-1 For pipes of copper,
brasses, copper-tin alloys and Cu- Ni alloys with Ni-content < 10% the corrosion allowance is to be
0.8mm. f'or pipes of Cu-Ni alloys with Ni- content ≥10% the corrosion allowance is to be 0.5mm. For
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media with small corrosive action in respect of the material employed, the corrosion allowance may be
reduced to zero. For pipes where there is a risk of heavy corrosion a greater corrosion aIlowance may be
required .
7 The value of t does not account for any negative manufacturing tolerance, therefore the nominal wall
thickness ta ,is not to be less than :
ta = a/1001t
−
Where:
a - percentage negative manufacturing tolerance (%)
8 Where piping is likely to be exposed to erosion e.g. mud/cement system, an erosion allowance is to be
specified to take into account likely service conditions .
11.8.3. Flexible piping
1 The locations of flexible elements are to be clearly shown in the design documentation .
2 Flexible piping parts approved for their intended use may be installed in locations where hard piping is
unsuitable .
3 Flexible piping elements are to be accessible for inspection.
4 Means are to be provided to isolate flexible piping if use in systems where uncontrolled outflow of
medium is critical .
5 The bursting pressure for flexible hoses is to be at least 4 times the maximum working pressure. Lower
bursting pressures may be specially considered for hoses with high pressure rate and large nominal
bores .
6 Flexible hoses and non-metallic expansion joints for hydrocarbon systems have to qualify a fire
endurance test according to the VR or equivalent. The flexible hose as to maIntain Its integrity and
functional properties for the same period as required for the total piping system and components .
7 Piping in which expansion joints or bellows are fitted is to be adequately adjusted, aligned and clamped.
Protection against mechanical damage may be required if found necessary .
8 End fittings are to be designed and fabricated according to recognized codes/standards .
11.8.4. Valves and other piping parts
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1 Screwed-on valve bonnets are not to be valves with nominal diameter exceeding 50mm .
2 Screwed-on valve bonnets are to be secured against loosening when the valve is operated .
3 IndIcators are to be provIded to show open and closed position of the valve.
4 Closing time of valves is to be selected so that no detridetrimental stresses are introduced to piping due
to hydraulic hammering
5 Piping parts not covered by recognized standards are to be approved for their intended use. Drawings
are to be submitted for approval, and supported by stress calculations. Application, type of medium,
design pressure, temperature range, materials and other design parameters are to be given. If the parts
have a complicated configuration that makes theoretical calculations unreliable, the parts may be
accepted based on certified prototype proof test reports that prove their suitability for the intended use .
11.8.5. Piping connections
1 The number of detachable pipe connectionsare to be limited to those which are necessary for mounting
and dismantling. The piping connections are to be in accordance with the applied code or standard or are
to be approved for their intended use .
2 Joints of pipes with outer diameter of 51mm and above are normally to be made by buttwelding, flanged,
or screwed union where the threads are not part of the sealing. Joints for smaller sizes may be welded or
screwed and seal welded if not intended for corrosive fluids. Tapered threads and double bite or
compression joints may be accepted after special consideration .
3 If the piping system is rated for 207 bar (3000 psi) or more, ordinary threaded connections are not to be
used .
4 Weld neck flanges are to be forged to a shape as close to the final shape as possible .
5 Tapered threads are to be used on couplings with stud ends where such couplings are permitted .
6 Calculations of the reinforcement are required :
(1) when weldolets of unrecognized type and shape are used in the branch connection .
(2) when the strength is not provided inherently in the components in the branch connection .
11.8.6. Supporting elements
1 Piping is to be supported in such a way that its weight is not taken by connected machinery or that heavy
valves and fittings do not cause large additional stresses in adjacent pipes .
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2 Axial forces due to internal pressure change in direction or cross-sectional area are to be taken into
consideration when mounting the piping .
3 The support of the pipimh is to be such that detrimental vibrations will not arise in the system .
4 Attachments welded directly to pipes are not to be used on piping rated 207 bar (3000 psi) or above.
Gland type (stuffing box) penetrations are to be applied for pipe penetratiolion through decks/bulkheads .
5 Attachments welded directly to pipes rated below 207 bar (3000 psi) are to be avoided. Where this
cannot used be avoid doubling plates are to be used, or the support is, by other means, to be welded to
the pipe in a way that introduces the minimum of sresses to the pipe surface from forces acting on the
support .
12. Oil production plant
12.1. Application
1 The requirements in this chapter apply to production plants, including production related equipment,
structures and systems, as listed in 3, which may be installed on units (herein after refered to as
production plant) are made to cover the safety of the production plant and personnel operating the plant,
as well as protection of the environment with respect to pollution .
2 The rules for production plant cover the following systems and arrangements on the unit, including
relevant equipment and structures :
(1) Production and export riser systems.
(2) Well control system.
(3) Riser compensating and tensioning system.
(4) Hydrocarbon processing system.
(5) Relief and flare system.
(6) Production plant safety systems.
(7) Production plant utility systems.
(8) Water injection system .
(9) Gas injection system.
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(10) Storage system.
3 The folowing is considered as main boundaries of the production plant, as relevant :
(1) Lower riser connection to sea floor system.
(2) Control system connection to sea floor system
(3) Connection to production buoy
(4) Shutdown valve at crude outlet from production plant to crude storage or loading buoy .
12.2. Supervision and Equipment certification
12.2.1. System design review
1 Production systems are to be approved according to the following principles :
(1) Design approval
(2) Survey of installation
(3) Functional test after installation
12.2.2. Equipment certification
1 Equipment referred to in these Rules is to be categorised as below :
(1) Category I: Equipment related to safety for which the Societys certificate is required. Category
I equipment is subdivided into IA and IB categorisation.
(2) Category II: Equipment related to safety for which a works certificate prepared by the
manufactured is accepted .
2 Depending on the required extent of survey by VR, caterogy I equipment is subdivided into IA and IB
with the specified requirements as below :
(1) Category IA: Class survey during fabrication ; Witness final functional, pressure and load test, as
applicable ; Review fabrication record.
(2) Category IB: Witness final functional, pressure and load tests as applicable; Review fabrication
record .
3 Equipment of category II normally accepted on the basis of a works certificate prepared by the
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manufacturer. The certificate is to contain the following data as a minimum:
(1) Equipment specificateion/ data sheet
(2) Limitations with respect to operation of equipment
(3) Statement from the manufacturer to confirm that the equipment has been constructed,
manufactured and tested according to the recognised methods, codes and standards.
Independent test certificate /report for the equipment or approval certificate for manufacturing
system may also be accepted .
12.3. Documentation
12.3.1. Design documentation for production systems and arrangement
1 The following documentation is to be submitted for approval:
(1) Well completion system arrangement;
(2) Process system arrangement including flaring and hydrocarbon storage ;
(3) Piping and instrumentation diagrams ( P & ID) for process and utility systems;
(4) Relief, depressurising and disposal systems
(5) Drainage syatems
(6) Control systems
(7) Process shutdown system
(8) Injection shutdown system
(9) Riser compensating and tensioning system
(10) Test programs
2 The following listed documentation is to be submitted for information, as relevant:
(1) Process description and operating philosophy;
(2) Process flow diagrams including heat and mass balances if available;
(3) Aplicable calculations including capacity, temperature and pressure calculations;
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(4) Heat radiation and dispersion calculations;
(5) Activation logic for depressurising systems;
(6) Process shutdown system philosophy;
(7) Injection shutdown system philosophy ;
(8) Corrosion/erosion monitoring and maintenance system;
3 Documentation requirement for riser systems, see 12.10.3.
4 Documentation requirement for electrical installations, see 12.12.2..
5 Documentation requirement for instrumentation and control systems, see 12.13.2.
12.3.2. Design documentation for equipment packages
1 For the equipment packages where system design is involved together with the equipment, e.g. turbine,
compressor, pump etc., the following design documentation for the systems is to be submitted for
appproval :
(1) Package/equipment arrangement with relevant description and specification ;
(2) Piping and instrumentation diagrams ;
(3) Control and monitoring systems/instrument list ;
(4) Lists with information of all relevant equipment in the systems;
(5) Support structures (skids);
(6) Test program.
12.3.3. Design documentation for category I equipment
1 The following design documentation is to be sumitted for approval :
(1) Drawings, including sufficient details and dimensions for evaluating the design;
(2) Bill of materials including material specifications, as necessary ;
(3) Test program .
2 The following design documentation is to be sumitted for information :
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(1) Design specifications/ data sheets, including specifications of work medium, pressure ratings,
maximum allowable working pressurre (MAWP), minimum/ maximum temperatures, corrosion
control, environmental and functionnal loads, etc. ;
(2) Strength calculations ;
(3) Lateral and torsional vibration analyses where appropriate ;
(4) Fabrication specifications including welding, heat treatment, type and extent of NDE, fabrication
method, etc.
12.3.4. Design documentation for category I piping
1 The following documentation is to be submitted for approval :
(1) A complete piping specification for all the different piping classes;
(2) Stress calculations or certified proof test reports for pressurized non-standard items ;
(3) Flow sheets of piping and instrumentation diagrams (P & ID) with reference to the appropriate
piping designation line ;
(4) Lists with all informations regarding the different items in the lines ;
(5) Pressure test plan.
2 The following design documentation is to be sumitted for information :
(1) Design code and dimensional standards ;
(2) Application;
(3) Medium ;
(4) Design pressure for each piping class ;
(5) Design temperature range ( maximum and minimum ) ;
(6) Material to be applied for all the pi[es, fittings, branches, unions, couplings, flanges, bolts, nuts,
gaskets, flexible elements such as compensators, flexible hoses etc .
(7) Materials to be applied for valve bodies, bonnets, stems, seat seals. actuator bodies etc;
(8) Corrosion allowance ;
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(9) Wall thickness or schedule for each line size ;
(10) Rating and type of flanges, valves, fitting, branches, weldolets, unions, blinds, etc ;
(11) List of special components if any ;
(12) Piping flexibility analysis when deemed necessary .
12.3.5. Documentation for structures
1 Design documentation for the following is to be submitted for approval:
(1) Structural drawings, with all relevant dimensions ;
(2) Details of padeyes ;
(3) Material specifications .
2 The following design documentation is to be sumitted for information:
(1) Arrangement drawing of the structure shwing equipment loads and locations ;
(2) Design calculations and, where relevant, alternative documentation in support of applicable
design;
(3) Relevant limitations ( e.g. design ambient temperature, operational conditions, etc.);
(4) Relevant fabrication specifications including welding, heat treatment, type and extent of NDE,
testing, etc.
12.3.6. Documentation on corrosion protection
1 For items submerged in water such as riser, cathodic protection specifications are to be submitted for
approval. For cathdic protection systems utilising sacrificial anodes the following information is normally
to be included as applicable:
(1) Type, amount, distribution and lifting of anodes ;
(2) Design current density .
2 With respect to internal corrosion and erosion in process piping and equipment, the corrosion resistance
of metallic materials and any linings or coatings is to be documented and approved.
12.3.7. Fabrication documentation
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1 A traceable fabrication record is to be maintained by the manufacturer. The rocord should ensure
relevant information regarding design specifications, materials fabrication processes, inspection, heat
treament, testing etc. can be checked in connection with product certification..
2 Category I equipment is to be accompanied by a Product Certificate
3 Category II equipment is to be accompanied by a Works Certificate or equivalent.
12.4. Materials and corrosion protection
12.4.1. General
1 Selection of materials is to be based on type and level of stresses, temperatures, corrosive and erosive
conditions, consequences and possibilities of failure associated with installation, operation and
maintenance.
2 For selection of acceptable materials suitable for H2S contaminated products ( sour service ) reference is
made to the recognized standard by VR .
3 The materials selected are to be suitable for the purpose and have adequate properties of strength and
ductility. Materials incorporated in any portion of an installation which are critical to the integrity and safety
are to have good weldability properties for manufacture and installation, if welding is to be performed.
Materials are to be corrosion resistant or protected against corrosion where this is deemed necessary.
4 Non-combustible materials are to be used. Where any required property do not permit the use of such
material, other alternative materials may be used as agreed upon between the Client and VR .
5 Materials are to be in accordance with recognised standards bearing in mind the specific requirements
of design codes/standards for limiting carbon content, carbon equivalent, etc. Where modified material
compositions or properties are necessary, specifically written specifications are to be submitted for
approval in each case. Such specifications are to include chemical composition, manufacturing
processes, material properties, mechanical testing procedures and non-destructive examination
procederes..
12.4.2. Corrosion Protection
1 Equipment and piping to be corrosion resistant or protected against corrosion where considered
necessary for safety or operational reasons .
2 Corrosion allowance of low alloy carbon steel is to be dependent on corrsivity of commodity, lifetime of
equipment and corrsion control method used.
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Table 12.4.2-1 Corrosion Allowance “c” for Steel Materials
Unit: mm
Service c
Saturated steam 0,8
Steam coils 2
Feedwater and blowdown pipes (for boilers) 1,5
Compressed air 1,0
Hydraulic oil 0,3
Lubricating oil 0,3
Fuel oil 1
Refrigerants 0,3
Fresh water 0,8
Hydrocacbon service 2
Mud/cement 3
Notes :
(1) An additional allowance for external corrosion is to be considered according to the figures given
in the Table, depending on the external medium .
(2) Where efficient protective methods against corrosion are used, the corrosion allowance may be
reduced up to 50%.
3 Dissimilar metallic materials in contact are to be avoided or adequately proteced against galvanic
corrosion .
4 External steel surfaces exposed to the marine atmosphere and splash zone are to be protected by
coating. Special metallic materials may be used.
5 Steel components submerged in seawater are to be externally protected by cathodic protection or a
combination of cathodic protection and coating .
6 Internal corrosion control is to be used if the commodity contains water or has a relative humidity, of
more than 50% and if the partial pressure of corrosive gases is above the following limits:
(1) Oxygen : 100 Pa
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(2) Hydrogen sulfide : 10 kPa
(3) Carbon dioxide : 20 kPa
Increased corrosivity due to combination of gases is to be considered.
7 Inhibitors are to be selected when relevant to suit the actual internal enviroment .
8 Corrosion monitoring is to be used where considered necessary .
12.4.3. Erosion
1 Precautions are to be taken to monitor and avoid erosion in process piping and equipment.
12.5. Design principles
12.5.1. General
1 The requirements in this part stipulate design principles for process systems and comprising equipment
related to safety .
12.5.2. Definitions and explanations
1 The following definitions and explations are to be used in this section besides the definitions and
explations given in 1.3
2 Accommodation area is the area which comprises public spaces, corridors, stairways, sanitary and
similar spaces, cabins, offices, service spaces, hospitals and similar permanently enclosed spaces.
3 Cofferdam is an isolating space ( The space may be a dry space or a tank )
4 Manual control is a control where the decisions on initiation and execution are made by personnel .
5 Failure in the Rule context is an event to a component or a system causing one or both of the following
effects:
- Loss of component or system function
- Deterrioration of functional capability to such an extent that safety is significantly reduced .
6 Monitoring systems comprise alarm and safety systems installed to monitor performance and react to
abnormal conditions.
7 Redundancy is the ability of a component or system to maintain or restore its function when a failure has
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occurred. (Redundancy can be achieved, for instance, by installation of more units or alternative means
for performing a function).
8 Remote control systems comprise all equipment necessary to operate units from a position where the
operator cannot directly observe the effect of his actions. Equipment necessary for remote operation of
locally situated manual operation devices is regarded as part of the remote control systems..
12.5.3. Design loads, general
1 Design limits, i.e. maximum and minimum allowable conditions for a component, are to take into account
the effects of operationnal conditions such as start-up, change-over, run-down, hydrate formation, water
hammer, and slugs.
2 Components in a system are to beadeqyately matched with regard to their function, capacity, strength
and interface compatibility. Any weak link in the system is to be located where it would cause least
damage, should it ever fail..
3 Each part of the production plant is to be designed for the most unfavourable load condition, for which it
is intended used.
4 A calculation should be made for each loading condition and item, taking into consideration the most
unfavourable combination of position and direction of loads which may occur simmultaneously.
5 All external loads which may impair the proper function of the production plant thus having signfivant
influence or cause a reduction of the safety, streng and reliability, are to be considered.
12.5.4. Environmental conditions
1 Test results or other relevant documentation confirming the component or systems suitability for their
intended purpose may be required.
2 Where applicable, the following aspects are to be taken into consideration when establishing the
environmental loads:
- The unit's motions( i.e. heave, roll, pitch, sway, surge and yaw )
- Wind forces
- Air and sea temperatures
- Waves
- Current
- Loads from possible snow and ice accretion .
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12.5.5. Design pressure and temperature
1 Due to internal or external conditions, the design temperature for which the component may be allowed
to operate with the corresponding design pressure is to be specified with adequate margins to cover
uncertainties in the prediction.
2 The consideration is to include start-up, shutdown and those abnormal conditions which are considered
likely to occur.
3 Studies, calculations, etc. to establish particular operational limitations not readity available, e.g. low
temperature in choke and well test systems, etc. are to be presented when deemed necessary.
4 All equipment is to be located to ensure safe operation and, if located in hazardous areas, is to be
suitably protected for installation in such areas. Equipment in hazardous areas are to be so protected that
maximum surface temperature doesnot exceed 80% of the autoignition temperature of the explosive
gas/air mixture. Where autoignition temperature is unknown, max. temperature of 200oC is to be applied.
12.5.6. Design safety factors
1 The safety factors to be used in determination of an acceptable stress level for the various load
conditions are to be established by the designer and included in the design documentation.
2 If not specified in this chapter safety factors are to be in accordance with relevant code, standard or
recommended practice for each particular component.
3 The yield strength used in calculations is not to exeed 0.85 of the specified minimum tensile strength .
12.6. Systems
12.6.1. General
1 Design limits, i.e. maximum and minimum allowable conditions for a component, are to take into account
the effects of operational conditions such as start-up, change-over, run-down, hydrate formation, water
hammer, and slugs.
2 Components in a system are to be adequately matcheted with regard to their function, capacity, strength
and interface compatibility. Should the system ever fail, any weak link is to be located where it would
cause least damage.
3 Whenit is essential for the safety of a system installation that tha function of a component is maintained
for a specific period of time in the event of fire, the qualyfying properties are to be verified.
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4 In the vent of failure, components and systems are to enter the least hazardous of the possible failure
modes.
5 The systems are to be so arranged that one single maloperation or malfunction willnot lead to a critical
situation for personnel or the unit.
Safety systems are to provide two independent levels of protection to prevent or minimise the effects of a
single malfunction or fault in the process equipment and piping system including their controls.
6 All equipment is to be equipped with indicating instruments considered necessary for safe operation .
7 All equipment and parts to be operated or subject to inspection and maintenance on board, are to be
installed and arranged for easy access.
8 All components shall be fitted with thermic insulation yo the extent necessary to achieve acceptable
protection of personnel .
9 Where there is a risk of hydrate formation or icing, facilities shall be fitted with possibilites for injection of
glycol or methanol, or other similar measures.
12.6.2. Control and monitoring
1 All machinery is to be equipped with indicating instruments considered necessary for safe operation of
the machinery.
2 All pressure systems are to be equipped with pressure relief devices to protect against pressure
exceeding the maximum allowable working pressure of the system.
3 The set pressure for pressure-relief devices is not to exceed the maximum allowable working pressure .
4 Systems for indication of valve positions are normally to be independent of the activating system .
5 Switch-over to stand-by systems is to be simple. This applies also in the event of failure in a control and
monitoring system.Indication is to be given to the operator when redundant systems are acivated .
12.6.3. Shut down
1 It is to be possible, either manually or automatically, to shut down equipment unit or installation, as
necessary, if an accident or an unpredicted failure occurs. Systems designed for automatic shutdowns
are also to be designed for manual shutdowns.
2 The shutdown system is to function independently and uniterrupted of loss main power.
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3 The shutdown system is not to have automatic reset. Arrangements for re-start are to be implemented
as deemed necessary .
4 Shutdown is to be initiated in a predetermined logical manner. Establishment of the system shutdown
logic and response time is to be based on consideration of the dynamic effects etc. in order to avoid
undesirable or abnormal conditions in other parts of the system .
5 In the shutdown systems where automatic protective actions are initiated upon detection of an abnormal
condition, the control station is to receive pre-alarm warning/signals indicating the locations of such
shutdown .
12.6.4. Equipment for safety control
1 Unattended systems are to be provided with safety control equipment if the failure of such systems can
endanger safety.
2 The equipment for safety control is to be independent of, and in addition to, the control systems used in
normal operation.
3 The equipment for safety control is to be designed with automatic monitoring and automatic initiation of
protective actions if an abnormal condition is detected. Manual intervention is to be an inherent part of the
design.
4 The safety control system, including sensors and valves, is to be designed fail safe, i.e. they should fail
to the predetermined safest position. For shutdown valves, this would normally imply that they fail to
closed position.
5 When the safety control system has been activated, it is to be possible, by means of central and local
indicators, to trace the cause of the safety action.
12.7. Production, injection and utility systems
12.7.1. General
1 This part gives requirements for the following :
(1) Safety systems with respect to production shutdown
(2) Relief, depressurising and disposal systems.
12.7.2. Definitions and explanation
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1 The following definitions and explations are to be used in this section besides the definitions and
explations given in 1.3 :
2 Abnormal condition is a condition which occurs when an operating variable ranges outside its normal
operating limits.
3 Alarm systems comprise the systems for warning of abnormal conditions ( including sensors, central
units and panels, and devices for calling the attention of the personnel )
4 Alarm is a combined optical and acoustic signal, where the acoustic part calls the attention of personnel,
and the optical part serves to identify the fault .
5 Control stations are those spaces in which the following equipment and functions are located :
(1) Control of the process shutdown system (PSD)
(2) Control of the emergency shutdown system (ESD)
(3) Radio and main internal communication central
(4) Fire and gas detection central
(5) Fire control and extinction central
(6) Fire extinguishing medium central
(7) Control of the emergency sources of power .
6 Depressurising valve is a valve installed to provide rapid reduction of pressure
7 Emergency shutdown (ESD) is a system for initiation of, either by central manual controls or automatic
controls, shutdown of all ignition sources and production facilities when abnormal condition arise.
8 Fail safe system is a system designed to take the predetermined safest mode upon loss of power or
signal failure.
9 Flare system is a system which dicposes of hydrocarbon gases by combustion .
10 Pressure relief system is a general term used for presure relief valves and rupture discsincluding inlet
piping and discharge piping .
11 Pressure relieving device is a generic term used for pressure relief valves and rupture discs .
12 Pressure relief valve is an automatic pressure-relieving device actuated by the static pressure upstream
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of the valve.
13 Process shutdown ( PSD ) is isolation of a given process station from the process by closing appropriate
shut down valves to shut in flow of hydrocarbons .
14 Set pressure is the inlet pressure at which the relieving device is adjusted to open under service
conditions .
15 Undesirable condition is an adverse occurrence or situation which poses athreat to safety such as
overpressure, underpressure etc.
16 The safety systems serve to limit the consequences of failure by intervening automatically in the
process when abnormal conditions arise, e.g. by starting standby pumps, stopping auxiliary engines, etc.
17 Knock-out drum is a small drum for elenimating substances off the gas.
12.7.3. Safety systems interconnections with emergency shutdown (ESD) system
1 The process shutdown ( PSD ) is to receive input from the ESD system, such that if the ESD is initiated,
this is to lead to the following :
(1) Shutdown valves at subsea wellheads are to close.
(2) All production activity is to shut down.
(3) All injection activity is to shut down
2 The ESD sequence and logic is to ensure that the shutdown takes place according to the fail safe
principle e.g. without causing further abnormal conditions in the process, injection and utility systems .
3 The following valves may be used as ESD-valves:
(1) Down hole safety valves
(2) Wellhead shut down (master ) valves.
12.7.4. Process shutdown ( PSD ) system
1 PSD is to be initiated in a predetermined logical manner. Establishment of the PSD system logic and
response time is to be based on careful consideration of the process dynamics, in order to avoid
undesirable or abnormal conditions other parts of the system .
2 The PSD system is to function uninterrupted of loss of main power.
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3 Where an automatic protective system is provided, the system is to allow for manual operation .
The system is to be so designed as to provide the operator with suffient alarms and status overview for
safe operation .
4 Automatic protective actions are to be initiated upon detection of an abnormal condition by a process
sensor.
5 PSD shutdown valves, designated as emergency shutdown ( ESD ) valves, are to provide a segregation
of production systems in consideration of general plant layout and the operation of the plant, and are to
be actuated in emergency situations.
6 The ESD and PSD valvels are to be provided with remote indication for open and closed position.
Closing the valves are to release alarm in the control station .
12.7.5. Relief, depressurising and disposal system - Design principles
1 The production plant is to be provided with pressure relief, depressurising and disposal systems
designed to :
(1) Protect equipment against excessive pressure .
(2) Minimise the escape of hydrocarbons in case of rupture .
(3) Ensure a safe collection and discharge of released hydrocarbon fluids.
2 The systems are to be designed to handle the maximum relieving rates expected due to any single
equipment failure.
3 The systems are to be designed according to the fail safe principle .
4 Appropriate measures are to be taken to prevent inadvertent closing of valves installed in association
with pressure relieving and depressurising devices .
12.7.6. Pressure relief system
1 All pressure systems are to be equipped with a pressure relief capability to protect against pressure
exceeding the maximum allowable working pressure of the system.
The pressure relief possibility is to be desgned to handle the maximum relieving rate expected.
2 Where two pressure relief possibilities are to provided for operational and maintenance purposes, it is
not to be possible to isolate both possibilities simultaneously.
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3 If more than one device is necessary to obtain 100% of the required maximum relieving rate, the system
is to be equipped with that number of pressure relief devices necessary to allow any one device to be
non-functional without reducing the capacity of the remaining devices below 100% of design rate.
4 For equipment containing substances that may render a pressure relief valve inoperative or, when rapid
rates of pressure rese may be encountered, rupture discs are to be used in lieu of pressure relief valves.
5 Hydrocarbon gas pressure relieving devices are to be connected to the flaring or cold vent system .
12.7.7. Depressurising system
1 All pressure systems handling toxic or flammable substances which can be blocked-in during a fire (e.g.
due to the ESD process ) are to be equipped with a depressurising system .
2 Cooling effects in process equipment, valves and discharge piping during the depressurising period are
to be evaluated for proper material selection.
3 Depressurising valves are to be provided with energised sources so as to open by uninterruptable stored
power supply. Remote, manual operation of depressurising valves is to be possoble at a safe distance
from the protected equipment, e.g. from a control station .
12.7.8. Gas disposal system .
1 The design of the flare, relief header and knock-out drum is to take into consideration relevant possible
low temperatures and vibration which occur when gas expands in the system .
2 The gas disposal system is to be designed such that the lowest pressure system that might be relieving
can enter the system without any reduction inrelieving capacity due to backpressure considerations.
3 Relieved hydrocacbons are to be routed through a liquid knock-out drum to a flare .
4 The header is to be self-draining to the liquid knock-out drum. Any liquid that cannot be safely handled
by a flare ( or a cold vent ) is to be collected in the drum with high level alarm.
12.7.9. Flare
1 The design of the flare system is to ensure that heat radiation and convection exposure to personnel,
structures and equipment are acceptable even during unfavourable wind conditions. Fot locations where
the heat radiation from the flare is high, the temperature rise and gradient in structural members, as well
as surface temperatures of exposed equipment are to be calculated and implications of calculatedand the
implications of the calculated result assessed.
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2 Radiation levels from flares are to be calculated based on recognised methods or by relevant testing.
Radiant heat intensities from the flare are not to exceed the followinf limits:
(1) 6,3 kW/m2: Heat intensity in areas where emergency actions, lasting up to 1 minute, may be
required by personnel without shielding but with appropriate clothing, or, in the case of
accidential ignition of a cold .
(2) 4,7 kW/m2 : Heat intensity in areas where emergency actions, lasting several minutes, may be
required by personnel without shielding but with appropriate clothing.
(3) 1,6 kW/m2 : Heat intensity at any location where personnel are continuously exposed
(4) Temperarure rating of electrical and mechanical equipment.
12.7.10. Cold vents
1 The height and location of cold vents are to ensure that vented gas is not ignited .
2 The heat radiation from a cold vent is to be considered in case of accidental ignition .
3 The dew point of vented gas is to be such that it wil not condense at the minimum expected ambient
temperature.
4 Cold vent piping is to be provided with a drain system, or a liquid collection system, to prevent liquid
accumulation in the cold vent line .
5 In order to avoid continuous burning in case of an accidental ignition, an extinguishing system is to be
provided .
12.7.11. Drainage system and facilties for produced water
1 Production plant drainage systems are to collect and direct escaped liquids to a location where there can
be safely handled and/or stored .
2 The production plant is to be equipped with one closed drainage system for hydrocarbon liquids, one
open system for hazardous areas and one open system for non-hazardous areas. The systems are to be
completely separared.
3 All drainage systems containing hydrocarbons are to be routed to facilities for cleaning .
4 Approved measures are to be taken in order to prevent spread of fire though the drainage system .
5 The system for produced water is to have facilities which effectively separate hydrocarbons from the
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water to an acceptable oil pollution level .
12.7.12. Separator system
1 The oil production separators are to be designed according to applicable parts of 14.6 and 14.7.
2 The separators are to have sufficient capacity to separate the components of the well stream and
effective means for removal of sand and water .
12.7.13. Water injection system
1 Water injection system which may contain the following parts :
(1) Sea water booster pumps
(2) Sea water fine filter
(3) Deaerator
(4) Injection pump with prime mover
(5) Chemical dosing system ( tanks, pipes, pumps etc. )
(6) Piping
Is to be designed according to the applicable parts of these Rules.
2 Check valves and ESD valves to be fitted on the injection line to the well.
12.8. Piping
12.8.1. General
1 The requirements in this section are applicable to piping and related fittings
12.8.2. Definitions and explanation
1 The following definitions and explations are to be used in this section besides the definitions and
explations given in 1.3 :
2 Hard piping is a piping made of metallic materials .
3 Line pocket is a space inside the pipe which is not affected by normal flow within the pipe .
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4 Utility piping is piping for support systems such as :
(1) Starting air for combustion engines
(2) Cooling water
(3) Steam or thermal fluid heating
(4) Lubricating oil
(5) Hydraulic power supply
(6) Pneumatic power supply
(7) Fuel oil or fuel gas supply
(8) Helicopter fuel
(9) Crude oil and gas used directly from production facilities
(10) Vent pipes
(11) Drainage
12.8.3. Design requirements - General
1 Relevant factors and combination of factors are to be taken into account during design when evaluating
possible failure modes such as, but not limited to :
(1) Corrosion/erosion types
(2) Vibration, hydraulic hammer
(3) Pressure pulsations
(4) Abnormal temperature extremes
(5) Impact forces
(6) Leakages
2 Piping systems are to be properly segregated so that utility media, e.g. steam, compressed air cooling
water etc., are not contaminated by flammabie fluids .
3 External and internal attachments topiping are to be designed so that they will not cause flattening of the
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pipe, excessive local bending stresses, or harmful thermal gradients in the pipe wall. Constructions
causing stress concentrations are to be minimised, particularly in cyclic service applications .
4 Line pockets are to be avoided as far as possible in all piping systems, and in particular in the following :
(1) Blowdown and relief valve discharge lines
(2) Compressor suction lines
(3) In lines where water can accumulate and freeze
(4) In lines carrying caustic or acidic fluids, or other fluids that may freeze .
(5) In lines which contain solids which may settle out
(6) In piping in which corrosive condensate may form
All equipment piping should be arranged to provide sufficient clearances for operation, inspection,
maintenance and dismantling with the minimum interference or removal of piping or equipment.
Attention should be paid to clearances required for removal of equipment such as pumps, pump
drivers, exchanger bundles etc.
5 All pipe runs are to be clearly identified by colour codes or by other acceptable means.
12.8.4. Wall thickness
1 The minimum design wall thickness (t) of piping is to account for strength thickness and allowances
below:
(1) Bending allowances (b)
(2) Allowances for threads
(3) Corrosion allowances (c)
(4) Erosion allowances
(5) Negative manufacturing tolerance
The minimum wall thickness of a straight or bent pipe is not to be less than:
t = t0 + C
Where :
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t0 - strength thickness
C - sum of allowances
The minimum nominal wall thickness is, however, not to be less than given in Table 12.8.4:
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Table 12.8.4-1 Minimum nominal wall thickness for carbon
Unit: mm
External diameter D (mm) Min. wall thickness (mm) Carbon steel pipes
10,2 - 12
13,5 - 17,2
20
1,6
1,8
2
21,3 - 25
26,9 - 33,7
38 - 44,5
2
2
2
48,3
51 - 63,5
70
2,3
2,3
2,6
76,1 - 82,5
88,9 - 108
114,3 - 127
2,6
2,9
3,2
133 - 139,7
152,4 - 168,3
177,8
3,6
4
4,5
193,7
219,1
244,5 - 273
4,5
4,5
5
298,5 - 368
406,4 - 457
5,6
6,3
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Table 12.8.4-2 Minimum nominal wall thickness for pipes of copper, copper alloys and stainless
steel
Unit: mm
Min. wall thickness (mm) External pipe diameter
D (mm) Copper Copper alloy and stainless steel
D≤ 10
10 < D ≤ 20
20 < D ≤ 44,5
1
1,2
1,5
0,8
1
1,2
44,5 < D ≤ 76,1
76,1 < D ≤ 108
108 < D ≤ 159
2
2,5
3
1,5
2
2,5
159 < D ≤ 267
267 < D ≤ 457
470
508
3,5
4
4
4,5
3
3,5
3,5
4
When the allowance for bending (b) is not determined by a more accurate procedure, or when the
bending is not carried out by a bending procedure ensuring a controlof the wall thichkness, the allowance
for bending is not to be less than:
b = 0tRD
251
Where:
D - outer diameter of pipe
R - radius of the bend
t0 - strength thickness
If the bending ratio D/R is not given this ratio is to be taken equal to 1/3.
Corrosion allowance (c) see Table 12.4.2-1.
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)
2 The strength thickness (to) is normally to be calculated according to the recognized standard by VR .
3 If a combined stress calculation according to Von-Mises Theory is applied for heavy pipes with extra
wall thickness, the equivalent combined stress at any point of the piping wall is not to exceed 60% of the
minimum specified yield strength of the material.
The equivalent combined stress as defined by Von-Mises is :
σe = 0,707 ( ) ( ) ( 2
θr
2
r1
2
1θ σσσσσσ −+−+−
Where
σe - equivalent (Von Mises) combined stress
σθ - circumferential or hoop stress
σ1 - longitudinal or axial stress
σr - radial stress
The calculations for σ0 ,σl ,σ0 may be on Lame's equations for thick cylinders .
4 Piping parts which are covered by recognised standards and have a complicated configuration that
makes theoretical calculations unreliable, may be accepted based on certified prototype proof test
reports. Prototype test methods and acceptance criteria are to be agreed with the Society.
12.8.5. Expansion joints and flexible hoses
1 The locations of expansion joints and flexible hoses are to be clearly shown in the design
documentation.
2 Piping in which expansion joints or bellows are fitted is to be adequately adjusted, aligned and clamped.
Protection of the expansion joint or bellow against mechanical damage may be required if found
necessary .
3 Expansion joints and flexible piping elements are to be accessible for inspection .
4 The bursting pressure for flexible hoses is to be at least 4 times the maximum working pressure. High
pressure hoses with large nominal bores are subject to special consideration. In no case, however, is the
burst pressure to be taken as less than 2,0 times the maximum working pressure.
5 Means are to be provided to isolate flexible piping if used in systems where uncontrolled outflow of
medium is critical.
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6 Flexible hoses and non-metallic expansion joints for flammable fluids systems have to qualify a fire
endurance test according to VR or equivalent. The flexble hose has to maintain its integrity and functional
properties for the same period as required for the total piping system and components.
7 End fittings are to be designed and fabricated according to recognised codes/standards .
12.8.6. Plastic pipes ( GRP or GRE pipes )
1 Plastic pipes of approved type and tested according to an approved specification may be used for the
following services:
(1) Fresh water pipes situated inside tanks used for carrying fresh water only .
(2) Fresh cooling water branch lines for auxiliary engines and compressors
(3) Sanitary supply and discharge systems.
(4) Air and sounding pipes for tanks intended for fresh water .
(5) Pipes for pneumatic and hydraulic instrumentation systems, within control cabinets located in
control rooms or machinery rooms with the following :
(a) Systems for remote control of
- Seawater valves
- Valves on fuel oil service tanks
- Valves in fuel oil systems
- Valves in water ballast systems, when applicable
- Fire extinguishing
2 Plastic pipes are not to be used in the following systems :
(1) Fire extinguishing systems
(2) Drain systems
(3) Sea water cooling systems and fresh water cooling systems other than those specifed in -1
(4) Feed water and condensate systems
(5) Pipes carrying oil or other flammable liquids.
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(6) Other piping systems where a possible leakage as a consequence of heat or flame may
endanger the installation .
3 Plastic pipes are in general not to be used for media with a temperature outside the temperature range
of 0o - 60oC. Pipes made of glass reinforced plastics may be accepted for a working temperature up to +
80oC.
4 Plastic pipes are not to be used for pressuried gases outside control cabinets.
5 When located in hazardous spaces, the surface resistance of the pipes is not to exceed 107 Ohm (Ω).
12.8.7. Valves and special items
1 Unwelded valves designed, fabricated and tested according to recognised standards will be accepted
based on manufacturers certification .
2 Special valves constructed by welding and flange rating and above are subjected to design review and
inspection .
3 The following documentation/information is to be submitted for evaluation for valves as described in - 2 :
(1) Cross sectional drawings and detail drawing with all dimensions of body, bonnet and stem and
other possible parts of importance to the strength of the valve .
(2) Pressure rating and temperature range
(3) Qualified welding procedure
(4) Material specifications
(5) Heat treatment specification
(6) NDT specification
4 Screwed-on valve bonnets are not to be used for valves with nominal diameter excceding 50 mm.
5 Screwed-on valve bonnets are to be secured against loosening when the valve is operated.
6 Indicators are to be provided to show open and closed position of the valve .
7 Weld necks of valve bodies are to be of sufficient length in order to ensure that the valve internals are
not distorted due to haet from welding and subsequent heat treament of the joints .
8 Closing time of valves is to be selected so that no detrimental stresses are introduced to piping due to
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hydraulic hammering .
9 Emergency shut-down valves that are not to be fitted sub-surface are to be fire tested according to
recognized procedure by VR .
10 Special items not covered by recognised standards are to be approved for their intended use. Drawings
are to be submitted for approval, and are to be supported by stress calculations. Application, type of
medium, design pressure, temperature range, materials and other design parameters are to be given .
11 Special items not covered by recognised standards having a complicated configuration that makes
theoretical calculations unreliable, may be accepted based on certified prototype proof test reports that
prove their suitability for the intended use .
12 Valves in the hydrocarbon process system which do not have metal to metal seat are to meet the fire
resistance requirements reference is made to the recognized standard by VR .
13 Upon failure in power supply, remotely controlled valves are to fail to the safest mode. (i.e. failure in
power supply is not to cause :
(1) Opening of closed valves
(2) Closing of open valves for the systems in which supply stream is not to be interrupted, e.g.
cooling water for emergency power generating machinery.)
12.8.8. Piping connections
1 The number of detachable pipe connections are to be limited to those which are necessary for mounting
and dismantling. The piping connections are to be in accordance with the applied code or standard or are
to be approved for their intended use.
2 Joints of pipes with outer diameter of 51 mm and above are normally to be made by buttwelding,
flanged, or screwed union where the threads are not part of the sealing. Joints for smaller sizes may be
welded or screwed and seal welded if not intended for corrosive fluids. Tapered threads and double bite
or compression joints may be accepted after special .
3 If the piping system is rated for 207 bar ( 3000 psi ) or more, ordinary threaded connections are normally
not to be used.
4 Weld neck flanges are to be forged to a shape as close to the final shape as possible .
5 Tapered threads are to be used on couplings with stub ends where such couplings are permitted .
6 Calculations of the reinforcement are required :
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(1) When weldlets of unrecognised type and shape are used in the branch connection.
(2) When the strength is not provided inherently in the components in the branch cconnection.
12.8.9. Supporting elements
1 Piping is to be supported in such a way that its weight is not taken by connected machinery or that heavy
valves and fittings do not cause large additional stresses in adjacent pipes.
2 Axial forces due to internal pressure, change in direction or cross-sectional area are to be taken into
consideration when mounting the piping.
3 The support of the piping is to be such that detrimental vibrations will not arise in the system.
4 Attachments welded directly to pipes are not to be used on piping rated 207 bar (3000 psi ) or above.
Gland type (stuffing box ) penetrations are to be applied for pipe penetrations through decks/bulkheads.
5 Attachments welded directly to pipes rated below 207 bar (3000 psi ) are to be avoided. When this
cannot be avoided, doubling plates are to be used, or the support is, by other means, to be welded to the
pipe in a way that introduces the minimum of stresses to the pipe surface from forces acting on the
support.
6 Pies and their supports are to be installed with sufficient flexibility so they do not take up hull forces
caused by by the units movements and temperature variations.
12.9. Equipment
12.9.1. General
1 The equirements in this part are applicable to the following:
(1) Unfired pressure vessels
(2) Boilers
(3) Heat exchangers
(4) Thermal fluid heaters
(5) Pressure containing components, which can be regarded as pressure vessels
(6) Atmospheric vessels
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(7) Pumps
(8) Compressors
(9) Combustion engines
(10) Gas turbines
(11) Transmission systems.
2 Equipments are to be complied with requirements according to 12.1 and 12.2.
3 Equipments are to be complied with material requirements according to 12.4.
4 Equipments are to be complied with general design requirements according to 12.5.
5 Equipments being used in production plants or other wire related to safety in conjuction with production,
is to be designed, manufactured, installed, tested and certified in accordance with these Rules and
recognised codes, standards or guilines .
12.9.2. Definitions and explanations
1 The following definitions and explations are to be used in this section besides the definitions and
explations given in 1.3 :
2 Atmospheric vessel is a vessel that contains a fluid at atmospheric pressure.
3 Boiler is defined as a pressure vessel or a pipe arrangement in which steam or hot water with a
temperature exceeding 120oC is generated by the application of heat resulting from the combusting of
fuel ( solid, liquid or gaseous ) or from hot combustion gases. Superheaters, economisers, rehaeters and
other pressurised parts including valves and fittings, connected directly to the boiler without intervening
valves, are to be considered as parts of the boiler.
4 Heat exchanger is a device for heating or cooling in which heat is transferred from one fluid to the other .
5 Pressure vessel is a vessel or tank that is subjected to internal or external pressure above or below
atmospheric pressure.
6 Thermal fluid heater is a heat exchanger in which hot fluid is circulated for the purpose of heating
another medium .
7 Equipment train is the general term used to define an integral package consisting of a driving unit and a
driven item together with their associated support functions (e.g. turbine and generator package).
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12.9.3. design documentation
1 The following design documentation is to be submited for approval
(1) Drawings, including sufficient details and dimentions for evaluating the design .
(2) Bill of materials including material specifications, as necessary
(3) Test program
2 The following design documentation is to be sumitted for information :
(1) Design specifications/ data sheets, including specifications of work medium, pressure ratings,
maximum allowable working pressurre (MAWP), minimum/ maximum temperatures, corrosion
control, environmental and functionnal loads, etc.
(2) Strength calculations .
(3) Lateral and torsional vibration analyses where appropriate .
(4) Fabrication specifications including welding, heat treatment, type and extent of NDE, fabrication
method, etc .
3 During fabrication, inspection and testing the documentation which verifies that the requirements have
been complied with, is to be made available to the surveyor .
12.9.4. Design requirements
1 The design is to be in accordance with the VR's rules, the recognised code, standard or recommended
practice for each particular component as outlined in 12.3.
12.10. Riser systems
12.10.1. General
1 The requirements in this part apply to rigid and flexible riser system connecting the completed subsea
well or subsea system including pipeline end manifold (PLEM) to the piping installation on the unit/vessel
for conveying hydrocarbons, injection of fluids and workover operations for wells .
2 The following are to be complied with as relevant : The requirements of 12.1 and 12.2, Material
requirements of 12.4, General design requirements of 12.5, Pressure retaining equipment requirements
of 12.9 and piping requirements of 12.8 .
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12.10.2. Definitions and explanations
1 The following definitions and explations are to be used in this section besides the definitions and
explations given in 1.3 :
2 Riser system includes the riser, its supports, riser end connectors all integrated components, corrosion
protection system, control system and tensioner system.
3 Riser is a rigid or flexible pipe between the connector on the unit/vessel and on the seabed ( baseplate,
wellhead, manifold).
4 Riser support is a structure for fixing the riser to the unit/vessel or for local or continuous guidance of the
riser, including buoyancy elements if applicable.
5 Riser component is an itemintegrated in the riser, such as a flange, a joint, a clamp, a connector, a valve
and fitting .
12.10.3. Documentation for approval
1 Design documentation for approval is to be submitted to the Society in triplicate, as below:
(1) Drawings:
(a) Arrangement drawing showing riser location with respect to the lacation of equipment like
crane, anchors and any activities which may effect the safety of riser system.
(b) General layout drawings of the riser system including location or related equipment and
systems connected at both ends.
(c) Drawings showing riser structure, pressure containing components, and protecting
structures.
(d) Drawing and description of control and systems
(2) Loads
(a) Calculation of functional loads .
(b) Calculation of environmental loads .
(3) Strength analysis
(a) Structural analysis, including control against excessive yielding, fatigue failure,
propagating ductile fracture and brittle fracture as applicable .
(b) Structural stability analysis, including control against buckling and excessive
displacements, as applicable.
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(c) Static analysis
(d) Dynamic analysis, including vibration analysis, if relevant .
(4) Materials and fabrication
(a) Material specifications for riser pipes, components bolts, nuts and welding consumable .
(b) Fabrication specification of pipes, and components including fabricating methods, welding,
type and extent of NDE, heat treatment, metal overlay, bolt prestresses, hydrotesting, etc.
(c) When applicable, results from laboratory testing of nonmetallic materials including but not
limited to, tensile strength, elongation, hardness, ageing resistance, adhesion, fatigue,
embrittlement, swelling, diffusion, blistering and fire resitance.
(5) Corrosion protection(as applicable)
(a) Specification for coating application .
(b) Specification for anodes
(c) Specification of cathodic protection system including design caculations .
(d) Description of anode location
(e) Drawing of anode
(f) Specification for protection of riser in critical areas such as in splash zone.
(g) Specification for internal corrosion control.
(6) Installation
(a) Test programs, for pressure and leakage testing of systems, and functional testing of
control and safety systems.
(b) Test program for final tests upon completion. The program is to include instructions
related to shutdown and start-up, controlled iby normal and redundant systems, remote
and local, during simulation of failure conditions.
12.10.4. Design requirements - General
1 The riser analysis is to take into account the following :
(1) Motion and offset of the unit/vessel,
(2) Interaction between riser and anchor chains,
(3) Interaction between risers
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(4) Permissible loads on sea floor equipment
2 Motions of the unit under first and second order wave, current and wind loads and their corresponding
static and dynamic effects are to be considered.
3 The response analysis of the riser under wave and current load is to accoun for dynamic and non-linear
response. Where it is not possible to account for these phenomena in the analysis, the uncertainties may
be resolved through model tests or conservative design assumptions.
4 Tension systems, if required, are to be designed with appropriate redundancy to ensure that the required
tension is always applied to the riser incase of failure of one tensioner.
5 Sufficient clearance is to be provided between the riser and adjacent structural members in order to
avoid interference during severe environmental conditions.
6 The riser is to be designed with sufficient flexibility and length to allow a deviation from desired position
caused by loss of one mooring line or a single failure in the position keeping system of the unit.
Disconnection of the riser must be possible whenever permissible limits are exceeded.
7 If drift off from the desired position would result in a hazardous situation e.g. damage of well head
provision is to be made for emergency release and disconnection of the risers .
8 Where emergency disconnection is provided it is to be possible to activate it from at least two separate
locations, e.g. production plant and bridge control stations.
12.10.5. Design requirements- Monitoring and control
1 Monitoring and control of riser system is to be perrormed from the production plant control station .
2 Control of unit/vessel movements as relevants for operation of riser system is to be performed from a
control station, normally at the bridge. Other posotions may be considered for special arrangement.
3 A communication system between the plant control station and bridge control station is to be provided.
4 The shut-off valve in the riser top and bottom connecting ends are to be in closed position before the
riser connectors can be disconnected. The closing time for shut-off of hydrocarbon flow is to be selected
so that no detrimental stresses are introduced due to hydraulic hamring.
5 For risers designed to withstand extreme motion with adequate margins, the alarm may be linked to the
positioning of the unit/vessel. A pre-alarm warning is to be given before these limits are excceded .
6 At least two independent and different release systems are to be provided for the disconnection of riser .
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12.11. Structures
12.11.1. General
1 The requirements in this part are applicable to the following :
(1) Support structure/skids for production facilities
(2) Flare structures.
(3) Conductor/riser support structures, where applicable.
(4) Derricks, where applicable
2 Structures are to be complied with the requirements of 12.1 and 12.2.
3 Structures are to be complied with material and corrosion requirements of 12.4.
4 Structures are to be complied with design loads requirements of 12.10.4.
12.11.2. Documentations for approval
1 Structure Design documents for the following is to be submited for approval:
(1) Structural drawings, with all relevant dimensions
(2) Details of padeyes
(3) Material specifications
2 The following design documentation is to be sumitted for information:
(1) Arrangement drawing of the structure shwing equipment loads and locations ;
(2) Design calculations and, where relevant, alternative documentation in support of applicable
design;
(3) Relevant limitations ( e.g. design ambient temperature, operational conditions, etc.);
(4) Relevant fabrication specifications including welding, heat treatment, type and extent of NDE,
testing, etc .
12.11.3. Design requirements
1 Skids and components that need to be lifted for maintenance/installation are to have properly designed
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lifting arrangements.
2 Structural parts e.g. substructure, skid base, tie-down system, are to be according to recognised
requirements by VR .
3 In designing the flare/burner boom structure due consideration is to be given to thermal loads during
flaring .
12.12. Electrical installations
12.12.1. General
1 Electrical installations are to be complied with the relevant requirements of electrical part .
12.12.2. Documentation
1 The following documents are as a minimum to be submitted for approval:
(1) Arrangement showing the location of main electrical components
(2) One line, wiring diagrams, cable schedules, equipment schedules, power distribution and main
cable layout .
12.13. Instrumentation and control systems
12.13.1. General
1 Scope :
(1) Process and production control.
(2) Process and production shut-down.
(3) Measurements indication of process variables
(4) Monitoring of oil production facilities
2 Instrumentation and control systems are to be in according to recognised standard by VR .
12.13.2. Documentation
1 The following documentation is, as a minimum, to be submitted for aproval:
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(1) Instrument list stating manufacture, type, function, set points etc.necessary to identify
components .
(2) System drawings (e.g. piping diagram) are to show where each component in the instrument list
is located.
(3) One line wiring diagrams, instrument loop diagrams, interface diagrams and cable schedules.
(4) Arrangement and layout drawings
(5) Test programs and verification plans, factory acceptance test programs, user and service
manuals .
12.14. Fire protection and extinction
12.14.1. General
1 The requirements regarding fire protection and extincition are in general to be as required in TCVN
5314:2001.
13. Helicopter deck
13.1. General
13.1.1. Application
1 Helideck equipment and arrangement are to be comply with requirements of relevant state agencies and
below requirements .
2 Load and strength requirements for helideck are mentioned in Hull Part TCVN 5310:2001
13.2. Arrangement
1 The helideck should be free of projections except that landing lights other essential projections may be
installed around the periphery of the deck provided they do not rise more than 0.15 m above the level of
the deck .
2 The helideck should have recessed tie-down points for securing a helicopter.
3 Periphery of the helideck shold be fitted with a safety net except where structural protection exxits. The
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net should be inclined upward and outwards from below the edge of the helideck to a horizontal distance
of 5m and should not rise more than 0.15 above the edge of the deck.
4 The helideck should have both a main and an emergency personnel access route located as far apart
from each other as practicable.
5 The helicopter deck should have drainage facilities to prevent the collection of liquids and prevent liquids
from speading to or falling on other parts of the unit having regard to the use of fire-fighting equipment
and possible spillage of fuel.
13.3. Equipment
1 A wind direction indicator should be located on the unit which, in so far as is practicable, indicates the
actual wind conditions over the helideck. Units on which night helicopter operations take place should
have provisions to illuminate the wind direction indicator.
2 The helideck should be marked as follows:
(1) The perimeter with a continuous white line with a width of 0.3 m;
(2) The unit's name should be provided on the helideck and be positioned on the obstacle side with
characters not less than 1.2 m in height and in a colour contrasting with the background;
(3) An aiming circle, concentric to the helideck, painted yellow with a inside diameter equal to 0.5
LD. The width of the line should be 1m .
(4) A white '' H '' centered on the landing area with the horizontal on the bisector of the obstacle-free
sector. The '' H '' should be 3 m high, 1.8 m wide with 0.4 m wide lines.
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