23376491-05-ag-piping.pdf

LARSEN & TOUBRO LIMITEDPAGE NO.- 1 OF 19

DATE:-01.11.2007MSQ (EPCC-1) UPGADATION PROJECT REV.NO.- 0

PROCEDURE FOR AG PIPING FABRICATION & ERECTION

PROCEDURE NO.-LT/MSQ/P/AG/005

CONTENTS

1.0 PURPOSE

2.0 SCOPE

3.1 STANDARD SPECIFICATIONS &

NORMAL PRACTICE

3.2 DEVIATION

4.0 FABRICATION

5.0 ERECTION

6.0 PERFORMANCE OF WELDS & HEAT TREATMENT

7.0 WELDING CONSUMBALES

8.0 SHIELDING & PURGING GAS

9.0 WELDING

10.0 VISUAL INSPECTION

11.0 REPAIRS OR REMOVAL OF DEFECT

12.0 INSPECTION AND TESTING

13.0 SAFETY

14.0 DOCUMENTATION

APPROVED BY L & T REVIEWED / APPROVED BY JACOBS





1.0 PURPOSE:

The purpose of this procedure is intended to cover the general requirements

for the execution of piping, pre-fabrication, assembly and erection of the

above ground pipe work at site.

2.0 SCOPE:

This procedure covers execution, inspection, testing, and method of record

keeping for fabrication & erection of all above ground piping systems as per

standard specification and normal practice.

3.1 CONTROLLING SPECIFICATIONS:

Approved PMCs standards and specifications Process and instrument diagram.

Piping materials specification

Pipe supports standards

Line list.

Job specification of non-destructive testing of piping as per Sec V &

standard spec

Welding specification for Fabrication of piping (3177-LSS-104)

Standard specification for Inspection, flushing piping system (3177-

LSS-106)

Specification for inspection, flushing & testing of piping

systems(3177-LSS-106)

ASME B 31.3 Process Piping

AME B 31.1 Power Piping






ASME Sec VIII code for Unfired Pressure Vessel

IBR Regulations

IS : 823 code for Procedure for Manual Metal Are Welding of Mild

Steel ( For Structural Steel)

Job specification for colour coding

3.2 DEVIATIONS

Where a deviation from the Basis of work and approved job procedure

described above is required or where the basis of work does not cover a

particular situation, the matter shall be brought to the notice of owner / PMC

and work carried out only after obtaining written approval from him in each

cases.

4.0 FABRICATION:

4.1 PIPING MATERIAL

Pipe, pipefitting, flanges, valves, gaskets, studs bolts etc. used in a given

piping system shall be strictly as per the Piping Material Specification for

the Pipe Class specified for that system.

For the purpose of common understanding the construction job procedure, to

be submitted by L&T , shall include proposal for

-Maximizing prefabrication, inspection and testing at fabrication shop with

minimum field joints

-Positive material identification, handling, storage & preservation.

4.2 DIMENSIONAL TOLERANCES

Dimensional tolerances for piping fabrication shall be as per standard no.

3177-LSD-1017. To take care of minor variations in the actual location (at

site) of equipments, inserts, structures etc., field welds shall be provided

during piping fabrication and an extra length 100 mm & above the dimensions






indicated in the drawing may be left on one side of the pipe at each field

welds.

4.3 IBR PIPING

The complete piping work shall be carried out as per Approved for

Construction drawings and sketches. For piping falling under IBR, necessary

approval of boiler inspector on the drawings shall be obtained prior to start of

fabrication and all works shall be carried out as per the requirement of IBR.

IBR approval to be taken on as built IBR Drg.

Field welding of weld joint nearest the pumps shall be done only after

pump and connected piping have been truly aligned.

4.4 EDGE PREPARATION

4.4.1 The edges to be welded shall be prepared to meet the joint design requirements by

any of the following method recommended:

a) Carbon Steel (C.S.)

Gas cutting, Machining or grinding methods shall be used. After gas

cutting, oxides shall be smoothened / removed by chipping and grinding.

b) Low Alloy Steel (Containing up to 5% Cr)

Gas cutting, Machining or grinding methods shall be used. After gas

cutting, machining or grinding shall be carried out on the cut surface.

c) High Alloy Steel (>5% Cr) & Stainless Steels (S.S), Nickel Alloys

Plasma cutting, machining or grinding methods shall be used. After plasma

cutting, cut surface shall be machined or ground smooth.

4.4.2 SPACING

)a For pipe wall thickness 5 mm and above, the ends to be welded shall secure






in position with the aid of couplers, yokes and C clamps, to maintain

perfect alignment. Yokes shall be detached after the completion of weld,

without causing any surface irregularity.

)b Tacks should be equally spaced. Minimum number of tacks shall be:

3 tacks - for 21/2 and smaller diameter pipes

4 tacks - for 3 to 12 diameter pipes

6 tacks - for 14 and larger diameter pipes

4.4.3 All piping spools shall be marked / stamped for proper identification like as line no.,

joints no., welder no., spool no.

4.4.4 CLEANING

)a The ends to be welded shall be properly cleaned to remove paint, oil,

grease, rust, oxides, sand, earth and other foreign matter. The ends shall be

completely dry before the welding.

)b On completion of each run, craters, welding irregularities, slag etc., shall be

removed by the grinding and chiselling. Separate grinding wheels and wire

brushes should be used for Carbon steels & stainless Steel

4.5 PIPE JOINTS

The piping class of each line specifies the type of pipe joints to be adopted. In

general, joining of line 2 and above in process and utility piping shall be

accomplished by butt weld. Joining of lines 11/2 and below shall be by socket

welding / butt welding / thread joints as specified in Piping Material

Specification.

Flange joints shall be used at connections to vessels, equipments, valves and

where required ease of erection and maintenance as indicated in drawings.

4.6 BUTT WELDED AND SOCKET WELDED PIPING

Edge preparation, alignment and fit up of piece to be welded, welding, pre

heating, post heating and heat treatment shall be as described in the welding






specification (3177-LSS-104) and NDT specification (18-3177-000-L-02-

0703-A4).

4.7 SCREWED PIPING

In general, galvanized piping shall have threads as per IS: 554 or ANSI B 2.1

NPT as required matching threads on fittings, valves etc. all other piping shall

have threads as per ANSI B 2.1, tapered unless specified otherwise.

4.8 FLANGE CONNETIONS

All range facings shall be true and perpendicular to the axis of pipe to which

they are attached. Flanged bolthholes shall straddle the normal centre lines

unless different orientation is shown in drawing.

4.9 BRANCH CONNECTIONS

Branch connections shall be as indicated in the Piping Material Specifications

for end preparation, alignment; spacing, fit up and welding of branch

connections refer welding specifications. Templates shall be used wherever

required to ensure accurate cutting and proper fit up.

Reinforcement pads shall be provided wherever indicated in drawings /

specifications / standard and codes etc.

4.10 BENDING

Bending of pipe shall be done as per ASME B31.3. Cold bend for lines 1

and below, with a bend radius of 5 times the nominal diameter shall be used

as required in place of elbows wherever allowed by piping specifications.

Bending of pipes 2 and above may be required in some cases like that for

headers, reactors etc.The competed bend shall have a smooth surface, free

from cracks, buckles, wrinkles, bulges, flat spot and other serious defect.

4.11 FORGING AND FORMING

Forging and forming of small bore fittings like reducing for piping 1 and






below, shall be as per ASME B 31.3 / ASME B 31.1.

4.12 MITRE BENDS AND FABRICATED REDUCERS

Mitre bends and fabricated reducers shall be governed by the piping material

specifications. Generally all 90 mitres shall be 4-piece 3-weld types and 45

mitres shall be 3-piece 2-weld types unless otherwise specified. Reducers

shall be fabricated as per directions of the PMC.The radiographic

requirements shall be as per Material Specifications for process and utility

systems and NDT specification for steam piping under IBR, radiographic

requirement of IBR shall complied with.

4.13 CUTTING AND TRIMMING OF STANDARD FITTINGS & PIPES

Component likes pipes, elbows, couplings, half couplings etc shall be trimmed

/ edge prepared wherever required to meet fabrication and erection

requirements, as per drawings and instructions of owner / PMC.

4.14 GALVANISED PIPING

Galvanised carbon steel piping shall be completely cold worked, so as not to

damage galvanised surface. This piping involves only threaded joints and

additional external threading on pipes may be required to be done as per

requirement. However threading after galvanising should be minimum.

4.15 JACKETED PIPING

The jacking shall be done in accordance with approved PMCs or licensors

approved specification as suggested in Piping Material Specification. Position

of jump over and nozzles on the Jacket pipes, fittings etc. shall be marked

according to pipe disposition and those shall be prefabricated to avoid

damaging of inner pipe and obstruction of Jacket space.

4.16 SHOP FABRICATION / PREFABRICATION

The purpose of Shop fabrication or prefabrication is to minimise work during






erection to the extent possible. Piping spool after fabrication shall be stacked

with proper identification marks, so as to facilitate their withdrawal at any

time erection. During the period all flange (gasket contact faces) and threads

shall be adequately fabricated by coating with removable rust preventive. Care

shall also be taken to avoid any physical damage to flange faces and threads.

4.17 ALIGNMENT

The pipes to be jointed by welding shall be aligned correctly with existing

tolerances on diameters, wall thickness and out of roundness and weld gaps.

The same alignment shall be preserved during welding.

4.18 LAYOUT, CUTTING & FITTING UP

)c For laying out headers, tees, laterals and other irregular details, cutting

template shall be used to ensure accurate cutting and proper fit up.

)d All cutting shall follow the outline of the templates.

)e Machine cut bevels to form the welding groove are preferred in carbon

steel pipe. However, smooth, clean, slag free flame cut bevels is

acceptable.

)f Tack welds with full penetration shall be used and shall become the part of

the finished weld and shall be carried out by qualified welders only.

)g Defective welds or tack welds with lack of penetration are not acceptable

and shall be chipped / ground out.

)h No temporary weld attachment shall be with extended clamps / attachment.

4.19 CLEANNING OF PIPING

)a On completion of fabrication, all pipes and fittings shall be cleaned inside

and outside by suitable means (Mechanical, cleaning tool, wire brush, etc.)

before erection to ensure that assembly is free from all loosed foreign

material such as scale, sand, weld, spatter particle, cutting chips etc.

)b All field fabricated piping shall also be cleaned at the competition of the






fabrication. All burrs, welding circles and weld spatters shall be removed

by any suitable means (Mechanical tools, wire, brush, etc.)

)c Both shop and field fabricated piping shall be blown out with compressed

air at the terminated specification of cleannning and capped.

)d Cleaning requirements for special services, if any, shall be as specified in

the piping material specifications.

)e S.S. jacketed piping requiring picking shall be pickled to remove oxidation

and discolouring due to welding.

5.0 ERECTION

5.1 PIPING ROUTING

Pipe to pipe, pipe to structure / equipments distances / clearance as shown the

drawings shall be strictly followed as these clearance may be required for the

expansion of piping / equipment.

5.2 COLD PULL

Wherever cold pull is specified, maintain the necessary gap, as indicated in

the drawing. Stress reliving shall be performed before removing the gadgets

for old pulling.

5.3 SLOPES

Slopes specified for various lines in the drawings / P&ID shall be maintained

during erection of piping spools.

5.4 EXPANSION JOINTS / BELLOWS

5.4.1 Installation of Expansion joints / Bellows shall be installed in accordance with the

specification and installation drawings.

5.4.2 Each expansion joints / bellows shall be blown free of dust / foreign matter with

compressed air or cleaned with a piece of cloth.

5.4.3 a) For handling and installation of expansion joints, great care shall be taken while

aligning. An expansion joints shall never be slinged from bellows






corrugations / external shrouds, tie-rods, and angles.

b) An expansion joints / bellows shall preferably be slinged from the end pipes /

flanges or on the middle pipe.

5.4.4 a) All expansion joint shall be procured at Installation length, maintained by means

of shipping rods, angles welded to the flanges or weld ends or by wooden or

metallic stops.

b) Expansion joints stop blocks shall be carefully removed after hydrostatic

testing. Angles welded to the flanges or weld ends shall be trimmed by saw as

per manufactures instructions and the flanges or weld ends shall be ground

smooth.

5.4.5 a) The pipe end sin which the expansions joints is to be installed shall be perfectly

aligned or shall have specified lateral deflection as noted on the relevant

drawings.

b) The pipes ends / flanges shall be spaced at a distance specified in the

drawings.

5.4.6 The expansion joints shall be placed between the mating pipe ends / flanges and shall

be tack welded / bolted. The mating pipes shall again be checked for correct

alignment.

5.4.7 Butt-welding shall be carried out at each end of the expansion joint. For flanged

expansion joints the mating flanges shall be bolted.

5.4.8 After the expansion joint is installed and shall ensure that the mating pipes and

expansion joints are in correct alignment and that the pipes are well supported

and guided.

5.4.9 The expansion joint shall not have any lateral deflection.

5.4.10 Precautions

1) For carrying out welding, earthing lead shall not be attached with the

expansion joint.






2) The expansion bellow shall be protected from arc welds spot and

welding spatter.

3) Hydrostatic testing of the system having expansion joints shall be

performed with shipping lugs in position. These lugs shall be removed

after testing and certification is over.

5.5 FLANGE CONNECTIONS

While fitting up mating flanges, care shall be exercised to properly align he

pipes and to check the flanges for trueness, so that faces of the flanges can be

pulled together, without inducing any stresses in the pipes and equipment

nozzles. Extra care shall be taken for flange connections to pumps, turbines,

compressors, cold boxes, air coolers etc. the flange connections to these

equipments shall be checked for misalignment, excessive gap etc. after the

final alignment of the equipment is over. The welding of flange shall be done

only after proper alignment of terminal equipment.

Temporary protective covers shall be retained on all flange connections of

pumps, turbines, compressors and other similar equipments, until the piping is

finally connected, so as to avoid any foreign material from entering these

equipments.

The assembly of a flange joint shall be done in such a way that the gasket

between these flanges is uniformly compressed. To achieve this bolt shall be

tightened in a proper sequence.

5.6 VENTS AND DRAINS

High point vents and low point shall be provided as shown in the drawings.

The details of vents and drains shall be as per piping material specifications /

jobs standards.

5.7 VALVES

Valves shall be installed with spindle / actuator orientation as shown in the






layout drawings. Care shall be exercised to ensure that globe valves, check

valves, and other unidirectional valves are installed with the Flow direction

arrow on the valve body pointing in the correct direction. If the direction of

the arrow is not marked on such valves this shall be done in presence of

Engineer-In-Charge.

5.8 INSTRUMENTS

Installation of in-line instruments such as restriction orifices, control valves,

safety valves, relief valves, rotameter, orifice flange assembly, venturi meters,

flow meters etc. shall form a part of piping erection work.

Fabrication and erection of piping up to first block valve / nozzle / flange for

installation of offline instruments for measurement of level, pressure,

temperature, flow, etc. shall also form part of piping construction work. The

limits of piping and instrumentation work will be shown in drawing / standard

/ specifications. Orientations / locations of take-offs for temperature, pressure,

flow level connections etc. shown in drawing shall be maintained

Flushing and testing of piping systems which include instruments mentioned

above and the precautions to be taken are covered in flushing, testing, and

inspection of piping (3177-LSS-106). Care shall be exercised and adequate

precautions taken to avoid damage and entry of foreign matter into

instruments during transportation, installation, testing etc.

5.9 LINE MOUNTED EQUIPMENTS / ITEMS

Installation of line mounted items like filters, strainers, steam traps, air traps,

desuperheaters, ejector, sample coolers, mixers, flame arrestors, sight glasses

etc. including their supporting arrangement their supporting arrangements

shall form part of piping erection work.

5.10 BOLTS AND NUTS

M/s L & T shall apply molycoat grease mixed with graphite powder (unless






otherwise specified in piping classes) all bolts and nuts during storage, after

erection and wherever flange connections are broken and made-up for any

purpose whatsoever. M/s L & T shall supply he grease and graphite powder

without price implication to owner. However wherever bolt tensioning is

called for the lubricants used shall be as per the bolt tensioning specification

duly reviewed by PMC.

5.11 PIPE SUPPORTS

Pipe supports are designed and located to effectively sustain the weight and

thermal effects of he piping system and to prevent its vibrations. Location and

design of pipes supports will be shown in drawings for lines of all sizes. All

supports provided should be as per the location and type considered during the

approval of stress analysis reports. If any change of route is to be done, stress

analysis to be done before carrying out site changes. This is applicable for the

pipelines identified for stress analysis, for rest of the pipelines; supports

should be as per drawing.

No pipe shoe / cradle shall be offset unless specifically shown in the

drawings.

Hanger rods shall be installed inclined in a direction opposite to the direction

in which the pipe moves during expansion.

Preset rods shall be installed inclined in a direction opposite to the direction in

which the pipe moves during expansion.

Preset lock pins of all spring supports shall be removed only after hydrostatic

testing and insulation is over. The following points shall be checked after

installation by designer & consultant with the PMC and necessary

confirmation in writing shall be given certifying that:

All restrains have been installed correctly.

Clearances have been maintained as per support drawings






Insulation does not restrict thermal expansion

All temporary tack welds provided during have been fully removed.

All welded supports have been fully welded.

Where practicable and except when otherwise shown on the drawings, valve

stems shall be installed in a vertical direction and shall not be installed with

below the horizontal axis.

6.0 PERFORMANCE OF WELDS & HEAT TREATMENT

6.1 PREHEATING

a) No welding shall be performed by without preheating the joint 100C when

the ambient temperature is below 100C.

b) Preheat will be applied with minimum as specified in welding chart.

c) Preheating shall be performed using resistance or induction methods.

Preheating by gas burners, utilising oxy-acetylene or oxy-propane gas

mixture.

d) Preheating shall extend uniformly to at least three times the thickness of the

joint, but not less than 50 mm, on both sides of weld.

e) Preheating temperature shall be maintained over the whole length of joint

during welding.

6.2 POST WELD HEAT TREATMENT

a) Post weld heat treatment, wherever required for joints between pipes, pipes

and fittings, pipe body and supports shall be carried out as per welding

specification chart.

b) Post weld heat treatment shall be done in a furnace or by using electric

resistance or induction heating equipment.

All welding consumable such as electrodes, filler wires, flux and gas shall

be stored, handled and use in accordance with the manufacturers

instructions.






7.0 WELDING CONSUMBALES

7.1 The welding electrodes and filler wires used shall be as per approved WPS/ welding

specification chart and B.T.C. of electrode / filler wire shall be submitted to

Jacobs for approval.

7.2 All electrodes shall purchased in sealed containers and stored properly to prevent

deterioration. The electrode removed from containers shall be kept in holding

ovens at temperatures recommended by the electrode manufacture. The

electrode shall handled with care to avoid any damage to the flux covering.

7.3 All low hydrogen type of electrodes shall be rebaked at 3500C for 1 hours minimum and

stored in ovens kept at 80-1000C before use.

7.4 The electrodes, filler wires and flux used shall be free from rust oil, grease, earth and

other foreign matter, which affect the quality of welding.

7.5 Tungsten electrodes used shall conform to ASME Sec. II C SFA 5.12 specification.

7.6 Only Owner/ PMC approved brands of electrodes shall be used.

8.0 SHIELDING & PURGING GAS:

8.1 Argon gas with a purity level of 99.995% shall be used for purging.

8.2 The purging shall be maintained during the root pass and for the first filling pass to

minimise oxidation on the inner side of the pipe, unless otherwise specified in

Welding Specification Chart.

8.3 Initial purging shall be maintained for sufficient period of time so that at least 4-5 times

the volume between the dams is displaced in order to completely remove the

entrapped air.

8.4 Dams, used for conserving inert gas during purging, shall be removed after competition

of the welding, and shall be accounted for. Wherever, removal of dams is no

possible after welding, use of watersoluble dams should be made.

9.0 WELDING

a) Qualified welders as per approved WPS, welding specification chart and






approved drgs, shall carry out all welding.

b) Welding technique / process followed during welding shall be as per

approved WPS.

10.0 VISUAL INSPECTION

Inspection of all welds shall carried out as per ANSI B 31.3 and specification.

Finished welds shall be visually inspected for parallel and axial misalignment

of the work, crack. Inadequate penetration, unrepaired burn-through,

dimensions, and other surface defects, and it shall present a neat workman like

appearance. Under cutting adjacent to the final bead on the outside of the pipe

shall not exceed 0.8 mm in depth of 121/2% of the pipe wall thickness,

whichever us smaller and the cumulative length shall not be more than 50 mm

in any continuous 300 mm length or weld.

11.0 REPAIRS OR REMOVAL OF DEFECT

Defects, which are not within the acceptable limits, shall be removed from the

joint completely by chipping or grinding.

When the whole joint us found unacceptable, the weld and the ends of the

joints shall be restored according to relevant under fabrication.

No repair shall be carried out without prior authorisation of the PMC.

12.0 INSPECTION AND TESTING

12.1.1 All NDT works like as RT, DPT, and MPT, UT etc.shall be

carried out by experienced/qualified personnel as per approved job

procedures.

12.1.2 The application of above NDT for welding shall be as per

inspection class mentioned in NDT specification no. 18-3177-000-l-02-0703-

A4 & approved L&T doc. No.-L&T/MSQ/NDT.SPEC/001

12.1.3 Welding repairs are unavoidable made on PWHT, and then

complete PWHT cycle must be repeated with a second heat chart.






12.1.4 After PWHT the hardness value on the weld, HAZ and parent

metal shall be measured both using Poldi type or portable hardness instrument

wherever PWHT is applicable and hardness requirement shall be as per

welding specification chart.

12.1.5 The field Hydro-test pressure shall not be less than the greatest

of the following:

11/2 times the maximum sustained operating pressure

11/2 times the maximum pipeline static pressure

Sum of the maximum sustained pressure or the maximum pipeline static

pressure and the maximum calculated surge pressure.

- the field test pressure shall wherever possible be not less than two

thirds of the works test pressure and shall be applied and maintained for at

least four hours.

- Where he field test pressure is less than two-thirds the works test

pressure, the period of test shall be increased to at least 24 hours. The test

pressure shall be gradually raised at the rate of nearly 1.0 kg/cm2/minute.

12.1.6 All above ground pipes shall be tested for leakages to a

minimum hydrostatic test pressure of 10 kg/cm2gauge or as per specification.

12.1.7 The joints of the pipe connecting the testing sections shall be

100% radiographed.

12.1.8 TEST MEDIUM

Construction water shall be generally be used as the testing medium for the

hydrostatic testing of Piping system.

12.1.9 CLEANING / FLUSHING

All system shall be cleaned and flushed free of all dirt, debris or loose foreign

material after testing.

12.1.10 TEMPORARY BLINDS






Open ends of piping systems such as at pumps or wherever equipment has

been removed or disconnected prior to hydrostatic testing, or at termination

point of piping branch connections shall be blinded off by temporary blind

flange made out of minimum 10 mm hick MS plate.

12.1.11 VENTING

All piping systems and equipments shall be properly vented to remove air

from system during filling or as shown in the drawings.

12.1.12 PRESSURISING

Pressure shall be applied by means of suitable test pump, which shall not be

connected to the system until ready to test. A pressure gauge duly calibrated

shall be provided at the pump discharge for guidance in bringing the system

upto pressure. An authorised operator shall attend the pump constantly during

the test. The pump shall be disconnected after the pressure test is completed.

The test pressure is to be maintained for sufficient time to permit compete

inspection of the system under test but in no case shall the time be less than

ten minutes.

12.1.13 TEST GAUGES

Test gauge shall be installed as close as possible to the lowest point in the

system being tested. Prior to installation, the test gauge shall be checked

against standard gauge or calibrated with the aid of a dead weight tester.

12.1.14 DRAINING

All lines and equipments shall be completely drained after the hydrostatic test

of a system has been completed. High point vents shall be open prevent

excessive vacuum and permit complete draining.

13.0 SAFETY

13.1 All safe measures shall be observed in welding and cutting and required PPE shall be

enforced to the job performer.






13.2 All Safety & regulatory practices during performance of Radiography work shall be

observed particularly personal protection from radiation either by distance, or

time or, shielding, or a suitable combination of all three.

13.3 During Radiography, also Radiation warning signal either visual or sound or both

shall be put to keep the unconnected people away to avoid any exposure.

13.4 During Hydrostatic or Pneumatic testing, people shall be warned by deploying danger

signal and cordoning the area to avoid any accidental injury.

14.0 DOCUMENTATION

All documents shall be prepared and maintained as per approved ITP No. : -

LT/MSQ/ITP/PIPE/AG/002 Rev. 0 and applicable approved formats as per

ITP.


3.1 CONTROLLING SPECIFICATIONS:

23376491-05-ag-piping.pdf

Documents

fabrication of piping

piping material specification

execution of piping

piping material pipe

given piping system

ground piping systems

approved job procedure

fabrication shop