asme code uses presentation

EQUIPMENTS PRESSURE VESSELS STORAGE TANKS AGITATORS REACTORS PUMPS COMPRESSORS BLOWERS MATERIAL HANDLING EQUIPMENTS –CRANES,

CONVEYERS, FORK LIFTS ETC

MECHANICAL DESIGN AND CODE USAGE FOR DESIGN

• PRESSURE VESSELS: - A PRESSURE VESSEL IS A CLOSED CONTAINER

OF LIMITED LENGTH THE WALLS OF WHICH ARE SUBJECTED TO A NET DIFFERENTIAL PRESSURE EITHER INTERNAL OR EXTERNAL - EXAMPLES OF PRESSURE VESSELS ARE: HEAT EXCHANGERS, REBOILERS, GAS CYLINDERS, COLUMNS, SURFACE CONDENSERS, JACKETED VESSELS ETC.



• WHAT IS MECHANICAL DESIGN OF EQUIPMENTS IT IS THE DESIGN OF EQUIPMENTS TO WITHSTAND THE

EXPECTED LOADS, STRESSES, AND CORROSION DUE TO FLUIDS AND ENVIRONMENT SO THAT THE EQUIPMENT WILL PERFORM SATISFACTORILY ALL THROUGH ITS EXPECTED SERVICE LIFE AT A MINIMUM TOTAL COST(CAPITAL COST PLUS MAINTENANCE/REPAIR COST)

• HOW IS MECHANICAL DESIGN DONE IT IS DONE AS PER THE PROCEDURE GIVEN IN THE

APPLICABLE CODES AND STANDARDS. FOR SPECIAL DESIGN FOR WHICH NO GUIDANCE IS PROVIDED BY THE CODES AND STANDARDS, THE PROCEDURE MAY BE ARRIVED AT BY MUTUAL DISCUSSION BETWEEN THE BUYER AND THE VENDOR. APPROVAL FOR THE SAME MAY THEN BE OBTAINED FROM THE APPROPRIATE CODE COMMITTEE.

• THE MINIMUM INFORMATIONS NECESSARY FOR MECHANICAL DESIGN - PROCESS DESIGN DETAIL IN THE FORM OF A PROCESS DATA SHEET - MATERIAL OF CONSTRUCTION - DESIGN TEMPERATURE AND PRESSURE - EXTERNAL PRESSURE IF THE EQUIPMENT IS UNDER EXTERNAL PRESSURE - FLOW RATE TO SIZE THE NOZZLES - VESSEL DIMENSIONS AND ORIENTATION (horizontal,vertical) - TYPE OF VESSEL HEADS TO BE USED - WIND AND SIESMIC LOADS - SUPER IMPOSED LOADS, SUCH AS INSULATION, PIPING etc. - REACTIONS OF SUPPORTS - IMPACT LOAD INCLUDING RAPIDLY FLUCTUATING PRESSURE - THERMAL STRESSES - CODES TO BE FOLLOWED - COST OF MATERIALS Besides the above , other information such as radiographic

examination, gasket type , flange facing , etc. also influence the mechanical design


• Design Steps:– Design input in the form of process data sheet.– Material selection.– Design calculations– Design of weld joints – Non Destructive testing (NDT) requirements– Requirements for heat treatment– Requirements for hydro test– Performance test– Design output ( Design data sheet, Design calculations,

Drawing)– Reference


DESIGN INPUT

PROCESS DATA SHEETS

Thermal (Process) input details

Transfer Rate . Service Clean W/Sq m 0C

CONSTRUCTION OF ONE SHELL Sketch (Bundle/NozzleOrientation)

Shell Side

Tube Side

Design/Test Pressure kPag

/ /

Design Temp. Max/Min 0C

No. Passes per shell

Corrosion Allowance mm

ConnectorsSize &Rating

In

Out

Intermediate

Tube No OD mm : Thk (Min/Avg) mm : Length mm :Pitch mm 30 60 90 45

Tube Type Material

Shell ID O D mm

Shell Cover (Integ.) (Remov.)

Channel or Bonnet Channel Cover

Tube sheet - Stationary Tube sheet - floating

Floating Head Cover Impingement Protector

Baffles-Cross Type %Cut ( Diameter / Area) Spacing : c/c Inlet mm

Baffle – Long Seal Type

Supports – Tube U-Bend Type

Bypass Seal Arrangement Tube-Tube sheet Joint

Expansion joint Type

V2-Inlet Nozzle Bundle Entrance Bundle Exit

Gaskets-Shell Side Tube Side

Floating Head

Code Requirements TEMA Class

Weight/Shell Filled with Water Bundle Kg

Remarks

MATERIAL SELECTION

MATERIAL SELECTION CRITERIA• Selection of materials : • Pressure Vessels are constructed from

– plain carbon steels, low and high alloy steels, other alloys, clad plate and reinforced plastics

• What factors one must consider while selecting material?– Suitability of the material for fabrication (in particular

welding)– Compatibility of the material with the process environment. – Cost and Availability – Mechanical Strength– Should be approved by the relevant Code

• Refer to the pressure vessel design codes and standards– which includes lists of acceptable materials

• in accordance with the appropriate material standards

• Selection of materials : The materials for construction is either provided by clients or is decided by the designer.Carbon and low alloy steels, nickel-chromium alloy nickel-copper alloys, admiralty brass etc are among the most important materials used for fabrication of pressure vessels. The materials should confirm to ASME Section-II and or other applicable standards. Some commonly used materials are:

• SA-516 GR60,70 - Plate (carbon steel)• SA-106 – Seamless pipe (carbon steel)• SA-350-Lf2 – Forgings (low alloy)• SA-193 – Bolt(low alloy steel)• SA-333 – Plate (low alloy steel)• SA-204 – Plate (low alloy steel)


DESIGN CALCULATIONS

Fundamental Principles• Principal Stresses

– the maximum values of the normal stresses at the point, which act on planes on which shear stress is zero

• Theories of failure• Elastic stability• Membrane stresses in shells of revolution• Flat plates (are used as covers for manholes, as

blind flanges and for the ends of small diameter and low pressure vessels– Types

• Clamped edges• Simply supported

Principal Stresses 1 & 2

– Longitudinal and circumferential stresses

3 – Radial stress

• Thin-walled 3 is small and can be ignored 1 & 2 can be taken as constant over the wall thickness

• Thick-walled 3 is significant 1 will vary across the wall

Stress Analysis• In the stress analysis of pressure vessels

– Stress components are classified as primary or secondary

• Primary stresses

– are those that are necessary to satisfy the conditions of static equilibrium

• eg. Membrane stresses induced by the applied pressure (hoop stress in a cylindrical shell) and bending stresses due to wind loads

– if they exceed the yield point of the material• gross distortion and in the extreme situation, failure of the

vessel will occur

Stress Analysis• Secondary stresses

are those that arise from the constraint of adjacent parts of the vessels– theses are self-limiting– local yielding or slight distortion will satisfy the conditions causing the

stress and failure would not be expected to occur in one application of the loading

• eg. Thermal stress set up by the differential expansion of parts of the vessel, due to

– different temperatures or the use of different materials– The discontinuity that occurs between the head and the cylindrical section

of a vessel is a major source of secondary stress– Other sources

• are the constraints arising at flanges, supports and the change of section

– For th combination of primary plus secondary stress intensity the limit is 3Sm

• DESIGN PRESSURE Vessel designed

– must be able to withstand the maximum pressure to which it is likely to be subjected in any given operation

For vessels under internal pressure– design pressure is normally taken as the pressure at

which the relief device is set• this will normally be 5-10% above the normal

working pressure– when deciding the design pressure

• good to add hydrostatic pressure in the base of the column if significant

For vessels subjected external pressure– should be designed to resist the maximum differential

pressure that is likely to occur in service

• DESIGN TEMPERATURE What effect it has on materials??

– Strength of metals decreases with increasing temperature

– Maximum allowable stress will depend on the material temperature

– What needs to be done from design point of view?

• Design temperature at which the design stress is evaluated

– should be taken as the maximum working temperature of the material

• Do make some allowances for any uncertainty involved in predicting vessel wall temperature

• DESIGN STRESS What effect it has on materials??

• From design point of view, it is necessary to decide– a value for the maximum allowable stress (nominal design

strength) that can be accepted in the material of construction

• How it is done??– By applying suitable design stress factor (factor of safety) to

the maximum stress that the material could be expected to withstand without failure under standard test conditions

– Design stress factor allows for any uncertainty in the design methods, the loading, the quality of the materials and the workmanship (refer to BS 5500)

• Design stress is based on– yield stress or tensile strength of the material at the design

temperature

(for materials not subject to high temperatures)

• DESIGN LOADS• A structure must be designed

– to resist gross plastic deformation and collapse under all the conditions of loading

Classification of loads– Major loads– Subsidiary loads

• Major loads– design pressure including any static head of liquid– maximum weight of the vessel and contents under

operating conditions– Loads supported by, or reacting on, the vessel– maximum weight of the vessel and contents under

hydraulic test conditions

• DESIGN LOADS Subsidiary loads

– Local stresses caused by supports, internal structures and connecting pipes

– Shock loads caused by water hammer– Bending moments caused eccentricity of the centre of

working pressure relative to the neutral axis of the vessel– Stresses due to temperature differences

• subsequent effect arising due to the differences in the coefficient of expansion of materials

– Loads caused by fluctuations in temperature and pressure

A vessel will not be subject to all these loads at the same time

• Designer must determine -possible combinations of these loads likely to result in worst

• CODES AND STANDARDS

• WHAT IS A PRESSURE VESSEL CODE

IT IS A SET OF RULES AND RECOMMENDATIONS FOR FOR MATERIAL SELECTION, DESIGN, FABRICATION, TESTING AND INSPECTION THAT OUTLINES A DISCIPLINE WITHIN WHICH THE EQUIPMENT HAS TO BE MANUFACTURED. THIS SET OF RULES IS POPULARLY KNOWN AS “CODE”

AND IN FORMULATING THESE RULES , THE ENDEAVOR IS TO LAY DOWN THE MINIMUM STANDARDS TO ENSURE SAFE USE OF THE VESSEL WITHIN THE DESIGN CONDITIONS.

• United States of America

• ASME - American Society of Mechanical Engineers code – This code is divided into several sections which cover

• 1) unfired vessels and 2) boilers• 3) nuclear reactor vessels and • 4) vessels constructed of fibre-glass-reinforced plastics


• Some Popular Codes for Pressure Vessels– ASME- Boiler and Pressure vessel code

• ASME Section VIII Div1&2• ASME Section III Div1 for nuclear components• ASME Section II • ASME Section V

– Indian Standard code for Unfired Pressure Vessels• IS 2825

– British Code• BS5500

– German Code• AD Markblatter

– Italian Code• ANCC

– French Code• SNCT


• Standards for Storage Tanks– TEMA – API

• API-660

• API-620

• API-650

– DIN- Material standard(EN)– IS - Indian Standards


• Design of Pressure vessels as per ASME SectionVIIIdiv1– This is the most widely used code for design of

Pressure Vessels Some Reference Paragraphs of ASME Section VIII

Div.1 pertaining to the Design of various Parts of a Pressure vessel

– Calculation of shell thickness : – For internal pressure:- UG-16 – General design requirements UG-27 – Thickness of shells under internal pressure

in terms of inside radius– Appendix1-1 - Thickness of shells under internal pressure in terms of outside radius


– Appendix1-2 – For thick cylindrical shell(when the thickness of shell under internal design pressure exceeds one-half of the inside radius , or When the internal pressure P exceeds 0.385SE)

– Appendix L-1 – Application of rules for joint efficiency in shells and heads of vessels with welded joints

• For external pressure:– • UG-16 - General design requirements• UG-28 - Thickness of shells and tubes under external pressure in terms of inside radius .• Appendix – L-3 to L-5 - Examples


• Heads : Ellipsoidal head:– for internal pressure :– • UG-32 – Thickness of formed head and sections

with pressure on concave side.• Appendix1-4 – Formulas for design of formed

heads of proportions other those given in UG-32, in terms of inside and outside diameter.

for external pressure:– UG- 33 – Required thickness of formed heads with

pressure on convex Side. Appendix L-6 – Examples


• Hemispherical head:–for internal pressure:–

UG-32 – Already explained above• Appendix 1-3: Thick spherical shells (when the

thickness of the shell of a wholly spherical vessel or of a hemispherical head under internal design pressure exceeds 0.356R, or When the internal pressure P exceeds 0.665SE)

• Appendix1-4: Already explained above• for external pressure:– • UG-33 – Already explained above • Appendix L-6 - Already explained above


• Torispherical head:– • for internal pressure:– UG-32 ; Appendix 1-4 - See 2.1.1• for external pressure UG-33 ; Appendix L-6 – See 2.1.2• Conical head:– • for internal pressure:– UG-32 ; UG-36 – Rules for reducer sections under internal

pressure; FIG. UG-36 – Large head openings – Reverse-Curve and Conical Shell-Reducer Sections ; Appendix1-4 ; Appendix1-5 – Rules for conical reducer sections and conical heads under internal pressure

• for external pressure:– UG-33 ; Appendix L-6


• Toriconical head: – • for internal pressure:– UG-32 ; UG-36 ; Fig.UG-36 • for external pressure:– UG-33 ; Appendix L-6 • Flat head:– UG-34 – Minimum thickness of

unstayed flat heads and covers ; Fig UG-34 –

Acceptable types of unstayed flat heads and

covers ; UG-39 – Reinforcement required for openings in flat heads


• Nozzle neck thickness : i) As per rule UG-45(a), the minimum nozzle neck

thickness shall be calculated using the formula: PRn

tr n = ( ---------------- + corrosion allowance) , SE – 0.6P

where Rn = Internal radius of nozzle ii) As per applicable rules for UG-45(b) the

nozzle wall thickness tn shall be Smaller of shell/head thickness at the nozzle location and the minimum thickness of standard wall pipe(the wall thickness listed in table 2 of ANSI/ASME B36.10M less 12.5% under tolerance) plus the corrosion allowance

The minimum wall thickness of nozzles tn shall be the larger of i) and ii) above.

• Heat treatment : UG-85 , UW-10, UW-40, UCS-56 , Table UCS-56, UCS-79(d) ,UCS-85, UNF-56, UHA-32, UHA- 105, UCL-34

Pressure design : UG-19 , UG-21, Max allowable working pressure -UG-98• Temperature design : UG-19 , UG-20• Materials: UG-4 to UG-15 , UG-18 ,UG-77, • UCL-11, UW-15 ,Table-NF-1 to NF-5• Inspection : UG-90 to UG-97, U-1(j)• Joint efficiency : UW-12 , Table UW-12• Lethal service : UW-2(a), UCD-2, UCI-2• Loadings : UG-22• Low temperature : UG-84, UW-2(b), UCS-65, • UCS-66, UCS-67, UNF-65, UCL-27, Part ULT• Radiographic examination : UW-11, UW-51, • UCS-57, UNF-57, UHA33 , UCL-35, • No radiograph -UW-11(c)

Maximum allowable stress value : UG-23, UW-12(c), UCS-23,UNF-23, UHA-23, UCL-2

TEST : Hydrostatic – UG-99, UCL-99,UCL-

52, Appendix 3 Pneumatic – UG-100, UW-50 Proof – UG-101

Flanges a) Integral type flange – UG-44, Appendix 2 b) Flat face flange – Appendix Y , Fig Y-231) Manhole cover plates – UG-11 , UG-4632) Full face gasket – Appendix 1-6 , 2-1

DESIGN OF WELD JOINTS

Joint Efficiency Factors– As per ASME VIII, Div 1 and 2

• All major longitudinal and circumferential butt joints must be examined

– By full radiography with few exceptions

• VIII-1 in particular permits various levels of examination of these joints

• Why these joints are examined?– To detect the internal defects in the weld

• Examination varies– From full radiographic to visual

Joint Efficiency Factors

– The degree of examination influences

• The required thickness through the use of Joint Efficiency Factors (E)

• Sometimes these are called as Quality Factors or Weld Efficiencies

– Serve as stress multipliers applied to vessel components

» When some of the joints are not fully radio graphed

– These multipliers results in an increase in the factor of safety as well as the thickness of these components

Joint Efficiency Factors– In essence, VIII-1 vessels have variable factors of safety

• Depending on the degree of radiographic tests of main vessel joints

• For e.g. Joint Efficiency Factor in a fully radio graphed butt-welded joints in cylindrical shells have a E = 1.0

– E= 1 corresponds to a safety factor of 4 in the parent material

• Non-radio graphed longitudinal butt-welded joints have an E value of 0.7

– This reduction in E corresponds to factor of safety of 5.71 in the plates

• Highest factor of safety due to a non radio graphed joint results

– In a 43% increase in the required thickness over that of a fully radio graphed joint

Joint Efficiency Factors

– Factors used to design a component are

• Dependent on the type of examination performed at the welds of component.

• For eg. The Joint Efficiency Factor in a fully radiographed longitudinal seam of shell course E = 1.0

– Taking the factor E as 1.0 implies that the joint is equally as strong as the virgin plate

– However, this number may have to be reduced, depending on the degree of examination of the circumferential welds at either end of the longitudinal seam.

– Several handbooks show some typical components and their corresponding Joint Efficiency Factors.

Welded Joint Categories (ASME VIII-1)

Category A joints consist mainly of longitudinal joints as well as circumferential joints between hemispherical heads and shells.

B joints are the circumferential joints between various components

Attachment of flanges to shells or heads is a Category C joint

The attachment of nozzle necks to heads, shells and transition sections is categorised as a D joint

Welded Joint Categories (ASME VIII-1)

•Four joint categories in VIII-1 do not apply to the following items- jacket closure bars- tube sheet attachments- ring girders (or supports)

•Degree of examination of the welds attaching these components to the shell or head is not covered in VII-1.

•Most designers assign a value an E value of 1.0 when calculating the shell or head thickness at such junctions.

The categories refer to a location within a vessel rather than detail construction.

Eg. Category C weld which identifies the attachment of a flange to a shell, can be either fillet, corner, or butt welded as illustrated on the next slide.

– This is the additional thickness of metal added to allow for material lost by corrosion and erosion or scaling

• Allowance to be used will be based on the agreement between the customer and manufacturer

– Corrosion is a complex phenomenon• it is not possible to give specific rules for the estimation of the

corrosion allowance required for all situations

– How do deal with this matter?• The allowance should be based on experience with the material

of construction under similar service conditions to those for the proposed design

• For carbon and low-alloy steels 2 mm (where no severe corrosion is not anticipated); 4 mm for severe conditions

CORROSION ALLOWANCE

Basic Mechanical Parts Details• Vessel Heads – Hemispherical, Ellipsoidal, Torispherical• Shell• Stiffening – Beams, Channels, Angles• Vessel openings – Nozzles, stub ends• Reinforcement Pads – compensation• Support design – Saddles, Skirt, Legs• Flanges and ratings

– Weld-neck, Slip on, Blind, Threaded, Socket Welded, Lapped

• Internals – weirs, supports, plates, distributors etc.• Maintenance Platform – ladders, walkways• Lifting Attachments – Lugs, Anchors

COSTOF

PRESSUREVESSEL

PRESSURE VESSEL

Horizontal pressurised Coagulation Tank

Entries and Nozzles

InletStandard nozzle

SS nozzle & welded neck joint(Std ANSI 150)

Vessel supports

Saddle Supports Welded Legs

Fittings

Lifting Lugs Stiffening Rings

• Storage Tanks• Code- API-620, 650• Design• Design of shell• Design of roof• Floating Roof• Fixed Roof

• Bottom Plate• Wind Girder• Wind Analysis• Siesmic Analysis• Anchor Bolt, Anchor Chair


STORAGE TANK

Heat Exchanger Details

PLATE

TYPE

HEAT

EXCHANGER

• PUMPS Pump Type Construction Style Construction

Characteristics Dynamic Type Pumps Centrifugal Single stage overhung, Impeller cantilevered(horizontal) process type beyond bearing Two stage overhung Two impellers cantilevered beyond bearings Single-stage impeller Impeller between bearings; between bearings casing radially or axially split

Chemical Casting patterns designed with

thin sections for high-cost alloys

Slurry Designed with large flow passages.

Multistage, horizontal Nozzles located in bottom half of casing.

split casing


Pump Type Construction Style Construction Characteristics

Dynamic Type Pumps Centrifugal Single-stage, process Vertical orientation. (vertical) type Multistage Many stages with low head per stage Inline Inline installation, similar to a valve High speed Speeds to 380 rps, heads to 5800 ft (1770 m). Sump Casing immersed in sump for easy priming and installation. Multistage,deep well Long shafts. Axial Propeller Propeller-shaped impeller.

Turbine Regenerative Fluted impeller. Flow path resembles screw around periphery.

Pump Type Construction Style Construction Characteristics

Positive Displacement Type Pumps

Reciprocating Piston, plunger Slow speeds. Metering Consists of small units with precision flow control system.

Diaphragm No stuffing box.

Rotary Screw 1, 2, or 3 screw rotors. Gear Intermeshing gear wheels.

• Standards• API 610 , ISO13709– Centrifugal Pump• API 674 – Positive displacement

pump(reciprocating)• API 675 – Positive displacement

pump(Control volume)• API 676 – Rotary pump• API 682 – Mechanical seal• API 670 – Vibration , Axial Position and

Bearing temperature monitoring systems


• Salient Features:• Flow• Head• Specific Speed• NPSH available• NPSH required• Pressure drop• Pump characteristics• Seals• Casings• Motor• BEP• Noise Control• Water Hammer



• It is advisable to use an eccentric reducer at the suction of a pump.

-An eccentric reducer should always be used when reducing into any pump inlet where vapour might be encountered in the pump age. The eccentric reducer prevents an accumulation of vapour that could interfere with pumping action.

-There are two types of eccentric reducer used in the suction line of a centrifugal pumps.1.FST:flat side at top.2.FSB:flat side at bottom.

-Always use an eccentric reducer at the pump suction when a pipe size transition is required. Put the flat on top when the fluid is coming from below or straight and the flat on the bottom when the fluid is coming from the top. This will avoid an air pocket at the pump suction and allow air to be evacuated.

-Concentric reducers will trap air. Never use it on suction side.