3dg-p45-00001(pipe stress analysis 190)

ENGINEERING DESIGN GUIDE

PETROCHEMICAL PLANT DESIGN

PIP~G STRESS ANALYSIS

Prepared by

Michael D Vasse

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This document and the d=ign it avers are the property of BECHTEL.They are merely loaned and on the borrowers express agreement thatthey will not be reproduced, copied, loaned, exhibited, or used exceptin the limited way and private use permitted by any written mnsentgivm by the lender to the borrower.

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TABLE OF CONT-

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

PURPOSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4m**

SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4

ASSOCIATED DESIGN GUIDES AND FORMS . . . . . . . . . . . . . . . . . . 43.1 Design Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,.43.2 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4 F:.DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5 .-

GENERAL PHILOSOPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

RESPONSIBILITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

GENERAL WORKING METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . 7r

SPECIFIC WORKING ~~ODS . . . . . . . . . . . . . . . . . . . . . . . . . . 108.18.28.38.48.58.68.78.88.98.108.11

Thermal Loads and StressComidemtiom . . . . . . . . . . . . . . . . . . 10Sustained hadsand StressComidemtiom . . . . . . . . . . . . . . . . . . 12Dynamic andOtherhadsand Stress Considerations . . . . . . . . . . . . 13had Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Rotating Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...16Air Cooled Heat Exchangers(Air Fans) . . . . . . . . . . . . . . . . . . . . 17 r-Shelland Tube Exchangers . . . . . . . . . . . . . . . . . . . . . . . . . ...18 k.FlredHeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...18Nozzle Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...18Buried Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...19Cryogenic Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...21

RECOmmG AND TRANS~TTAL OF S=S ENGINEERINGDATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...22 -L9.1 Piping CriticalUlne Lii . . . . . . . . . . . . . . . . . . . . . . . . . . . ...229.2 Stress Sketches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..229.3 Calculation Index . . . . . . . . . . . . . . . . . . . . . . . ..$. .$.. . ...239.4 Expansion Joint Data Sheets . . . . . . . . . . . . . . . . . . . . . . . . . ...239.5 Spring Data Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...23

CHECKING STRESS CALCULATIONS. . . . . . . . . . . . . . . . . . . . ...23r.,L

10.l Preliinary Review... . . . . . . . . . . . . . . . . . . . . . . . . . . . ...23 ,.1-10.2 Criticallines in Dossiers . . . . . . . . . . . . . . . . . . . . . . . . . . . ...2410.3 Calculations relatingto the Groups in10.2 . . . . . . . . . . . . . . . . . . 25

ENGINEERING DESIGN GUIDE EDGP5301-L Rev. O Page 2 OF 25

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APPENDIX A BASIC DATA REQUIRED AT STARTOF PROJECT AND DEFAULT VALUESFOR INITIAL CALCULATIONS.

APPENDIX B A SIMPLIFIED METHOD FOR PIPINGD~IGNERS TO ASS= PIPING FLEXIBILITY.

APPENDIX C PIPING Sm!j SKETCH (CAD DRAFTED)

APPENDIX D S-S AND SUPPORTS CRITICAL LINE LIST

APPENDIX E STRESS CALCULATION INDEX

ENGINEERING DMIGN GUIDE EDGP5301-L Rev. O

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1.0 PURPOSE

The purpose of this Design Guide is to provide uniform guidelines and information foruse by Piping Stress Engineers to ensure a cohesive approach to the piping stressanalysis of petrochemical plants. Ii

2.0 SCOPE

This Design Guide does not cover all the technical aspects of the piping stress analysis.It is a general one covering most circumstances, but may be deviated from, to suitspecific job or local requirement with the expressti agreement of Engineering IManagement. ~

3.0 ASSOCIATED DESIGN GUIDES AND FORMS

3.1 Design Guides

EDG-P5401-L (Rev. O) Pipe Suppofis.

EDG-P5302-L (Rev. O) Piping Stress Critid Line List

EDG-(tba)-L (Rev. O) Design Guide for Equipment and Nozzle hadings.

3.2 Forms

P & CE L-5421 FEB 78 Bellows Expansion Joints Data Sheet

GR(A4) 2356 7/90 Bechtel StandardCalculation Sheet.

Appendix C Piping Stress Sketch. (CAD Drafted)

Appendix D Stress and Supports Critical Line List

Appendix E Stress Calculation Index


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4.0 DEFINITION

Critical Line Lti (EDGP5302-L)

In this Design Guide, the Cntid Line List refers to the Piping Stress Critical Line List.

5.0 GENERAL PHILOSOPHY

The basic responsibility of the Stress Engineer is to ensure that piping is routed andsupported so that no damage occurs to either the pipe or associated equipment due tothe effects of thermal expansion or contraction, or loads resulting from weight,pressure, wind earthquake, pulsation, shock, foundation settlement, etc.

The purpose of this Design Guide is to ensure the sound and uniform approach to thereview of the mechanical safety of the piping and related systems and to be able toproduce evidence that this has been done satisfactorily. It is also to ensure that evidenceof compliance with applicable codes is produ~.

To aid in this endeavour, the following poinfi should be followed:-

a.

b.

c.

d.

e.

f.

g

Only enter essential results / data on stress sketches.

Identify worst operation cases before running wmputer checks, then run thesecases only.

If a Worst case is not immediately obvious, run all the nwssary cases but aftera visual review of the outpufi, choose only the extreme cases for detailed reviewand results transposition with a note saying that these are the worst load/stressconditions and the other conditions that were reviewed to come to this wnclusion.

Review all configurations using visual/approximate methods prior to computercalculations so the wnfigurations with obvious problems may be discussed withthe piping designers prior to setting up the mmputer run.

Inform piping design of any wnfigurations that have been passed but have loadsor stresses that are close to the allowable values, and freeze the arrangement.

Keep the designs realistic: Minimise the use of super special supports requiringhigh tolerances or complex designs. If these are required it tends to indicate thata re-route is necessary.

Wherever possible, avoid the use of flexible connectors (bellows, etc). The useof springs and snubbers should also be kept to a minimum.

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ENGINEERING DWIGN GUIDE EDGP5301-L Rev. O Page 5 OF 25

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6.0

6.1

6.1.1

6.1.2

6.1.3

6.1.4

6.1.5

6.1.6

6.1.7

6.1.8

6.1.9

6.1.10

h. The use of cold spring should be kept to a minimum and should not be usedaround any rotating equipment.

i. Where max. operating or design temperatures appear high by mmparison with kother available data, discuss it with the systems/mechaniM engineer prior tocalculation of the system, highlighting the impact on the piping/equipment if thetemperature proves inaccurate.

RESPONSIBILIT~

The Stress Engineer shall:

Establish the Critical Line List. Continuously update the List to record the progress ofwork on all critical lines.

Establish the allowable imposed nozzle loads onto the equipment by consultation withthe mechanical/equipment group at the outset of a contract

Carry out a flexibility and support review of any Piping Studies produ~ for proposalsif required.

Ensure that all Code, Client and Inspection Authority requirements pertaining to PipingStress Analysis are taken into account.

Establish all operating functions for lines to be analyzed by reference to the linedesignation tables and/or discussions with the systems/mechanid engineer. Theseinclude start-up, shutdown, steam-out, various wmbinations of equipment working andidle, bypasses in and out of use, de-inking, etc.

In the early design stage, review Piping Studies for flexibility and support of majorcritid lines, and comment accordingly.

Review all lines on the Critical Line List and formally wmment via the Stress Sketchor Stress Comment Forms as appropriate.

Evaluate nozzle loads as required and transmit to relevant section, if limiting values arenot known.

Check flanges for leakage where bending moments are large, including flangedconnections at equipment.

Establish with the civil/structural engineer any criteria for settlement, loads onpavements, platforms, piperacks and any other structure.


I6.1.11

6.1.12

6.1.13

6.1.14

6.1.15

6.1.16

6.1.17

6.1.18

6.1.19

6.1.20

6.1.21

6.1.22

7.0

7.1

Calculate and transmit all significant support, guide and anchor loads on structuresand/or foundations to Civil/Structural group. Significant loads are loads greater than 5KN or 1000 lb, loads greater than those established in section 6.1.10, and loads notestablished in section 6.1.10.

Locate and design all spring supports and indicate required loads and movements on theStress sketch.

Check all pipe supports produced for the critical lines, and revise where necessary.

Specify any reinforcement required at branch connections, (other than forintemal/extemal pressure considerations which are revered by the Piping MaterialSpecification), or at wncentrated loading points.

Specify expansion joints as rquired.

Specify any cold spring found to be necessary.

Check position of fixed and sliding supports of heat exchangers, horizontal drums, etc.

Review Vendors Drawings for equipment nozzle loadings. Comment as necessary anddiscuss with Equipment Engineer any special requirements (eg leaving heater nozzlesunrestrained so as to utilize the inherent flexibility of the tubes, etc).

Ensure all information affecting other groups and/or Vendors is properly recorded andpromptly transmitted.

Prepare and file all calculations in accordance with the requirements of this instructionand project requirements.

Investigate queries r~ived from site giving advim and solutions as necessary.

When requested, check critid pipe supports and expansion joint installations at siteprior to mechanical completion to confirm that design requirements have been met.

GENERAL WORKING METHODS

The method of assessing pipes will mme under one of three categories :

a. Computer. In this case the piping system will be modelled and calculatedusing a piping stress computer program. (Bechtels ME101 LEAP,Caesar II, or any other program approved/specified by the clienton a project.)

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b. Approximate. In this case hand dculation techniques using nomography, charts,simplified formulae, or simplified computer programs are UW toprove the acceptability of the system. They may also be approvalby comparison with similar systems.

Simplified computer programs are hand calculator type programsthat analyses simple shapes using standard calculation methods(e.g. elastic mntre method) and should be checked and approvedbefore use.

c. Visual. In this case simple techniques of approximate guided cantilevertype or by background knowledge/experien~ are used to approvethe system with minimal calculations.

7.2 The approval method is ultimately the responsibility of the individual Stress Engineer.The basic split of calculation types is as follows:

a. Visual or Approximate : (The temperatures refer to Design temperatures)

Lines attached to rotating equipment:

Lines of 50mm (2)NB and under.Lines of 100mm (8)NB and under@ less than 150C (300F)Lines of 150mm (6)NB and greater @ between -20C (4F) and 70C (150F)

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All other lines:

Lines of 80mm (3)NB and under.

The following sizes must be also@ above -45C (-43F):Lines of 150mm (6)NB through 300mm (12)NB @ under 155C (400F)Lines of 350mm (14)NB and greater@ under 150C (300F)

The above list is to be used as a guide only, and for any special piping (e.g. linedpipe) computer dculations should always be considered.

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b. Computer Calculations :

All lines not in a. and lines over 80mm (3)NB attached to sensitive equipment.


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7.3 For all dculations, the wmbination of conditions that muld tharetidly occur so asto produ~ the maximum stress and equipment loading should be considered. Thiswnsideration should include but not be restricted to the following areas (See alsoParagraph 8.4):

a. Thermal expansion due to :

Design TemperatureSteam out.Steam or electrical tracing.Any Purging.Atmospheric and Solar Temperatures.

b. Movement of pipes attachments due to:

Vessel or equipment thermal growth.Column or other vessel or equipment Sway. (from seismic, wind or any

other source).Structural sway. (from seismic, wind or any other source).Settlement.

c. Wind, snow or other environmental loadings.

d. Dead weight and pressure loadings.\

e. Vibration caused by:

Earthquake.water hammer.sudden valve opening or closing.Pulsating flow.Mechanically indud vibration from compressors or other equipment.Vortex Shedding.

7.4 After a review, the Stress Engineer indicates any rerouting, additional supporting orguiding and locates any anchors or line stops required. If there-routing is not acceptablealternatives are discussed with appropriate back-up calculations until an acceptablearrangement is found.

7.5 Where appropriate, wpies of the Stress sketch together with the Stress SketchContinuation Sheet showing imposed loadings is passed to the Equipment group and/orthe Civil/Structural group.

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ENGINEERING D~IGN GUIDE EDGP5301-L Rev. O Page 9 OF 25

8.0 SPECIFIC WORKING METHODS

This section addresses various specific topics within the scope of piping stressengineering without any reference to any specific project. Hence they arerecommendations that should be tempered by the n-ssities of the specific projectconcerned and good engineering judgement.

8.1 Thermal bads and Stress Considerations

8.1.1 Elastic Modulus

Thermal loads should be calculated using the elastic modulus at the maximumtemperature for hot lines, and the minimum temperature for cold lines.

Thermal stresses should be calculated using the elastic modulus at 70F (21. 1C) forall hot lines and the elastic modulus at the minimum temperature for mld lines.

Hot lines are those primarily subject to thermal expansion, and cold lines are thoseprimarily subject to thermal contraction.

8.1.2 Flexibility Temperatures

The temperatures to be considered in thermal analysis are:

a) Design/Upset Temperature.

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This temperature is quoted in the line designation tables and is the maximumtemperature that the line is wnsidered to see.

If the line considered is un-insulated, the design temperature used, if above 38C(1OOF)maybe up to 5 % less (dculated from installation temperature - see alsoappendix A.2). This value should be wnfirmed with the systems engineer.

b) Normal Operating Temperature.

This temperature is quoted in the line designation tables and is the temperaturethat the line is considered to see during normal operation.

Generally this temperature is not considered unless adjacent connecting pipe orequipment have a higher differential between their operating temperatures, thanbetween their design temperatures.


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c)

d)

e)

f)

g)

h)

Solar and Ambient Temperatures.

These temperatures should be considered when dculating line stress mges andmust be wnsidered for applied loads if higher than the Design temperature.

Steam out.

Steam out temperatures and the lines which will be steamed out should beestablished with the process group at the beginning of the project.

Steam out temperatures will be considered for flexibility analysis if in excess ofdesign conditions. As this event is of short term duration, the allowable stressmay be increased by 1.33 times as per ASME B3 1.3 section 302.2.4. It shouldalso be considered that loads on equipment for this condition may be increasedby up to 2 times for short term duration. However, this should be confirmed withthe equipment manufacturer as soon as possible during design.

Consideration should also be given to whether equipment and piping are st~medout together or separately.

Steam tracing.

Steam tracing temperature should be used for flexibility calculations if it isgreater than the design temperature. (Electrically trad lines should be calculatedusing their design temperature.)

Regeneration

Catalyst regeneration should be considered carefully and accurate values fortemperature, frequency and duration of the pruss obtained. The allowable stressrange may have to be redud as per table 302.3.5 of ASME B3 1.3 to avoidfatigue failure.

DeCoke

This extreme condition that is of short duration. It will be considered forflexibility analysis, but the allowable stress may be increased by 1.33 times as perASME B31.3 section 302.2.4.

Fire

Temperatures produced by fire are a special consideration. For this case thedesign considered should be that the system maybe over-strained, but it must notfail under fire conditions. The principal is that after a fire all affected pipingwould be replaced. Fire temperaturesare obtained from the systems engineer.


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8.2

8.2.1

8.2.2

8.2.3

i)

j)

Internally Lined Pipe.

For wncrete lined pipe for water lines, the expansion temperature to be used isthe Solar temperature, or if the line is buried or externally insulated the line willbe at ambient condition.

For Refractory lined pipe, the metal temperature will be significantly less than thecommodity temperature. An accurate skin temperature should be obtained.

Pipe Bowing

Where there is seen to be a differential temperature around the circumference ofa pipe, as in a flare line subject to radiant heat on the top of it, or a LNG line atstart-up when the lower half of the pipe is cooled before the line fills and CQOISthe top half of the pipe, then the effect of pipe bowing should be wnsidered.

Temperature differentials should be obtained from the process group.

Sustained Loads and Stress Considerations

Design Pressure

This Pressure is quoted in the line designation tables and is the maximum pressure thatthe line is considered to see.

Bourdon Tube Effect

This is the stiffening effect at the elbows caused by the internal pressure tending tostraighten the pipe out. It is most notimble, and should be particularly considered inthin walled large diameter pipe.

This effect should not be considered in cold lines where the pipe is contracting as it aidsthe contraction of the pipe and is hen= a less conservative assumption.

Operating Pressure

This pressure is quoted in the line designation tables, and is used in injunction withthe operating temperature when dculating total operating loads on equipment

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I8.2.4 Hydrotest / Pneumatic Test

The support system should be strong enough to support the pipe when it is beinghydrotested with temporary supports if necessary. Itcanbe assumed that theline is notinsulated during hydrotesting.

If the pipe cannot be supported or if it will cause load problems on the structural steel,then a pneumatic test may be considered.

The piping wall should be sufficiently thick to resist hydrotest or air test withoutyielding.

8.2.6 Vacuum Design

Lines subject to vacuum or sub-sea lines with a resultant external pressure should bechecked to ASME section VIII Div. 1 section UG-28 (Thickness of Shells and Tubesunder extemd pressure)

8.2.7 Operating Weightk

Operating weight is the weight of the pipe with all insulation, mmponents andcommodity included, and all items permanently attached to it.

8.2.8 Occasional Weight

This is an added weight that occurs occasionally such as snow, im, wind etc.

In addition the affects of traffic on buried pipelines should be considered.

8.3 Dynamic and Other Loads and Stress Considerations

8.3.1 Seismic

In the absence of project specific information use the UBC (UBC Part III sec. 2330&seq.) method to model seismically generated dynamic loads as equivalent laterallyimposed static loads. A Dynamic response spectrum analysis should only be mnsideredif required by the project.


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I8.3.2 Dynamic loads from equipment.

Some equipment, noticeably reciprocating compressors and pumps generate pulsationscausing vibration. To minimise this problem fluid damping bottle should be designedinto the system, and the stress engineer should ensure that the fundamental frequenciesof the system (dculated from a computer dynamic analysis) is not a multiple of theoperating speed of the equipment. Similarly, the stress engineer should dculate thespan for the hold-downs such that the piping mechanical frequency does not match themachines natural frequency. (See also API 618)

In some cases, notably that of reciprocating compressors, an analog study is undertaken,usually by a s~ialist or outside consultant.

8.3.3 Wind : See Appendix A

8.3.4 PSV and Rupture Disc Reaction

The load generated when a PSV opens or a Rupture Disc ruptures should always bewnsidered.

F,.*. C

Simplified formulae to give these loads are (including an impact factor of 2):

PSV Reaction: Force F = o.6&+l)AP.

Rupture Disc Reaction: Form F = 0.378~+ l)APr-

Where h= CplcvA= Orifim AreaP = Absolute Pressure

(All in mnsistent units)

If the loads calculated from the above formulae are unduly large, then the calculationquoted in code ANSI/ASME B31. 1 should be used to calculate the load moreaccurately.

8.3.5 Slug Flow and Valve opening/closure

Slug fIow is the condition of a bolus of liquid flowing along a pipe. A similar effect canoccur when a valve is suddenly shut off or opened and a shock wave passes down thepipe (Waterhammer).

The impact of a slug or the wave front of liquid from an opening valve onto an elbowcan be excessive, so that this condition should be kept to a minimum by usingdtemative designs if possible.

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IThe static force on a 90 Elbow due to slug flow impinges at 45 to the direction offlow into the elbow radially outwards from the elbow. The load with a 2 times impactfactor is:

F =2.0x pxAx V2/g (in consistent units)

Where F = Force,P = Density of fluidA= Pipe internal areav= Fluid Velocityg= gravitational constant

8.3.6 Settlement

Loads and stresses caused by differential settlement between different supports andquipment should always be considered. This often is achieved by the use of flexiblepiping and the use of springs.

8.3.7 Friction

bads on supports, anchors, guides, line stops and equipment nozzles should alwaysconsider friction effects.

Friction effects can never be used to reduce applied loads..

8.4 had Combinations,.

8.4.1 Load Summary:

a) bads and stresses should be considered to be caused by expansion due to theworst OR

Design Temperature.Normal Operating Temperature.Solar / Ambient Temperatures (Depending on Insulation).Steam out.Steam tracing.RegenerationDecokePipe BowingEquipment Expansion


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Ib) Sustained bads and Stresses should be considerd due to:

8.4.2

8.4.3

8.5

8.5.1

Design PressureHydrotest / Pneumatic TestVacuum DesignOperating WeightOccasional WeightHydrotest Load

c) Dynamic and Other Mads and Stress:

SeismicDynamic loads from equipment.WindPSV and Rupture Disc ReactionSlug Flow and Valve opening/closureSettlement

Equipment and Pipe Support Loads

a) Maximum allowable loads applied to equipment Nozzles should be agreed withthe equipment vendor as early as possible, but in the absence of any otherinformation the values quoted in the Design Guide for Equipment and Nozzlehadings (EDG-(tba)-L) should be used.

b) hads on equipment and pipe supports that should be mnsidered are themaximum wmbination of cases shown in (8.4.1). Dynamic and other loads (8.4.1(c)) need not be considered to be acting simultaneously, except for settlement.

Pipe Stress

Maximum Allowable Stress wmbinations that should be considered are the maximumStress Range (8.4. 1 (a)), Sustained Stress and mional Stress combination of casesshown in (8.4.1). Dynamic and other loads (8.4.1 (c)) need not be considered to beacting simultaneously, except for settlement.

Rotating Equipment

Pumps

a) The kd Stress Engineer must review tie client and job s~ifications on eachproject to ascertain the philosophy regarding types of pumps and their allowablenozzle loads.

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Ib) Generally it is recommended to use API 610 type pumps wherever possible.When ANSI pumps are used, allowable nozzle loads should be requested from thevendors.

c) A full investigation of all possible operating ~nfigurations of a set of two ormore pumps should be conducted before the worst case or cases are analyzed.

8.5.2 Compressors and Turbines.

a)

b)

c)

c)

d)

Generally, the allowable loads on these pieces of equipment are governed by amultiple of the loads quoted in NEMA SM 23.

Wherever possible, the deadweight loads on the nozzles should be as close to zeroas practical by the use of spring supports (As per mmments in NEMA SM 23)

Spring support variability around the equipment should be kept as low as practicalto keep cold nozzle loads to a minimum.

Piping systems with Mission-Duo type Check Valves should be well supportedbecause of rotational creeping of the flange faces due to the long stud bolts.

Turbine piping analysis should include bypass line hot with trip and throttle valveclosed (i.e. equipment cold) as well as all operating and upset conditions.

8.6 Air Cooled Heat ~changers (Air Fans)

8.6.1 Number of passes

a) An Air Fan with an odd number of passes has the inlet and outlet header boxesat opposite ends of the exchanger and is preferred as there is no problem withdifferential expansion between headers.

b) With even pass Air Fans, the inlet and outlet are on the same header box at oneend of the exchanger. If the header box is separated into two parts instead of adesign with a centre baffle, the differential expansion between the headers is nolonger a problem. Otherwise, the differential expansion between the inlet andoutlet manifolds should be carefully considered, and adequate flexibility put intothe discharge lines from the exchanger to the manifold.

c) The expansion of the tubes can be controlled by placing directional anchors at theheader box. The location of these anchors should be carefully mnsidered tooptimise the piping routing. It may be an advantage to allow some header boxesto float free and be moved by the manifold expanding through short feed lines.

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I8.7

8.7.1

8.7.2

8.7.3

8.8

8.8.1

8.9

8.9.1

8.9.2

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d) In some cases it is advisable to install thrust blocks between header boxes toremove the loads transmitted to the nozzles via friction resistanm of the headerboxes. If the gap between the header boxes is large (over 200mm) the use ofPTFE slide pads should be considered instead of thrust blocks.

e) The clearances between the header box and the steel supports as it may benecessary to cold-spring the headers to accommodate the thermal expansion.

Shell and Tube Exchangers

Anchor Location

The stress Engineer should ensure the fixed and sliding ends are located on the ends thatgive the best advantage.

Stacked Exchangers

Where exchangers are stacked, all interconnecting pipes should be reviewed for stress.

Where vendors supply exchanger arrangements that appear questionable, the stressengineer should ask for back-up calculations from the vendor to prove that there willbe no flange leakage.

Exchangers equipped with bellows should be checked for loading, deflection orangulation. Usually, expansion joints on exchangers are not designed for appreciablelateral deflection.

Fired Heaters

Full appreciation of the effect of the external piping on the internals of the heater shouldbe considered and full consultation with the heater vendor should be conducted to=rtain all the expansions and movementi within his heater before a rigorous stressanalysis is conducted.

Nozzle Flexibility

Loads on Columns, drums, tanks and horizontal vessels by wnsidering the flexibilityof the nozzle connections to the vessel, instead of considering it as a fixed anchor.

If the nozzle flexibility is not available from the equipment vendor, it can be calculatedusing one of the following documents:

a) British Standard BS5500 Appendix G : Stresses from local loads.

b) Bechtel S.F. Standard Drawing : C-722 : spring constants for ro~tion ofNozzles in Cylindrical Shells.

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Where k = Coefficient = 45 in imperial units7 in Si units.

It is also necessary to know the expansion out of a buried section of pipe into the open.

The position where a buried line becomes fully restrained is known as the virtualanchor. The distance of the virtual anchor from where the line ceases being buried is \L (Ft) (m)

Then : L =

Where A=a =

e =

E =P =s =

P =f =

((E.e - p.S) + P.a)/f

Cross Sectional Area of Pipe Metal (in2)

Soil friction can be simplified to:

Flow Area of PipeThermal StrainElastic ModulusPoissons RatioHoop Stress in the PipeInternal Pressure in the PipeSoil Friction

f =

Where Wg ==

Ws ==

Wp =D=h =d =

K1 =fr =

ENG~ERING DESIGN GUIDE

Wg.fr

(wS + Wp)Total Weight acting on the pipe(2. D.h.d/~)Weight of soil on the pipeWeight of Pipe and ContentsPipe DiameterHeight of soil above top of pipeDensity of Soil(Typically 100 lb/f?)Unit mrrection coefficientCoefficient of Soil Friction(Typically = 0.5)

EDGP5301-L Rev. O

(in)(in/in)(psi)

(psi)(psi)(Lb/ft)

(Lb/ft)

(Lb/ft)(Lb/ft)(in)(in)(lblft)

(12)

(mm*) _(mm?

(MPa)

(MPa)(MPa)(N/m) .

,.

(N/m)m.

(N/m)(N/m)(mm)(mm)(N/m)

Page 20 OF 25

I ..&

.

This formula for Ws applies to fairly rigid pipe and must be re-considered for thinwalled lines over 24 NB.

The growth out of the buried section of the pipe into the open is Def (in) (mm) andcan be calculated from:

T*-,

Def = K1.L. [e + (P.ti(A.E)) - (mu.S/E) - (f.L/(2. A.E))]

8.10.5 The buried pipe must also be checked for stability to ensure that the compressive forcein the restrained section does not make the pipe bow out of the ground.

To check this bowing wndition the following steps should be taken (Using nomenclatureas per section 8.10.4 and 8.10.3)

a) Calculate the Critical BucNing Length Lc :

Lc = u (4.E, I/Fa)ln (in) (mm)

Where: I = Pipe Section Moment of Inertia (in) (mm) ~

b) Calculate the theoretical height of pipe bowing @b) due to compression.

Db = [(4.e.ti/#) - (D2/2)]1n (in) (mm)

c) Calculate the pipe sag (Dw) due to weight over the same length.

Dw = (Wg.Lc4/(384.E. I.Kl)) (in) (mm)

d) If Dw > Db then the system is stable, otherwise extra weightshould be put on tie pipe to prevent it bowing outof the ground.

8.11 Cryogenic Pipe

Cryogenic piping includes all piping that operates below -lOOC (-148F), and is morecritical than other low temperature piping as:

.

a) Special attention is required to prevent water incursion into the insulation as this .will freeze and breakdown the insulation. This is achieved by ensuring a vapourbarrier around the whole system without any breaks.


I I

9.0

9.1

9.2

b)

c)

d)

Special cryogenic supports and anchors have to be used to prevent lowtemperatures affecting the support steel and stopping iw build-upon the suppotiscreating unwanted anchor points.

Cryogenic anchors and line-stops should be given special attention as they tendto be bulky and require more room than normal line-stops to install. (SeeStandard Supports Al 1, S31, S32 and S33)

The material Elastic modulus increases by around 5% at these temperaturesmaking the whole system stiffer and incraing loads and stresses.

Special care must be made with any bellows as they must be protected from icingup and being crushed. One method of doing this is to use a double bellows systemseparated by insulation where the external bellows is used as a vapour banier,preventing the formation of ice in the active internal bellows. The material of thebellows should be specially considered to prevent any brittle fracture of the thinflexing membrane. Cryogenic systems antaining bellows should not normally behydrotested as water will tend to be caught in the convolutions forming ice thatdamages the convolutions during service.

RECORDING AND TRANSMIITAL OF STRESS ENGINEERING DATA

Piping Critical Line Liit

The Piping Critical Line List is produced and operated in amrdance with EngineeringDesign Guide EDG-P5302-L: Piping Stress Critical Line List.

Stress Sketches

The Stress Sketch is

a. Pipe Support/details.

used to transmit the following information:-

Anchor /Guide information to piping design, including spring

b. Routing revisions: For piping design.

c. High line movements over 75mm (3): for piping layout.

d. Equipment loads: for the vessel and mechanical equipment groups.


1.;.

I

I

I1--

9.3 Calculation Index

-

9.4

9.4.1

9.4.2

9.5

10.0

10.1

10.1.1

10.1.2

This will be produced in conjunction with the critical line list. See Engineering DesignGuide EDG : Critical Line List.

Expansion Joint Data Sheets

Bellows Expansion Joints

Form No. : P & CE L-5421 FEB 78 Bellows Expansion Joints Data Sheet or -similar document is used for the requisition of bellows expansion joints.

Victaulic and Viking-Johnson Type Expansion Joints

These types of expansion joints fall within the category of Piping Specials and aretherefore specified using a standard drawing sheet (Form No P & CE A-5204 oralternative) showing a sketch of the joint together with the appropriate dimensions and _movements etc. .

Spring Data Sheets

Appropriate data sheets for the type of spring designed, together with an index sheetand spring summary sh~t (see EDG-P5401-L Pipe Supports) are used to requisitionPipe Support Springs. The data sheets must be supplemented by a Spring Design

Specification and the appropriate Paint Spification. ._

CHECKING STRESS CALCULATIONS

Preliminary Review n.

At the preliminary issue stage, all Stress Sketehes shall be reviewed by the StressEngineer to approve the general approach to the dculation and to ensure the overalldculation looks reasonable.

Subsequent to this issue, the stress dossiers shall be maintained with details of any .,signifies.nt changes marked on the redueed mpies of the stress sketches, dated withappropriate mmments relating to the aeeeptanee or otherwise, of the changes. e


m

10.2 Critical lines

The checking of calculations fall into 3 categories:

10.2.1 Complete check.

This check will require the following :

a)

b)

c)

d)

e)

o

g)

h)

If it does not exist, a plot of the input geometry may be created to assistchecking. If multiple computer runs have been run, the secondary runs may alsobe plotted.

Complete check of the computer input gmmetry and inputted parameters (weight,expansion rates, applied loads and movements etc .). Ensure the date of the runsmatch the latest version in the network.

Check of the basic Data: Temperatures, Pressures, Insulation, Commodity, PipeMaterial and wall thickness against the latest line list and Piping materialspecification.

Check additional dculations of line weight, expansion rates, modulus ofelasticity, allowable stresses, wind loads, sway, seismic coefficients, nozzledeflections etc.

Check results tally with values and comments shown on the stress sketch.

Check that all relevant load cases have been run.

Check that the piping system is adequately supported / restrained.

Check that de compliance is documented.

10.2.2 General check

a) If it does not exist, a plot of the input geometry may be creati to assistchecking. If multiple computer runs have been run, the ~ndary runs may alsobe plotted.

b) Spot check of the computer input geometry (10% of dimensions + reviewing (a)above). Check inputted parameters (weight, expansion rates, applied loads andmovements etc.).

c) Ch~k of the basic Data: Temperatures, Pressures, Insulation, Commodity, PipeMaterial and wall thickness against the latest line list and Piping materialspecification.

-


7

I.

\. \

I ..A

10.2.3

10.3

10.3.1

10.3.2

10.3.3

d) Review additional dculations of line weight, expansion rates, modulus ofelasticity, allowable stresses, wind loads, sway nozzle deflations etc. (i.e. ensurethe values are reasonable)

e) Check results tally with values and comments shown on the stress sketch.

f) Check that all relevant load cases have been run.

g) Chuk that the piping system is adequately supported / restrained.

h) Check that code compliance is documented.

General Review

In this case the stress sketch should be reviewed to ensure the basic temperature datarelates to the latest Line List and any associated calculations are correct.

Calculations relating to the Groups in 10.2

The calculationsas follows:

falling within complete check category (See paragraph 10.2. 1) are

All calculations relating to the following equipment :

a) Air fans

b) Compressors

c) Turbines

d) Arrangements of three pumps connected together by piping at elevatedtemperatures.

e) All other equipment where Nozzle loads are above 75% of the allowable values

f) All calculations where the stress range is above 75% of the basic SA value inASME B31.3.

The calculations falling within General check category (See paragraph 10.2.2) are allcomputer dculations not included in 10.3.1.

The calculations falling within General Review category (See paragraph 10.2.3) areall non-computer calculations (approximate calculations and visual review).


I k

APPEND~ A TO ENG. DESIGN GUIDE EDGP5301 REV. O PAGE Al OF A3

APPENDIX A Basic Data Required at the Start of a Projeet and Default values forInitial Calculations. r,

The following information should be confirmed with the appropriate project standards andspecifications at the outset of a project.

If the information is not readily available the values given below may be used as interim valuesuntil confirmation can be obtained from the client or appropriate authority. w

..

A. 1 Piping Code: .:

Chemical Plant and Petroleum Refinery Piping ASME B3 1.3 (Latest Edition)

A.2 Temperatures:

England

Northern Europe& Canada

Central Europe

USA

Middle EastAfrica, Far East& Tropical Climates

All Locations :

AmbientInstallationsolar



AmbientInstallation

solar


Steam out

-10C (14F) to 300c (860F).: 5C (41F): 35C (95F)

o -20C (-4F) to 30C (86F).: OC (32F): 35C (95F)

-20c (-4F) to 40C (104F).: OC (32F): 50C (122F)

o -20C (-4F) to 40C (104F).: OC (32F)or 21C (70F): 50C (122F)

: OC (32F) to 50C (155F): 20C (68F): 85C (185F)

: 150C (302F)

L

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APPENDIX A TO ENG. DESIGN GUIDE EDGP5301 REV. O PAGE A2 OF A3

A.3

A.4

A.5

A.6

A.7

Wind Loads:

Wind loads may be Ca.lculatti using one of the following codes:

a) Based on BS CP3 Chapter 5: Code of Basic Data for the Design ofBuildings - Chapter 5: bading - Part 2:Wind Loads

In the absence of further information, use a design wind speed of 40 m/s with a.

Topography factor S1 of 1.0, ground roughness of 2 witi building class B (tocalculate factor S2 as per table 3), and factor S3 of 1.0.

b) Based on Uniform Building Code Part II : Wind Design

In the absence of further information, use a basic wind speed of 90 mph with aExposure type C, Cq factor of 0.8, qs factor of 20.8 lb/f~ and an Importancefactor of 1.0. ~

Wind Deflection of Columns and Structures

Initial calculations can use a value of L/200 where L is the elevation of the column orstructure. This should be confirmed by the vessel/structural group for the specificcolumn of structure as soon as possible.

Coefficient of Friction.

steel to steel : Coefficient of Friction = 0.3Steel to Concrete : Coefficient of Friction = 0.8S-1 to PTFE/ Polished Stainless Steel : Coefficient of Friction = 0.1

Settlement5.

Values for absolute and differential settlement on a plant should be established at theoutset of the project.

Earthquake

Values for earthquake accelerations on a plant should be established at the outset of theproject. ..

,

Use : Uniform Building Code Part III : Earthquake Design.

R.

I , lb

APPENDIX A TO ENG. DESIGN GUTDE EDGP5301 REV. O PAGE A3 OF A3

A.8 Column Skirt ExpansionThe temperatures used for calculating skirt expansions are taken from the equation:

T*2

Average Skirt Temp (C)= (T-Ta)F + Ta

Ta= Ambient Temp. (C)T = Temp @ top of Skirt (C)F = 83.6/((Kh/t) + 15.5) [(Kh/P5) > 120]K= Insulation Constant = 1.0 Firebnck Insulated

= 1.6 Non-insulatedh = Skirt Heightt = Skirt wall thickness.

A.9 Insulation Weight

Until definitive values are available use 150 Kg/m3 (9.4 lb/F~) or 175 Kg/m3(11 lb/ft)insulation density. T

A. 10 Pipe Wall Thickns Retirement Thickness

When calculating the pipe wall thicknesses for piping classes etc., if the pressure is low,the thinnest wall thickness required for pressure design may be too thin for reasonablemechanical strength. Hence a minimum thickness is required for basic mechanicalstrength purposes. This value is known as the retirement thickness.

Thus, if the pressure design thickness calculated is less than the retirement thickness theretirement thickness should be used in its place.

The Retirement thickness values to be used are:

Line size Range (NB) : Retirement Thickness:(in) (mm) (in) (mm)

1/2 to 1 1/2 15 to 40 0.02 0.512t04 50 to 100 0.06 1.526 to 12 150 to 300 0.09 2.2914 to 24 350 to 600 0.12 3.0526 to 46 650 to 1150 0.15 3.8148 and above 1200 and above 0.20 5.08

E.

APPENDIX B TO ENG. DESIGN GUIDE EDGP5301 REV. O PAGE B1 OF B2

APPENDIX B A Simplified Method for Piping Designers to Asses Piping Flexibility. w

B. 1

B1.1

B1.2

B1.4

B.2

B2.1

B2.2

B2.3

.& k

PURPOSE

The purpose of this guide is to assist the piping designers to allow for sufficientflexibility whilst routing piping.

FThe method to be employed is simple, quick, and conservative, but does not considerequipment loads. This is not seen as a problem as the Stress Engineers will cover thischeck during their review of the piping.

This guide is NOT intended to circumvent the assessment of piping systems by thestress Engineer.

THE STRESS FLEXIBILITY EQUATION

The quation is based on the guided cantilever method.

To dculate the required leg, use the following Equation:

(s= also fig Bl)

Lr = K. (D. T. Le)ln

Where Lr = Required leg to absorb expansion of Le. (mm) (in)D= Pipe Actual OD in inches (of Lr) (in) (in)T = Pipe Design Temperature - 10C (50F) (C) (F)Le= Length of pipe that is expanding. (mm) (in)K= Constant see B2.3

Values of the constant K:

Material

Carbon St~l & bw Alloy Steelto 5Cr Steel

12 Cr Steel and Austenitic StainlessSteels (Not L grade)

Value of K in:Imperial Units

0.185

0.21

S1 Unitsexcept NB

1.25

1.4

IAPPENDIX B TO ENG. DESIGN GUIDE EDGP5301 REV. O PAGE B2 OF B2

Fig. B1

Diagram Showing Expansion of Typical L Shape

B3 METHOD LIMITATIONS

B3. 1 This equation becomes less accurate for pipes in the following categories:

a) Lines with a Le/D ratio less than 5..*-

-4

b) Non-Metallic Piping

c) Using the K values given for Pipes at Temperatures over 300C (572F).

d) Pipe runs with changes in diameter in length Lr.r,

.

B3.2 This method is based on allowable piping stress. It does not consider imposed moments .on anchor points or equipment nozzles.

Hence for sensitive equipment, this method is only a first pass method for the designerto get a feeling of the sort of leg sizes that are required.

I . APPENDIX C TO ENG. DESIGN GUIDE EDGP5301-L REV. O PAGE Cl OF ClCAD Drafted Piping Stress Sketch : stored in file STRESS2.DGN

r

.

.

.

I APPENDIX D TO ENG. DESIGN GUIDE EDGP5301-L REV. O PAGE 1)1 OF D1Stress and Supports Critical Line List: stord in file S-S1 .DGN

ENGINEERING STANOMD -Cl

ST~S ~ -TS CJ?ITCM lIM L~Tam

mm

1 1 I 1

i 1 I i IiI

II

I I

i

1

1

1 I1 1

,

\ I 1I J

I

t 1I

I II I \

I II

tI

I 1

I I

I I1 1

1KH2 FOR ~V& STATUS :

I I I 1 Ia I i I MCHTEL CMPORATW

1

t

.

.,,-

-.

.

APPENDIX E TO ENG. D~IGN GUIDE EDGP5301-L REV. O PAGE El OF El

Stress Calculation Index: stored in file S-S1.DGN

ENGINEERING STANDARDSTRESS C4CULATION NDEX

w. I

STRESsREVIEW COOE (METHOD): C : COUPuTER tiYSiSA.: ~OXUATE C&CUiTIONv : Vlsuk INSPECTION..

m PIPING STRESS Calculation INDEX l-Pw k 1 m.

,.

,.

1i-:

.

3dg-p45-00001(pipe stress analysis 190)

Documents

o design guide

piping stress engineers

piping stress analysis

stress sketches

scopethis design guide

piping flexibility

checking stress calculations

associated design guides