piping stress analysis

7/21/2019 Piping Stress Analysis

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This content provides you with sample piping stress analysis EngineeringSpecification that is used in industrial plant construction works.

1. Piping Stress Analysis - Scope

This specification prescribes the basic requirements for stress analysis of the pipingsystems to be performed during the piping design work for use in industrial plant.

2. References

The latest edition / version of the following codes, standards and specifications shall form apart of the requirements of this specifications.

2.. !iping Stress "nalysis # $odes and Standards

"S%E &'.' !rocess !iping

"S%E section ())) div &oiler and !ressure (essel $ode

"S%E section ())) div 2 *ule for $onstruction of !ressure (essels

"!) +, $entrifugal pumps for petroleum, heavy duty chemical, andgas industry services

"!) +-, $entrifugal compressors for petroleum, chemical, and gasservice industries

"!) +, *eciprocating compressors for petroleum, chemical, and gas

service industries

"!) +, 0ired heaters for general refinery services

"!) +, 1elded steel tanks for oil storage

"!) ++, Shell and tube type heat echangers for general refinery services

"!) ++, "ir#$ooled heat echangers for general refinery services

"!) *!2 Si3ing, selection and installation of pressure 4 relieving device

in refineries

5E%" S%2', Steam turbine for mechanical drive service

1*$ -, 6ocal stresses in spherical and cylindrical shells due toeternal loading

1*$ 27-, Supplement for 1*$ -



E8%", Standard of epansion 9oint manufacturers association 4 "S%E +.7, "S%E +.2

2.2. !iping Stress "nalysis # *elated Specifications and *eferences

Engineering specification for !iping :anging ; Support

Engineering specification for !iping <esign

Engineering specification for Thermal )nsulation =:>T?

Engineering specification for Thermal )nsulation =$>6<?

Engineering specification for !iping %aterial

3. Piping Stress Analysis -Design Conditions

The piping stress analysis shall include the following loading effects asapplicable.

'.. !iping Stress "nalysis # 1eight Effects

The weight load shall include the pipe weight, weight of content, insulation weightand weight of fittings and any inline equipment. 0or piping systems, which aretested hydraulically and have content with specific gravity less than ., a hydro#test run shall be performed assuming a specific gravity of . to establish thestructural design loads.

'.2.

!iping Stress "nalysis # Thermal Effects

Temperature to be used in the piping fleibility analysis shall be the maimumdifferential temperature between any of the following applicable conditions.

'.2.. !iping Stress "nalysis # )nstallation Temperature

? %aimum dry bulb temperature of @A$ shall be taken as the installationtemperature for cold insulated piping service.

2? %inimum dry bulb temperature of A$ shall be taken as the installation

temperature for bare/hot insulated piping service.

'.2.2. !iping Stress "nalysis # $alculation Temperature

? >perating temperature as stipulated in the line list.

2? )n addition, the following temperature condition shall be considered in thecalculation when lines are specified in the line inde.

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• Start#up / shutdown temperature

• Steam out temperatureB 5ormal steam out temperature should not

eceed 2A$ for saturated steam. This steam out temperature shall beconsidered only for fleibility purposes of hydrocarbon serviced lines.

• <ecoking temperature

• *egeneration temperature

'? 0or piping which normally have no flow =such as drains, start#up lines, etc.? theflow calculation temperature shall be determined as follows.

• 0or insulated piping, -C of operating temperature shall be taken.

• 0or un#insulated piping, 2C of operating temperature shall be taken.

• 0or section between stand#by equipment and cut#off valve, installation

temperature shall be taken.

• 0or piping which have warming#up by#pass, operating temperature shall be

taken for all section.

'.'. !iping Stress "nalysis # !ressure Effect

%aimum operating pressure and minimum vacuum pressure shall be taken as thecalculation pressure as per "S%E &'.', unless otherwise specified.

'.@. !iping Stress "nalysis # 0riction Effects

'.@. 0riction effects shall be considered in the design of anchor on hori3ontally long runpiping system with >< larger than inch.

'[email protected] 0ollowing friction factor shall be used for computing the frictional resistance.

Surface Friction Factor

Steel to Steel .'

Steel to Teflon .

Teflon to Teflon .+

Steel to $oncrete .

'.. !iping Stress "nalysis # 1ind and Earthquake Effects



'... 1ind and earthquake effects shall be checked in formal computer analysis,if eperienced stress engineers decide it necessary. 1ind loading shall beconsidered for si3es 2@5& and over, for heights more than m above gradewhere not shielded. 0or earthquake loading the equivalent static force analysismethod shall be applied. The wind load and Earthquake as acting separately in

two lateral condition 7D apart. 2.

4.0 Piping Stress Analysis - Design and Analysis Reuire!ents for Fle"i#ility

@.. !iping to purged vessels that cannot be disconnected during purging shallbe designed with sufficient fleibility to accommodate the thermal displacementof the vessel.

@.2. The use of cold spring in piping, which connects to rotating equipment, isprohibited.

@.'. )f temperature, resulting in short term loading as those stated in !ara.'.2.2.2? is specified in the line list, thermal effect by this temperature shall also beconsidered in the analysis. :owever, the reaction loads at equipment shall not betaken from this alternate analysis case.

@.@. 0leibility

? The required fleibility of the piping shall be achieved by a suitable layoutconfiguration without the need for epansion 9oints, first. Epansion 9oints shall be

used only where bends, offsets or epansion loops are not deemed feasible. )nthis case, the stiffness of epansion 9oint shall be considered in any fleibilityanalysis. "nd, the destabili3ing effects of unbalanced pressure thrusts shall beaccounted for in the piping design.

2? Epansion 9oints shall be used only with adequate guides and anchors andwhen the fluid plugging properties cannot make the epansion 9oint ineffective.

'? &ellows type epansion 9oints shall be avoided in services that cooking canoccur. )f a suitable piping configuration can not be designed to eliminate the 9oint,connections shall be provided to enable flushing of the area between bellows and

liner to be carried out in a non#coking medium.

@? Torsional rotation of the bellows shall be avoided. This twisting generallyproduces etremely high shear stresses in the bellows so where torsionalrotation cannot be avoided special hardware shall be used to limit the amount of torsional shear stress in the bellows.



? The maimum, minimum and installation temperatures shall be accuratelystated in data sheet to be prepared by the designer. 1here the ambienttemperature can vary significantly during pipeline construction, pre#positioning of the Epansion 8oint at installation may be required.

+? The Epansion 9oint manufacture shall be advised if the Epansion 9oint will beinsulated and the manner by which the Epansion 9oint will be insulated in order to properly design the component parts.

-? The movements to be absorbed by the epansion 9oint shall include not onlypiping elongation or contraction, but also movement of attached vessels,anchors, etc. and the possibility of misalignment during installation. Fnlessincluded in the design requirements, misalignment of the Epansion 9oint shall beavoided.

? 1here movements are cyclic, the number of cycles epected shall be

specified. "s in the case of pressure, the movement specified shall be realistic. "n ecessive safety factor can result in an Epansion 9oint, which isunnecessarily fleible thus its stability under pressure is unnecessarily reduced.

7? )f the flowing medium can pack or solidify, provisions shall be made to prevententrapment or solidification of the material in the convolutions, which could resultin damage to the Epansion 9oint or pipe line.

? The predicted amplitude and frequency of eternal mechanical vibrations tobe imposed on the bellows, such as caused by reciprocating or pulsating

machinery, shall be specified. " resonant condition in the bellows will result in agrossly reduced fatigue life and shall be avoided.

@.. The fleibility analysis shall be in accordance with "S%E &'.' and shall bebased upon the total displacement strain imposed upon piping system includingthe effects of equipment settlement or anchor movement, if applicable.

@.+.. The computed stress range shall be less than allowable stress range asdefined in "S%E &'.' unless otherwise specified.

@.-. Thermal movements shall be limited to 'mm between anchors and to

mm at pipe bends or turns. :owever, greater movements will be considered if the availability of space and the capacity of the anchorage to accept theincremental loads are confirmed.

@.. Start#up, shut#down and steam#out where applicable and upset conditionsincluding short#term ecursions to higher temperature or pressure as well asnormal operating conditions, shall be considered in fleibility analysis. This is



particularly pertinent to loads applied to connecting equipment. The effect of vibration from machinery on connecting piping shall also be assessed.

@.7. 0lare system piping shall be designed to take care of epansion, movementor vibration caused by the most severe operating or emergency conditions. !ipe

shoes or saddles shall be furnished on the main flare header at all supports.

@.. $old spring shall be used as much as practical to reduce forces onequipment no33les and to prevent interference from epanding lines.

@.. The use of cold spring for piping systems, which connected to rotatingequipment, is prohibited.

@.2. The combinations of the loads shall conform to the applicable piping code.

@.'. )mpact loads caused pressure relief through a safety valve shall also becalculated in accordance 1ith G "!) !* 2 G.

$.0 Piping Stress Analysis - %ine Classifications

..Each piping system shall be classified as grade H"I, H&I and H$I according tothe severity of its design condition and need for special design. Each graderequires the following methods for stress analysis.

• Jrade H"IB 8udgment based on the eperience of stress engineer.

• Jrade H&IB The simplified method according to !ara.'7.@ of "S%E &'.'.

• Jrade H$IB 0ormal computer analysis.

.2. 0or the following 'I and larger lines, formal computer stress analysis methodis requiredB

. !rocess, regeneration and decoking lines to and from 0ired :eaters andSteam Jenerators.

2. !rocess lines to and from &lowers.

'. Steam lines to and from Turbines.

@. Suction and discharge line of !umps.



. Suction and discharge line of $ompressors.

.'. The 9udgment of grade for all piping ecept that connected to rotatingequipment shall be in accordance with the criteria shown on fig..

.@. The 9udgment of grade for all piping connected to rotating equipmentincluding air fin cooler and fired heater shall be in accordance with the criteriashown on fig.2.

&.0. '"ternal %oad %i!its on 'uip!ent

+.. *otating Equipment

The allowable no33le loads for rotating equipments shall be limited to thosespecified in their governing Engineering specifications and standards to whichthe equipment is designed, unless otherwise specified by applicable vendors.

0or "5S) and )S> pumps, allowable no33le loads shall be those as other statedin table 2 of "!) + unless otherwise specified by vendors.

+.2. "ir 0in#$ooled Echangers

The allowable no33le loads for air fin cooled echanger shall be limited to thosespecified in Engineering specifications and vendor recommendation and "!) ++.!iping to air fin cooled echanger shall be designed to take into accountclearances between the frame and the header bo of each bundle. "nd, thrustblocks between tube bundles shall be used whenever possible to minimi3e

friction loads at piping takeoffs and anchors, and to meet allowable loads at theno33les.

+.'. Echangers =Shell and Tube?

0or piping connected to heat echangers with TK@A$ or !K' kg/cm2g, thepipe bending stress due to thermal epansion at the echanger no33le shall belimited to - kg/cm2 using a rigid no33le analysis. )f above criteria is eceeded,locali3ed stress at the no33le#to#shell be calculated by 1*$ - and 1*$ 27-,and these computed stress value shall be limited in accordance with "S%E

SE$T)>5 ())).

0or piping connected to heat echangers with TL@A$ or !L' kg/cm2g, thepiping imposed loads shall be transmitted to the vendor for his approval.

+.@. !ressure (essels and $olumns



0or piping connected to pressure vessels and columns with TK@A$ or !K'kg/cm2g, the pipe bending stress due to thermal epansion at the pressurevessels and columns no33le shall be limited to @' kg/cm2 using a rigid no33leanalysis.

)f above criteria is eceeded, 1*$ - and 1*$ 27- shall be used for calculatelocali3ed stress at the no33le#to#shell, and these computed stress value shall belimited in accordance with "S%E SE$T)>5 ())).

0or piping connected to pressure vessels and columns with TL@A$ or !L'kg/cm2g, the piping imposed loads shall be transmitted to the vendor for hisapproval.

+.. 0ired :eaters and Steam Jenerators

The allowable no33le loads and moments for fired heater shall be limited to those

specified in relevant Engineering specification or "!) + or values that areacceptable to heater vendor.

<isplacement of tubes shall be approved by the heater vendor and the effect of epansion and/or displacement of the tubes shall be reflected in the stressanalysis of piping system.

"ny heater designed with a floating coil =all spring or counter weight mounted?shall be provided with fail#safe limit stops in all directions.

$omputer analysis of piping systems connected to floating heater coils shall

include the heater coil or an approimate model of the coil as part of systems andthe effects of internal guides and restraints. 1here heater coils are floating, thesupport of the connecting piping system shall be completely and independentlybalanced so that no dead loads imposed on coil.

+.+. !ackaged Equipment

Eternal load limits are to follow the vendor recommendations.

(.0. Piping Restraints

-.. !ipe supports shall be spaced so as not to cause ecessive deflection at anypoint along the unsupported section of the pipe. "s a general guide for pipinglocated in process area, the maimum mid span deflection shall not be allowed toeceed 2 mm and for piping in pipe way, the mid span deflection betweenstraight run of piping shall not be allowed to eceed 2 mm.



-.2. The design, selection, fabrication and installation of piping support shall be inaccordance with the HEngineering Specification for !iping :anging and SupportI.

-.'. !iping sub9ected to two#phase flow and connected to reciprocatingcompressor shall be supported as rigidly as possible while maintaining

acceptability of pipe stresses and equipment no33le loads.

-.@. 0or nonmetallic piping, vendorMs recommendation for fleibility analysis,support spacing and support type shall be utili3ed.

).0. *iscellaneous

.. *eports

0inal calculation of the grade H$I and the grade H&I which are analy3ed by formalcomputer analysis will be submitted to owner for record and site modification of

piping. The piping systems which are classified as grade H&I shall be analy3ed byformal computer analysis if eperienced stress engineers decide it necessary toprove that the systems meet the allowance of this specification. The reports shallcomprise of the followingB

• &asic data and calculated conditions

• 6ayout isometric and support type and location

• 6oad cases and calculated member stresses

• 0orces, moments and displacement reports

• Spring hanger and epansion 9oint design parameters

.2. Fnits

%etric units =kg, mm, kg#m, kg/cm2? shall be used as a unit of control for analysis.

.'. Softwares

$"ES"* )) (er @.2 =produced by $>"<E )nc.? will be used for formal computer analysis

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