8/9/2019 Basics of Pipe Stress Analysis ( Must Read )

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BASICS OF PIPE STRESS ANALYSIS: A PRESENTATION

Contents

Objectives of Pipe Stress Analsis

!overnin" Co#es an# Stan#ar#s

Stresses in a Pipin" Sste$

Re#%cin" Pipin" Stresses

Basic Allo&able Stress

Loa#s on a Pipin" Sste$

'or( Flo& )ia"ra$

Stress Criticalit * Analsis +et,o#

Pipin" Stress Analsis %sin" Soft&are Caesar II

Tpe of S%pports

-%estionnaire

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Objectives of Pipe Stress Analysis:Structural Integrity:

)esi"n a#e.%ac for t,e press%re of t,e carrin" /%i#0

Fail%re a"ainst vario%s loa#in" in t,e life ccle 0 Li$itin"

stresses belo& co#e allo&able0

Operational Integrity:

Li$itin" no11le loa#s of t,e connecte# e.%ip$ent &it,in

allo&able val%es0

Avoi#in" lea(a"e at joints0

Li$itin" sa""in" * #isplace$ent &it,in allo&able val%es0

Optimal Design: Avoi#in" e2cessive /e2ibilit an# also ,i", loa#s on

s%pportin" str%ct%res0 Ai$ to&ar#s an opti$al #esi"n forbot, pipin" an# str%ct%re0

Governing Codes and Standards:

Co#es an# Stan#ar#s specif $ini$%$ re.%ire$ents for

safe #esi"n an# constr%ction 3i0 e0 provi#es $aterial4#esi"n4 fabrication4 installation an# inspection

re.%ire$ents05 Follo&in" are t,e co#es an# stan#ar#s %se# for Re6ner

Pipin":

70 AS+E B8708: Process pipin" Co#e

90 AS+E B8707: Po&er Pipin" Co#e

80 Centrif%"al P%$ps: API 7;

0 Centrif%"al Co$pressors: API 7=

0 Reciprocatin" Co$pressors: API 7?

=0 Stea$ T%rbines: NE+A S+98@ API 79

?0 Air Coole# eat E2c,an"er: API 7

0 Fire# eaters: API >;

7;0 Flat Botto$ 'el#e# Stora"e Tan(s: API >;

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770 eat E2c,an"ers: TE+A@ en#or Speci6c0

790 essel@Col%$n: en#or Speci6c

Stresses in a Piping System:

So%rces for "eneration of stress in a Pipin" Sste$:

70 'ei",t

90 Internal@E2ternal Press%re

80 Te$perat%re c,an"e

5 D T,e s%$ of t,e

lon"it%#inal stresses4 SL4 in an co$ponent in a pipin"sste$4 #%e to s%staine# loa#s s%c, as press%re an#&ei",t4 s,all not e2cee# t,e pro#%ct S, 2 ' 0 ',ere4S,Basic allo&able stress at $a2i$%$ $etal te$perat%ree2pecte# #%rin" t,e #isplace$ent ccle an# '&el# jointstren"t, re#%ction factor0

Press%re Stresses are ta(en care of b calc%latin" an#selectin" proper pipe t,ic(ness0 T,e press%re t,ic(ness 3t5of a strai",t pipe can be obtaine# as per AS+E B8708 fro$t,e e.%ation 3Cla%se 8;

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Fig !: "#uation for $%ic&ness Calculation for Straig%tPipe based on AS'" ( )!)

C,an"e in len"t, of a pipe of len"t, L #%e to te$p

c,an"e 3GT5 is "iven b GLL H GT ere4 H Co efficient oft,er$al e2pansion c,an"e in len"t, of %nit len"t,

ele$ent #%e to %nit c,an"e in te$p0 T&o DH val%es in Co#e 3Table C7 an# C8 in AS+E B8708

Appen#i2 C5:

Table C7 #enotes total linear t,er$al e2pansion bet&een

=;; F to In#icate# te$p 3%nitin@7;;ft50

Table C8 #enotes $ean coecient of linear t,er$al

e2pansion bet&een =;; F to in#icate# te$p 3Jin@in@;F50

E2pansion stresses are "enerate# &,en t,e free t,er$al

"ro&t, #%e to te$perat%re c,an"e is restricte#0 T,ese areself li$itin" or relentin"0

SIF3 Stress Intensi6cation Factor5: T,is is t,e ratio of t,e

$a2i$%$ stress intensit to t,e no$inal Stress0 SIF factorsfor #iKerent co$ponents can be obtaine# fro$ Appen#i2 )of AS+E B87080

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)isplace$ent Stress Ran"e #%e to t,er$al e2pansion is

calc%late# base# on e.%ation SE 3 Sb9M< St95;0>per e.%ation 7= fro$ AS+E B87083 cla%se 870

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As per AS+E B8708 cla%se 8;9080 DT,e s%$ of t,e

lon"it%#inal stresses4 SL4 #%e to s%staine# loa#s4 s%c, aspress%re an# &ei",t4 an# of t,e stresses pro#%ce# boccasional loa#s4 s%c, as &in# or eart,.%a(e s,o%l# be

7088 ti$es t,e basic allo&able stress4 S, Co#e #oes not e2plicitl e2plain t,e stresses "enerate#

#%e to vibration0

T,e vibration proble$s are solve# b en"ineerin"

j%#"$ent an# e2perience0

+educing Piping stresses:

S%pports for 'ei",t

Fle2ibilit for t,er$al loa#in" E"0 E2pansion Loops0

Fle.ibility c%ec& /as per clause )!01!2 AS'" ()!)3: Refer Fi"0 above0

-oads on a Piping System:There are two types of loads which acts on a piping system Staticloads and !ynamic "oads

Fig!: ".amples of Static -oads

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Static loads are those loads which acts #ery slowly and the system getsenough time to react against it. E$amples of static loads are shown in%ig.1

Fig*: ".amples of Dynamic -oads

&n the other hand dynamic loads acts so 'uicly that the system doesnot get enough time to react against it. E$amples of dynamic loads areshown in %ig.

4or& Flo, Diagram:The interaction of *iping Stress team with other disciplines in any

organi+ation are shown in %ig. 3

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Fig): Inter Departmental Interaction ,it% Stress $eam

Stress Criticality and Analysis 'et%ods:

i",l Critical Lines 3Stea$ t%rbine4

Co$pressor connecte# pipelines5: B Co$p%ter Analsis

+o#eratel Critical Lines 3AFC connecte# lines5: B

Co$p%ter Analsis

Lo& critical Lines : is%al@Si$ple +an%alCalc%lation@Co$p%ter analsis an#

Non Critical Lines: is%al Inspection

Stress Analysis using Caesar II :

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Inputs:

Stress Iso$etric fro$ Lao%t !ro%p

L)T An# P*I) fro$ Process

E.%ip$ent !A an# Ot,er #etaile# #ra&in"s fro$+ec,anical

Process /o& #ia"ra$@#atas,eet if re.%ire# fro$ process

Pipin" +aterial Speci6cation

PS@ Control alve !A an# )atas,eet fro$

Instr%$entation

Soil C,aracteristics fro$ civil for %n#er"ro%n# analsis

No11le loa# li$itin" Stan#ar#s

Plot Plan for 6n#in" PP elevation an# e.%ip$ent

orientation0

!overnin" Co#e

Analysis:

C,ec(in" t,e co$pleteness of t,e pipin" sste$

receive# as a stress pac(a"e0

No#e n%$berin" on stress Iso0

Fillin" t,e #esi"n para$eters 3)esi"n te$p4 press%re4

Ope0 Te$p4 +in0 Te$p4 Fl%i# #ensit4 +aterial4 Line Si1e an#t,ic(ness4 Ins%lation t,( an# #ensit4 Corrosion allo&anceetc5 on stress Iso0

+o#elin" t,e pipin" sste$ in Caesar %sin" para$eters

fro$ stress Iso0

Anal1in" t,e sste$ an# obtainin" res%lts0

Conclusion 5 +ecommendation :,hether to accept thesystem or to suggest necessary changes in layout and supporting tomae the system accepta-le as per standard re'uirements.Output:

Final $ar(e# %p Isos to Lao%t

S%pport Loa#s to Civil

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Sprin" an"er )atas,eets0

)atas,eets for Special S%pports li(e S&a brace4

Str%ts4 Sn%bbers etc0

SPS #ra&in"s Stress Pac(a"e 6nal #oc%$entation for recor#s

$ype of Supports:

Rest

!%i#e

Line Stop

Anc,or

ariable Sprin" an"er Constant Sprin" an"er

Ri"i# an"er

Str%ts

Sn%bbers

S&a Braces etc

',at are t,e vario%s tpes of loa#s &,ic, ca%se stressesin t,e pipin" sste$

',ic, co#e #o &e refer for Re6ner Pipin"

',ic, stan#ar# "overns t,e #esi"n of P%$ps

T,e coecient of t,er$al e2pansion of a s%bstance is

70? $$@$@)e"0F0 ',at is its val%e in $$@$$@)e"0C0

Calc%late t,e $ini$%$ pipe t,ic(ness of a sea$less 7;

NB A7; !r B $aterial &it, #esi"n press%re of 9; bars03)esi"n Te$p 8>; #e"ree C an# Corrosion allo&ance70 $$5