basics of pipe stress analysis ( must read )
TRANSCRIPT
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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