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ASME B31.3 PIPE WALL THICKNESS

CALCULATION

• Introduction to Pipes

• Pipe wall thickness calculation

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INTRODUCTION

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•Pipes are thin cylindrical shells which is usedtransportation of fluids.

•ASME B 36.1 is the di!ensional standard for"elded and Sea!less "rou#ht Steel Pipe $%S&'(%S& and 'AS).

•ASME B 36.1* is the di!ensional standard forAustenitic + Stainless Steel Pipes.

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• Pipes ,ased on the process of !anufacturin# are classified into -Sea!less Pipe& Electric usion "elded Pipe $E")& Electric/esistance "elded Pipe $E/"). (here are also other types such aSpiral "elded pipe& %entrifu#al %ast pipe etc.& ,ut is not suita,lefor pressure applications.

• Pipes ,ased on types of !aterials are classified into %ar,on Steelpipe& 'ow (e!perature %ar,on Steel Pipe& 'ow Alloy Steel Pipe&Stainless Steel Pipe are the !aterials used in !a0or pipin# desi#n.(here are also !aterials such as ast alloy& Inconel& Monel& %u2iAlloy& %/P& 4/P etc.& are used for special applications.

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• Pipes are !ade of standard si5es hain# seeral ran#e of wallthickness or wei#ht.

• 478419International Standards8A!erican8ASME8ASME8ASME B36

1M21**6.P:

• 478419International Standards8A!erican8ASME8ASME8ASME B361*M21*;<.P:

• Pipes are known ,y o!inal Pipe Si5e PS $in inches) and:ia!eter o!inal : $in !!).

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• =pto 1>? PS the o!inal dia!eter is appro@i!ately eual toinside dia!eter of pipe.

• A,oe 1>? PS the o!inal dia!eter is eual to the outerdia!eter of the pipe.

• Pipe wall thickness is desi#nated ,ased on wei#ht and schedule.

• (he older syste! desi#nates pipe as Standard $S)& E@tra Stron#$S) and :ou,le E@tra Stron# $S) which is ,ased on pipewei#ht.

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• (he newer syste! desi#nates wall thickness ,y SchedulesC suchas Sch 1&>&3&D&6&;&1&1>&1D&16. or "rou#ht steelpipe& Sch <S& 1S& DS& ;S. or Stainless Steel Pipe.

• or!ally for all pipe si5es SchD corresponds to Standard $S) andSch; corresponds to E@tra Stron# $S).

• %o!!ercial pipes are nor!ally aaila,le in 6!& 1>! len#th.

• Pipes are connected throu#h flan#es& weldin# $,oth ,utt andsocket weldin#)& threaded.

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• :i!ensional standard for flan#es is ASME B16.< upto >D? PS&ASME B16.D Series B a,oe >D? upto 6FPS& a,oe that A""A

%2> which ran#es fro! DF PS to 1DDF PS.

• :i!ensional Standard for Butt2weldin# end pipe is ASME B16.*&and for Socket welded and threaded pipe ASME B16.11.

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PIPE WALL THICKNESS CALCULATION

• Pipe wall thickness desi#n is for internal pressure.

• "hen calculatin# pipe wall thickness operatin# pressure andoperatin# te!perature is always !ultiplied ,y a factor of 1.< to#et the desi#n para!eters. (his factor is called safety factor.

• (he pipe wall thickness euation #ien in ASME B31.3 is ,ased onoop stressC tGP:+>S& where t2thickness& P2 Internal Pressure& S2oop Stress.

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"here&t - wall thickness of pipe in $!!)+$inch)

P2 :esi#n internal Pressure $PSI) +$MPa)+ Bar

:2 Huter dia!eter of pipe $!!)+ $inch)

S2 Allowa,le stress for the !aterial of pipe $SI) +$MPa)+ Bar

E2 "eld Juality factor

"2 "eld Stren#th reduction factor

K - %oefficient of !aterial used

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• 1 inch G ><.D!!

• 1 ,ar G 1D.< psi G 1 pa

• 1 ksi G 1 psi

• Pipe wall thickness desi#n calculation can ,e done ,yC

• 'ine ratin# condition and lan#e $ull) /atin# condition.

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• In any plant pipin# falls under&

  1<L&3L 2 *& 6L2 <& *L&1<L&><L 2 <.

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• 'ine ratin# condition 72

• In this !ethod the pipe thickness is calculated for the each and eeryline accordin# to the line ratin# or particular line desi#n conditions.

• (his is !ethod is #enerally used for lar#e dia!eter pipes or special

cases such as use of costly alloys $such as ast alloy& %u2i& Inconeletc. )

• Pipes in *L and a,oe.

•  It is not preferred for cases where lar#e nu!,er of pipes procured forsi!ilar desi#n conditions.

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• lan#e ratin# condition72

• In this !ethod the pipe thickness desi#n calculation is done ,ased onthe flan#e ratin#.

• Pipe is !ade stron#er than flan#e.

• (his desi#n is !ade to !ake the procure!ent !ore econo!ical.

• In this case in any case only flan#e fails and not the pipe& which saesa hu#e cost in a process plant.

• /atin#+ %lass of lan#e as per ASME B16.< are2 1<& 3& D& 6&*& 1<& and ><.

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• A corrosion allowance ,ased on process data is added to desi#nthickness to #et the !ini!u! reuired thickness. or!ally for %Spipe it is 3.!!. or SS pipes its .!!.

• A !ill tolerance of 1>.< is added to the reuired thickness forsea!less and !ill2rolled pipe and a !ill tolerance of .3!! isadded to the reuired thickness of plate fa,ricated pipe. /ef Std.AS(M 1.1 for !ill tolerance.

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• Mini!u! selectin# thicknessfor %S

• NF - 1.1+>F Sch.;

• >F2 6F Sch.D

• ;F21DF Sch.>

• Mini!u! selectin# thicknessfor SS

• Sch. D !ini!u!.

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SAMPLE CALCULATION FOR LINE CONDITION

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SAMPLE CALCULATION BY FLANGE RATING

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