Pwht Procedure

Po st W We e ld He a t Tre a tm e n t Procedure DOC DO C REF: ISB/ PWHT/  WHT/ 

Issued on: …01 June 2010…

 __________________  Binu Jos Jo se p h General General Ma nag er

Th is d o c u m e n t is iss issu e d fo r use use d b y IBR IBRA HI HIM M BIN S. S. AL A L BRA HI HIM M EST. ( IS  ) ISB  Neither Neither the w hole hole no r a ny pa rt of this this d oc ument m a y be rep rod uc ed in a ny  form form w ithout p rior written written c onsent onsent of ISB 

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POST WELD HEAT TREATMENT PROCEDURE TABLE OF CONTENTS

SECTION AND DESCRIPTION

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1.0

SCOPE …………………………………………………………………….

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2.0

REFERENC ES ……………………………………………………………..

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3.0

PERSON HANDLING THE PWHT ACTIVITIES ………………………….

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4.0

DESCRIPTIO N OF REQUIRED EQUIPMENT & MATERIALS …………..

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5.0

SURFACE CONDITIONS ………………………………………………...

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6.0

METHOD ………………………………………………………………….

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7.0

BASIC REQUIREMENT TO CA RRYOUT PWHT AND THE METHODOLOGY ………………………………………………………...

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8.0

PWHT (Post Weld Hea t Trea tm ent) …………………………………..

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9.0

PRECAUTIONS …………………………………………………………...

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10.0

DOCUMENTATIONS …………………………………………………….

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11.0

REPORT & RECORDS ……………………………………………………

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ATTACHMENT Follo ws 

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1.0

2.0

Scope 1.1

This p roc ed ure sta te s explic itly in d et a il the minimum req uirem ent for the exte rna l loa d , Po st Weld Hea t Trea tm en t (PWHT) sha ll b e c a rried o ut b y the ele c tric a l resista nc e m et ho d fo r ve ssels, nozzles, pip es & e xcha ng es.

1.2

This p roc ed ure c ove rs d esc rip tion o f the e q uip me nt, metho d of hea ting, loc ation a nd type o f hea ting e leme nts temp erature m ea sureme nt and thermo c oup le loc ation.

1.3

Po st We ld Hea t Trea tm en t (PWHT) sha ll b e in a c c o rd a nc e w ith ASME B31.3, ASME B31.4 and ASME B 31.8 latest edition.

References Unless stated otherwise all codes and standards referenced in this procedure shall be of the latest issue (including revisions – addenda and supplements) and the following d oc ume nts sha ll be referred to a long with this p roc ed ure. a ) ASME Sec tion VIII Division 1 - Boiler & Pressure Ve ssels c od e, b ) ASME B31.3 - Ch em ica l Plant a nd Pet roleum Ref inery Piping  c ) ASME B31.4 - Liqu id Pet roleu m Tran sp orta tio n Piping Syste ms  d ) ASME B31.8 - Ga s Transmission a nd Distribu tio n Piping Systems 

3.0

Person ha nd ling the PWHT a c tivitie s 3.1

Health & Safety All personals working in the heat treatment shall be trained and cautioned a b o ut the p ossible p lunge rs in PWHT w o rk. It sha ll b e the resp on sibility of t he em p loyed PWHT op erat or to ensure p erson a l safety & to ensure whether the facilities with respect to scaffolding, lighting are fully sufficient, before commencement of any job. All cables shall be tied up p rop erly & ne a tly to avo id d a ma ge s to c a b les & pe rsonne l injuries to op erators.

3.2

Qualification The b a sic req uirem ent for PWHT op erat or sha ll b e tha t he shou ld e ither be a science/technical graduate or an electrical apprentice high school graduate with ba sic electrica l knowledg e to undertake the he at trea tment at the site.

4.0

Desc ription of Req uired Equip me nt & Ma terials 4.1

Equip me nt The eq uip me nt sha ll b e o f a p rop er make & it should b e b ea ring p rop er electric al po wer input/ output.

Power distribution (supply) shall be of 380/440V Ph, with either single phase secondary output or step down transformer secondary output (heat treatment unit) sup p lying low volta g e c irc uits. The te mp eratu re c on trol eq uipm ent sha ll b e operated manually or through regulators or it shall be (made) operated

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a utom a tica lly with the help o f mo d ula r c ontrols. The c ha rt type tem p erature rec order sha ll be used for rec ording te mp . The freq uenc y of ca libration of te mp rec order sha ll b e three m onths & a prop er va lid sticker sha ll be disp laye d on the tem p rec order.

4.2

Materials All the connection materials required for the heat treatment, shall be of sta nda rd q uality & it shall be selec ted free of d efec ts.

5.0

Surfac e Cond itions The w eld s to b e he a t trea te d sha ll b e p rep a red free of g rea ses, lubric a nts d ust a nd c oa tings to a void d am a ge & short circ uiting of a c c essories eq uip me nts. Prior to the sta rt o f the PWHT, co mp on ent sha ll b e c hec ked to ensure t ha t a ll restrains are removed and the component is free to expand and contract and suitable and suffic ient sup p orts a re u sed . During heat treatment it shall be necessary to protect from oxidation the mechanical surfac es line flang e fa c es, threa d ed holes, threa d s b y the a p p lic at ion o f c oa ting suc h a s de oxaluminite or any ot her suita b le c oa ting ma terial. PWHT sha ll follow a ll we lding a nd rep a irs b ut sha ll b e p erform ed p rior to a ny hyd ro te st or other loa d test. Where p ra ctica ble, open p ipe ends of c om po nent shall be closed off to p revent the c oo ling effec ts assoc ia ted with d ra ughts (chimney e ffec ts). Heating elements shall be securely fixed in contact with the work piece by stainless steel or mild steel banding to suit the application. Under no circumstances shall g a lvanized wire o r ot her fixings likely to b e d et riment a l to t he p ipe m a te rial be u tilized . Up on c om p letion o f the Post Weld Heat Trea tme nt, the the rmo c oup le sha ll be removed and the areas of attachment dressed by either grinding or filling before being non-destructively examined using either dye penetrate or magnetic particle inspection methods by Client (if required) Client’s representative will sign and date the c olumn insp ec tion a fter Hea t Trea tme nt.

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6.0

Method The p roc ed ure for PWHT ha s to b e follow ed for the va rious ste el g ra d es a s m ent ioned below. Material Grade Alloy Steels ASTM A 335 P4

Tem p era ture Range 7050 - 7490

Hea ting/ Soa king Tim e 2 Hrs/ 25m m w a ll th ic kne ss so a king 2 hrs m inimu m

Ra te of Hea ting 1000 C /  Hrs/25mm wall thickness

Ra te of Cooling 1000 C / hrs /  25mm wa ll thickness

7050 - 7600

2 Hrs/ 25m m w a ll th ic kne ss so a king 2 hrs m inimu m 2 Hrs/ 25m m w a ll th ic kne ss so a king 2 hrs m inimu m 2 Hrs/ 25m m w a ll th ic kne ss so a king 2 hrs m inimu m 1 Hrs/ 25m m w a ll th ic kne ss so a king 1 hrs m inimum

1000 C / Hrs/  25mm wa ll thickness 1000 C / Hrs/  25mm wa ll thickness 1000 C / Hrs/  25mm wa ll thickness 2220 C / Hrs/  25mm wa ll thickness

1000 C / hrs /  25mm wa ll thickness 1000 C / hrs /  25mm wa ll thickness 1000 C / hrs /  25mm wa ll thickness 2220 C / hrs /  25mm wa ll thickness

7050 - 7490

7300 - 7900

5900 - 6500

7.0 7.1

Ba sic Req uirem ents to c a rryo ut PWHT a nd the m etho d olo g y Thermo c oup les a ) The th ermo c oup les sha ll b e o f the typ e ‘ K’ i.e. nickel-c hrom ium / nickel – a luminum typ e in a c c orda nc e with BS 1041. Pa rt – 4. The the rmo c ou p les shou ld ha ve initial c a lib ra tion check.  All the the rmo c oup le w ires should ha ve va lid c ertific a te o f co nforma nc e w ith a to leranc e of 305mm ≤610 – 3 T/ C. III. Fo r p ipe s ha ving d iam et er > 610; - 4 T/ C. If multiple he a ting zone s a re used b eing no t m onitored b y a prima ry T/ C, then a d d itiona l req uirem ent s of T/ C shou ld b e d one . d ) Fo r loc a lized PWHT of ve ssels it sho uld b e m o nito red using a m inim um of fo ur set s o f the rmo c oup les, with ea c h set ha ving o ne T/ C o n the inside & o utside surfa c es. The positioning of each set shall be done on the weld center line at 90 0 spa c ing a round the vessel c irc um ferenc e. We ma y req uire a d d itiona l T/ C if multiple hea ting zone s a re used & wh en it is not m onito red b y a p rim a ry set o f T/ C. As per client’s requirement or as per code additional thermocouples shall be fixed to c onfirm hot zone or grad ient limitation. •

e ) Thermoc oup le extension c a b le should b e nec essarily c omp ensa ting c ab le with connec tion through p lug & soc ket a s Cop pe r lea d (+ve) to nickel chromium (Non Ma gnetic) Co nsta nta n lea d (-ve) to nickel a luminum (Mag netic) f)

of

c op p er-c onsta nta n

The th ermo c oup les & p ositions sha ll b e ide ntified on th e p a rticula r te mp eratu re rec ording c hart by numb er of c olour / symb ol of sta mp

g ) After the c om p letion of PWHT rem ove the the rmo c oup les & g round smo othly the a rea , to clean & we thus achieve sound metal. As per the specification / instruction of the insp ec to r the a rea s a re t o b e e xa mined b y MT or PT a fter grind ing.

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7.2 I.

II.

III.

IV. V.

7.3 I.

II.

III.

IV. V.

Elements The c irc um ferential ba nd w idth w hich ha s to b e he a te d sha ll b e m inimum Six (6) time s the thickness of the shell material being welded from each edge of the weld, but not less tha n25mm , wh iche ver is g rea ter. The ma terial temp erature shall exce ed half the hea t trea tme nt temp erature ove r a b a nd at least 2.5 □ Rt w here ‘ R’ is the b ore rad ius & ‘ t’ is the nom inal wa ll thickne ss on ea c h side of the we ld times. For welds on pipes diameter≥250mm, the elements shall be divided in to two or more c ontrol zone s, b eing to p & b otto m w ith p a ds a pp lied symm etric a lly. If the e lem ents a rrang em ents is not b eing c a p a b le o f d esired c onfigura tion the n. The c ente r time c irc umferential ga p b etw ee n two ba nd s sha ll not e xc ee d 30mm o r ‘ t’ w hic he ve r is lesse r. The long itudinal ga p s be twe en eleme nts sha ll not b e mo re tha n the wa ll thic kness or 50mm, whichever is less. We should be careful to ensure that there are no gaps in 6’O clock position. If the w elds a re o f two sep a ra te w a ll thickne ss the n the e leme nts sho uld b e so a rra ng ed to give sid e to sid e c ontrol in ad dition to top & b otto m c ontrol. In the c a se o f inc lined or vertic a l we ld s the p a d s sha ll b e a rrang ed ab out the we ld to g ive indep end ent co ntrol ab ove & b elow w eld ce nterline. Elem ents are a tta c hed by Bla c k a nnea led iron wire Mild stee l 12mm wide b a nd ing stra p . The rma l Insula tion Therma l insulation should b e a c hieved b y follow ing m ea ns. With c era m ic fib er, usua lly in sta inless ste el m esh a s fo rm of m a t, minimu m d en sity of Wool, mineral with m inimu m d ensity o f 80Kg / m3 96Kg / m 3 The insula tion d ista nc e shall be up to a minimum d ista nc e o f 305mm b eyond the e dg es of the hea ting b and s or up to a distanc e d etermined by the produc t of b ore rad ius times the m a xim um w a ll thic kness w hic he ve r is less. The num be r of layers & e xtent of insulat ed area shall be d ep end ent on * Wall thickness * Pip e o r fitting d iame ter * Gra d ient requirem ent * Site c on d ition s In a ll c a ses the m inim um req uirem en t sha ll b e t w o (2) laye rs for d en sities (80Kg / m3 & 96Kg / m 3) Insulation shall be fixed using black annealed iron wire taking care, not damaging or c utting into the insulation. By follow ing p rop er PWHT c yc les, the item or the p a rticular joint sha ll b e c om p leted & th e c oo ling rate should be c ontrolled unde r insula tion.

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7.4. I. II. III.

IV.

8.0. I.

II. III.

IV.

V. VI. VII.

9.0. I. II.

Tem p era ture Rec ord ing Tem p erat ure rec orde rs sha ll be c a lib ra te d a fter eve ry three m on ths or afte r rep a ir. The c a lib ra tion c ertific a te should b e kep t & a sticker shou ld b e stuc k on th e instrum ent . The te mp eratu re rec orde r sha ll b e o f the p ot entiom et ric self-c om p ensa ting typ e. The c hart should a lso b e a tta c hed to rec ord a ll rea dings. The sp ee d of the c ha rt should b e a d justed a t 25mm / hr, rec ording a ll monitoring of thermocouples, it should also be giving information’s of the difference in temperatures a nd the d ifferent trend s d uring the he at ing & c oo ling c ycle. The time te mp erature c ha rt should b e reco rd ing the hea t trea tme nt of those w elds unde rg oing the sa me c ycle for any pa rticula r sec tion. PWHT (Post Weld ed Hea t Trea tm e nt) Applicable codes shall be adhered to while demy stress relieving reductions in soak te mp erature, whic h a re a llow ed b y ASME sec . vii (Dir 1), a re no t p ermitted if hea t treatment is required due to service condition (sour service) or in cases where hardness c ont rols a re sp ec ified . Stress relieving t ime te mp erat ure sha ll b e a p p lica b le ove r a n a rea of m in 6t inche s (t = wa ll thickne ss of p ipe ) on b ot h side s of t he w eld b ut it should not b e less tha n 1” on b ot h side s. Sta rt the hea t trea tme nt c ycle on a n auto prog ra m w here in hea ting ra te sha ll not m ore than 2220C per hour, divided by maximum material thickness in inches, but in no case ab ove 2220C o n rea c hing 3160C . The soa k temp erature is d ete rmined or ad justed a s a me a n d ifferenc e in the up p er & lowe r limits. The m a ximum va riation in tem p erature sho uld no t b e m ore tha n 400C . So a king time sta rts whe n a ll thermo c oup les ac hieve this tem p erature. The c oo ling ra tes shou ld no t b e m ore tha n 2220C / hr divided by maximum material thickne ss in inc hes b ut no c a se a b ove 2220C . After attaining 3160C p owe r c ould b e turned off & on co oling the we ld to b elow 1500C the insulation / eleme nts c ould b e rem ove d. The m inim um soa king time sha ll b e o ne ho ur. The PWHT soa k pe riod sha ll b e in a c c orda nc e with the 80% limita tions as a p p lica b le t o the PQR’ s used d uring fab ric a tion. The c ont ra c to r’ s PQR c ould b e refe rred wh ile d oing PWHT. Precautions Che c k all ca b le c onne c tions using p rop er plugs & soc kets. Protec t the pow er c ab les & thermo co uple ca ble from d am ag e.

10.0. Documentations I. Proc ure the ap p rova l of the PWHT c ycle & a ssignm ent for the we ld joint to b e he a t treat ed . The d et a ils to b e inc lude d in the w ork shee t a re a s follow s: Ma te rial, wa ll thickne ss of shell, hea ting & c oo ling rat es, soa king t em p erat ure & t ime. II. Inform the c lient if you notice any d eviation in the hea t trea tme nt c ycle. 11.0.

Rep o rt & Rec o rds

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The he a t trea tme nt c ycle c ha rt shall b e treate d a s the p roo f & rec ord for any h.t completion. ISB te c hnician s will fill out t he rec ord shee ts of Hea t Trea tm ent (sa mp le a tta c hed ) p rior to sta rt o f a ny PWHT a nd c lient sha ll autho rize sp ec ifica tions c om p lying w ith g ove rning c od e. On c om p letion, the rec ord of the Heat Trea tme nt along with cha rt will b e subm itted to the c lient, as minimum the follow ing informa tion will be p rovide d : a . Client Id ent ity b . Contrac t/ Job Ide ntity c . Sp ec ifica tion Det a ils d . Spo ol numbe r, diamete r and weld numb ers e . Ma teria l sp ec ifica tion f. Thermoc oup le loca tions g . Hea ting a nd C oo ling Ra te h. Soa king (holding ) time i. Tec hnic ian na me  j. Location map of particular vessels k. Date a nd C hart spe ed Rec ords sha ll be ma intained for a m a ximum of three m onths with a ll cha rts & d oc ume nts.

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TABLE 1 Typ ic a l Ap p lic a tion For Ce ra m ic Hea ting Elem ents Elem ent CP3

Dim ensions *WxL 75 x 670

Volts 60

KW 2.7

CP4

100 x 500

60

2.7

150 x 330

60

2.7

CP8

205 x 250

60

2.7

CP10

255 x 205

60

2.7

305 x 165

60

2.7

CP15

380 x 145

60

2.7

CP16

410 x 125

60

2.7

CP21

535 x 100

60

2.7

610 x 85

60

2.7

1200 x 45

60

2.7

255 x 85

30

1.35

CP20L

500 X 45

30

1.35

CP24H

635 X 330

220

9.9

CP6

CP12

CP24

Ide ntity

Hea vy wa ll hea ting elem ents

Stand ard hea ting elements

Long strip heating elements

CP48 CP10L

Sho rt strip he a ting e leme nts

Electrical

* The w idt h W – d eno tes the d ista nc e a c ross the ta ils in mm L  – d eno tes the leng th in mm

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IBRAHIM BIN S. AL BRAHIM EST.

EXAMINATION PROCEDURE

Document# ……………………….

Page

Approved by: General Manager

Issue date: ………………………………

ATTACHMENT

THERMOCOUPLE LOCATIONS

DIA ≤ 305 MM

DIA > 305 MM ≤ 610 MM

DIA > 610 MM

NOTE: 1. "

" is Thermocouple Location

2. Additional Thermocouple wil l be used i f multipl e heat control zones are used, in which a controlzone is monitored by any of the Primary Thermocouple.

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