CB372

8/10/2019 CB372

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C oiled Tubes

Sug g est ed Fie ld Weld ing Pro ced ure (GTAW) f o rCoiled Tub ing Gra d es HS70, HS80, HS90, HS110

CONTACTTen a ris Coiled Tub es8615 E. Sam Houston Pkwy N.77044 Houston Texas [email protected](1) 281 458 2883 tel

(1) 281 458 2886 fax

This gu ideline m ay be u sed to qualify w eld procedures for allgauges and grades of Tenaris coiled tubing up to and includingH S-110™ . The success or failure o f butt w elds on coiled tubingis highly dependent on the skill of the w elding personnel, thetype of w elding equipm ent used, the m etho d of heat extractionduring w elding, and the level of non-destructive exam inationafter the w eld is com plete. C aution should be exercised w henusing strings con taining butt w elds because the q uality of thew eld affects the yield strength and the resistance to environ-m ental cracking. A s w ith all w elding procedures, Tenaris C oiledTubes recom m end s qualifying a w eld procedure by m echanicaltesting sam ples prior to w elding on actual strings.

Tw o things m ust be considered prior to w elding coiled tubing:the w elding equipm ent and the w elding person nel. These tw ovariab les dictate joint design, alignm en t clam p design, an dchill block design.

Joint DesignTypically a square butt w eld w ill be used for tubing w hich is lessthan or equal to 0 .125" thick and a “V”groove w ill be used forheavier w all tubing. H ow ever, the decision to use a square buttjoint versus a “V”groove should be based on the available w eld-ing equipm ent and skill of the o perator. For instance, an auto-

m atic orbital w elding m achine m ay be cap able of a full-penetra-tion w eld in a single-pass on 1.25 " O D X 0.156 " w all coil tub -ing. H ow ever, in the field w here less sophisticated equipm ent isavailable, such tubing m ay be considered “heavy-gauge”and am ultiple pass, “V”groove procedure w ou ld be used. W hen uti-lizing a “V”groove procedure, the bevel angle m ay vary from30° to 45° depending on the am ou nt of pen etration the equ ip-m ent and/or op erator is capable of. A good rule of thum b forV-groove w elds is a 37° bevel w ith a 1/16" gap and a 1/32"-1/16"land. For m anual square groove butt w elds, Tenaris Coiled Tubesrecom m ends using a 1/32" to 1/16" gap betw een tube ends.

Alignment clampsU sing an orbital w elding m achine w ill also d ictate the shape o fthe align m ent clam p: low clearance align m ent clam ps m ay beused w ith au tom atic equipm ent w hereas a m anu al w eld w illrequire m ore access to the en tire g irth of the w eld. The align-m ent clam ps shou ld ensure p rop er align m ent of the axis andgap m aintenance during w elding .

Chill blocksStandard chill blocks for m anual w elding should be m ade fromcop per m aterial, 3"- 4" long, 3/8" (m inim um ) thick an d the IDof the ch ill block sho uld m atch the

° -Water Cooled

Silver Solder Tubing to Block

CopperChillBlocks

Detail A-1, A-2

30º 45º

Pipe Clamp Coiled Tubing

Detail A-1Square Groove: <0.125"

0-1/6" Gap

Detail A-2“V” Groove: >0.125"

0-1/6" Land and Gap

Water Cooled

8/10/2019 CB372


O D of the p ipe. The thicker the ch ill block, the m ore h eat itw ill extract; chill blocks m easuring 0.5" - 1.0" thick are o ftenused in the field. The en d o f the chill block m ay be beveled ata 30° to 45° an gle for easier access. C hill blocks for orbitalw elding equipm ent w ill have to be custom design ed and test-ed to ensure proper heat extraction. Tenaris C oiled Tub es rec-om m ends that all H S-90™ and H S-110™ strings be w elded

w hile using w ater-cooled chill blocks for heat extraction. Inaddition, w ater-cooled chill blocks should be used on low ergrades of coiled tubing w ith w all thicknesses greater than andincluding 0.190". Standard chill blocks m ay be used on low ergrades w ith w all thicknesses less than 0.190" how ever, cau-tion should b e used as low er yield strengths m ay exist. W ateror ethylene g lycol circulation m ay b e applied w ith running tapw ater or a 5 g allon b ucket w ith a sm all pum p. Soldering o rbrazing a copper tube to the back end of the chill block w illprovide an adequate couple betw een the chill block and thew ater sou rce as sho w n below .

Below is a step-by-step procedure for w elding coiled tubing1. Straigh ten bo th ends of tub ing to be w elded. C ut ends oftubing square o r m achine a b evel using a b eveling tool,grinder, or file. D eburr all cut edges.

2. If the tub ing is w et inside, place a sm all am ount of solubletissue o r toilet paper abo ut 12 " from the end of the tube tostop seepage.

3. U sing a sm all flat/curved tip chisel, or a sm all round/curvedfile, taper/rem ove the inside w eld b ead 0 .25"- 0.5" from theend of the tube. A chisel ground w ith a cu rve sim ilar to the IDof the p ipe w orks best for this procedure. Extrem e care shouldbe taken not to nick o r cut the ID of the p ipe. If a n ick o r cutis m ad e into the tub e w all, or an y of the p ipe w all is filed off,cut that section off an d start over. It m ay b e n ecessary torem ove the b ead before doing the final w eld preparation instep 1.

4. Po lish the end of the tube using em ery cloth or a fine w irebrush abou t 2 inches back from the end on the O .D . andabout 1 inch b ack from the en d o n the I.D . The final appear-ance sho uld be sm oo th shiny m etal on the O .D . and I.D . ofthe tube. C ircum feren tial grooves an d grinding m arks signifi-can tly decrease fatigue life and should be polished sm ooth

using em ery cloth or a fine w ire b rush. Please assure that allsand pap er and em ery cloth is N O T alum inum oxide.

5. U se alcohol or other appropriate degreasing agen t to cleanthe inside and outside o f the tube. A ssure that the surfacesnear the w eld prep are clean and dry. D o not use gasoline.A void contam inating the clean surfaces during alignm ent instep 6. Re-clean if necessary after alignm en t.

6. Position tube ends in a fixture so that the ends are b utted

together. U se a straight ed ge (at least 8 inches long) to assurealignm ent on all axes. In order to m aintain the p roper gapw idth, use a sm all piece of w eld consum able betw een the tw opipes during the alignm ent process. It is also recom m endedthat you leave the spacer w ire in w hile w elding the first sideof the tube to p revent the gap from closing. Rem ove the spac-er before w elding the o ther side.N O TE: It is extrem ely im portant to assure that the tubes are buttedsquarely and the tube lengths adjacent to the w eld are straight.

7. Position chill blocks (heat sinks) on either side o f the joint tobe w elded. For groo ve w elds, the chill blocks m ay be m ovedto the ed ge of the groove during the root pass, and thenm oved ap proxim ately 3/16 " aw ay from the ed ge d uring sub -sequen t passes. C hill blocks for m aterial thicker than 0.190"or grades greater than H S-80‘should be w ater-coo led form axim um heat extraction. For square butt w elds, the chillblocks sho uld be placed abou t 3/16 " from the edge of thetube. See the “C hill Block”section on page 1 for m ore infor-m ation on chill block d esign.

8. W ind curtains shall be positioned to insure there is no airm ovem ent in the vicinity of the w eld during the w eldingprocess, w hich could interrupt the co ver gas.

9. The full penetration w eld shall be accom plished using theG TAW (a.k.a. TIG ) process w ith high frequency start and a3/32-inch thoriated tungsten electrode. Scratch starting m aycontam inate the w eld an d is no t recom m end ed. A75% H elium /25 % A rgon shielding gas m ixture w orks w ell forthis type o f full penetration w eld. W elding param eters shouldbe D C EN , 50-100 A M PS, 9-15 V O LTS, and 1 -2.5 ipm , how everthese m ay vary slightly based on the w elding m achine you areusing. 100% A rgon shielding gas is suitab le but w ill requirehigher am perages for full penetration, and m ay increase H A Z(H eat A ffected Zone) hardnesses. Tenaris C oiled Tubes recom -m end s using A W S ER70S-2 or ER7 0S-6 1/16-inch diam eterw eld consum able for all w elds on H S-90 ‘grade tub ing and

below . (con tinued)

www.tenar is .comJanuary 2007 . © Tenaris. A ll rights reserved

8/10/2019 CB372


For H S-110‘coiled tubing, Precision Tube Technology recom -m ends using A W S ER80 SD -2 1/16 " filler m aterial. The w eldshall be m ade using a single-pass stringer bead w ith a 0.25 -0.50 inch overlap on the start and stop. Proper cleaningbetw een each pass is recom m ended for heavier tub ing . Asm all am ount of oscillation m ay b e necessary to assure tie inof both sides of the w eld. H ow ever, large am ounts of oscilla-

tion should be avo ided as w ide bead s tend to decrease fatigueresistan ce of the string.

10. Rem ove chill blocks and allow to cool to touch after eachpass. W hen using w ater-cooled chill blocks, leave b locks inplace, and allow blocks to coo l to touch before proceed ing .

11 . A fter the w eld is com plete, rem ove chill blocks and dressthe w eld bead to w ithin -0.00 0/+0.005 in of the tube surface.The finish shall be sm ooth w ith no nicks or cuts.N ote: do n ot rem ove m aterial from the parent tube surface.Factory w elds are dressed w ith a sm all hand grind er to rem ovethe cap of the w eld, and then filed sm ooth w ith a flat file.Final finishing is done w ith em ery cloth until sm ooth. It is nec-essary to rem ove the cap prior to rad iography to ensure a fullpenetration w eld.

12. It is vital that X-rays be m ade of each w eld. A procedurefollow ing A SM E Section V, A rticle 2 using the double-w all,double-view ing techniqu e for com plete coverage and capableof very high qu ality (2T-hole # 7 penetram eter) is recom m end-ed for detecting sm all defects. Experience has show n that lackof penetration and even very sm all defects can lead to suddenfailure. W elds are rejectab le for any defect: porosity, undercut,lack o f pen etration, lack of fusion, cracks or underfill.

Recom m ended Equ ipm ent and Sup pliesEquipm ent/Tools:H igh frequ ency start G TAW m achine:150 A m p m inim um , rem ote pedal controlBeveling M achine, 4" G rinder, or FileRou nded C hiselH am m er

Fine W ire Brush (Ro un d)D rill/D ie G rinderA lignm ent C lam pStraight-Ed geW ire C uttersFlat File (Finishing O D )Portable Bandsaw or H acksawC opper C hill Blocks(Water Bucket and Pump if Required fo r w ater cooling)

Su pplies3/32" Thoriated TungstenER70 S-2 o r ER70 S-6 (H S-90 ‘and b elow ) orER8 0SD -2 (H S-11 0‘) W eld C onsum ableLeather G lovesW elding H oodProtective w indshield or TarpA lcohol/D egreasing A gentLint Free RagEm ery ClothTissue Paper

www.tenar is .comJanuary 2007 . © Tenaris. A ll rights reserved

C hill Blocks

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CB372