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WELDING OF HDPE PIPES AND FITINGS
WELDING OF HDPE PIPES AND FITINGS REVISION RECORD Rev . N° 01
ON-HOLD POINTS N°
Reason for Revision
Revised on Page
Issued for Review
Reason for On-Hold-Status
LIST O !TT!CH"ENTS N°
Des#ri$tion
Date 30.06.2014
Page
Date
Page
Date
Contents GENERAL DATA.......................................................................................................................................
). TESTIN* THE &ELDIN*.....................................................................................................................
GENERAL DATA
Location: Gas Conditioning Facility Bulbuceni Scope: Establishing the procedure for welding HDPE pipes and fittings.
WELDING OF HDPE PIPES AND FITINGS Customer:S.C. O! PE"#O S.$. Contractor :S.C. $#$% G$&.S.$ . %
PROCEDURE
%.%
&elding 'et(ods
%.%.%
+utt ,elding
"his welding procedure can be done only with special e'uip(ent. "he ends of the pipes or fittings are fi)ed in the special (echanical adaptors of the welding e'uip(ent which has a special (echanical or hydraulic unit that allows (o*e(ent and (aintaining pressure on the pipe ends. "he energy necessary for welding is transferred *ia a heating plate with controlled te(perature. $fter re(o*ing the plate+ the ele(ents to be welded are pressed against each other with a specific pressure without any other added (aterial. "hese steps are represented bellow in figure ,.
Weldin preparation
Before beginning the weld the te(perature of the heating ele(ent will be chec-ed. "his can be done with the help of a surface te(perature (easuring de*ice. n the case of auto(ated butt welding e'uip(ent+ te(perature control is done auto(atically and welding can be done only after the re'uired te(perature is reached. "o pre*ent cooling through the e)tre(ities of the pipes by the air current+ the ends will be shut. "o obtain opti(u( welds+ the heating ele(ent will be cleaned when necessary with clean paper soa-ed with ethylic alcohol. "he surface of the heating ele(ent (ust be intact in the wor- area. "he pipes will be aligned a)ially before fi)ing in the welding e'uip(ent. Easy a)ial (o*e(ent of the welded ele(ents will be assured by using rollers or pendulu( suspension. "he e)tre(ities of the pipes to be welded (ust correspond/ o*als will be ad0usted with appropriate e'uip(ent. "he surface to be welded will be (illed before welding with clean e'uip(ent as to be parallel after fi)ing. De*iations fro( parallel (ust not e)ceed the *alues presented in table ,. Tale % "a/i'u' s$a#e ,idt( et,een 'illed surfa#es Pipe exterior diaeter #axiu space widt$ !" !" under 3%% 0( % 400 & 630 1( 0 630&'00 1( 3 '00&1000 1( % over 1000 2( 0
WELDING OF HDPE PIPES AND FITINGS De*iations fro( coa)iallity (ust not e)ceed 1+, ) wall thic-ness. Surfaces to be welded (ust not be dirty nor touched by hand. illed (aterial fro( inside the pipe will be cleaned. Weldin e!ecution 2hen butt welding the surfaces to be welded will be brought to weld te(perature *ia heating plate and are 0oined under pressure after it is re(o*ed. "he te(perature of the heating ele(ent is 3114331 C. n case of thinner walls the higher te(perature will be used and in case of thic-er walls the lower one. See figure 3. º
igure )
Alinment "he surfaces to be welded are (o*ed towards the heating ele(ent until they are 0oined parallel and co(pletely to it. "his is can be seen in the welding sea(. $lign(ent is co(plete when the height of the welding sea( is the sa(e all around the pipe. $lign(ent is co(plete when the height of the weld sea( corresponds to the *alues in table 3 Tale ) *uide values for utt ,elding at )0°C )al !lign'e Heating l nt /eating t$ic #iniu tie 10 x *ne sea wall ss $eig$t +0( t$ic*ness !s" !" 1% ,- 2
n this fa5e the surfaces to be welded are preheated at a constant pressure of 1+,6 78((3. $lign(ent pressure will be e)erted during the entire align(ent period. Heatin
WELDING OF HDPE PIPES AND FITINGS n order to (o*e to the heating phase+ the surfaces (ust be touching the heat plate under reduced pressure. For this the pressure will be reduced al(ost to 1 9(a). 1+13 78((3:. During the heating phase+ heat enters the surfaces and brings the( to welding te(perature. Heating ti(es will be ta-en fro( "able 3+ colu(n ; "emo#in t$e $eatin plate $fter heating+ the heating plate (ust be re(o*ed without da(aging the ends of the pipes. "he surfaces to be welded are then i((ediately 0oined. "his phase (ust not ta-e (ore ti(e than that indicated in "able 3+ Colu(n <+ in order to a*oid the cooling of the surfaces to be 0oined and thus producing a defecti*e weld. %oinin "he surfaces to be welded (ust be 0oined slowly. "he pressure needed for 0oining (ust applied laniary as (uch as possible. "he ti(e necessary for increasing pressure to (a)i(u( is ta-en fro( "able 3+ Colu(n 6. Specific 0oining pressure is 1+,6 78(( 3. =oining pressure (ust be (aintained throughout the entire cooling period+ 9see "able 3+ Colu(n >:. Great (echanical load during re(o*al fro( the fi)ing e'uip(ent is allowed only after prolonged cooling. $fter 0oining a *isible double e'ual weld seal (ust be *isible. "he shape of the sea( gi*es guiding infor(ation about the unifor(ity of the welding. Possible different sea( shape (ay be e)plained by different flow beha*ior of the welded (aterials. %.%.)
Ele#tro fusion ,elding
2ith electro fusion welding the welding surfaces 9pipe e)terior and electro couple interior: are heated to weld te(perature *ia electric current passing through e(bedded wires+ close to the interior surfaces of the electro couple. By heating the pipe a dilatation of the (aterial 9precisely calculated: ta-es place and produces the necessary pressure for welding. "he para(eters of the welding and the current necessary for the electro couple are controlled and registered by the welding e'uip(ent. "he electro couple contains a bar code which contains the necessary infor(ation for welding. Guide *alues of these para(eters are found in the following table? E/terior dia'eter 6''7
&elding ti'e 8se#9 at an e/terior te'$erature of
0ºC in 20 2% 32 40 %0 63 50 110 12% 160 1'0
)0ºC
20ºC
30 C
in
ax
in
ax
in
ax
in
1
26
1
26
1
26
1
26
10
1
26
1
26
1
26
1
26
10
1
3%
1
33
1
31
1
26
10
1 3
2'
45
26
4%
2%
44
23
42
1%
41
6
35
6%
3'
62
36
60
1%
25 %1
1
113
66
106
62
100
%'
54
20
12%
153
11
1'1
110
11
103
160
20
16'
2%4
1%5
240
1%0
22
141
21%
30
% 120
206
311
154
25%
1'4
2'0
1%
266
30
264
401
2%0
3'1
23'
363
22
346
30
134 206
25'
4%%
2'3
433
20
412
2%
354
30
1 26 1 26
42 65
ax
%0ºC
"ini'u' #ooling ti'e 6'in7
ax
WELDING OF HDPE PIPES AND FITINGS 200 22%
15 20
346
%21
325
456
314
44
300
4%3
30
31
%60
3%3
%34
33
%10
322
4''
30
21' 325 2' 423 314 4' 364 %4 350 %''
Weldin preparation
"he pipe (ust be clean in the welding area. $fter cutting to desired length the surface of the pipe is scrapped on a length greater than that inserted into the electro couple. "hus+ it can be seen after the welding has ended that this operation has been e)ecuted. "he scrapped surface is degreased with a special nap-in that contains isopropyl alcohol or si(ilar. "he electro couple is re(o*ed fro( its bag+ without touching the interior. "he ends of the pipes (ust be cut perpendicular with ade'uate e'uip(ent. "he o*alnes of the pipe (ust not be greater than ,+6 @ of the e)terior dia(eter. f necessary ade'uate e'uip(ent (ust be used to bring the( bac- to round shape. "he electro couple is inserted onto the pipe without e)cessi*e force and afterwards the ends of the pipe are fi)ed in a speciali5ed de*ice so as not to (o*e during welding. "he electro couple should be easy to insert. "he contactors for lin-ing to the welding de*ice (ust be accessible. "he bar code is then read to gi*e the de*ice the necessary data about the electro couple. Weldin e!ecution
"he cables of the welding e'uip(ent are connected to the electro couple. "he e'uip(ent is operated according to (anufacturer instructions. $fter welding and cooling ti(e ha*e passed+ the fi)ing de*ice is opened. So(e electro couples allow *isual chec-ing of the weld+ (elted polyethylene is seen in specially designed areas or there are ,+ 3 s(all indicators that rise to the surface of the electro couple if the welding was successful. %.%.2
Ele#tro fusion #onne#tion fittings
"hese so called Asaddle fittings ha*e a support surface for fusion+ a branch with a threaded lid 9used for guiding the -nife when (a-ing the hole in the pipe on which the fitting is (ounted: and the actual connecting branch. For electro fusions welding the following steps are ta-en? Step &: 'ar(in t$e )usion sur)ace o) t$e pipe *main pipe+ to ,$ic$ -ou are connectin . dirt and i(purities are cleaned with a clean cloth/ . without re(o*ing the fitting fro( its pac-age+ it is placed on the (ain pipe. "he contour is (ar-ed clearly and continuously around the connection fitting.
Step /: Preparin t$e )usion sur)ace o) t$e pipe to ,$ic$ t$e connection is made 4 a scrapper is used to ta-e off a layer of 1+341+< (( fro( the (ar-ed surface/ 4 all the polyethylene re(ains (ust be re(o*ed. "he clean surface (ust not be touched.
WELDING OF HDPE PIPES AND FITINGS Step 0: C$ec(in t$e connection )ittin 4 the fitting is re(o*ed fro( the pac-age without touching the contact surface/ 4 the correct si5e will be chec-ed/ 4 the lid is re(o*ed and the chec-ing of the cutting branch will be done. Step 1: Gettin t$e connection )ittin in place 4 the screw for fi)ing the de*ice (ust be co(pletely unscrewed/ 4 the connecting surface is chec-ed again for i(purities. 7o fusion surfaces are touched/ 4 the fitting is set into the de*ice/ 4 the fitting is fi)ed onto the prepared surface of the pipe 9(ain pipe:/ 4 the tightening screw is turned until the correct pressure is indicated/ 4 the co*ers of the electric connectors are re(o*ed/ 4 during this step the connecting pipe will also be prepared according to earlier instructions for welding pipes *ia electro fusion. "he pipe is place in the connecting branch of the connection fitting. Step 2 Electro )usion process 4 cables are connected to the support ter(inals/ 4 the fusion ti(e indicated on the stic-er is chec-ed and entered into the ti(er of the control unit/ 4 the start button is pushed/ 4 cables are re(o*ed carefully without (o*ing the fitting/ 4 the cooling ti(e on the stic-er is respected. Step 3: Final operations 4 all tools are re(o*ed/ 4 0oints are *isually inspected+ insuring that fusion indicators are not stic-ing out/ 4 the pipe on which the fitting was (ounted is drilled and the cap on the cutting branch is closed bac-. ). TESTIN* THE &ELDIN*
4 the hydraulic test will be done on sections of (a)i(u( 6114,111 (+ ensuring all fittings are in place/ 4 all testing e'uip(ent will be chec-ed before testing/ 4 each section tested will be closed4off at the ends and anchored so as to resist to the forces that appear during testing/ 4 all 0oints will be cleaned to easily see any lea-ing/ 4 e(ptying all air in the pipe is i(portant for the accuracy of the test and thus the filling of the pipes (ust be done in a controlled way+ eli(inating the air while filling it and pressuri5ing it. "he following steps will be ta-en for testing? 4 pu(ping e'uip(ent will be installed at the lowest end/ 4 e*acuation *al*es and airing *al*es are (ounted on the lowest respecti*ely the highest end of the pipe/ 4 the air *ent are opened/
WELDING OF HDPE PIPES AND FITINGS 4 at each (ano(eter will sit an obser*er with a synchroni5ed watch with those of the other obser*ers/ 4 the pipe is filled with water+ the air *ents are closed and the pu(ping is continued until desired pressure is achie*ed/ 4 the testing pressure is (aintained by additional pu(ping+ for ;1 (inutes+ to sustain the e)pansion of the polyethylene pipe/ 4 the pressure (ust then be relie*ed by rapid e*acuation of water fro( the pipe until the no(inal pressure is obtained at the control (ano(eter/ 4 the *isual testing of the pipe is perfor(ed to chec- for lea-s/ 4 the (ano(eter *alues are read and written down e*ery? 4 14,1 (inutes reading at e*ery 3 (inutes/ 4 ,14;1 (inutes reading at e*ery 6 (inutes/ 4 ;141 (inutes reading at e*ery ,1 (inutes. "he pressure should increase due to the *iscos elastic response of the (aterial. "he testing is successful if after 1 (inutes+ the pressure drop is not lower than ,1@ of the testing pressure and no lea-s appeared. "he results of the pressure test can be influenced by the air that wasnt co(pletely re(o*ed fro( the pipe or by air te(perature *ariations. t is reco((ended that testing ta-e place in days without great *ariations in te(perature. During cold periods 9under 1 1 C:+ e(ptying the pipe is done i((ediately after testing. f the test is not satisfactory the deficiencies will be fi)ed and the test will be redone. "he results are recorded into a report that will be an integral part of the preli(inary and definiti*e co((issioning of the pipe. $fter all wor- is done+ a test on the entire length will be done+ under operating conditions. $fter a satisfactory test+ the pipe section will not be sub0ected to any other welding operations or hot and cold defor(ations.