CA1167290A - Apparatus for flash welding of pipes - Google Patents

Abstract

AN APPARATUS FOR FLASH WELDING OF PIPES

Abstract An internal apparatus for flash welding pipes toge-ther in end to end relationship both under factory condi-tions and in the field, for example in laying trunk pipe-lines, comprises an elongate supporting member carrying an axially movable clamping assembly with electrode jaws for clamping one pipe, an axially immovable clamping assembly with electrode jaws for clamping the other pipe, and a do-ughnut-type welding transformer. The welding transformer is disposed at the side of the axially immovable clamping assembly, which is distant from the joint. The invention consists in that the axially immovable clamping assembly is mounted on the elongate supporting member in a manner to provide an annular clearance therebetween such that there are extending therethrough two coaxial contact tub-es, which are electrically insulated from one another and connect the welding transformer with the electrode jaws, whereby in operation a welding circuit is established.

Description

~ackground o~ the In~ention 1, ~ield Q~ the In~ention The present invention relate3 to app~ratu~ ~or fla~h welding o~ p~pesJ which may be used both under ~ield con-dition~ ~or e2ample in laying trun~ pipeline~ ~nd undex factory condition~9 that is ~or welding pipes o~ xelati~e-ly large diameter~
~ he axisting app~ratus for ~la~ welding of pipe~
can ba clas i~ied into one of the three ~ollowi~g catQgo-ries:
(1) external welder~, ~rherein ~11 the meohanism9 in-cluding the welding trans~o~mer, i~ ~rranged outside the pipes to be welded;

(2) internal welder~t whexein all the mech~ni~m, i~-cluding the we~ding txans~o~mer9 is arra~ged in~ide the pipes to be welded9

(3) combination welders, wherein centering ~nd up-setti~g mechanism~ are accomodated i~side the pipes to be welded, where~ the welding trans~o~mer and current-cont-~:
a~t: mschani~m~ are outside the plpe~, :: External welders are recommended for weldi~g pipe~o~ relatively small diameters~ one would naed a heavy ~nd cumber~omQ ~xternal welder to ~eld large~diameter pipe~O
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In the ca-~e o~ exte~nal weldex~, it is very di~icu t to inspect the joint.

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Internal welders are recommended for welding large-diameter pipes both in the field and under factory conditions when the welder is moved from one joint to another as is the case of laying a trun~ pipeline. The size of an internal welder is restricted by the pipe diameter, and thus first-class design and manufacture are imperative, especially with regard to the welding transformer and current-contact elements.
Combination welders are normally rec~mmended for welding medium-diameter pipes (820 to 1020 mm) under factory conditions. The mechanism of such welders is found both inside and outside the pipe, wherefore the mechanism and the joint are not easily accessible. The large size is another disadvantage of combination welders.
Therefore, the internal welders are best suited for flash welding of large-diameter pipes.
2. Description of the Prior Art U. S. Patent ~o. 3,164,712 teaches an apparatus for flash welding of pipes, designed to operate inside the pipes and comprising an elongate supporting member carrying an axially movable and an a~ially immova~le clamping assemblies for clamping the pipes, which assemblies having electrode jaws connected through a current lead-in to a welding transformer.
The prior art apparatus comprises a doughnut-type ~ , ' ,.

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welding trans~o~mer arranged on one of the cylinders in the axially immovable clamping ~ssembly, that i~ clear o~
the joint. The electrode jaw3 a~d the tran~fo~mer are con-nected by means o~ fle~ible buses~ ~ha electrode jaws are equidistantly arranged sn a circumference and in~ul~ted ~rom the struoture of the apparatus~
In operation, the ~lashing action is initiated but OXl some portions of the end face of the pipe~ being ~eld-ed, i.e~ on the portions which are in the close~t pro~lmi-ty to each other, inasmuch as the pipes are not ideal both alo~-g the circum~erence and over the end ~a¢e. A~ the fla-shing proceeds the whole end face is brought in contact.
As a conse~uence at the initial ~tage o~ the fl~shing ac tion the tran~former operates partlally, that is some o~ -it~ windings only are under load and those are windings that are closest to the end face portions being flashed there~ore the trans~o~ner power i~ con~umed fractio~ally nd the initial stage of -~lashing i~ too pro}onged~ The duration of the initi~l stage of ~ hin~ a~ect~ the du-ration o~ the ~hole welding proces~ which restrict~ a po~ible increase in the producti~e capacity o~ the prior art ~pparatu~.
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Summar~ o~ the Invsntion ~; An object o~ the invention i~ to provide an appara-tus ~or flash welding o~ pipe~, designed to oper~te in3ide the pipe~, having a impli~ied ourre~t laad-in~

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~ nother object o~ the invention is to pro~ide an ap-paratus Lor ~lash welding o~ pipe~, designed to operate inside the plpe~, which~ due to a ~truoturally 3implified current lead-i~, provides for a reduced initiA1 stage of flashing.
Sbill another ob~ect of the invention i~ to provide a~ apparatus for ~lash welding o~ pipe~9 designed to ope-rAte inside the pipes~ which ~eature~ a~ ~mproved produc ~ion capaci~y~
Yet another object o~ the invention i~ to provide an apparatu~ ~or ~lash welding of pipes~ da~igned to operate in~ide the pipe~, whi¢h is more reliable 1~ operation.
The~e and other object~ o~ the invention are attai-ned by the provision of an annular clearance between the axi~lly immoYable clamping assembly and the elongate sup-porting member and the arrangement o~ a contact tube mean~
in the clear~nce~ ~he contact tube mean~ compri~e~ two co-a~ial contact tube~ 9 which are electrioally insulated ~rom one another, ana each ha~ one end thereo~ termin~ti~g at corre~ponding tap~ o~ the doughnut~type welding tran~for-mer and the other one electrically connected bO corre~pon-ding alectrode jaw~ of both the axially movable and the a~ially immo~able clampin~ a~emblie3J
Su~h ~ contact tube mean~ mple in oonstru¢tion and hence it enh~nce~ the reliabilit~ of the apparatus ~or a~h welding o~ pipe~. With ~uch a contact tube mea~ the 5 ~

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input power from the welding transformer is reduced and the time of the initial stage of flashing is shortened, which improves the productive capacity of the apparatus for flash welding of pipes.
The eLectrical connection of each contact tube with the electrode jaws may be realized by means of a flexible cable to maintain the same electrical connection as the jaws move radially in clamping the pipes prior to welding and releasing thern after welding.
In one aspect of the present invention, there is provided an appaxatus for flash welding of pipes, designed to operate inside the pipes and comprising an elongated supporting mernber with an axis adapted to coincide with the axis of the pipes to be welded. An axially movable clamping assembly for clamping one of the pipes to be welded is mounted on the elongated supporting member and carries electrode jaws. A flash-ing and upsetting assembly is operatively connected with the axially movable clamping assembly for aligning the pipes to be welded as flashing and upsetting actions proceed. An axially immovable clamping assembly -for clamping the other one of the pipes to be welded is mounted on the elongated supporting mernber in spaced circumferential relationship therewith and also carries electrode jaws. A doughnut-type welding transformer is mounted on said elongated supporting member adjacent the side of said axial~ly ~immovable clamping assembly distant -from the electrode jaws thereof. Two contact tubes electrically insulated from one another are coaxially disposed between the axially immovable clamping assembly and the elongated supporting member with one end of each of said contact tubes terminating at corresponding taps of said welding transformer, while the other one i5 electrically connected to corresponding electrode jaws of both axially movable and axially immovable clamping assemblies.
Brief Description of the Drawing A better understanding of the present invention will be had from a consideration of the following detailed description of a preferred embodiment thereof, ta~en in conjunction with the accompanying drawing, wherein:
Figure 1 is a view in longitudinal section of an apparatus for flash welding of pipes, embodying the present in~entive concept, and Figure 2 is a sectional view taken along the line II-II of Figure 1.
Description of the Preferred Embodiment Referring now to Figs. 1 and 2 of the accom-panying drawing, an apparatus 1 for flash welding of pipes is accommoda-ted inside the pipes 2 to be welded and comprises an elongate supporting member 3 whose longitudinal axis ~:;

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coincides with the axi~ o~ the pipes 2 to be welded. ~Ioun-ted Oll the elongate supporti~g member 3 in a coaxial arra ngement are a doughnut-type weldin~ tran~fo~ner 4 and two pipe clampi~g a~semblies 5 ~nd 6 e~ch pro~ided with ~ hyd-raulic drive 7 and wherein the a~sembly 5 i~ axially i~mo-vable ~vhereas the as~embly 6 is axially movable~
Also mounted on the elong~te ~upportillg member 3, coaxially therewith~ i~ a pipe ~la~hing and up~etting a~
sembly 8 provided with ~ hydraulic drive 9 o~ its own and movably connected with the axially movable clamping ~em-bly 60 The apparatu~ i~ mo~able along the inside o~ the pipe~ by a trolley 10 having wheel~ 11 dr~n by ~ ~uit-~ble motor (not sho~m)~
Ri~idly mou~ted at the oppo~ite end~ o~ the elongate ~upporting member 3 ar~ two be~ring disc~ 12 and 13 bet~
~een which mounted on roller ~upport~ 14 ~nd ~paced along the member 3 are three ~leeve member~ 15~ 16 and 17~ ~he ~irst and se~ond ~leeve member~ 15 and 16 are incorporat ed in the pipe ~lamping assemblies 5 and 6 respectivaly~
whereas the third ~lee~e member 17 is incorporated in th~
pipe ~lashin~ and upsetting a~sembly 8~
: ~he Qxially immov~ble clampi.ng a~mbly 5 and the elongate supporti~g member 3 are arran~ed in a manner to de~ine an annul~r clearance therebetwee~ which is clear-ly seen in the drawi~g wherei~ the ~leeYe mamber 15 i9 hoY~ as havi~g no direct co~tact with the supporting mem-ber 3.
As can be seen in Fig. 1, the bearing disc 12 is arranged behind both the welding transformer 4 and the sleeve member 15 as viewed from the joint side, that is the welding trans~ormer 4 .is mounted adjacent the side of the axially immovable clamping assembly 5, which is distant ~rom the joint of the pipes 2. The sleeve member 17 o~ the pipe ~lashing and upsetting assembly 8 is arranged close to the bearing disc 13 and cou~led thereto by means of its hydraulic drive 9. The sleeve member 16 of the axially movable clamping assembly 6 is interposed between the sleeve member 17 and the pipe joint and coupled to the sleeve member 17 by its hydraulic drive 7 for moving the same along the elongate supporting member 3.
The pipe clamping assembly 5 comprises clamping levers 18 equidistantly and symmetrically arranged in relation to the longitudinal axis of the supporting member 3. One end 19 of each lever 18 is pivoted as at 20 to the bearing disc 12' for a rotary movement thereof in the radial direction, whereas the other end 21 is pivoted as at 22 to the end of its respective expansion lever 23.
The opposite ends o~ the expansion levers 23 are pivoted as at 24 to the portion 25 o the sleeve member 15, which is nearest -the pipe joint. The ends 21 of the clamp-ing levers 18 carry electrode jaws 26 connected to corres-ponding taps of the transformer 4 via a current lead-in, - 8 ~

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aq will be hereinaf-ter de~cribed.
~ he axially movable clampin~ a~3embly 6 i~ of a si-milar design and differ~ from the pipe clamping a~embly 5 only in that each olamp~ng le~r 27 ha~ o~e end 28 thareof pi~oted as at 29 to the sleeve member 17 of the fls~hing and upsetting a~embly 8, wherea~ the oppo~ite end 30 i9 pivoted a~q at 31 to the e~d of it~ re~pective expan~ion lever 32~ The opposite ends of th~ expan~ion leveræ 32 are pivoted as at 33 to the portion 34 o~ ths qleeve member 16, which is near~t the pipe joint~ The ands 30 o~ tha clamp-ing levers 27 carry electrode jaws 35 oonnected to oorre~-ponding (unlike tho~e connected to the electrode ja~ 26) ~ap~ of the tran~former 4 via a current lead-in corre~po~-`ding to the de~criptio~ which will be herein~ft~r made.
The ~urrent lead-in oonnecting th~ corresponding tap~ of the welding tran~fo~mer 4 with the electrode jaw~
26 and 35 compri~e~ two contact tub~ 36 ~d 37 extending in the a~nular clearanc~ defined by the axially immovable cl~mping a~embly 5 and the elo~g~te ~pporting member 3.
~he contaat tube~ 36 ~nd 37 are mounte~ coaxially and in sulated ~rom o~e anothQr by ~ ulation li~er 38~ The end~ of the contact tube~ at one ~ide thereof are te~mina-, : ~
ted at oorre~ponding (dif~erent~ tap~ o~ the welding tran-sformer 4 and at the other side ara electrically connected to the oorre~pQnding electrode a~w~ 26 ~nd 35 through fle xible ¢able~ ~uch a~ at 39 and 40~ l~heraby in operation a - 9 _ ~ .

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welding circuit i~ establishedJ
In oparation, the apparatus i~ driven into one of the pipes 2 to be welded so as to po~ition the pipe end between the jaws 26 and 35. ~'he hydxaulic drive 7 of the axially immovable clamping a~sembly 5 i9 actuatad and dri-ves the ~leeve member 15 on it~ roller ~upport 14 along the supporting member 3 toward the ~oint~ ~ile the ~leeve member 15 is driven along the ~upporti~g member ~he lever~
23 ca~not move together with the ~leeve member 15 in tran-slation bu~ in rotation about 24 only~ A~ the lever~ 23 xotate they change thelr position relative the ~upporting member 3 and expand the clamping leve~ 18 radially9 whe-reby the leYers 1~ approach the inner ~ide o~ the pipe~ 2 and a furth~r movement of the ~leeve member 15 in the ~a~e direction make~ the ~avr~ 26 abut the pipe to alamp the same pipe in po~ition and align the apparatu~ with the pipeO Now the other pipe length l~ ~lipped over the free end of the apparatu~ until it abut~ the end face of the former pipe~ ~hi~ pipe i~ clamped b~ mean~ of the pipe clamping a~embly 6 i~ a manner ~imilar to clamping the other pipe~ A~ ~oon a~ the other pipe i~ olamped the two pipe3 are ali~ned on -their end ~aces and the a~i~ o~ the apparatu~ is coi~cident ~ith the ~xis o~ the pipe~
Ne~t power is supplied to the welding transfo~mer ~
and the pip9 ~la~hlng and upsetti~g a~sembly 8 i9 actuated to drive the pipe olamping assambly 6 and the pipe cl~mped ' - 1 0 .

thereon in the direction o~ the other pipeO Now current from the ~econdary winding~ of the welAing transformer 4 is appliod to the joint and thus an electrlc circuit i9 establi~hed, which circuit including the contact tubes 36 and 37, the ~lexible cables 39 and 40 a~ well a~ the jav~s 26 and 35~ Since the end ~aces of the pipes usually have surface irregularitie~ the portion~ in cont~ot are ~u~ed until all the end face is ~u~ed to complete ~lashing and then upsetting by the as~embly 8 follows~
~ nhile the flashing action pro¢eed~ the contact tubes act a~ a current ~ummingiup mean~ and Q current distribu-tor~ that i~3 it applie3 current i~ due moment of the fla-~hing action and to a due portion of the joint 9 thereby flashing i~ i~ten~ified and the initial ~tage of fla~hing i~ reduoed ~ccordi~gly.

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Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for flash welding of pipes, designed to operate inside the pipes and comprising:
an elongate supporting member whose axis can coincide with the axis of the pipes to be welded, an axially movable clamping assembly for clamping one of the pipes to be welded, mounted on said elongate supporting member and carrying electrode jaws;
a flashing and upsetting assembly operatively connected with said axially movable clamping assembly for aligning the pipes to be welded as flashing and upsetting actions proceed;
an axially immovable clamping assembly for clamping the other one of the pipes to be welded, mounted on said elongate supporting member in spaced circumferential relationship therewith and carrying electrode jaws;
a doughnut-type welding transformer mounted on said elongate supporting member adjacent the side of said axially immovable clamping assembly, which is distant from the electrode jaws thereof;
two contact tubes electrically insulated from one another and coaxially disposed between said axially immovable clamping assembly and said elongate supporting member, one end of each of said contact tubes terminat-ing at corresponding taps of said welding transformer, while the other one being electrically connected to corresponding electrode jaws of both said axially movable and said axially immovable clamping assemblies.

2. An apparatus as claimed in claim 1, wherein each contact tube is electrically connected to the electrode jaws by means of a flexible cable.