GB2229386A - Machine for resistance butt welding of pipes - Google Patents

Abstract

A machine comprises a housing (1) receivable inside the pipes (2 and 3) to be welded to both sides of a joint-to-be (4), having mounted thereon a flash and upset mechanism (8) operatively connected with clamping mechanisms (6 and 7). The clamping mechanisms comprise clamping bars (25) carrying shoes (37, 38, 39, 40) arranged at their respective end portions (32 and 33) in two annular rows. The clamping bars (25) are mounted for radial translation with respect to the housing (1) and are connected therewith through spreadable actuated members (22 and 23) and slanting pivotable links (26). The portion of each clamping bar (25) intermediate the end portions (32 and 33) thereof is flexible within the elastic deformation limits to allow accurate seating of the shoes. The pivot axis of each pivotable link (26) on the respective clamping bar (25) extends intermediate the shoes (37 and 38, or 39 and 40) of the respective adjacent annular rows. <IMAGE>

Description

BACHIKE POR RESISTANCE BUTT WELDING OF PIPES The invention relates to equipment for resistance butt welding of pipes, and more particularly it relates to inter-pipe machines, i.e. machines received inside the pipes to be welded, operated for resistance butt welding of annular joints of pipes.

The invention can be implemented in construction of trunk fuel gas and oil pipelines.

The essence of the invention resides in a machine for resistance butt welding of pipes, receivable in the pipes to be welded to both sides of a joint-to-be, comprising a housing having a longitudinal axis alignable with the common axis of the pipes and having mounted thereon a welding transformer, clamping mechanisms for centering and secure ing the pipes to be welded, electrically connected to the welding transformer, and mounted thereon a flash and upset mechanism operatively connected with clamping mechanisms including clamping bars carrying clamping shoes on their end portions, mounted for translatory motion relative to the housing and operatively connected therewith through spreadable actuating members and inclined pivoted links, in which machine, in accordance with the invention, the clamping shoes on the respective end portions of the clamping bars of the clamping mechanism are arranged in two annular rows, the pivot axis of the link connecting each respective clamping bar with either one of the pair of the spreadable members extending intermediate the shoes of the adjacent rows, the portion of each bar intermediate its end portion being flexible within the elastic deformation limits.

Unlike machines of the prior art where the geometry of the clamping action is defined by all the clamping shoes or dies of the clamping mechanism on account of the rigidity of the clamping bars of this mechanism, the machine of the present invention has the efforts of the shoes at different ends of the clamping mechanism independent from one another owing to the elasticity of the central portions of the clamping bars, whereby the geometry of the clamped surface within the area of the engagement of the shoes therewith at each end of the clamping mechanism can differ from that at the other end of the mechanism, w::icn weansthat the latter's design provides for self-alignment of the clamping bars along the respective generatrices of the inner surface of the pipe being clamped.This feature in combination with the disclosed arrangement of the points of connection of the pivoted links with the clamping bars (and, hence, of the points of application to these bars of the effort developed by the actuator) ensures Inli- form transmission of the clamping effort to all the shoes of each clamping bar and reliable electric contact between the current-conducting shoes and the pipe, which allows to extend the field of applications of the disclosed machine for resistance butt welding to pipes with any commercially acceptable deviations from the strictly regular standard geometrical shape.

The optimized distribution of the clamping effort and the increased area of contact with the pipe being clamped owing to the double-row arrangement of the shoes at each end of the clamping mechanism further provide for reducing the strain in the clamping bar, so that the latter can have smaller dimensions and weight, thus reducing the spe cific amount of metal in the machine being discussed.

The present invention will be further described in connection with its embodiment, with reference being made to the accompanying drawing showi#a a longitudinally sec- tional view of a machine for resistance butt welding of pipes, constructed in accordance with the invention.

In the drawing, the machine for resistance butt welding of pipes has a tubular housing 1 accommodated inside the pipes 2 and 3 to be welded to both sides of the joint- to-be 4. The housing 1 supports a welding transformer 5 in the zone of the Joint 4, clamping mechanisms 6 and 7 disposed to the opposite sides of the welding transformer 5, and a flash and upset mechanism 8 operatively connected with the two clamping mechanisms 6 and 7 for transmitting therethrough the effort to the pipes 2 and 3 to be welded, to effect their opposing axial displacement in the course of the welding.

The flash and upset mechanism 8 includes two thrust rings 9 and 10 fast with the respective ends of the tubular housing 1, and a movable ring 11 mounted on the housing 1 for axial reciprocation between the thrust ring 10 and the clamping mechanism 7. The movable ring 11 is operatively connected to the upset actuator 12 in the form of hydraulic cylinders uniformly spaced about the housing 1.

The housings 13 of the respective hydraulic cylinders are secured to the thrust ring 10, and the respective rods 14 of their pistons 15 are rigidly attached to the movable ring 11. The actual number of the hydraulic cylinders in the upset actuator 12 can be any, depending in each specific case on the size of the pipes 2 and 3 to be welded, defining the dimensions and capacity of the machine. With the diameter of the pipes 2 and 3 to be welded being relatively small, the actuator 12 can be in the form of a single hydraulic cylinder concentrically enclosing the housing 1 extending through the bore in its piston and piston rod. The upset actuator 12 can be of other suitable known designs providing for translatory motion of the associated members.

Uniformly spaced about the periphery of the thrust ring 9 are slots 16 made in this periphery, accommodating pivots 17 rigidly secured in the opposite walls of these slots, i.e. in the thrust ring 9, for pivotably supporting the respective first links 18 operatively connecting the flash and upset mechanism 8 with the clamping mechanism 6.

The periphery of the movable ring il intermediate the hydraulic cylinders of the upset actuator 12 also has slots 19 made therein for accommodating pivots 11 rigidly secured in the opposite walls of those slots, i.e. in the movable ring 11, for pivotably supporting the respective second links 21 operatively connecting the flash and upset mechanism 8 with the clamping mechanism 7.

Each clamping mechanism 6 and 7 includes a pair of axially spreadable members (rings) 22 and 23 received about the tubular housing 1 for axial reciprocation under the action of an axial displacement actuator 24, and clam ping bars 25 uniformly spaced about the respective spreadable rings 22 and 23 and operatively connected therewith by pivotable links 26. The actual number of the bars 25 can be three or more, depending on the diameter of the pipes 2 and 3 to be welded.

The axial displacement actuator 24 includes several hydraulic cylinders uniformly spaced about the tubular housing 1. The housings of the hydraulic cylinders are se- cured to the ring 13, while the pistons 28 with their rods 29 are attached to the ring 22. With the pipes 2 and 3 to be welded being of a relatively small diameter, the actuator 24 can be in the form of a single hydraulic cylinder with its piston and rod having a cylindrical through bore slidingly received about the tubular housing 1. Other structural implementations of the axial actuator are possible, provided the suitable known design employed and appropriately connected with the spreadable rings 22 and 23 is operable for their simultaneous axial displacement along the housing 1 in opposite directions.

In the embodiment being described, the pivoted links 26 are pivotably attached in slots 30 provided in the respective peripheries of the rings 22 and 23 intermediate the hydraulic cylinders of the axial displacement actuator 24, on pivots 31 rigidly secured in the opposite walls of the slots 30, i.e. in the respective rings 22 and 23.

In accordance with the invention, each clamping bar 25 has two end portions 32 and 33 interconnected by a central portion or web 34 of a smaller cross-sectional area than the end portions 32 and 33, calculated for limited flezi- bility of the web 34 within the limits of elastic deformation of its material. In other words, the central portion 34 is an elastic flexible web between the two more massive and strong end portions 32 and 33. Although the bar 25 is shown solid in the appended drawing, it can alternatively be assembled of several parts.

To attach the respective pivoted links 26 to the end portions 32 and 33 of each clamping bar 25, slots 35 are provided in these end portions 32 and 33, opening from the end faces of each bar 25. The side of the end portions 32 and 33, opposite to the slots 35 and 36, carries respective clamping or engagement shoes 37, 38, 39 and 40 of which the shoes 40 on the respective end portions 33, which are the closest to the joint 4 of the pipes 2 and 3 to be welded, are current-conducting and are electrically connected to the welding transformer 5 via flexible buses 41. The adjacent shoes 37 and 38 carried by the respective end portions 32 of all the clamping bars 25 of either clamping mechanism 6 and 7 are arranged in two parallel annular rows.Similarly, two parallel annular rows are formed by the adjacent shoes 39 and 40 carried by the respective end portions 33 of all the clamping bars 25. In the embodiment being described and illustrated in the appended drawing each clamping bar carries one shoe in each respective annular row; however it is possible that each clamping bar should carry more than one shoe in each respective annular row. The pivoted links 26 connecting the ring 22 with the respective clamping bars 25 extend into the slots 35 of these bars and are connected therewith through pivots 42 arranged intermediate the shoes 37 and 38 of the adjacent annular rows, which provide for uniform distribution of the clamping effort among the rows of the shoes 37 and 38.

The pivoted links associated with the flash and upset mechanism 8 extend into the same slots. In the clamping mechanism 6, they are the respective first links 18 connected to the clamping bars 25 through respective pivots 43, and in the clamping mechanism 7, they are the respective second links 21 connected to the clamping bars 25 through respective pivots 44.

The pivoted links 18, 21 and 26 are so arranged that at any possible relative positions of the rings 9, 11, 22, 23 and of the clamping bars 25 they should maintain their slanting attitude. In this, in accordance with the respective directions of transmission of the efforts of the upset actuator 12 and axial displacement actuator 24, the respective first and second links 18 and 21 are slanting in opposing senses, whereas the eternal or outermost ends of the pivotable links 26 connected with the respective spreadable rings 22 and 23 are spread apart.

The thrust ring 9 of the machine is connected to the latter's travel mechanism 45. The pumping station and hydraulic control and communication components of the machine are not shown in the appended drawings for clarity sake.

The operation of the disclosed machine for resistance butt welding of pipes is, as follows.

The travel mechanism 45 of the machine is operated to move the machine into the pipeline under construction, so that the free end of the pipeline, which is the free end of the pipe 2 already welded thereto, should be situated intermediate the respective current-conducting shoes 40 of the clamping mechanisms 6 and 7.

Working fluid under pressure is supplied into the above-piston spaces of the hydraulic cylinders of the actuator 24 of the clamping mechanism 6 to project the piston rods 29 of the pistons 28 from the respective housings 27 and thus to drive apart the spreadable rings 22 and 23 along the periphery of the tubular housing 1. Correspondingly, the pivoted links 26 connected with the respective rings 22 and 23 turn on their pivots 42, moving the clamping bars 25 associated with these pivots 42 radially outwardly with respect to the housing 1, until the clamping and current-conducting shoes 37-40 firmly engage the inner surface of the pipe 2, clamping the pipe 2 and centering the machine with respect to the pipeline. Then the pipe 3 to be welded is put about the exposed end of the machine and moved into engagement with the end of the pipe 2.The pipe 3 is subsequently clamped by the clamping mechanism 7 in a manner similar to the pbovedescribed procedure of clamping the pipe 2 by the mechanism 6, the pipe 3 being automatically centered with respect to the pipe 2, i.e. the pipeline.

The welding transformer 5 is turned on, so that welding current flows into the Joint area 4 through the fle xible buses 41 and current-conducting shoes 40. In accordance with the preselected operation programme, the working fluid under pressure is fed into the above-piston spaces B of the hydraulic cylinders of the upset actuator 12, so that the piston rods 14 of the hydraulic cylinders move the movable ring 11 towards the Joint 4, with the respective second pivoted links 21 turning on their pivots 44 and applying an additional clamping effort to the clamping bars 25 of the clamping mechanism 7.Simultaneously, the housings 13 of the hydraulic cylinders of the upset actuator 12 are urged by the pressure of the working fluid, in reaction, awsy from the pistons 15, transmitting this effort via the thrust ring 10 and tubular housing 1 to the thrust ring 9 which is thus moved towards the joint 4, with the first links 18 turning correspondingly and applying a similar additional clamping effort to the clamping bars 25 of the clamping mechanism 6. With the now developed clamping effort maintaining rigid and firm engagement of the shoes 37-40 of the respective clamping bars 25 of the clamping mechanisms 6 and 7 with the pipes 2 and 3, the fusion of the ends of the pipes 2 and 3 in the area of the Joint 4 results in their being gradually displaced in opposition towards each other, i.e. in the clamping me mechanism 7 moving the pipe 3 towards the pipe 2 under the effort applied to the movable ring 11 of the flash and offset mechanism 8.

With the welding procedure completed, the working fluid under pressure is directed into the under-piston spaces of the respective hydraulic cylinders of the upset actuator 12 and of the axial displacement actuators 24, and the mechanism of the machine return to their abovedescribed initial positions. The travel mechanism 45 is operated to move the machine to the successive Joint area, and the abovedescribed sequence of operations is repeated.

When the pipes 2 and 3 to be welded have relatively great deviations from the regular cylindrical shape (dents, tapering portions, etc.), the radial spreading of the clamping bars 25 is not accompanied by all the shoes 37-40 engaging simultaneously the inner surface of these pipes 2 and 3, so that the clamping effort is initially distributed not uniformly. This results in the corresponding strain developing in the respective bars 25, bringing about their flexing in the area of the elastic web (central portion) 34, and thus adJusting these bars 25 to the actual shape of the respective generatrices of the surfaces being clamped.The self-alignment of the respective shoes 37-40 along these generatrices brings about re-distribution of the clsmping effort they apply to the respective pipes 2 and 3, ensuring reliable electrical contact between the currentconducting shoes 40 and the pipes 2 and 3, and reducing the bending torquf at the endangered cross-sections (in the areas of the pivots 31 and 42), so that the entire structure can be made less heavy, with a reduced metal input and enhanced reliability. The said is also achieved owing to the double-row arrangement of the respective clamping shoes 37-40 at both sides of each clamping mechanism 6 and 7, with a greater area of contact with the surfaces being clamped and substantially lesser loads per unit area of these surfaces.

The abovementioned advantages of the disclosed machine provide for implementing the highly efficient technology of automatic resistance butt welding with pipes having con siderable taper deviations, and in numerous cases such pipes amount to as much as 20 % of the entire stock of pipes available for welding, which otherwise would have been welded either manually or by the automatic electricarc welding technology, significantly stepping up the cost of construction of truck pipelines and prolonging the construction time.

Claims (2)

WE CWM:

1. A machine for resistance butt welding of pipes, receivable inside the pipes to be welded to both sides of a joint-to-be, comprising a housing having a longitudinal axis alignable with the common axis of the pipes to be welded and having mounted thereon a welding transformer, clamping mechanisms for centering and securing the pipes to be welded, electrically connected with the welding transformer, and a flash and upset mechanism operatively connected with the clamping mechanisms for actuating the pipes to be welded via these mechanisms through opposing axial displacement toward each other in the process of welding, each clamping mechanism including a pair of spreadable members interconnected by an axial displacement actuator, movably mounted on the housing, and clamp nag bars with clamping shoes on their end portions, arranged about the spreadable members for radial translation and connected tD these members at the end portions by slanting pivoted links, the clamping shoes on the respective end portions of the clamping bars of the clamping mechanism being arranged in two annular rows, the pivot axis of the link connecting each respective clamping bar with either one of the respective spreadable members of the pair extending intermediate the shoes of the respective adjacent annular rows, the portion of each clamping bar intermediate the end portions thereof being flexible within the elastic deformation limits.

2. A machine for resistance butt welding of pipes, substantially as hereintofore described and illustrated in the appended drawing.