WO2010064082A1

WO2010064082A1 - An improved system for butt welding pipes conveying water, gas and other fluids under pressure

Info

Publication number: WO2010064082A1
Application number: PCT/IB2008/052754
Authority: WO
Inventors: Pietro Succio; Giuseppe Succio
Original assignee: Pietro Succio; Giuseppe Succio
Priority date: 2008-07-09
Filing date: 2008-07-09
Publication date: 2010-06-10

Abstract

A butt welding system is described for pipes for conveying water, gas, and other pressurised fluids, comprising welding equipment (10) provided with annular jaws (20) for retaining respective pipes (26) to be welded, each comprising a complementary fixed vice element (22') and removable vice element (22'), wherein the welding equipment (10) is operatively sloped so as to have a lower radial coupling section (32) of the vice elements (22', 22') tilted, with respect to the vertical plane, an angle in the range of 0° - 10°, and can be moved along a transverse moving closer/apart direction of the jaws in open condition with respect to the pair of pipes being welded. The system comprises a plurality of supports (70) for the pipes, arranged upstream and downstream of the welding equipment (10), adapted to define a support surface for the pipes (T) at a height from the ground substantially corresponding to that of the retainer jaws (20) and to allow the axial sliding of the pipes with minimum friction.

Description

An improved system for butt welding pipes conveying water, gas and other fluids under pressure

The present invention regards the butt welding of pipes, in particular polyethylene pipes for conveying water, gas and other pressurised fluids, and more specifically it refers to a welding system according to the preamble of claim 1.

Over the last few years, the choice of plastic material pipes for conveying different types of fluid has become widespread, and in particular in public utility networks, where they are increasingly used in the distribution of gas and water.

Plastic pipes are preferred over the traditional steel pipes for their particular lightness characteristics, which allow facilitated transporting and placing, good resistance to different types of corrosion and erosion and high thermal and electrical insulation. Further economical advantages derive from the lower placement costs.

The use of polyethylene (PE) pipes in the distribution of pressurised fluids has been confirmed over the last few decades. Such development must, necessarily, be accompanied by a suitable quality of the manufactured products. Particular care must be given in the work site operations so to avoid compromising the legal compliance of the pipes.

The transportation operations, as well as the loading and unloading operations from the transport means, and the extracting operations in the work sites - with which the single pipes are aligned along a trench - must occur with suitable mechanical means, such as cranes or lift trucks, and in any case attention must be made so to not drag the pipes, provided in bars or in rolls, on the sides of the transport means and on hard and angular objects. In addition, the pipes must never be dragged on the ground, in order to prevent the formation of chips at the ends and scratches or longitudinal notches of even great depth, which can compromise the quality characteristics of the pipe and the reliability guarantees of the piping. The pipe storing operations must also be compliant with legal requirements, providing for the protection from solar rays and rain of the pipes stacked for a long period outdoors.

Even during a limited storing period, as in the case of prearrangement of a set of pipes in work sites for use the following work days, the pipes' physical and mechanical properties can be altered. For example, they can be made oval due to excessive heat during the summer months, or they can be deformed by curving or twisting due to the arrangement for a long time on uneven ground.

Such drawbacks significantly affect the piping assembly process, in terms of execution time and quality of the results.

Generally, in order to make piping intended to convey pressurised fluids over long sections, pipes are traditionally used of length in the range of 6 - 12 meters, having a nominal diameter in the range of 90 mm - 630 mm for conveying gas and in the range of 90 mm - 1600 mm for conveying water, which are assembled via butt welding, in particular by means of a process of contact welding with a thermal element. One such welding process provides that the joint surfaces are initially heated up to melting or softening via contact with a thermal element and subsequently, after removing it, they are joined together under pressure so as to obtain their welding.

The welding equipment for work sites with contact thermal elements, used for making butt joints of pipes and/or fittings made of polyethylene (PE), are well-known in the field and their characteristics are briefly described below, with reference to the welding arrangement according to the prior art shown in figure 1.

Each equipment piece comprises a base body or frame body with two supports, one fixed and one movable, each bearing a respect pair of retainer jaws for locking the pipes to be welded; a hydraulic control unit, adapted to control the movement of the movable support of the jaws for bringing the ends of the pipes closer together or further apart during the various steps of the welding process; a miller for working the end surfaces of the pipes be- fore welding, and a plate thermoelement for heating and softening the pipe edges to be welded.

The jaws are adapted to lock the pipes to be welded via circumferential tightening, and are provided of various sizes in order to be adapted (possibly by means of insertable reduction rings) to the various possible pipe dimensions. They must surround at least 95% of the circumference of the pipe and be sized so to uniformly adhere to the pipes without damaging their surface.

Each jaw is composed of two complementary curved vice elements, one of which is stably bound to the support and the other is movable with respect thereto (for example, it can be overturned around a hinge, or it can be completely separated therefrom), which in the coupled condition define a circular opening within which a respective pipe is received.

The vice elements composing one jaw are coupled at two radial sections of the jaw which are diametrically opposed from each other, or having in any case an angular arrangement such that the angular opening of the fixed vice element is not greater than 180°, in order to allow the insertion and extraction of the pipes with respect to the jaw.

One pair of jaws is movable with respect to the other via translation of the related movable support along parallel guide elements (opposite with respect to the axis of the pipes to be welded), so to allow a limited relative movement of the ends of the pipes during the welding steps. This allows bringing the ends further apart and closer together, respectively for allowing the interposition of the miller and the thermoelement during the preliminary welding steps, and the pressure joining during the actual welding, avoiding bending of the vice devices and ensuring that the traction and thrust of the pipes always occurs axially.

The structure of the frame of the welding device ensures the necessary rigidity and stability in all welding operation steps.

The hydraulic control unit is adapted to control the movement of the movable support of the jaws and the application of the pressures between the elements to be welded required by a welding cycle. In particular, it controls the relative approaching and moving away of the ends of the pipes during the various working and welding steps, and ensures a continuous adjustment and maintenance of the necessary welding pressure.

The miller, conventionally a miller with rotating disc, is adapted to smooth the ends of the pipes by simultaneously working on the two opposite faces and operating in a right angle work position with respect to the theoretical (ideal) axis of the pipes to be welded. It is configured so to bring the shavings outside the pipe.

Finally, the thermoelement, with full disc or circular ring shape, has opposite flat and parallel heating surfaces, adapted to be arranged in contact with the surfaces of the edges of pipes to be softened.

The described equipment must ensure that the welding process can be conducted respecting a correct axial alignment of the pieces to be welded and a suitable parallel plane of the end surfaces to be welded. In order to meet the desired alignment and parallel conditions, one operates by making the pipes rotate until they reach a favourable coupling condition, taking care to not damage the surfaces of the pipes received in the jaws.

During a welding operation, the pipes must be locked in the jaws in the abovementioned alignment and parallel conditions, while ensuring the possibility of axial movement without considerable friction, in order to allow the pipes to move away and approach each other for the insertion of the miller, the thermoelement, and the final pressure welding. For these operations, the pipes can slide on saddles or supports which facilitate its translation without risking damage by scraping on the ground.

Following the alignment of the pipes and their preparation via milling and cleaning of the surfaces to be welded, the correct welding cycle provides for the execution of the following steps:

- bringing the edges of the pipes to be welded close to the thermoelement, and heat- ing such edges;

- removing the thermoelement and attaining the contact position of the edges with progressive increase of the pressure until pre-established welding pressure is reached as a function of the diameter and thickness of the pipes to be welded;

- pressure welding for a predetermined time period as a function of the pipe thickness; and

- natural cooling of the welded joint, possibly removed from the welding equipment without being subjected to appreciable forces;

- removing the welding seam that has formed.

At the end of every welding cycle, the joint cooling time having also elapsed, the partial piping welded by the welding equipment is removed, in order to prepare a new welding cycle between the end of the piping and a further pipe.

The extraction from the open jaws occurs via lifting of the pipes from the partial opening of the fixed vice element and relative moving away of the equipment. This nevertheless leads to the risk of contact with the surfaces of the jaws and scratching of the pipes, compromising the reliability of the manufactured piece.

With the increase of the diameter and thickness of the pipes to be welded, the weight of the same is also increased, so that the described operations must be carried out with the aid of mechanical lifting means, employing a greater number of workers on the ground and driving machinery.

In the end, this causes an increase in work costs, a slow down of the work, and a greater bulk of machinery in the work site, which is also negatively reflected in a greater extension of the work site area. Disadvantageously, the latter condition leads - in the case of piping laid underground along road beds - to the total closure of traffic along the roads affected by the work, instead of a simple restriction of the available transit lanes.

In the arrangement and execution of the welding, a technical improvement of the processes is therefore desirable, in order to ensure effective compliance with the laws and a greater reliability of the manufactured products, reducing operation times and costs.

The object of the present invention is therefore to provide an improved butt welding system for pipes for conveying water, gas and other pressurised fluids which ensures a quick execution of welding, maintaining the quality of the manufactured pieces.

A further object of the invention is that of providing a welding system which requires a lower number of operators for carrying out the welding process, facilitating the operations required by the process and in general every work site operation.

According to the present invention, such objects are achieved by a system having the characteristics referred to in claim 1.

In summary, the present invention provides an improved pipe butt welding system comprising a component arrangement such to allow a radical transformation of the removal technique of every pair of welded pipes, so to permit the positioning of a subsequent welding section. Specifically, in contrast with a prior art technique of "transverse" removal, in which the removal of the pipe occurred by lifting and extraction the pipes from the partial opening of the open jaws, here an innovative technique is described for "axial" or "longitudinal" removal, in which the removal of the pipe occurs via sliding along its longitudinal direction, after a previous movement away of the welding equipment.

The terms "transverse", "longitudinal" and "axial" are always referred to below in this description with reference to the arrangement of the pipes forming the piping under construction, while the terms "vertical" and "horizontal" are used with their common meaning to define the orientation with respect to the ground, where the equipment is situated and where the laying of the piping occurs, and the terms "upstream" and "downstream" are referred to the welding operation.

The system provides for the operative arrangement of the welding equipment along a pre- determined slope which allows having the elements of the jaws of the machine in a substantially vertical position with respect to the working plane, so to facilitate the removal of the equipment from the welded pipes without any lifting of the latter.

The installation of the welding equipment on a translatable base, in a guided manner in at least two orthogonal directions in the working plane allows the equipment movement in the axial direction, i.e. length of the piping, and in the transverse direction, i.e. in the moving- away direction from the piping.

Firstly, this allows an operator in the assembly step, before a new welding, to correctly position the pipes with respect to the longitudinal placement of the equipment frame, avoiding manual corrections by the operators which can be difficult to undertake and not very precise in the case of particularly heavy pipes.

Secondly, it becomes possible to move the equipment and welded piping away from each other for the axial extracting of the piping, without risks of scratching, otherwise inevitable with the sliding of the pipes on the jaws. Advantageously, the latter operation allows the removal of a just welded and still to be cooled section from the equipment, and the immediate presentation of a new welding section.

Due to the arrangement of supports for the pipes upstream and downstream of the welding apparatus, made with rollers for the support and the sliding of the pipes with minimum friction and conveniently arranged on the same plane as the welding equipment and along the axis of the piping, the innovative system permits avoiding forces on the welding section until the cooling step is completed, while allowing a simultaneous subsequent welding cycle, without compromising the welding just carried out.

Advantageously, time loss, the use of lifting means and transport of the pipes, as well as the number and physical effort of the workers employed are reduced to a minimum.

Further characteristics and advantages of the invention will be set forth in more detail be- low in the detailed description of an embodiment thereof, given as exemplifying and non- limiting, with reference to the attached drawings, in which:

Figure 1 is a perspective view of a welding equipment in the arrangement according to the prior art;

Figure 2 is a partial side elevation view of a welding equipment in the arrangement according to the invention;

Figure 3 is a perspective view of a support platform of a welding equipment according to the invention;

Figure 4 is an overall schematic representation of a welding arrangement according to the invention; and

Figures 5a - 5e are schematic illustrations of the main steps of a welding process carried out with the system that is the subject of the invention.

A welding equipment 10 of known type is shown in figure 2 in a side view according to the arrangement, subject of the invention, that corresponds to the actual arrangement in work sites, and in figure 3 an overall perspective view is shown of a related support structure. The equipment 10 is supported by a base 12 slidably mounted on a pair of parallel guides 14 along a first direction Dl, transverse with respect to the arrangement of the piping. The base 12 and the respective translation guides 14 form part of a saddle 16 that can be translated in a guided manner along a substantially longitudinal direction D2, i.e. parallel to the extension of the piping. Hydraulic actuating devices are provided for the actuation of the translation of the base 12 and the saddle 16 respectively in the directions Dl and D2.

In figure 2, a jaw 20 of the welding equipment is depicted, of which at least a fixed vice 22' and a complementary movable vice 22" are shown. The element 22", which can be removed and coupled to the fixed element 22' by means of screws 24, is shown separately from it in the open jaw condition. A pipe received precisely in the circular opening of the jaw is indicated in cross-section at 26.

Designated 30 and 32 are upper and lower radial coupling sections of the jaw vice elements. The lower radial section 32 lies in a tilted plane with respect to the vertical axial plane of the jaw, at an angle in the range of 0 - 10°, preferably in the range of 0° - 2°. Still more preferably, the lower radial section 32 lies in the vertical axial plane of the jaw.

Figure 3 shows overall a support structure 40 of the welding equipment 10, formed by a tubular metal frame of generally rectangular form, supported at the four vertices by respective ground support legs 42, advantageously provided with respective independent raising means for adjusting the height of the structure with respect to the ground.

Two accessory support surfaces are indicated at 44, adapted to receive the auxiliary equipment of the welding equipment, such as for example, the miller and the thermal element, contained in related seats.

Figure 4 shows an overall view of a butt joint system according to the invention in its work site arrangement for the laying of pipes underground in a trench S.

With T₁, the various pipes are indicated which contribute to the formation of the overall piping. In the example, the pipes Ti and T₂ are welded at the joint Gi₂, and the pipe Ti is partially laid underground in the trench S. The welding equipment 10 (only schematically depicted here in order to not affect the clarity of the drawing) is arranged at the facing ends of the pipes T₂ and T₃ to be welded, for attaining the joint G₂₃.

Upstream of the equipment 10, a further pipe T₄ is previously coupled to the pipe T₃, at the end opposite that currently subject to welding, through a fitting element 50 and a tie-rod device 52.

The fitting element 50 is formed as a tubular element and comprises end portions of lower size than the inner diameter of the pipes, adapted to be inserted therein at the facing ends to be welded, and an intermediate spacer portion, of a size preferably equal to the external diameter of the pipes, adapted to be interposed between the ends of the pipes in order to keep them a predetermined distance apart. The overall longitudinal dimension of the fitting element must in any case be less than the operative path of the movable support of the jaws of the welding equipment, in order to allow, with its movement, the separation of the pipes and the extraction of the element 50 before the beginning of the welding cycle.

The tied rod device 52 is coupled to the ends of the pipes through a pair of bands passing through respective end slots of the tie rod, each of which is wrapped around a pipe and tightened by means of a ratchet mechanism.

The pipe T₄ is housed in a store M for storing a bundle of pipes T₅-Tg to be subsequently welded. The store M has a stacking area with a levelled support surface composed of a horizontal grate or plank 60 on which the pipes can be supported without touching the ground, adapted to allow the rolling of the pipes in a horizontal direction D3, substantially orthogonal to the longitudinal sliding direction of the pipes towards the welding equipment, indicated by the arrow D4.

Advantageously, at least a peripheral portion of the surface 60 is provided with a plurality of equidistant roller devices 62, with rotation axis transverse to the direction of the pipe assembly, in order to allow the longitudinal sliding of the same towards the welding equipment with minimum friction.

Upstream and downstream of the welding equipment, a plurality of supports for the pipes 70 are arranged in succession, in the form of stands bearing roller .devices 72 adapted to allow the support and sliding of the pipes with minimum friction.

hi the currently preferred embodiment, each support 70 comprises a pair of roller devices 72 in a V arrangement for the transverse containment of the received pipe, and is provided with means for adjusting the height with respect to the ground, adapted to permit the horizontal alignment of the supports so as to keep the pipes at a height from the ground substantially corresponding to that which the pipes have when they are received in the welding equipment. In this manner, the pipe movement, both inside the store M along the direction D3 and in the longitudinal assembly direction D4 towards the welding equipment, and subsequently the extraction from the equipment and arrangement in the trench S, occurs in a facilitated manner, without requiring excessive physical force of the operators, nor mechanical lifting means for the pipes.

Moreover, since the pipes are always based on the roller device 72 at single contact points, they do not run the risk of being damaged by scraping on the ground and can be moved longitudinally without alteration of the welded surfaces or cancellation or removal of writing on the surface.

Of course, the representation of figure 4 is given merely as an example, in particular regarding the number and arrangement of the supports 70 for the pipes. In addition, for the sake of drawing clarity, size scales were not respected with regard to the length of the single pipes, so that each of these is, in reality, advantageously supported by at least one support pair. Moreover, conveniently, a further pair of supports 70 can be arranged near the support structure 40 of the welding apparatus. Finally, the supports downstream of the welding equipment can be provided in a greater number than that depicted, particularly for fully supporting a pair of pipes already welded and thus allowing the cooling of the welding joint (G]₂ in the figure) in a raised position from the ground, at the same time as the execution of a new welding (G₂₃) at the subsequent joint section.

The welding process is described in detail with reference to figures 5a-5e, which represents a front view of the system at the welding equipment 10.

Figure 5a shows an initial step of the welding operations, in which a first pipe Ti is brought forward via sliding on supports 70 towards the equipment 10. The latter is shown with the jaws 20 in open condition and, although difficult to appreciate from the figure, it is arranged in a withdrawn position on the structure 40 so as to not interfere with the pipe movement operations. The pipe Ti is made to slide past the equipment, bringing with it the next pipe T₂ connected to it through the tie rod 52 and separated by the interposed fitting element 50.

Advantageously, the tie rod 52 is arranged at the longitudinal top line of the pipe and does not interfere with the supports 70 in the sliding of the pipes.

The positioning of the joint section G₂₃ between the pipes T₂ and T₃ at the welding equipment can be imprecise. The correct position of the equipment 10 is reached by moving the saddle 16 in the direction D2 for a correct alignment of the pairs of jaws 20 with the respective end portions of the pipes T₂ and T₃.

Once the most suitable operating position is reached, the welding equipment 10 is moved forward along the guides 14 so as to surround the pipes with their fixed vice elements 22'. The jaws 20 are locked via coupling of the removable elements 22" on the fixed vice elements 22', then the welding equipment is controlled according to the prior art by moving the movable jaw support so to move the pipes away from each other and to allow the extraction of the fitting element (figure 5c).

It is noted that in this case, no axial rotation of the pipes is necessary for reaching an optimal alignment, since such operation is previously undertaken upstream, at the same time of a welding operation of the preceding joint (if there is one), preferably by the workers not involved in the welding step and thus more effectively employing their time.

Then the miller is inserted and the ends of the pipes are brought into contact with the milling disc for the fine working of the edges of the portions to be welded. The equipment is then controlled by moving the movable jaw support for moving the ends of the pipes away from each other, the milled surfaces are cleaned and the thermoelement is inserted (see figure 5d), once again bringing the ends of the pipes close together, in contact with it.

After heating, the movable support of the equipment is once again moved for moving the ends of the pipes away from each other, allowing the extraction of the thermoelement and subsequently bringing the ends of the pipes in contact with each other, exerting a predetermined pressure, for the conclusion of the welding operation (figure 5e).

Once a predetermined welding time has elapsed, the piping is brought forward via sliding on rollers and subsequent welding cycles are carried out, in an analogous manner to that described above.

Advantageously, all components of the system can be transported by a single lorry equipped with lifting equipment and body of about 6 x 2.40 meter size, adapted to house the welding equipment, the roller supports and the store. The preparation of the equipment on the work site and the execution of the welding operations require the assistance of only two operators, the pipe arrangement operations being particularly facilitated.

The extension of the work site is substantially linear, since it is not necessary to flank the pipes with lifting means and transport means of the pipes being worked, so that it is possible to occupy only part of the road bed in which the operation is being completed, without total interruption of traffic circulation.

For the trench laying, after the welding of a pre-established number of pipes, the supports 70 of stationary type shown in the figure are substituted with saddle supports, movable on wheels, to which the piping is bound by means of bands, so to be able to move the piping in the trench, possibly by means of movement machines, always maintaining it above the ground.

It is noted that the embodiment proposed for the present invention in the preceding discussion has a merely exemplifying and non-limiting character. A man skilled in the art of the field can easily actuate the present invention with embodiments and details that are different from that described and illustrated above, which however do not depart from the principles set forth and are therefore comprised in the protective scope of the present invention, defined in the attached claims. This holds true, for example, for an alternative embodiment for welding directly in trenches, in which every component of the described system, and in particular the store M and the support and movement structure 40 of the welding equipment, is provided with wheels for its translation along a piping to be welded and which is maintained stationary.

Claims

1. A butt welding system for pipes for conveying water, gas and other pressurised fluids, comprising welding equipment (10) provided with at least two annular, axially-aligned jaws (20) for retaining respective pipes (T) to be welded and relatively movable in an axial direction for moving the ends of the pipes close together and apart, wherein each jaw (20) comprises a complementary fixed vice element (22') and removable vice element (22"), which can be coupled at a first and a second radial section (30, 32) and arranged for defining, in the coupled condition, a circular opening adapted to receive a respective pipe (26), characterised in that the welding equipment (10) is operatively arranged sloping so as to have a lower radial coupling section (32) of the vice elements (22', 22") of the jaws (20) arranged in a plane that is tilted, with respect to the vertical axial plane, an angle in the range of 0° - 10°; in that it includes support and movement means (12, 14, 16) for the welding equipment (10), arranged for moving the equipment (10) along at least one transverse moving away/closer direction of the fixed vice elements (22') of the jaws (20), in open condition, with respect to the pipes (T) being welded; and in that it comprises a plurality of supports for the pipes (70), arranged upstream and downstream of said equipment (10) and adapted to define a support surface for the pipes (T) at a height from the ground substantially corresponding to that of the retainer jaws (20), so as to sustain the pipes (T) substantially in line with the crossing direction of the openings of the jaws (20) of the welding equipment (10), and to allow the axial sliding of the pipes (T) with minimum friction.

2. A system according to claim 1, characterised in that said support and movement means (12, 14, 16) of the welding equipment (20) are arranged for moving the equipment along a longitudinal direction, parallel to the pipes to be welded.

3. A system according to claim 2, characterised in that said support and movement means (12, 14, 16) of the welding equipment (20) comprise a support frame (40) adapted to permit the arrangement of the equipment (20) at a predetermined height from the ground, on which a slidable saddle is mounted (16) in a guided manner along said transverse and longitudinal directions.

4. A system according to claim 3, characterised in that said support and movement means comprise hydraulic actuator means of said saddle (16).

5. A system according to any one of the preceding claims, characterised in that said supports for the pipes (70) comprise roller devices (72), rotating around an axis lying in a plane transverse to the pipe.

6. A system according to claim 5, wherein said supports for the pipes (70) comprise a pair of rollers (72) arranged in a V in a plane transverse to the pipe.

7. A system according to claim 5 or 6, wherein said supports for the pipes (70) comprise elevator means for adjusting the height of the roller devices (72) with respect to the ground.

8. A system according to any one of the preceding claims, characterised in that it comprises a store (M) for storing a bundle of pipes (T₄-T₉) to be welded, arranged upstream of the welding equipment (20) and comprising a base area (60) adapted to receive said pipe bundle (T₄-T₉), a portion of which is arranged aligned with the assembly direction of the pipes and provided with roller devices (62) rotating around an axis lying in a plane transverse to the pipe and adapted to allow the axial sliding of the pipes (T₄) with minimum friction.

9. A system according to any one of the preceding claims, characterised in that includes at least one tubular fitting element (50) of a pair of pipes to be welded (T₃, T₄; Ti, T₂), comprising end portions adapted to be inserted in the pipes at the respective ends to be welded, and an intermediate spacer portion, adapted to be interposed between the ends of the pipes for maintaining the pipes separated by a predetermined distance.

10. A system according to claim 9, characterised in that it includes at least one tie-rod device (52) adapted to be coupled to the ends of a pair of pipes to be welded (T₃, T₄), between which said fitting element (50) is arranged.