GB2129897A - Joining pipes - Google Patents

Abstract

A method of joining together a pair of pipes (1, 2) includes providing a hollow spigot (3) on the end of the pipe (1) and a hollow socket (4) on an end of the pipe (2), the internal dimension of the socket being such as to correspond with and fit closely around an external surfaces (6) of the spigot. The spigot and socket are telescopically interengaged with sealing means (8) disposed therebetween in fluid-tight manner and the free end portion of the socket is secured to an adjacent part (11) of the spigot to join the pipes together. <IMAGE>

Description

SPECIFICATION A method of joining together a pair of pipes This invention relates to a method of joining together a pair of pipes and is particularly concerned with pipes of which at least the inner surfaces are coated with a heat degradable material such as plastics for example. The invention also embraces a composite pipe incorporating a pair of pipes joined together by the method of the invention.

Pipes of various length are very often connected together to form water installations and other piping systems, the pipe joints being very commonly effected by welding. A problem arises when coated pipes are welded because the heat of welding can destroy the coating at the welding location and it can be extremely difficult to make good the internal coating in particular, especially when long pipe lengths of relatively small diameter are employed. If the coating is not repaired, or the repair is inadequate due to the difficulties involved, the pipe remains vulnerable to attack by corrosive influences.

An object of the invention is to provide a method of joining together a pair of pipes which permits the use of welding without subjecting the pipe coating to the deleterious effects of excessive heat arising from the welding operation.

According to the invention, a method of joining together a pair of pipes comprises providing a hollow spigot on an end of one pipe, and providing on an end of the other pipe a hollow socket of internal dimension such as to correspond with and fit closely around an external surface of the spigot, assembling the spigot and socket in telescopic relationship with sealing means disposed between adjacent internal and external surfaces of the socket and spigot respectively and arranged to effect a fluid-tight seal between said surfaces, and securing the free end portion of the socket to an adjacent surface of the spigot or its associated pipe so as to join the pipes together.

Preferably, the free end portion of the socket is secured to the spigot or its associated pipe in fluid-tight manner, conveniently by welding.

From another aspect of the invention, a composite pipe comprises a pair of pipes, one of which has a generally co-axial hollow spigot and the other of which has a complementary socket within which the spigot is closely engaged, sealing means being provided between the external surface of the spigot and the internal surface of the socket and arranged to effect a fluid-tight seal between said surfaces, and the spigot and socket being secured together so as to interconnect the pair of pipes.

The sealing means is preferably a ring of resilient material which may conveniently be housed in a groove formed in one of said surfaces.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:~ Figure 1 is a representation in longitudinal cross section of one manner of carrying out the method of the invention, and Figures 2 and 3 are diagrammatic representations of an alternative method of carrying out the invention.

Referring to Figure 1, this shows a pair of pipes 1 and 2, the pipe 1 having secured to one of its ends a spigot member 3 and the pipe 2 having secured to one of its ends a socket member 4. The spigot and socket members may conveniently be secured to the pipes by welding for example at locations A and B. The spigot member has a cylindrical spigot portion 5, of which the outer cylindrical surface 6 is of diameter such as to fit closely within a socket portion 7 of the socket 4.

The spigot portion 6 is provided with an external annular groove 8 within which is disposed an annular seal 9, such as an O-ring for example, the seal being somewhat compressed so as to provide a fluid-tight barrier between the surface 6 of the spigot and the co-operating surface 10 of the socket. A radial flange 1 1 of the spigot extends outwardly of the spigot surface 6 and provides a face 12 opposite and adjacent to the free end face 13 of the socket member 4. The spigot and socket are rigidly connected together by welding together said faces 12 and 13 at location C.

The method of the invention is performed by welding the spigot and socket members to the ends of the pipes in coaxial alignment with the latter as illustrated, inserting an 'O'-ring or the like in the groove 8 and inserting the spigot member into the socket member until these items reach the positions shown with the 'O'-ring under some compression to effect a fluid-tight seal between the surfaces 6 and 10. Although the welding at locations A and B will probably cause damage to any coating on the inner and/or outer surfaces of the pipes 1 and 2, any such damage may be readily made good before the pipes are interconnected by assembly of the spigot and socket members and welding these members together at location C.Since the latter welding operation takes place away from the pipes 1 and 2, the risk of damage occurring to the coating inside the pipes from excessive heating is minimised. Sealing of the pipe contents is performed by the annular seal 9 and the weld at location C excludes ingress of dirt and moisture.

It will be seen that a chamber 14 is defined at one side of the spigot portion 5 between internal surface portions 15 and 16 respectively of the spigot member 3 and socket member 4 to one side of the spigot portion 5. This chamber can be used to cause increased heat dissipation from the area of the weld by providing a flow of air or other gas such as Argon through the chamber via an inlet 17 and outlet 18. The use of Argon and/or other gases can assist the welding process as well as providing a cooling effect. After completion of the welding process, pressure testing of the welded joint may be effected by injecting a suitable gas, such as air or liquid such as water, under pressure into the chamber 14 using the inlet and outlet 17, 18.

It is sometimes necessary to break into an existing pipeline in order to insert an additional component such as a T-junction for example. This again raises problems of damaging the coating of the existing pipe and/or additional component and the method of the invention can be used to overcome these problems, in the manner illustrated in Figures 2 and 3.

Having divided the existing pipe and removed a section thereof if required, one end thereof, in this case the end 1, is moved out of axial alignment with the other end and the additional component (not shown in detail) is secured to that other end and provides a tubular portion 2B for reconnection with the pipe portion 1. A spigot member 3A is then secured to the free end of the tubular portion 2B as by welding for example.

The socket device 4 for use in this arrangement is double ended, having a first socket member 4A corresponding to the spigot member 3A, the first socket member being joined by a tubular portion 4B of appropriate length to a second socket member 4C. A second spigot member 3B corresponding to the socket member 4C is secured, as by welding, to the end of the pipe end 1 and the socket member 4C is then engaged over the spigot 3B and the assembly brought to the position shown in Figure 2 in which the socket member 4A is spaced from the spigot member 3A enabling the pipe end 1 to be brought once more into axial alignment with the tubular portion 2B, as shown.The socket device 4 is then moved axially to the position shown in Figure 3 in which the socket member 4A is fully engaged over the spigot member 3A and in abutment, or nearly so, with a radially outwardly extending flange 1 1 of this spigot member. Welding is then effected at location D to join the socket device to the spigot member 3A. The aforesaid axial movement leaves a gap between the free end of the socket member 4C and flange 1 A attached to the pipe end portion 1 and this is now filled by interposing a ring 20 and welding this in position at locations E and F in order to connect the socket device to the pipe end portion 1. The ring 20 may conveniently be in two arcuate pieces to facilitate its installation around the assembly, the two pieces being subsequently permanently joined together, as by welding.

Seals 8 are located in the spigot portions in the manner described previously to provide fluid-tight seals between the mating portions of the spigot and socket members, the welds at D, E and F also serving to prevent ingress of foreign material. It will be seen that the pipe end portion 1 and tubular portion 2B of the additional component are again largely protected from excessive welding heat by virtue of the method of the invention. Any damage resulting from welding for the purpose of securing spigot and socket members to pipes can normally be satisfactorily made good through the spigot or socket member before the final sealing and welding connections are made.

A chamber 14 is again formed between socket member 4c (and attached ring 20) and spigot member 3B, and/or between the socket member 4A and spigot member 3A, enabling fluid flow to be provided in the chamber through ports (not shown) for heat dissipation and pressure testing purposes as described above.

It will be appreciated that the shapes and sizes of the various spigot and socket members may be varied according to the conditions of use and that the seals used may be of any convenient form and may be housed in the socket members, rather than in the spigot members as shown.

Claims (10)

1. A method of joining together a pair of pipes comprising providing a hollow spigot on an end of one pipe, and providing on an end of the other pipe a hollow socket of internal dimension such as to correspond with and fit closely around an external surface of the spigot, assembling the spigot and socket in telescopic relationship with sealing means disposed between adjacent internal and external surfaces of the socket and spigot respectively and arranged to effect a fluid-tight seal between said surfaces, and securing the free end portion of the socket to an adjacent surface of the spigot or its associated pipe so as to join the pipes together.

2. A method according to Claim 1 wherein the free end portion of the socket is secured to the spigot or its associated pipe in fluid-tight manner.

3. A method according to Claim 1 or Claim 2 wherein the pair of pipes is obtained by dividing an existing pipeline and securing to one of the pipe ends thus formed are additional component providing a tubular portion now forming one pipe of the pair to be joined to the other of the pair, securing spigot members respectively to the ends of the pair of pipes, placing one socket end portion of a double-ended socket member over one spigot and, with the spigots in axial alignment, moving the double-ended socket member axially to engage the other socket end portion over the other spigot and bring the free end of that socket into abutment with a part of the associated spigot or pipe to which it is to be secured, securing said socket free end to the spigot or pipe with which it is in abutment, introducing means forming a tubular bridging member between the free end of said one socket end portion and a part of the associated spigot or pipe to which it is to be secured and securing it in position at both ends thereof, thereby joining said pipe ends together.

4. A method according to any one of Claims 1 to 3 wherein said securing is effected by welding.

5. A method according to any one of the preceding claims wherein a chamber is defined by the or one or more of the socket members and corresponding spigot portions for the reception of fluid.

6. A composite pipe made by the method according to Claim 1 and comprising a pair of pipes, one of which has a generally co-axial hollow spigot and the other of which has a complementary socket within which the spigot is closely engaged, sealing means being provided between the external surface of the spigot and the internal surface of the socket and arranged to effect a fluid-tight seal between said surfaces, and the spigot and socket being secured together so as to interconnect the pair of pipes.

7. A composite pipe made by the method according to Claim 3 and comprising a divided pipeline to one end of which is secured an additional component providing a tubular portion forming one pipe of the pair to be joined to the other of the pair, spigot members secured respectively to the ends of said pipes, a doubleended socket member engaged over the spigots with one of the sockets secured to its associated spigot or pipe and the other socket secured to its associated spigot or pipe by the intermediary of an annular member connected at one end to said other socket and at its other end to its associated spigot or pipe, sealing means being provided between the external surfaces of the spigots and the internal surfaces of the corresponding sockets.

8. A composite pipe according to Claim 7 wherein a chamber is defined by at least one of the sockets and its corresponding spigot for the reception of fluid.

9. A method of joining together a pair of pipes substantially as hereinbefore described, with reference to Figure 1 or Figures 2 and 3 of the accompanying drawings.

10. A composite pipe substantially as hereinbefore described with reference to Figure 1 or Figures 2 and 3 of the accompanying drawings.