GB2112097A

GB2112097A - Sealing joints in pipes

Info

Publication number: GB2112097A
Application number: GB08231834A
Authority: GB
Inventors: Howard Hardwick; David Macgregor Mills; Richard Walker Thomson
Original assignee: PRESS CONST Ltd; PRESS LEAKAGE CONTROL SERVICES
Current assignee: PRESS CONST Ltd; PRESS LEAKAGE CONTROL SERVICES
Priority date: 1981-11-10
Filing date: 1982-11-08
Publication date: 1983-07-13
Also published as: GB2112097B

Abstract

In a method of sealing gas-main pipe joints an annular mould (1) is applied to the inner surfaces of pipe ends (11 and 12) on each side of the joint and covering the joint. The edges of the mould are clamped to the respective pipe ends by expanding bands (4) applied internally of the fitted mould and a sealant resin is injected between the mould and the inner surfaces of the pipe ends and into any spaces in the joint. The injected sealant resin is allowed to cure and the bands and the mould are removed. <IMAGE>

Description

SPECIFICATION Sealing joints in pipes large enough in diameter for entry of personnel This invention relates to a method of sealing in pipes large enough in diameter for entry of personnel, for example gas-main pipes.

When natural gas began to be used instead of town gas it was found that the extra dryness and higher pressures of natural gas caused the sisal, which acted as a seal at gas-main pipe joints to deteriorate more rapidly than was the case with town gas. Many sealing methods were proposed and were reasonably successful but with the larger diameter mains it was found necessary to excavate at each joint in order to seal the joint externally. One method of external sealing that was proposed involved the external application of a steel or canvas muff about the joint and to apply a sealant resin known under the trade name "Encapress" between the muff and the joint. It has also been proposed to seal internally using a rigid assembly of segmental parts which are expanded sealingly to engage the inside of the pipe and again to apply the sealant resin.This assembly remains in the pipe and is costly.

An object of the invention is to provide a method of sealing for example, larger diameter gas-main pipe joints which reduces the amount of excavation necessary and thereby reduces the inconvenience to the public and traffic by making it unnecessary to excavate at each joint.

According to the invention there is provided a method of sealing joints in pipes large enough in diameter for entry of personnel, comprising the steps of applying an annular mould to the inner surfaces of the pipe ends on each side of the joint and covering the joint, clamping the edge portions of the mould to the respective pipe ends by expanding bands applied internally of the fitted mould, injecting under pressure a sealant resin between the intermediate portion of the mould and the inner surfaces of the pipe ends and into any spaces in the joint, allowing the injected sealant resin to cure, and finally removing the bands and the mould.

Optionally, the mould is thin enough for its flexibility to facilitate its application to the inner surfaces of the pipe ends but thick enough to prevent appreciable distension of the intermediate portion by the injected sealant resin. In this case the mould has a shallow channel extending longitudinally along one side in the intermediate portion and the mould is applied so that the channel faces outwards and covers the joint.

Preferably, a release agent is applied to the surface of the channel.

The sealant becomes cured in the cross sectional shape of a letter T, the arms of the T being the portion which filled the channel in the mould and the leg of the T being the portion which filled any spaces in the joint and extending radially outwards. This cross-sectional shape has the advantage that the gas pressure in the pipe aids in maintaining the sealing of the joint in use.

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which:~ Fig. 1 is a cross-section of a pipe at a joint showing how the sealant resin is applied; Fig. 2 is a section to an enlarged scale on line A-A in Fig. 1; Fig. 3 shows, to the same scale as Fig. 2, a detail of the mould viewed in the direction of arrow B in Fig. 1, and Figs. 4 to 7 are also to the same scale as Figs 2 and 3 and show respectively a plan view of an expansion buckle of a clamping band, a side view of the buckle, a slotted lug forming part of the buckle, and a section through the clamping band at the same location as Fig. 3.

In the drawings, a neoprene mould 1 is provided in the form of a strip. The ends of the strip are shown in Fig. 3 with interengaging formations 2 and in Figs. 2 and 7 with a shallow channel 3 extending longitudinally along one side.

Provided for use with the mould 1 are two bands 4 of mild steel. Details of the ends of each band 4 are shown in Figs. 4, 5 and 6. Near one end of each band 4 an outstanding lug 5 is welded and apertured to receive a screw 6 which is threaded into a nut 7 welded to the lug 5. At the other end of each band 4 there are welded two outstanding lugs 8 provided with slots 9 for slidably receiving the end portion of the band beyond the lug 5.

Intermediate the ends of each band 4 there is welded an overlying lug 10 extending beyond one edge of the band.

In use, a release agent is applied to the channel 3 and the mould 1 is applied in the form of an annulus to the inner surfaces of the pipe ends 1 1 and 12 (see Fig. 2) on each side of the joint so that the channel faces outwards and covers the joint.

In Fig. 1 the ends of the mould are at the bottom of the pipe. The two bands 4 are then applied to the respective edge portions of the mould 1 as shown in Fig. 2 and expanded by means of the screws 6 so as to clamp the edge portions of the mould 1 to the inner surfaces of the respective pipe ends 11 and 12. As shown in Fig. 1 ,the buckles are shown at the left hand side whereas the lugs 10 are at the bottom at the location of the ends of the mould 1. At this location a steel plate 13 is retained between the bands 4 by the lugs 10 and a rubber gasket 14 is retained between the plate 13 and the ends of the mould 1.

A sealant resin 1 5 is injected under pressure, via a valve 16 through the mould 1 into the channel 3 so as to fill the channel 3 and any spaces in the joint. An air release means 17 is provided at the top of Fig. 1, i.e. substantially diametrically opposite the valve 16, so that when the resin begins to emerge from the means 17 the operator knows that the resin has filled all the available spaces. The injected sealant resin is allowed to cure and finally the mould 1 and bands 4 are removed leaving a reliable seal.

The operator can then move along inside the pipe to the next joint without the need for excavation at that joint. It is envisaged that excavation using the above method could be as far apart as 300 to 400 yards.

Instead of the mould 1 being in the form of a strip having ends, it can be made in the form of an annulus of a diameter substantially equal to the internal diameter of the pipe.

The mould 1 is thin enough for its flexibility to facilitate its application to the inner surfaces of the pipe ends 1 1 and 12 but thick enough to prevent appreciable distension by the injected sealant resin of the intermediate portion between the bands 4. It has been found that if the mould is thin enough to be appreciably distended by the injected sealant resin the edges of the mould tend to move towards each other, either slipping between the bands 4 and the inner surfaces of the pipe ends 1 1 and 12 or pulling the bands 4 towards each other. To prevent this the edges of the mould may be thickened and/or the bands may be braced apart. This adds to the cost of the parts and complicates the performace of the method as compared with the method described and illustrated.

Claims

1. A method of sealing joints in pipes large enough in diameter for entry of personnel, comprising the steps of applying an annular mould to the inner surfaces of the pipe ends on each side of the joint and covering the joint, clamping the edge portions of the mould to the respective pipe ends by expanding bands applied internally of the fitted mould, injecting under pressure a sealant resin between the intermediate portion of the mould and the inner surfaces of the pipe ends and into any spaces in the joint, allowing the injected sealant resin to cure, and finally removing the bands and the mould.

2. A method according to claim 1, wherein the mould is thick enough to prevent appreciable distension of the intermediate portion by the injected sealant resin, has a shallow channel extending longitudinally along one side in the intermediate portion, and is applied so that the channel faces outwards and covers the joint.

3. A method according to claim 2, wherein a release agent is applied to the surface of the channel.

4. A method according to claim 1, 2 or 3, wherein the mould is provided in the form of a strip the ends of which have interengageable formations.

5. A method according to claim 1, 2 or 3, wherein the mould is provided in the form of an annulus.

6. A method of sealing gas-main pipe joints, substantially as hereinbefore described with reference to the accompanying drawings.