GB2174776A - Sealing pipelines - Google Patents

Abstract

A method for injecting sealant into the gap between a spigot-socket type pipe joint by way of a pre-existing lead-yarn seal involves boring a hole 9 through the lead part 10 of the seal into the yarn 13 (if any), inserting one end of a metal tube into the hole 9 until at least a portion 15 is located within the hole 9, radially deforming the tube outwardly in such a way that the portion 15 of the tube tightly engages the wall of the hole 9, and injecting sealant into the joint gap by way of the tube. The tube has a branch pipe 2 for connection to the hose 3 of a sealant injection device. The tube also contains a swage pin, the head 5 of which is located at the end of the tube and the tail of which extends through the tube and out from the other end of the tube where it is connected to a device such as a gun, for withdrawal of the pin when it is required to deform the tube. It is stated that the device could also be used to inject sealant directly through the wall of the pipeline. <IMAGE>

Description

SPECIFICATION Improvements in injecting sealant into a pipeline The present invention relates to the injection of a sealant into a pipeline and in particular into pipeline joints.

The majority of cast iron gas mains in current use in Great Britain include spigot-socket type joints. The gap between the spigot and the socket was sealed at the time these mains were laid with lead-yarn seals.

In making the seal, the yarn was first packed into the gap between the spigot and socket. The lead in its molten state was poured into the gap adjacent the yarn and was allowed to solidify. The lead tends to shrink over the years and leave gaps and crevices for the leakage of gas through the joint. Providing the yarn is still present however, and moreover is maintained in a moist condition itwill swell and maintain an effective seal even though the lead shrinks. Therefore, in this case, the lead may merely be serving as a retaining ring for the yarn.

In former years gas mains carried coal gas which had a relatively high moisture content and thus maintained the yarn in a moistened and thereby swollen condition. However, after the change over to natural gas it was found that the yarn tended to shrink and in some cases disappear altogether due to its dehydration by the relatively dry natural gas.

Consequently with the shrinkage or even disappearance of the yarn, gas leaks through the lead seals have become a common problem.

It is known to reseal such joints by injecting into the yarn (if any) but in any case, into the joint gap beyond the lead seal ie. on the pipeline bore side of the pre-existing seal, a curable chemical sealant from a point or points externally of the joint and allowing the material to cure in situ in the joint gap.

It is also known to inject such sealants into the joint gap on the pipeline bore side of the seal by way of hole drilled through the spigot and then to allow the sealant to cure in situ in the joint gap.

It is an object of the present invention to provide an improved method and apparatus for the injection of such sealants.

According to one aspect of the present invention, there is provided a method for injecting sealant into a pipeline, the method comprising boring a hole through the wall of the pipeline at a point along its length, inserting one end of a deformable tube into the hole until at least a portion of the tube is located within the hole, radially deforming the tube outwardliy to such an extent that at least the portion of the tube within the hold expands radially to engage with an form a seal with the wall forming the hold and injecting sealant into the pipeline by way of the tube.

According to another aspect of the present invention there is provided apparatus for injecting sealant into a pipeline, the apparatus comprising a deformable tube having one end for insertion into a hole bored through the wall of the pipeline at a point along the length of the pipeline so that at least a portion of the tube is located within the hole, the tube also having a connector for connecting the tube to a sealant injection device so that sealant can be injected into the pipeline by way of the tube and means for radially deforming the tube outwardly to such an extent and in such a manner that at least the portion of the tube within the hole expands radially to engage with and form a seal with the wall forming the hole while after deformation of the tube sealant can reach the tube by way of the connector.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which : Figure 1 is a section through the one form of apparatus, Figure 2 is a view in section of part of a typical spigot-socket joint in a gas-main showing in particularthe existing lead-yarn seal with a hole bored through the lead into the yarn, Figure 3 is a view similar to that shown in Figure 2 showing a portion of the deformable tube located within the hole before the tube is deformed.

Figure 4 is a view similar to that shown in Figure 3 showing the tube after deformation, Figure 5 is a section through another form of apparatus looked at in perspective, Figure 6 is a view in section of part of a spigotsocket joint in a gas main with a hole bored through the existing seal and with the apparatus, also shown in section, in position before the deformable tube is deformed, and Figure 7 is a view similar to Figure 6 showing the situation after expansion of the tube.

Referring to Figures 1 to 4the apparatus in this embodiment comprises a deformable tube 1 or a metal such as mild steel, the tube 1 having a branch pipe or side tee 2 for connection to the hose 3 of a suitable sealant injection device (not shown). The assembly includes a swage pin 4, the head 5 of which is located at the end 6 of the tube 1 to be inserted into the hole to be bored in the lead seal.

The tail 7 of the pin 4 extends through the tube 1 and out from the other end 8 of the tube 1.

The diameter of the pin head 5 is slightly larger than the internal diameter of the bore of the tube 1 for a purpose which will become apparent.

Referring to Figure 2, as a first step in the method, a hole 9 is bored in the lead seal 10 in the joint gap between the spigot 11 and socket 12. As shown in Figure 2 the hole 9 extends through the lead seal 10 and into any yarn 13 which may be present. But in any case the hole 9 must extend at least through the lead 10 to permit sealant to be injected into the joint gap 14 beyond the lead. If not already done, the swage pin 4 should be inserted into the tube 1 as shown in Figure 1.

In the next step shown in Figure 3, the end 5 of the tube 1 is inserted into the hole 9 until a portion 15 of the tube 1 is located within the hole 9. Clearly the diameter of the hole 9 must be large enough to permit the pin head 5 and the portion 15 of the tube 1 to locate in the hole 9. At this stage, the pin head 5 provides a temporary barrier to the flow of any gas from the main into the tube 1 through the hole 9.

Finally, (Figure 4) the tail 7 of the pin 4 is connected to a suitable withdrawal device such as a gun which is actuated to draw the pin head 5 along the tube 1 towards but not beyond the far end 16 of the tube 1 but at any rate past the branch pipe 2.

By withdrawing the head 5 of the pin 4 in this manner the tube 1 is deformed radially outwardly and both its internal diameter and more importantly its external diameter are expanded.

Provided that the dimensions of the tube 1, pin head 5 and the diameter of the hole 9 are appropriately selected, the external wall of the tube 1 will form a seal with the wall of the hole 9. This will prevent the escape of gas between the tube 1 and the hole 9 and any gas will be forced to flow along the tube 1.

In the position shown in Figure 4 the pin head 5 will form a barrier to the escape of gas from the far end 16oftube 1.

Sealant can now be pumped under pressure from the injection device so that it can enter the joint gap 14 beyond the lead 10 by way of the branch pipe 2 and the tube 1.

The sealant will tend to flow around the annular gap formed at the joint and form a new seal after the sealant has been allowed to cure. The pressure of any gas flowing in the main will also tend to blow the sealant towards the lead 10 and at least some of this sealant will penetrate any gaps and crevices between the lead 10 and the pipes 11 and 12 forming the joint to provide an enhanced sealing effect.

Referring to Figures 5 and 6 where parts similar to those shown in Figure 1 to 4 bear identical reference numerals, the apparatus comprises a length of deformable tube 21 of a metal such as mild steel and a sleeve 22 having a portion 23 to receive one end 24 of the tube 21, the sleeve 22 having intermediate its ends a branch pipe or side tee 25 for connection to the flexible hose 26 of a sealant injection device (not shown). The sleeve 22 and pipe 23 form a tee-block formed of a metal such as mild steel. The apparatus also includes a swage pin 27, the head 28 of which is located at the end 29 of the tube 21 to be inserted into the hole to be bored in the lead seal. The tail 30 of the pin 27 extends through the tube 21 and out of the far end 31 of the sleeve 22.

The sleeve 22 is formed with a bore having three different diameters. The bore has a widest part 32 adjacent the tube end of the sleeve 22 and its narrowest part 33 adjacent the far end of the sleeve 22. A central part 34 lies intermediate the other parts 32and33.

The tube 21 is arranged to have an external diameter which is slightly less than the internal diameter of the bore part 32 so that a rear portion of the tube 21 can locate with clearance within bore part 32.

The diameter of the pinhead 28 is slightly larger than the internal diameter of the tube 21 for purposes which will already be evident from the description of Figures 1 to 4.

In addition however, the diameter of the pin head 28 is slightly smaller than that of the bore part 32 but is larger than that of bore part 34 and is significantly larger than that of bore part 33.

Referring to the drawings, the first step in the method involves boring a hole 9 through the lead seal 10 into the joint gap between the spigot 11 and socket 12. As previously mentioned with reference to the description for Figures 1 to 4 the hole 9 should extend through the lead seal 10 and into any yarn (not shown) which may be present but in any case the hole 9 must extend at least through the lead 10 to permit sealant to be injected into the joint gap (not shown) beyond the lead 10.

In the next step of the method, the tube 21 is located within the portion 23 of the sleeve 22 and the tail of the swage pin 27 is inserted into the end 29 of the tube 21 and is pushed through the tube and sleeve until the tail emerges from the far end 31 of the sleeve.

In the next step shown in Figure 6, the end 29 of the tube 21 is inserted into the hole 9 until that portion of the tube outside the sleeve 22 is located within the hole 9. Clearly the diameter of the hole 9 must be large enough to permit both the pin head 28 and the end portion 29 of the tube 21 to locate in the hole 9. At this stage, the pin head 28 provides a temporary barrier to the flow of any gas from the main into the tube 21 through the hole 9.

Finally as shown in Figure 7, the tail 30 of the swage pin 27 is connected to a suitable withdrawal device such as a gun (not shown) which is actuated to draw the pin head 28 along the tube 21 towards the far end 31 of the sleeve 22.

As shown in Figure 7 the pin head 28 is pulled beyond the side tee 25 to the boundary between the narrow and central bore parts 33 and 34 so as to uncover the passage formed by the tee 25 to permit the injection of sealant.

As previously described, withdrawing the head 28 of the pin in this manner causes the tube 21 to be deformed radially outwardly so that both its internal diameter and more importantly its external diameter are expanded.

Providing the dimensions of the tube 21,the hole 9 in the lead seal 10 and the internal diameter of the wide bore part 32 are appropriately selected, the tube will seal both against the wall formed by the hole and also against the internal wall of the bore part 32 as shown in Figure 7.

The pin head 28 itself also forms a seal with the central portion 34 of the bore which is deformed by movement of the head 28 through the bore. This prevents the escape of gas from the far end 31 of the sleeve 21.

The flexible hose 26 may then be connected to the side tee 25 (if not already connected) and the sealant is pumped under pressure from the injection device so that it can enter the joint gap beyond the lead 10 by way of the tube 21 and flow in the manner previously described with reference to Figures 1 to 4.

The application system described can be used to apply any type of curable chemical sealant in liquid of paste form. We have found that sealants of the anaerobic type, that is those which polymerise spontaneously in the absence of air, are particularly effective in sealing the lead-yarn type of spigotsocket joints found in gas mains. While in the examples described, the hole for injection of the sealant into the joint gap has been bored through the annular lead seal, it will be appreciated that access to the joint gap can equally well be reached by way of the spigot. Thus the sealant can also be injected by boring a hole through the spigot into the joint gap and then carrying out either of the procedures described above.

It will also be appreciated that the procedures described could be used to inject sealant into any type of spigot-socket joint (not necessarily those of the lead-yarn type) and into pipe joints other than the spigot-socket type eg. mechanically clamped pipe joints and butt-joints.

Furthermore the procedure can be used to inject sealant directly into the pipeline through the wall where this is required or appropriate.

The procedures are designed for the injection of sealant into gas-carrying mains but they could be used to inject sealant into any appropriate fluidcarrying pipeline and even into pipelines which are "dead" ie. currently not carrying any fluid at all.

Claims (12)

1. A method for injecting sealant into a pipeline, the method comprising boring a hole through the wall of the pipeline at a point along its length, inserting one end of a deformable tube into the hole until at least a portion of the tube is located within the hole, radially deforming the tube outwardly to such an extent that at least the portion of the tube within the hole expands radially to engage with and form a seal with the wall forming the hole and injecting sealant into the pipeline by way of the tube.

2. A method as claimed in claim 1 in which the point in the wall of the pipeline comprises a joint between two pipes and the hole is bored into the joint gap.

3. A method as claimed in claim 2 in which the joint is of the spigot-socket type with a pre-existing seal between the spigot and socket, the hole being bored through the seal into the joint gap on the pipeline bore side of the pre-existing seal.

4. A method as claimed in claim 2 in which the joint is of the spigot-socket type with a pre-existing seal between the spigot and socket, the hole being bored through the wall of the spigot into the joint gap on the pipeline bore side of the pre-existing seal.

5. Apparatus for injecting sealant into the pipeline, the apparatus comprising a deformable tube having one end for insertion into a hole bored through the wall of the pipeline at a point along the length of the pipeline so that at least a portion of the tube is located within the hole, the tube also having a connector for connecting the tube to a sealant injection device so that sealant can be injected into the pipeline by way of the tube and means for radially deforming the tube outwardly to such an extend and in such a manner that at least the portion of the tube within the hole expands radially to engage with and form a seal with the wall forming the hole while after deformation of the tube sealant can reach the tube by way of the connector.

6. Apparatus as claimed in claim 5 in which the tube has a branch intermediate its ends to form the connector for connecting the tube to the sealant injection device.

7. Apparatus as claimed in claim 6 in which the means for radially deforming the tube outwardly comprises a pin having a head for positioning initially beyond the insertion end of the tube and a tail which is adapted, when the head is in its initial position, to extend through the tube from the insertion end towards and out of the other end of the tube, the dimension of the head being such that on pulling the head from the insertion end of the tube to a point beyond the branch connector the tube is caused to deform radially outwardly to such an extent that the portion of the tube within the hole expands radially to engage with and form a seal with the wall of the hole.

8. Apparatus as claimed in claim Sin which the connector comprises a sleeve having one end to receive the other end of the tube so that the remainder of the tube is located within the sleeve, the sleeve having a branch intermediate its ends to connect the sleeve to the sealant injection device.

9. Apparatus as claimed in claim 8 in which the means for radially deforming the tube outwardly is effective in radially deforming the tube outwardly to such an extent that the portion of the tube located within the sleeve can expand to engage with and form a seal with the sleeve.

10. Apparatus as claimed in claim 9 in which the means for radially deforming the tube outwardly comprises a pin having a head for positioning initially beyond the insertion end of the tube and a tail which is adapted, when the head is in its initial position, to extend through the tube from its insertion end and through the sleeve towards and out of the other end of the sleeve, the dimension of the head being such that on pulling the head from the insertion end of the tube to a point beyond the sleeve branch, the tube is caused to deform radially outwardly to such an extent that the portions of the tube within the wall of the hole and within the sleeve expand respectively to engage with and form seals with the wall of the hole and the sleeve.

11. A method for injecting sealant into a pipeline substantially as hereinbefore described with reference to Figures 1 to 4 or Figures 5 to 7.

12. Apparatus for injecting sealant into a pipeline substantially as hereinbefore described with reference to Figures 1 to 4 or Figures 5 to 7.