GB2119058A

GB2119058A - Sealing pipe joints

Info

Publication number: GB2119058A
Application number: GB08310561A
Authority: GB
Inventors: Frederick Arthur Jordan
Original assignee: Furmanite International Ltd
Current assignee: Furmanite International Ltd
Priority date: 1982-04-28
Filing date: 1983-04-19
Publication date: 1983-11-09
Also published as: GB8310561D0; GB2119058B

Abstract

A method of sealing a leaking pipe joint comprises uncovering part of the leaking joint and drilling and tapping an injection point 18 in the bell part 12 of the joint which point coincides with a joint cavity 40; fitting a hop tap adaptor in the injection point, attaching a hot tap tool to the adaptor and drilling the injection point through to the joint cavity; closing the valve adaptor and replacing the hot tap tool by an injection gun containing a sealant 49 of polyurethane elastomer containing rubber crumb; opening the valve adaptor and injecting sealant; and after curing of the sealant removing the valve adaptor and plugging the injection point. <IMAGE>

Description

SPECIFICATION Sealing method and apparatus This invention concerns method and apparatus for sealing leaking pipe joints and particularly concerns a method of sealing leaking bell and spigot pipe joints.

Normally leaks in bell and spigot pipe joints are cured by encapsulating the whole joint with an approved resin. The encapsulation method requires that the joint be fully excavated, cleaned by shot blasting, primed and protected from adverse weather conditions before the resin is applied. This method can, therefore, be inconvenient, difficult and time consuming to carry out especially if the pipe is in use, i.e. "hot".

The object of this invention is to provide a method of sealing leaking pipe joints which does not require full excavation, cleaning or priming of the joint.

According to this invention there is provided a method of sealing a leaking pipe joint wherein sealant is injected directly into the joint to flow around the joint to provide an effective seal.

The choice of sealant is important in that if it does not have a suitable viscosity it will either not flow around the joint or will not be retained in the joint.

A suitable sealant is a polyurethane elastomer, possibly containing rubber crumb. Preferably, the sealant has a viscosity of between 1900 cps and 2800 cps (Brookfield RVF4 at 24"C, a cure time for 100 g of 4 to 5 minutes at 240C and a cured hardness of 90 to 96 Shore A. The rubber crumb, if present, is preferably, below 2 mm mesh size and preferably in amount of about 22% by weight. Suitable catalyst may also be included in the sealant to enable curing at low temperatures.

The preferred method comprises the steps of uncovering part of the leaking joint, forming an injection point in a part of the joint coinciding with a joint cavity and injecting sealant into the joint cavity.

The drilling and injection steps are both preferably carried out in a sealed manner i.e. so as not to reduce escape of materials from the pipeline.

An advantageous sequence of method steps is as follows. Firstly, part of the leaking joint is uncovered and an injection point is drilled and tapped in the bell part of the joint, which injection point coincides with the joint cavity. A hot tap adaptor is fitted in the injection point, a hot tap tool attached to the adaptor and the injection point drilled through into the joint cavity. The valve adaptor is then closed and the hot tap tool replaced by an injection gun filled with sealant. The valve adaptor is then opened and the sealant injected into the joint cavity. After injection of sufficient sealant, the valve adaptor is closed and the sealant allowed to cure. When sufficient time has elapsed for the sealant to cure the valve adaptor is removed and the joint tested for leakage. If the joint is sealed, the injection point is plugged say with a grub screw.

The method of the invention is particularly suitable for gas pipe joints as the sealant will be carried into the leakage points by the flow of escaping gas.

The method can be carried out quickly and simply and can restore sealing gaskets to their original condition. Also, the joint will still be able to flex and conform to ground settlement.

The method of this invention can be made suitable for many types of joint with variations in the injection technique and of the sealant. Examples of joints on which the method may be used are as follows: Stanton Wilson joint Screwed gland joint Staveley OBT hook bolted joint Clay cross set screw joint Stanton Bolton gland joint Stanlock joint Ledd/yarn joints The invention also includes the apparatus for carrying out the above described method.

The invention will now be further described by way of example only, with reference to the accompanying drawings, in which; Figure 1 is a section through a gas pipebell and spigot joint drilled and tapped to receive a valve adaptor; Figure2 is a section through the joint of Figure 1 with a valve adaptor and hot tap tool fitted; Figure 3 is a section through the joint of Figure 1 with an injection gun fitted; and Figure 4 is a section through the joint of Figure 1 with sealing completed.

Referring to the drawings, a gas pipe joint has a bell 12 on one pipe-end into which is screwed spigot 14 on adjacent pipe end and between which a gasket 16 is compressed.

The bell 12 has been partly drilled and tapped to provide a bore 18 for fitting a hot tap valve adaptor 20 (see Figure 2).

The adaptor 20 has a body 21 of generally cylindrical cross-section with an axial passage 22 therethrough. One end 23 of the body 21 is narrower and has an external screw thread 24 for screwing into the bore 18 in the bell 12 of the gas pipe joint. An end portion of the passage 22 remote from end 23 of the body has a greater diameter than the rest of the passage 22 and is screw threaded internally for attachment of hot tap tool 28 or injection gun 29. The passage 22 is closed or opened by rotatable valve member 30 which has a transverse through-hole 31.

When the through-hole 31 is aligned with the passage 22 either a drill bit 32 or sealant can pass down the passage 22.

After the adaptor 20 has been fitted the hot tap tool 28 is attached for drilling of a hole through to joint cavity 40.

The hot tap tool 28 (Figure 2) has a hollow cylindrical body 33 with an externally screw threaded end portion 34 for fitting to the valve adaptor 20. At the other end of the body 33 is a cap 35 sealingly secured to the body 33 but through which rod 36 passes, the rod 36 being attached at its upper end to drill chuck 38 and having attached to its other end drill bit 32. A seal is also provided betwen the cap 35 and the rod 36 so that when the valve adaptor is opened and the bore 18 drilled through to joint cavity 40 there is little risk of leakage.

After drilling, the drill bit is withdrawn sufficiently to enable the valve adaptor to be closed and the hot tap tool is then replaced by injection gun 29.

The injection gun 29 has a hollow cylindrical body 42 with a valve portion 43 at one end which screws into valve adaptor 20 and a cap 44 at the other end through which passes a plunger 46 to force sealant 49 into the joint cavity 40 when both valve member 47 of valve portion 43 and valve member 30 of the adaptor are in the open position.

The sealant 49 (Figure 4) enters cavity 40 and flows around the joint. Pressure of fluid in the pipe forces the sealant into the leakage points to form a fresh seal. When sufficient time has elapsed for the sealant to have cured, the injection gun and valve adaptor are removed and the hole 18 plugged with a grub screw 50.

Claims

1. A method of sealing a leaking pipe joint comprising injecting sealant directly into the joint to flow around the joint to provide an effective seal.

2. A method as claimed in claim 1 wherein the sealant has a viscosity such as to enable it to flow around the joint but be retained in the joint.

3. A method as claimed in claim 2 wherein the sealant has a viscosity of between 1900 and 2800 cps.

4. A method as claimed in claim 1,2 or 3 wherein the sealant is a polyurethane elastomer.

5. A method as claimed in claim 4 wherein the elastomer contains rubber crumb.

6. A method as claimed in claim 5 wherein the rubber crumb is 2 mm mesh size.

7. A method as claimed in claims 5 or 6 wherein the elastomer contains about 22% by weight rubber crumb.

8. A method as claimed in any one of claims 1 to 7 comprising the steps of uncovering part of the leaking joint, forming an injection point in a part of the joint coinciding with a joint cavity, and injecting sealant into the joint cavity.

9. A method as claimed in claim 8 wherein the injection point is formed by drilling in a sealed manner.

10. A method as claimed in claim 8 or 9 wherein the injection of sealant is carried out in a sealed manner.

11. A method as claimed in claim 8,9 or 10 comprising the following steps: (1) uncovering part of the leaking joint and drilling and tapping an injection point in the bell part of the joint, which injection point coincides with the joint cavity; (2) fitting a hot tap adaptor in the injection point attaching a hot tap tool to the adaptor and drilling the injection point through to the joint cavity; (3) closing the valve adaptor and replacing the hot tap tool by an injection gun containing sealant; (4) opening the valve adaptor and injecting sealant; and (5) after curing of the sealant removing the valve adaptor and plugging the injection point.

12. Apparatus for carrying out the method as claimed in any one of claims 1 to 11.

13. A method of sealing a leaking pipe joint substantially as hereinbefore described with reference to the accompanying drawings.