GB2119806A

GB2119806A - Durable elastomer-based sealants

Info

Publication number: GB2119806A
Application number: GB08310562A
Authority: GB
Inventors: Frederick Arthur Jordan
Original assignee: FURNAMITE INT Ltd
Current assignee: FURNAMITE INT Ltd
Priority date: 1982-04-28
Filing date: 1983-04-19
Publication date: 1983-11-23
Also published as: GB2119806B; GB8310562D0

Abstract

A sealant for sealing pipe joints comprises a curable elastomer and a pulverulent filler, e.g. a polyurethane elastomer and rubber crumb.

Description

SPECIFICATION Sealants This invention concerns a sealant for use in sealing leaking pipe joints, particularly 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".

Our copending application no.

(P1079) proposes 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 used in the method is of importance in that if it does not have a suitable viscosity it will neither flow around the joint nor be retained in the joint.

The object of this invention is to provide a sealant which may be used for sealing leaking pipe joints.

According to this invention there is provided a sealant comprising a curable elastomer and a granulated or pulverulent filler.

Preferably the elastomer sets to substantially the same hardness as the filler and is compatible therewith. A suitable elastomer is a two part polurethane elastomer and a suitably compatible filler is rubber crumb.

A curing catalyst may be included in the polyol part of the polyurethane elastomer to enable curing at lower than ambient temperatures.

The elastomer preferably has a viscosity of from 1900 to 2800 cps (Brookfield RVF4 at 240C), a cure time for 100 g of 4 to 5 minutes (240C), and a cured hardness of 90 to 960 Shore A.

The amount of filler needed in the sealant will depend to a certain extent on the severity of the leak. The filler is present mainly to prevent the elastomer being blown out of the leaking joint and so the severer the leak the more filler will be needed. A filler content of 10% by weight or more, of preferably from 18 to 27% by weight may be suitable and in fact a filler content of about 22%, has been found to be adequate for most leaks. Also, the particle size of the filler is of importance and is preferably below 2 mm mesh, especially below 1 mm mesh.

The sealant may be made by mixing of the ingredients in the appropriate amounts. For a two part curable elastomer the filler is preferably added to only one component, the other component being admixed just prior to use, e.g.

for a polyurethane elastomer the crumb would be included in the polyol component.

The sealant of the invention may be used in the following method of sealing a leak in a bell and spigot type joint.

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.

This method and the sealant of the invention are particularly suitable for sealing 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.

Examples of joints on which the sealant may be used are as follows: Snodland joint Stanton Wilson joint Screwed gland joint Staveley OBT hook bolted joint Clay cross set screw joint Stanton Bolton gland joint Stanlock joint Lead/yarn joints This invention will now be described by means of the following Example.

Example A sealant for use in sealing pipe joints is made by first mixing 3.5 parts polyol 1 part rubber crumb of particle size less than 2 mm and 0.14 parts heavy metal catalyst. To this mixture is added on site 1 part of isocyanate.

The resultant mixture has a viscosity in the region of 1900 to 2800 cps (Brookfield RVF4 at 240C) a cure time for 100 g of about 4-5 minutes and a cured hardness of about 90 to 960 Shore A.

One use of the sealant of this invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a section through a gas pipe bell and spigot joint drilled and tapped to receive a valve adaptor; Figure 2 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 1 6 is compressed.

The bell 12 has been partly drilled and tapped to provide a bore 1 8 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 aiso provided between the cap 35 and the rod 36 so that when the valve adaptor is opened and the bore 1 8 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 1 8 plugged with a grub screw 50.

It will be appreciated that the sealant of this invention is also suitable for sealing leaks in other than bell and spigot joints but is particularly suitable for sealing leaks in gas pipe joints.

Claims

1. A sealant comprising a curable elastomer and a granulated or pulverulent filler.

2. A sealant as claimed in claim 1 wherein the elastomer sets to substantially the same hardness as the filler and is compatible therewith.

3. A sealant as claimed in claim 1 or 2 wherein the elastomer is a two part polyurethane elastomer.

4. A sealant as claimed in claim 1,2 or 3 wherein the filler is rubber crumb.

5. A sealant as claimed in claim 3 or 4 wherein the polyurethane elastomer includes a curing catalyst in its polyol component.

6. A sealant as claimed in any one of claims 1 to 5 having a viscosity of from 1900 to 2800 cps (Brookfield RVF4 at 240C).

7. A sealant as claimed in any one of claims 1 to 6 having a cure time for 100 g of 4 to 5 minutes at 240C.

8. A sealant as claimed in any one of claims 1 to 7 having a cured hardness of 90 to 96 Shore A.

9. A selant as claimed in any one of claims 1 to 8 wherein the filler has a particle size of below 2 mm.

10. A sealant as claimed in claim 9 wherein the filler has a particle size of less than 1 mm.

11. A sealant as claimed in any one of claims 1 to 10 containing from 10% by weight of filler.

12. A sealant as claimed in claim 11 containing from 18 to 27% by weight of filler.

13. A sealant as claimed in claim 12 containing about 22% by weight of filler.

14. A sealant substantially as hereinbefore described with reference to the Example.