GB2201612A

GB2201612A - Sealing material in sheet or strip form

Info

Publication number: GB2201612A
Application number: GB08704933A
Authority: GB
Inventors: Michael James Rees
Original assignee: ALBION CONCRETE PRODUCTS LIMIT
Current assignee: ALBION CONCRETE PRODUCTS LIMIT
Priority date: 1987-03-03
Filing date: 1987-03-03
Publication date: 1988-09-07
Also published as: GB8704933D0

Abstract

Two pipes are sealed together by a strip comprising an outer inexpansible layer 12 and an expansible inner layer 13 which is constrained by the outer layer to enter the joint space 26 between the pipes to seal it. Layer 12 may be dimensionally stable and layer 13 may comprise a pre-compressed expansible foam, which can be pre-impregnated with wax or bentonite clay. Alternatively outer layer 12 may be heat shrinkable. <IMAGE>

Description

Sealing material in sheet or strip form This invention relates to sealing material in sheet or strip form. The use envisaged is for sealing joints in pipelines, culverts and other architectural, civil engineering or agricultural structures.

In many instances, absolutely watertight seals of, for example, drainage conduits, are not essential provided there is only limited leakage. Interengaging conduit sections are well known, and the present invention aims to provide an easily and rapidly applied seal for the joints between sections. Sealing 'bandages' similar in concept to a large sticky tape have been known, but these do not provide sufficient sealing ability or physical adaptability for many purposes.

Accordingly, the invention proposes a sealing material in sheet or strip form having two layers, a first layer which is flexible and dimensionally stable, and a second layer mounted on the first which in use is capable of expansion in thickness from an initial thickness which is retained for at least a limited time period. The expansion may occur automatically, or be promoted by external action. In use for sealing, the material is placed with the second layer against the joint to be sealed and the surrounding area. The first layer serves as a covering which is fixed in place, and when the second layer expands beneath it, the second layer forces its way into the spaces of the joint to seal it.

The invention in another aspect proposes a seal on a pipe comprising a sealing material around the pipe, the sealing material being in sheet or strip form having an outer layer forming an inexpansible collar, and an inner expansible layer which is kept in a compressed state within the collar and which creeps into the recesses of the pipe to seal it.

In order that the invention shall be clearly understood, several exemplary embodiments will now be described with reference to the accompanying drawings, in which: Fig.l shows a roll of sealing material according to the invention; Fig.2 shows a cross-section of a pipe with the sealing material in use; and Fig.3 shows a section on 3-3 in Fig.2.

A roll 10 of sealing material has a short length 11 unrolled. The roll is about 10 to 25 cms wide and has a first or outer layer 12 of dimensionally stable but flexible heavy-grade plastics sheet such as coextruded polyethylene. This may have a thickness of up to 0.5 mms, i.e. 500 microns and does not stretch if handled manually. Bonded to the layer 12 is a second or inner layer 13 of polyurethane foam which is impregnated with a non-bio-degradable wax.

In manufacture, the second layer 13 is compressed to between one quarter and one twentieth, preferably about one fifteenth, of its thickness in its relaxed, uncompressed state. In this condition it is immediately tightly rolled upon itself. So long as it is not unrolled, the second layer is unable to expand.

At the end ll which is unrolled and left, the second layer 13' will gradually expand to its natural unrestrained thickness. The rate at which it does this depends upon the ambient temperature, since this determines how soft the wax becomes. In practice, the second layer will expand, albeit slowly, even in the field at freezing point and below. In summer sunshine, it may require only an hour or two.

As a consequence, the roll of sealing material must be carefully stuck so that it cannot unroll. In certain circumstances, it may be advisable to keep the roll cooled or refrigerated until it is required.

Figures 2 & 3 illustrate how the sealing material is used to seal a pipe joint. The adjacent ends 21, 22 of two lengths of pipe are joined with an ogee joint, but not otherwise sealed. They are shown at a slight angle 23 to each other. The pipes being only for drainage of surface water do not need to be totally watertight, but must prevent more than a limited flow in or out, and in particular must not allow silt to flow inwards. The seal is designed to prevent the ingress of plant roots and allows for normal flexing of the pipeline and joints in use due to ground movement.

A length of sealing material as described in Figure 1 is cut off the roll 10, sufficient to go around the pipe joint and provide a certain overlap 24. The material is pulled tight manually, and an adhesive, strong adhesive tape 25 or a mechanical device is used to hold it in place. At this stage, the outer (first) layer 12 does not stretch, and the inner layer 13 is still in its compressed state. The Figures, however, show the material after a certain time has elapsed, during which the wax impregnation has softened and the layer 13 has expanded. Since it is trapped in an inexpansible collar formed by layer 12, it can only expand inwards, and does so to fill the irregularities of the outer surface of the pipe joint, in particular any spaces between 'the abutted ends 21, 22 such as the space 26 formed by the angle between them.It cannot expand as much as it wishes, so there is a constant pressure maintained against the surface of the pipe which keeeps the joint sealed against both egress and ingress of water.

After application of the material, the space around the joint is back filled with soil and stones, and tamped solid. This ensures that there is no chance of the sealing material expanding even if the adhesive or adhesive tape failed.

In a modification, the second layer is a foam impregnated with bentonite clay in a carrier material such as diesel oil. Bentonite has the property of expanding when contacted by water (but not oil) to thirteen times its previous volume. When the water dries out, it shrinks again. If a pipe joint is wrapped with a sealing material having bentonite as the inner layer and still dry, as soon as some water leaks out of the joint the bentonite will expand to fill the cracks and seal them.

In a further modification the part-expanded foam is recompressed by shrinking and tensioning the outer layer 12. This allows all the spaces between the outer layer 12 and the surface of the pipe to be filled at lower temperatures whilst retaining the expansion properties previously mentioned, between the shrinking outer layer and the expanding inner layer 13.

In another modification the second layer is not a foam but is bentonite clay on or in a strip of nylon or other suitable plastics carrier material.

In a further modification, the first layer 12 may be a heat shrinkable plastic, which can be heated after the material has been placed around the pipe and secured.

This can provide a circumferential tension which is very difficult to produce in any other way. It may be possible to dispense with pre-compression of the second layer, which is forced to conform to the pipe surfaces by the pressure generated by shrinkage of the collar.

Claims

Claims

r 1. A seal for a pipe comprising a sealing material arranged to be placed around the pipe, the sealing material being in sheet or strip form having an outer layer forming an inexpansible collar, and an inner expansible layer which is arranged to be kept in a compressed state within the collar and to creep into the recesses of the pipe to seal it.
2. A seal according to claim 1, wherein the outer layer is of a heat-shrinkable material.
3. A seal according to claim 1, wherein the outer layer is of dimensionally stable material.
4. A seal according to claim 3, wherein the inner layer is of wax-impregnated foam.
5. A seal according to claim 3, wherein the inner layer is of foam impregnated with bentonite clay.
6. A seal according to claim 3, wherein the inner layer comprises bentonite clay on or in a strip of plastics material.
7. A seal substantially as herein described with reference to the accompanying drawings.
8. An arrangement comprising two pipes sealed endto-end by a seal according to any preceding claim.
9. A sealing material in sheet or strip form having two layers, a first layer which is flexible and dimensionally stable, and a second layer mounted on the first which in use is capable of expansion in thickness from an initial thickness which is retained for at least a limited time period.
10. A sealing material substantially as herein described with reference to the accoanyi drawings.
11. A method of sealing a joint between two pipes arranged end to end, comprising surrounding the joint with a strip of material comprising a generally inexpansible outer layer and a generally incompressible inner layer whereby in use the material of the inner layer is constrained by the outer layer to enter the joint to seal it.
12. A method according to claim 11, wherein the outer layer is dimensionally stable and, after application, the material of the inner layer is arranged to expand.
13. A method according to claim 11, wherein, after application, the inner layer is compressed by tensioning the outer layer.
14. A method according to claim 8, wherein a heatshrinkable material is employed as the outer layer and it is tensioned by applying heat thereto.
15. A method of sealing a joint between two pipes substantially as herein described with reference to the accompanying drawings.