GB2072299A - Method and device for compensating for expansion movements in a pipe run - Google Patents

Abstract

Expansion movements in critical expansion regions (D1, D2) of pipework (1) laid in the earth (3) are compensated by enclosing these regions in a sleeve (2) of closed-cell compressible or differentially compressible material whose supporting strength can be elevated by the compressive force of the surrounding earth (3). In its unloaded state the sleeve (2) has a circular cross-section. The sleeve (2) is tightly connected at its ends to the pipework (1) by clamp means (5) to guard against the ingress of earth. <IMAGE>

Description

SPECIFICATION Method and device for compensating for expansion movements in a pipe run This invention relates to a method of and a device for compensating for expansion movements in the critical expansion zones of a pipe run designed to be laid in the ground.

With pipe runs laid in the ground, as for example for remote heating etc., it is well known that a problem exists in respect of the so-called critical expansion zones where the pipe branches, turns corners, narrows etc. in the pipework system, at which positions, because of thermal expansion, lateral movements can arise in the relevant pipe sections which, with unprotected laying of the pipework in the earth, can lead to impairment of the corrosion-protective layer and/or the insulation of the pipework, with the consequent damage to the pipes by corrosion.

The attempts up until now to encase the pipes additionally in the region of the critical expansion zones has shifted the problem only temporarily to the sheathing, and additional difficulties then arise due to the ingress of earth between pipe and sheath and into the jacket.

It is therefore an object of the present invention to provide a method of the type first described above which ensures that the aforementioned lateral movements of the relevant pipe sections arising from expansion forces in the pipework system are compensated so that the effects of wear and tear do not adversely affect either the sheathing or the pipe.

This is achieved in accordance with the present invention by virtue of the fact that the pipe run is encased in these regions with a sleeve of closedcell compressible or differentially compressible material which is compressed by the force exerted by the packed earth in order to give the sleeve increased supported strength in its outer zone.

By this means it is then possible to produce a pipe casing which by virtue of the compression arising from the pressure of the earth, has such a high physical strength in its outer zone that any further loads imposed from outside, such as for example from road traffic, are withstood without the sleeve losing its inner flexibility and consequently its capacity to compensate for the expansion movements.

Preferably, the method is such that the sleeve of closed-cell compressible or differentially compressible material is encased by a sheath of reinforcing material.

Furthermore, it is advantageous if the pipe sleeve, at its ends, is connected to the pipework sufficiently tightly to prevent the ingress of earth.

The present invention is also concerned with a device for carrying out the method of the invention, which device is characterised by at least one sleeve of closed-cell compressible or differentially compressible material encircling a pipe in the region of one or more critical expansion zones, the supporting strength in the outer zone of the material being increasable by the compressive force of the earth under which the pipe is buried, and the sleeve having a circular cross-section in its unloaded state.

This device can advantageously be formed in such a way that the sleeve of closed-cell compressible or differentially compressible material is encased by a sheath of reinforcing material.

Preferably, the sleeve is connected at its ends to the pipework by shrink-fit collars, pipe clips or the like to provide a tight seal against the ingress of earth.

In order to cater for differences in diameter of adjacent pipe sections, it is preferable if the sleeve encircles the pipe with a small gap therebetween in the unloaded state.

In order that the invention may be fully understood one preferred embodiment in accordance with the invention will now be described by way of example and with reference to the accompanying drawing, in which: Fig. 1 is a schematic illustration of a bend or change of route of a pipe run laid in the earth; and, Fig. 2 is a cross-sectional view, on an enlarged scale, of a pipe which is sleeved in accordance with the invention in the region of a critical expansion zone.

The pipe run shown in Fig. 1 laid in the earth 3 includes a 900 bend or change of direction with two critical expansion zones D1 and D2 where lateral movements of the various pipe sections can arise in the event of thermal expansion forces occurring.

In order to compensate for these lateral movements, the pipe sections are encased in the expansion zones D1 and D2 with a sleeve 2 of closed-cell, compressible material such that the sleeve material, after the system has been laid in the earth 3, is compressed by the compressive force exerted by the earth.

The choice of the sleeve material and its arrangement is selected so that the sleeve 2, after its compression, has a sufficiently supporting physical strength in its outer region, without losing its flexibility in its inner region.

Materials suitable for this include polyethylene, soft PVC foam or any other decay-resistant and closed-cell material, so long as it has the necessary flexibility.

The sheathing can be prefabricated as a slideon sleeve, as half-sleeve sections, as a split full sleeve, or as a mat or trapezoidal mat which is arranged to be wound helically around the pipe.

In order to be able properly to encase a pipe run with pipe sections of varying diameter in a satisfactory manner, for example as shown in Fig. 1, it is advantageous if the pipe sleeve 2 encircles the pipe 1 in the unloaded, i.e.

uncompressed, state with a small gap between sleeve and pipe. When the sleeve material is compressed under the pressure of the earth it then adapts itself to the contours of the pipe section around which it is fitted.

With the method described above it has been shown that the supporting function and the compressive strength of the sleeve 2 after the compression of the sleeve material by the compressive force of the earth is improved if the inner region cells of the sleeve 2, in the region indicated at 6 in Fig. 2, are very greatly reduced due to the circular form of the sleeve.

In the normal way, one would assume that in the event of lateral movement of the encased tube 1 high pressure forces would be necessary in order to compress the enclosing cushion 6 of the sleeve 2 outwardly to compensate for the movement; however, this is not so, since as the tube moves laterally, although one section of the sleeve is indeed compressed, the opposite sleeve section is unburdened by the tensile forces which occur in the circumferential direction, with the result that the whole movement is absorbed within the annular expansion layer 6 of the sleeve 2 without the movement being transferred outwardly to the outer zone of the sleeve 2.

In a preferred embodiment, the sleeve 2 is improved by providing it with a further jacket or sheath 4 of reinforcing material.

It is also advantageous if the pipe sleeve 2 is connected tightly to the pipe 1 and the ends of the sleeve by shrink collars 5, pipe clips or the like in order to prevent the ingress of earth between pipe and sleeve.

From the foregoing description one thus has a method and device for compensating for expansion movements in the critical expansion zones of a pipe run designed to be laid in the earth, the features of the method and device being suitable for all possible requirements and applications.

Naturally, within the framework of the invention, various modifications are possible. For example, as shown in Fig. 2, the sleeve 2 which surrounds the pipe 1 can be provided with an inner layer 7 of conventional insulating material, for example mineral wool. The outer sleeve 4 should have a sufficiently supporting physical strength to withstand the load exerted by the earth and traffic loads. For this purpose one can use for example the closed-cell material described above with greater pipe thickness, or other decayresistant materials, such as PVC film, polyethylene film, or even concrete.

Additionally, it may be desirable for the sleeve to be formed from a trapezoidal mat of closed-cell compressible material, or even differentially compressible material.

Claims (10)

1. A method of compensating for expansion movements in a pipe run laid in the earth, the compensation being provided in the region of the critical expansion zones of the pipe run, in which the pipework is encased in said regions with a sleeve of closed-cell compressible or differentially compressible material which is compressed by the force exerted by the packed earth in order to give the sleeve increased supporting strength in its outer zone.

2. A method in accordance with claim 1, in which the sleeve of closed-cell compressible or differentially compressible material is surrounded by a sheath of reinforcing material.

3. A method in accordance with claim 1 or 2, which includes connecting the ends of the sleeve tightly to the pipework to prevent the ingress of earth.

4. A method in accordance with any preceding claim, in which the sleeve is formed from a trapezoidal mat.

5. A device for carrying out the method as claimed in any of the preceding claims, characterised by at least one sleeve of closed-cell compressible or differentially compressible material encircling a pipe in the region of one or more critical expansion zones, the supporting strength in the outer zone of the material being increasable by the compressive force exerted by the earth, and the sleeve having a circular crosssection in its unloaded state.

6. A device in accordance with claim 5, in which the sleeve of closed-cell compressible or differentially compressible material is encased in a sheath of reinforcing material.

7. A device in accordance with claim 5 or 6, in which the sleeve is connected at its ends to the pipework by fastening means to prevent the ingress of earth.

8. A device in accordance with claim 7, in which said fastening means includes shrink-fit collars or pipe clips.

9. A device in accordance with any of claims 5 to 8, in which the sleeve surrounds the pipework in the unloaded state with a small gap between sleeve and pipe.

10. A method of compensating for expansion movements in a pipe run laid in the earth substantially as hereinbefore described with reference to the accompanying drawing.

1 1. A device for compensating for expansion movements in a pipe run laid in the earth substantially as hereinbefore described with reference to the accompanying drawing.