GB2167828A

GB2167828A - Lining of water supply pipes

Info

Publication number: GB2167828A
Application number: GB08527017A
Authority: GB
Inventors: William George Bradley
Original assignee: MERCOL DESCALING CO Ltd
Current assignee: MERCOL DESCALING CO Ltd
Priority date: 1984-11-29
Filing date: 1985-11-01
Publication date: 1986-06-04
Also published as: GB8430143D0; GB8527017D0

Abstract

A method of treating underground water supply pipes by coating them with cold setting resin materials. So that the surface of the coated pipe will be free of any sticky layer of material which has not been fully cured, the method includes the initial step of mixing with at least one of the coating materials a quantity of at least one substance of an oily or greasy nature. The resin may be epoxy or polyester and the substance may be paraffin, petrolatum or silicone.

Description

SPECIFICATION Lining of water supply pipes The invention relates to the lining of water supply pipes.

It has for many years been known to line underground water supply pipes by coating them with bitumen and to use chlorinated solvents when applying the coating. The lined pipes have of course been flushed through with clean water before water has been supplied through them for domestic use. Nevertheless, some water engineers now take the view that the use of chlorinated solvents in pipes which are to carry drinking water is a health hazard.

With a view to solving this problem it has previously been proposed to line underground water supply pipes with cold setting resin materials, notably epoxy cold setting resins and polyester cold setting resins but a problem with such materials is that because the coating operation is carried out in the cold damp conditions which exist within underground pipes, there remains at the surface of the coated pipe a thin sticky layer of material which has not been fully cured. Indeed, because of the action of the atmosphere at the exposed surface of the coating material, there is produced a surface film of material which is of a different chemical composition to the substrate. Consequently, even after flushing, and perhaps over a period of long use, constituents of the coating materials have been able to leach out at the interior surface of the lined pipe.These organic leachates are deemed by Water Authorities to be objectionable even at concentrations as low as small parts per billion. Furthermore, such a sticky coating can provide a surface to which bacteria can cling and draw sustenance from the water passing through the pipe. The object of the invention is to provide a method of applying a cold setting resin coating to a water supply pipe such as to render the coated pipe free of the surface film previously found.

According to the invention, there is provided a method of lining a water supply pipe by coating it with a cold setting resin material, the method including the steps of mixing together a liquid or plastics coating medium and a liquid curing agent or initiator and of distributing the mixture upon the walls of the pipe to be coated, the method also including the initial step of mixing with the liquid or plastics coating medium, or with the liquid curing agent or initiator, or with both, a quantity of at least one substance of an oily or greasy nature, but being a substance which will not support microbiological activity, such that there is formed at the exposed surface of the coated pipe a film of the oily or greasy substance which protects the underlying cold setting resin material at least until the latter has become fully cured.Examples of oily or greasy substances which can be used for performing the invention are liquid paraffin and petrolatum and silicone fluids, or mixtures of these various substances.

The steps of mixing together the liquid or plastics coating medium and the liquid curing agent or initiator, with the oily or greasy substance added to one or both of them, and distributing the mixture upon the walls of the pipe to be coated may be effected by traversing two flexible pipes through the pipe to be coated, feeding the liquid or plastics coating medium through one of said two flexible pipes, feeding the liquid curing agent or initiator through the other of said two flexible pipes, and mixing together the two substances in a distributing device connected to the ends of said two flexible pipes, the mixture then being distributed upon the walls of the pipe to be coated.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a diagrammatic view of a part of apparatus for carrying out the treatment of an underground pipe by a method embodying the invention, and Figure 2 is a partly schematic perspective view of part of the apparatus illustrated in Figure 1.

Referring now to the drawings, apparatus for use in lining the internal walls of pipes by the inventive method includes a drum 10 mounted for rotation about a horizontal axis in a stand 12 including a pair of opposed mounting brackets 14. The stand is mounted on wheels 16 so that it may readily be moved from place to place.

Flexible pipes 18 and 19 are coiled upon the drum 10, and are provided for the purpose of conveying, respectively, a liquid or plastics coating medium and a liquid curing agent or initiator to a spraying or distributing device 20 being traversed along an underground pipe 22 by a pull applied to said flexible pipes. The ends of said flexible pipes remote from the spraying or distributing device are connected to a shaft 24 at the axis of the drum, the connection being shown diagrammatically in Figure 2.The liquid or plastics coating medium, and the liquid curing agent or initiator, are conveyed to the respective pipes 18 and 19 along passageways extending through the shaft 24, connectors 26 and 27 being provided at one end of said shaft for the connection thereto of non-rotatable conduits 28 and 29 for conveying the coating medium and curing agent or initiator under pressure from respective pumps (not shown) housed in pump units generally indicated 30 and 31.

A further flexible pipe 32 is also coiled upon the drum 10 and is provided for the purpose of conveying air under pressure to a compressed air motor (not shown) forming part of the device 20, the latter being a device for intimately mixing together the liquid or plastics coating medium and the liquid curing agent or initiator and for distributing the mixed substance upon the wall of the pipe 22. (The device 20 which is illustrated in Figure 1 is shown to include a plurality of flails 34 which are driven by the compressed air motor so as to make repeated impacts or rapid wiping actions upon the coated wall of the pipe 22 in the wake of a distributing member 36 also driven by the compressed air motor).The end of the pipe 32 remote from the spraying or distributing device is also connected to the shaft 24 and air under pressure is delivered thereto along the axis of the shaft from the end remote from the connectors 26 and 27.

A connector (not shown) is provided for the connection of a nonrotatable conduit 38 to the shaft 24, said conduit communicating with a source of compressed air.

Means are provided for rotating the drum 10 at a substantially constant speed to draw the pipes 18, 19 and 32, and with them the spraying or distributing device 20, along the pipe 22. Said means include a compressed air motor 40, a reduction gear unit 42 and respective chain drives 44 and 46 between the motor and gear unit and between the gear unit and the drum.

The pump units generally indicated 30 and 31 are disposed side by side and include respective reservoirs for the liquid or plastics coating medium and for the liquid curinq agent or initiator. They are mounted on wheels 50 so that they can readily be moved from place to place. Respective covers 52 on the reservoirs are removable to disclose filling orifices through which the reservoirs can be charged with the liquid or plastics coating medium and with the liquid curing agent or initiator respectively. Means (not shown) are provided whereby the pump units are operated in timed relation to the rate of traverse of the flexible pipes along the pipe to be coated so that the coating medium and the curing agent or initiator are mixed together in the correct proportions and the coating applied to the walls of the pipe 22 in a required thickness.

The inventive method for which the apparatus referred to above can be used includes the initial step of mixing with the liquid or plastics coating medium, or with the liquid curing agent or initiator, or with both, a quantity of at least one substance of an oily or greasy nature but which will not support micro-biological activity. Such a substance and one which will be completely harmless in a coating material to be applied to domestic water supply pipes, is liquid paraffin.Another is petrolatum. (In Figure 2, for the sake of diagrammatic illustration, the cover 52 is shown to have been removed from the reservoir of the pump unit 31 and a quantity of a suitable oily or greasy substance is being added to the liquid curing agent or initiator, but it will be understood that in practice the addition will usually have been made to one or other, or perhaps both, of the materials during its composition).

The effect of mixing a quantity of the oily or greasy substance to the liquid or plastics coating medium, and/or with the liquid curing agent or initiator, will be to form at the exposed surface of the coated pipe a film of the oily or greasy substance. This surface film of the substance, which is of course completely harmless, protects the underlying cold setting resin material at least until the latter has become fully cured. Consequently, there is not formed the usual sticky film of resinous material at the exposed surface of the coating from which constituents have previously been able to leach out. However, it is found that other advantages result from the addition of the oily or greasy substance to the liquid or plastics coating medium and/or to the liquid curing agent or initiator. For example: 1.A water supply pipe which has been lined by the inventive method can be returned to service very much sooner than a pipe which has been lined with a cold setting resin material by previously used methods, 2. The addition of the oily or greasy substance to the liquid or plastics coating medium and/or to the liquid curing agent or initiator renders the finished coating more impervious to water throughout the subsequent life of the pipe.

3. The addition of the oily or greasy substance to either of the coating materials renders that material impervious to atmospheric attack during its storage and prior to its use in coating an underground water pipe.

(Amine hardeners in particular are subject to atmospheric attack.

As stated above, a range of oily or greasy substances will be found to be useful in carrying out the invention, the only criteria being that the substance employed must be harmless in drinking water in the very small amounts which may be found for some time after lining a water pipe by the inventive method,and must not support micro-biological activity. In addition to liquid paraffin and petrolatum it is thought than silicone fluids, that is to say oils, waxes and greases, could usefully be employed since they all give a high wetting angle.

Claims

1. A method of lining a water supply pipe by coating it with a cold setting resin, the method including the steps of mixing together a liquid or plastics coating medium and a liquid curing agent or initiator and distributing the mixture upon the walls of the pipe to be coated, the method also including the initial step of mixing with the liquid or plastics coating medium, or with the liquid curing agent or initiator, or with both, a quantity of at least one substance of an oily or greasy nature, but being a substance which will not support micro-biological activity, such that there is formed at the exposed surface of the coated pipe a film of the oily or greasy substance which protects the underlying cold setting resin material at least until the latter has become fully cured.

2. The method claimed in claim 1, in which the steps of mixing together the liquid or plastics coating medium and the liquid curing agent or initiator, with the oily or greasy substance added to one or both of them, and of distributing the mixture upon the walls of the pipe to be coated is effected by traversing two flexible pipes through the pipe to be coated, feeding the liquid or plastics coating medium through one of said two flexible pipes, feeding the curing agent or initiator through the other of two said flexible pipes, and mixing together the two substances in a distributing device connected to the ends of said two flexible pipes, the mixture then being distributed upon the walls of the pipe to be coated.

3. The method claimed in either one of the preceding claims, in which the oily or greasy substance used for mixing with the liquid or plastics coating medium, or with the liquid curing agent or initiator, or with both, in the initial step in the method is liquid paraffin or petrolatum or a silicone fluid or a mixture of these various substances.

4. A method of lining a water supply pipe by coating it with a cold setting resin material, substantially as hereinbefore described with reference to the accompanying drawings.