GB2108866A - Coating of water supply pipes - Google Patents

Abstract

A method of coating the interior surfaces of water supply pipes with a cold setting resin material by traversing two flexible pipes through the pipe to be coated, feeding a liquid or plastics coating medium through one of said two pipes and feeding a liquid curing agent or initiator through the other of said two flexible pipes, the two substances being mixed together in a distributing device and distributed upon the walls of the pipe to be coated. So that the coated surface can be made inhospitable to bacteria, one or other of the two substances is first mixed with a quantity of a bactericide.

Description

SPECIFICATION Coating of water supply pipes The invention relates to the internal coating of water supply pipes.

It has for many years been known to coat underground water supply pipes with bitumen and to use chlorinated solvents when applying the coating. The coated 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 coat 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 in that sometimes, and perhaps over a long period of use, constituents of the materials have been able to leach out to the interior surface of the pipe, possibly to support bacteriological growth. The coated surface of a waterpipe, even though not itself actively supporting the parasitic growth of bacteria, can nevertheless provide a surface to which the 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 coating to a water supply pipe such as to render the surface of the coated pipe, even a neutral nonleaching surface, inhospitable to bacteria and therefore to inhibit their proliferation and growth.

It has previously been-proposed to coat the interior walls of pipes with a cold setting resin material by a method which includes traversing two flexible pipes through the pipe to be coated, feeding a liquid or plastics coating medium through one of said two flexible pipes, feeding a liquid curing agent or initiator through the other of said two flexible pipes, and mixing together the liquid or plastics coating medium and the liquid curing agent or initiator 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.

According to one aspect of the invention, there is provided a method of coating a water supply pipe with a cold setting resin material by this previously proposed method, but the method including the initial step of mixing with the liquid or plastics coating medium or with the liquid curing agent or initiator a quantity of a bactericide the presence of which in the resultant pipe coating will inhibit the growth of bacteria. The bactericide will preferably be one which is virtually insoluble in water so that the bacteriostatis will be long lasting, that is to say will last as long as the pipe lining. Such bacteriostasis may be such as to be effective or most effective against one or more particular member of the class of microscopic unicellular or filamentous plants or organisms commonly referred to as bacteria. The bactericide may for example by metallic copper or cuprous oxide.

According to another aspect of the invention, there is provided, for use in carrying out the inventive method referred to, a quantity of a liquid or plastics coating medium and a quantity of a liquid curing agent or initiator, the liquid or plastics coating medium or the liquid curing agent or initiator having been mixed with a quantity of a bactericide.

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:~ Fig. 1 is a diagrammatic view of a part of apparatus for coating an underground pipe by a method embodying the invention, and Fig. 2 is a partly schematic perspective view of part of the apparatus illustrated in Fig. 1.

Referring now to the drawings, apparatus for use in coating the internal walls of pipes by the method referred to 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 Fig. 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 Fig. 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 non-rotatable 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 curing 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 iniator 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, a quantity of a bactericide the presence of which in the resultant pipe coating will inhibit the growth of bacteria. Such a bactericide and one which will be completely harmless in a coating material to be applied to domestic water supply pipes may be constituted by metallic copper or cuprous oxide, or the like. In Fig. 2 the cover 52 is shown to have been removed from the reservoir of-the pump unit 31 and a quantity of the bactericide is being added to the curing agent or initiator.It could have been added to the coating medium instead of to the curing agent or initiator (except for the fact that the latter will usually be of a thinner consistency than the coating medium so that the bactericide will more easily be able to be intimately mixed therewith) and it will of course be understood that in practice the addition will usually have been made to one or other of these substances during its composition.

Thus there is provided a method of coating water supply pipes with a cold setting resin material in such a way that the coated pipe will exhibit at least some degree of bacteriostasis. The type of bactericide to be used in any particular circumstances and/or particularly suitable to the method of application described above will be known to a bacteriologist. It is thought that this method of maintaining a coated water supply pipe free from bacteriological growth will be superior to the common method of adding traces of chlorine to the water supply because in practice it is impossible to ensure that a chlorine residual remains throughout the length of a water supply pipe. The coated pipe will not merely have a neutral surface to which bacteria might cling and draw sustenance from the water passing through the pipe but will be a surface actually hostile to the bacteria.

Claims (6)

1. A method of coating a water supply pipe with a cold setting resin material, the method including 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 a liquid curing agent or initiator through the other of said two flexible pipes, and mixing together the liquid or plastics coating medium and the liquid curing agent or initiator 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, the method including the initial step of mixing with the liquid or plastics coating medium or with the liquid curing agent or initiator a quantity of a bactericide the presence of which in the resultant pipe coating will inhibit the growth of bacteria.

2. A method of coating a water supply pipe according to claim 1, in which the bactericide is one which is virtually insoluble in water so that the bacteriostasis will be long lasting, that is to say will last as long as the pipe lining.

3. A method of coating a water supply pipe according to either one of the preceding claims, in which the bacteriostasis is such as to be effective or most effective against one or more particular member of the class of microscopic unicellular or filamentous plants or organisms commonly referred to as bacteria.

4. A method of coating a water supply pipe according to any one of the preceding claims, in which the bactericide is metallic copper or cuprous oxide.

5. In combination, for carrying out the method claimed in any one of the preceding claims, a quantity of a liquid or plastics coating medium and a quantity of a liquid curing agent or initiator, the liquid or plastics coating medium or the liquid curing agent or initiator having been mixed with a quantity of a bactericide.

6. A method of coating a water supply pipe substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.