DEVICE AND METHOD FOR TEMPORARILY BLOCKING THE BORE OF A PIPE THROUGH WHICH A FLUID FLOWS

Abstract: A kit is provided for temporarily blocking the bore of a pipe through which a fluid flows, the kit comprising an expansible flexible bag seal which is inserted through a hole provided in the wall of the pipe and means for injecting into the bag seal a quantity of a material adapted to expand in situ in the bag seal and inflate the bag seal to seal against the inside of the pipe. The pipe may be a gas main and the material may be an expandable synthetic resin foam. The bag seal is removed by injecting thereinto a substance capable of dissolving the foam so that the bag seal can be at least partially deflated.

Description: The present invention relates to the temporary blocking of the bore in a pipe through which a fluid flows and is particularly directed to the temporary blocking of mains carrying natural gas. Where repairs to a section of a gas main are to be carried out or where a section of the main is to be partially or completely replaced it is frequently necessary temporarily to block the bore or main at a point or points upstream of the section. This prevents the flow of gas to the section of the main downstream of the blockage so that the necessary work can be carried out. At present such temporary blockage is performed with the aid of an expansible bag of the type having an innermost inflatable bladder usually of rubber contained with an outermost protective bag of nylon or some such similar material. In use of such bags, a hole is drilled in the wall of the main and the bag is inserted into the main by way of an insertion device in the form of a sealable tube which is temporarily securable in the hole so drilled. Once inside the main the inner bladder is inflated by a supply of pressurised gas e.g. compressed air, by way of a pipe connected to the mouth of the bag, the pipe also providing means for locating the bag inside the main through the insertion tube which forms a gas-tight seal around the pipe. Inflation of the bladder causes it to expand and force the outer bag to engage with the inner wall of the main to form a seal against the wall of the main. The bag is removed by deflating the bladder and then withdrawing the pipe from the main via the hole and the insertion tube. Unfortunately the outer protective bag and even the inner bladder are frequently ripped or torn as they are withdrawn from the main. This renders the bag totally unserviceable and it is not an uncommon occurrence that such bags are irreparably damaged after just one operation. Since these bags are relatively expensive, the overall cost of the repairs or replacement operations is increased owing to the wastage of such bags. It is an object of the present invention to provide means whereby this overall cost may be reduced. UK Published Patent Application No. 2157390A (Steve Vick) discloses a technique for temporarily blocking the bore of a pipe through which a fluid flows, which technique involves the use of an expansible bag seal for insertion through a hole provided in the wall of a pipe, using injection means to inject into the bag after insertion a quantity of a material which expands in situ within the bag seal (e.g. polyurethane foam) and inflates the bag seal against the inside of the pipe. According to one aspect of the present invention, we provide a kit for temporarily blocking the bore of a pipe through which a fluid flows, the kit comprising an expansible flexible bag seal for insertion through a hole provided in the wall of the pipe, a quantity of material for injection into the bag seal after its insertion into the pipe, the material being adapted to expand in situ within the bag seal and inflate the bag seal against the inside of the pipe and means for injecting the material into the bag seal, a quantity of a substance being provided for subsequent injection into the bag seal to dissolve the material within the bag seal after expansion so that the bag seal can be at least partially deflated by dissolution of the material to enable the bag seal to be removed from the pipe by way of the hole after use. According to another aspect of the present invention, we provide a method for temporarily blocking the bore of a pipe through which a fluid flows, the method comprising inserting an expansible flexible bag seal through a hole provided in the wall of the pipe and then injecting into the bag seal a quantity of a material which is adapted to expand in situ in the bag seal and inflate the bag seal to seal against the inside of the pipe, a quantity of a substance capable of dissolving the material within the bag seal being injected into the bag seal after inflation to dissolve the material within the bag seal so that the bag seal can be at least partially deflated by dissolution of the material to enable the bag seal to be removed from the pipe by way of the hole after use. The material may be in the form of a preformed expandable synthetic resin foam. A suitable foam may be produced by mixing together compounds CDN 15A and CDN 15B manufactured by Chemence Ltd., the mixture being injected into the bag. Alternatively the material may comprise components for mixing within the bag seal to form the expandable foam. A suitable solvent for dissolving the foam is acetone. The bag seal can comprise a single bag rather than a double-bag. The bag may be of a relatively cheap material such as polythene. Since the bag seal itself, the foam and solvent can be of relatively cheap materials the components are disposable and the system provides a cheap disposable means for temporarily blocking the bore of a gas main. The bag of for example polythene can as conventional be inserted into the main by way of a sealable insertion tube whose end is temporarily located in a hole drilled in the wall of the main. The mouth of the bag is first secured to the end of a pipe before insertion and the bag is inserted in the main by pushing the pipe through the tube into the main, the tube forming a gas-tight seal around the pipe. A suitable quantity of preformed expandable foam produced by mixing together CDN 15A and CDN 15B is then injected into the bag by way of the pipe. The foam is allowed to expand and inflate the bag to form a seal against the inner wall of the main. To remove the bag a suitable quantity of a substance capable of dissolving the foam is injected into the bag by way of the pipe. A suitable substance is acetone and this is allowed to dissolve the foam so that the bag is at least partially deflated. The pipe is then withdrawn through the tube to remove the bag from the main. Since the bag, the foam and solvent are disposable it does not matter whether the bag is damaged since it will not be re-used.

Claims: A kit for temporarily blocking the bore of a pipe through which a fluid flows, the kit comprising an expansible flexible bag seal for insertion through a hole provided in the wall of the pipe, a quantity of material for injection into the bag seal after its insertion into the pipe, the material being adapted to expand in situ within the bag seal and inflate the bag seal against the inside of the pipe and means for injecting the material into the bag seal, characterised in that a quantity of a substance is provided for subsequent injection into the bag seal to dissolve the material within the bag seal after expansion so that the bag seal can be at least partially deflated by dissolution of the material to enable the bag seal to be removed from the pipe by way of the hole after use. A kit as claimed in claim 1, characterised in that the material is a preformed expandable synthetic resin foam. A kit as claimed in claim 2, characterised in that the material comprises components for mixing within the bag seal to form the expandable synthetic resin foam. A method for temporarily blocking the bore of a pipe through which a fluid flows, the method comprising inserting an expansible flexible bag seal through a hole provided in the wall of the pipe and then injecting into the bag seal a quantity of a material which is adapted to expand in situ in the bag seal and inflate the bag seal to seal against the inside of the pipe, characterised in that a quantity of a substance capable of dissolving the material within the bag seal is injected into the bag seal after inflation to dissolve the material within the bag seal so that the bag seal can be at least partially deflated by dissolution of the material to enable the bag seal to be removed from the pipe by way of the hole after use. A method as claimed in claim 4, characterised in that the material is an expandable synthetic resin foam. A method as claimed in claim 5, characterised in that the material comprises components for mixing within the bag seal to form the expandable synthetic resin foam.

Inventors: CLOUGH, PETER SPENCE
Applicants: BRITISH GAS PLC
Application year: 1989
Main classification: F16L55
IPC codes: F16L55