GB1328886A - Sealing of pipe joints - Google Patents

Abstract

1328886 Sealing pipe joints BRITISH GAS CORP 31 Aug 1971 [19 Aug 1970 ] 39966/70 Heading F2P Apparatus for internally sealing a joint in a pipe-line comprises a tubular pig 8 having wheels 30, 32 for supporting it coaxially in the pipe, two seals 35, 37 spaced apart and extending around the pig for sealing a space between the periphery of the pig and the internal surface of the pipe, a supply tube 7<SP>1</SP> for supplying sealant to the pig and thence through the wall of the pig to the space between the seals and a device carried by the pig for sensing the position of the joint as the pig is moved along the pipe so that the pig can be accurately located with its seals evenly spaced on the two sides of the joint before the sealant is supplied under pressure. As shown the seals 35, 37 are supported on tubular members 23, 24 and are inflatable into contact with the internal surface of the pipe by nitrogen or other inert gas supplied through pipes 40, 41 from the space between the sealant supply pipe 7<SP>1</SP> and a coaxial tube 7. The sealant is fed from pipe 7<SP>1</SP> to a central member 26 having bores 60 and non-return valves 61 leading to the space between the seals when these are inflated. The pig is of hollow construction so that gas can pass therethrough when the pig is located in the pipe. The pig carries an electromagnetic sensor (66, Fig. 4, not shown) for location of the pig and a pressure transducer (65) for sensing the pressure of the sealant. Electric cables from these are led back through the tube 7 to a monitoring and pig moving console (Fig. 1, not shown). In use the pipe line is broken into and fitted with a by-pass and a pig trap for feeding the pig into the pipe-line, the pig is moved along the pipe line until the sensor locates a joint, the seals are inflated to seal off a space either side of the joint and sealant is pumped into the space to seal the joint. The seals are then deflated and the pig moved to the next joint.