TEMPORARY OR PERMANENT BLOCKING OF THE BORE OF A PIPE

Abstract: A method is provided for temporarily or permanently blocking the bore of a gas service pipe (5). In the method a resilient ball (6) is forced along the pipe (5) from the gas meter tap end of the pipe (5) by gas pressure, the ball (6) forming a force fit sufficient to resist any attempt to dislodge it by the pressure of gas in the pipe (5). The ball (6) is forced to a position where it is outside the gas consumer's premises (1).

Description: The present invention relates to means for the temporary or permanent blocking of the bore of a pipe through which fluid flows and is particularly directed to the temporary blocking of a service pipe carrying natural gas. The present invention is divided out from copending European Patent application 88 306 369.5 (EP-A-0 300668). Should a gas supplying authority wish to cut off the supply of gas to a consumer for any reason (e.g. the consumer has defaulted on payment of a bill), safety regulations require that the gas supply be eventually cut off at a point outside the consumer's property or premises. One method of achieving this is to dig down outside the property or premises to the service pipe connection to the main and then to cut the service pipe and plug it with a settable sealing compound to cut off the supply. In the case where the property comprises a block of flats the service pipe may be sealed by an expanding polyurethane foam. The above method is inconvenient since it involves excavation to cut off the supply and it is therefore an object of the present invention to provide a means for cutting off a gas supply without this disadvantage. EP-A-0167986 (WAF) discloses a seal which is adapted to form within the bore of a pipe through which fluid flows a force fit sufficient both to resist any attempt to dislodge it by the pressure of the fluid and to prevent the fluid flowing past it. The seal is in the form of a resilient ball having means permitting the ball to be releasably connected to a tether, in the form of a wire which holds the releasable connecting means captive. According to the present invention we provide a seal which is adapted to form within the bore of a pipe through which fluid flows a force fit sufficient both to resist any attempt to dislodge it by the pressure of the fluid and to prevent the fluid flowing past it is a resilient ball having means permitting the ball to be releasably connected to a tether, characterised in that the means is held captive by the ball. An embodiment of the invention will now be particularly described with reference to the drawings in which:- Figure 1 is a schematic arrangement of a typical property connected to a natural gas supply, Figure 2 illustrates suitable equipment for effecting the seal, and Figure 3 is a view partly in section of a suitable seal and associated cable and stop for limiting the distance travelled by the seal along the service pipe. Referring to Figure 1, there is shown located within an outhouse or garage 1 adjacent to the dwelling 2 a gas meter 3 and gas meter tap 4 which latter enables the consumer to turn off the gas supply. The gas is supplied to the meter 3 by means of a service pipe 5 which is connected at its far end to a feeder main (not shown). To satisfy safety regulation, should it prove necessary for the gas supplying authority to cut off the consumer, the gas supply must be cut off at a point outside the outhouse 1 i.e. at a point in the service pipe which lies below ground. In the case of the present invention, this is generally effected in the following manner. Firstly, the gas meter tap 4 is closed to shut off the gas supply to the meter 3. Next the gas meter tap 4 is disconnected from the meter 3 and then a compressible seal is inserted into the now open outlet end of the gas tap 4, the seal forming within the tap 4 and also within the bore of the service pipe 5 a force fit sufficient to resist attempts by the gas pressure to dislodge it. The gas meter tap 4 is then opened and the seal is forced along the service pipe 5 to a suitable point beyond the outhouse e.g. to a point in the underground section of the service pipe 5. As shown in Figure 3 the seal may be in the form of a ball 6 of a resilient compressible material e.g. a resilient thermoplastic. The ball 6 may be forced along the service pipe 5 by pressurised gas e.g. natural gas. The ball 6 itself is held on a flexible steel tether or cable 7. The latter has an externally threaded end 8 which is releasably screwed into an internally threaded bush 9 held captive within the ball 6. A movable stop 10 is threaded on the cable 7 to adjust the length of cable 7 following the ball 6 for the purpose to be described. The stop 10 can be releasably secured to the cable 7 by means of a thumb-screw 11 which engages the cable 7 as shown. The ball 6 is moved by applied gas pressure pushing a grease lubricant ahead of it until the stop 10 engages with a predetermined limit means and the cable 7 becomes taught. The gas pressure behind the ball 6 is then released and the cable 7 unscrewed by twisting it to release its end 8 from the bush 9. The cable 7 can then be removed, the gas tap 3 closed and the service pipe 5 capped off, if necessary. The length of cable 7 between the ball 6 and the stop 10 can be adjusted to ensure that the ball 6 is outside the consumer's dwelling. If it is intended permanently to block the bore of the pipe the ball may simply be left in position. In addition the pipe may be plugged with a suitable sealant at a point within the pipe between the ball and the pipe outlet. If however, it is possible that the consumer may be reconnected at some time in the future the pipe is not plugged with sealant. In order to reconnect the consumer to the gas supply the ball 6 may be sucked out of the service pipe by means of a vacuum pump. It may be necessary to spray the walls of the service pipe with lubricant to effect such removal. The equipment shown in Figure 2 comprises a reception chamber 20 for the ball, having one end 21 for connection to the gas tap outlet 22 and an opposite end 23 comprising a gland (not shown) through which the cable 7 can be inserted, the gland in use forming a seal with the cable 7. Valves 24,25 on opposite sides of the chamber 20 provide means for connecting the chamber 20 to a source of compressed natural gas where the ball is to be forced up the pipe or to a vacuum pump where the ball is to be removed from the pipe. The opposite end 23 of the chamber 20 has a nut 26 serving as a limit for movement of the cable stop 10. In use of the equipment to insert the ball 6 into the service pipe 5, the threaded end 8 of the cable 7 is inserted through the gland end of the chamber 20 and is then screwed into the threaded bush 9 of the ball 6. The ball 6 is then pulled by the cable 7 into the chamber 20. The chamber 20 is then connected to the gas tap outlet 22 (the tap at this stage being closed) and the valve 24 say is connected to a supply of compressed natural gas (the valves 24,25 being closed). The gas tap 4 is opened and then the valve 24 is opened causing the ball 6 to be forced along the service pipe 5 until the stop 10 engages with the nut 26. The stop 10 is then released from the cable 7 and is slid away from the nut 26 to enable the cable 7 to be released from the ball 6. Any excess gas pressure in the pipe 5 is released by opening the other chamber valve 25. The gas tap 4 may then be closed and the chamber 20 removed from the gas tap 4. In order to remove the ball 6 from the pipe 5, the chamber 20 is reconnected to the gas tap 4 and a vacuum pump is connected to the valve 24 say (both valves 24,25 being closed at this stage). The gas tap 4 is opened and then the valve 24 is opened to cause the ball 6 to be sucked out from the service pipe 5 into the chamber 20. The gas tap 4 is then closed and the chamber 20 removed from the gas tap 4. The method described enables the consumer to be cut off at a point outside the consumer's premises without the need to excavate whether the cut off is temporary or permanent. Where the cut off may be temporary, reconnection can be made quite simply from within the consumer's premises once again obviating the need for excavation.

Claims: A seal which is adapted to form within the bore of a service pipe through which fluid flows a force fit sufficient both to resist any attempt to dislodge it by the pressure of the fluid and to prevent the fluid flowing past it is a resilient ball (6) having means (9) permitting the ball (6) to be releasably connected to a tether (7), characterised in that the means (9) is held captive by the ball (6). A seal as claimed in claim 1, characterised in that the means is an internally threaded bush (9) for connection to the externally threaded end (5) of a tether (7). An assembly including the seal as claimed in claim 1 or claim 2, characterised in that a tether (7) is provided for releasable connection to the ball (6). An assembly as claimed in claim 3, characterised in that a stop (10) is provided for location on the tether (7). An assembly as claimed in claim 4, characterised in that the stop (10) is adapted for adjustable positioning along the tether (7).

Inventors: SMITH, PETER
Applicants: BRITISH GAS PLC
Application year: 1988
Main classification: F16L55
IPC codes: F16L55