PIPELINE CLEANING METHOD AND APPARATUS

Abstract: A method of cleaning a pipeline (2) for transporting a fluid, in particular a gas, more particularly a gas which forms an explosive mixture when mixed with air, comprises removing debris from the pipeline (2) by means of a collecting device and a removal unit (56). The pipeline (2) is cleaned in a commissioned state, without interrupting the flow of fluid through the pipeline, by removing a mixture of fluid and debris from the pipeline (2) by means of suction, separating the debris from the fluid and re-injecting the cleaned fluid into the pipeline (2). A cleaning unit (10) for carrying out the method according to the invention comprises, connected in series, first means for connecting the cleaning unit to the pipeline, an inlet (12) for purging gas, first valve means (14, 16), one or more separation stages (18, 28, 38) for mechanical separation of debris from the gas/debris mixture, a blower (40) for creating suction, second valve means (48) connected in parallel with the blower (40), third valve means (50, 54), and second means for connecting the cleaning unit to the pipeline.

Description: Title - PIPELINE CLEANING METHOD AND APPARATUS The present invention relates to an improved method for cleaning a pipeline, in particular a gas main, and to an improved apparatus for carrying out the method. Gas mains can contain a substantial amount of debris, for example light dust through to heavy scale, or foreign bodies and other intruding material. This material needs to be removed in particular before any internal inspection or repair is carried out and because it reduces the carrying capacity of the main. It is known to clean gas mains in a decommissioned state, but this has the disadvantage that the gas supply to the customers supplied by that main has to be interrupted while the cleaning is being carried out, thus causing inconvenience and difficulties to these customers. It is an object of the present invention to provide a method of cleaning a pipeline, in particular a gas main in which the above disadvantages are reduced or substantially obviated. It is a further object of the present invention to provide an apparatus for carrying out the cleaning method. The present invention provides a method of cleaning a pipeline for transporting a fluid, in particular a gas, more particularly a gas which forms an explosive mixture when mixed with air, which method comprises removing debris from the pipeline by means of a 2 collecting device and a removal unit, characterised in that the pipeline is cleaned in a commissioned state, without interrupting the flow of fluid through the pipeline, by removing a mixture of fluid and debris from the pipeline by means of suction, separating the debris from the fluid and re-injecting the cleaned fluid into the pipeline. In particular, the present invention provides a method of cleaning a pipeline for transporting a fluid, in particular a gas, more particularly a gas which forms an explosive mixture when mixed with air, which method comprises the steps of (i) inserting into the pipeline to be cleaned a device for scraping the internal wall of the pipe and collecting the debris deposited by this scraping, together with loose debris in the pipe; (ii) propelling the collecting device, together with the collected debris, along the pipeline to a collection point; (iii) introducing a removal unit in the pipeline for location close to the collecting point and (iv) removing debris from the pipeline by means of this removal unit characterised in that the pipeline is cleaned in a commissioned state, without interrupting the flow of fluid through the pipeline, and the removal unit comprises a suction head 3 which is powered by a vacuum unit located in a cleaning unit, which cleaning unit is connected to the pipeline to be cleaned at a first point, close to the collection point for debris, and at a second point downstream (with respect to the direction of fluid flow) of the first point, and a mixture of gas and debris is removed by suction from the pipeline at the first point, passed through the cleaning unit, the debris is separated out from the gas/debris mixture as it is passed through the cleaning unit and the cleaned gas is returned to the pipeline at the second point. In a preferred embodiment of the method according to the invention, the cleaning unit is provided, close to its first connection point, with an inlet for purging gas, and purging gas is supplied to the cleaning unit during the cleaning process. The present invention further provides a cleaning unit for use in the pipeline cleaning method according to the invention, characterised in that the cleaning unit comprises, connected in series, first means for connecting the cleaning unit to the pipeline, first valve means, one or more separation stages for mechanical separation of debris from the gas/debris mixture, a blower for creating suction, second valve means connected in parallel with the blower, third valve means, a non-return valve, and second means for connecting the cleaning unit to the pipeline. The cleaning unit according to the present invention preferably further comprises a plurality of sensors for measuring the pressure at a plurality of points in the cleaning unit, and control system for registering the output of the sensors, determining whether a hazard 4 condition exists and taking appropriate action. The control system is preferably designed to indicate where in the cleaning system, a hazard condition has originated. The control system is particularly preferably adapted to allow the cleaning system only to operate within pre-set system parameters. The present invention further provides a trailer unit which comprises a cleaning unit mounted on a trailer, within a housing. A preferred embodiment of a method according to the invention, and a preferred embodiment of a cleaning unit according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram, showing a preferred embodiment of a cleaning unit according to the invention, connected to a pipeline and Figure 2 is a perspective view of a cleaning unit according to the invention mounted in a housing unit on a trailer for transport, and connected to a gas main. As can be seen from Figures 1 and 2, the cleaning unit shown generally at 10 comprises a pipe 2 detachably connected in a fluid tight manner at both a first access point 4 and a second access point 6 to a gas main 8. At access point 4 the pipe 2 may be insertable into the main 8 by a selectively variable amount. An openable and closable inlet 12 for 5 purging gas is provided in the pipe 2 close to the point 4. A first manual valve 14 and first automatic valve 16, with pneumatic control, are provided in the pipe 2 downstream (with respect to the gas flow) of point 4. On the downstream side of the first automatic valve 16, a first separation stage 18 is located. This first separation stage 18 comprises a cyclone separator 20 connected by means of a manual valve 22 to a disposal chamber 24, which is vented to the atmosphere via a further manual valve 26. Opening the valve 22, periodically, allows separated debris to drop from the cyclone separator 20 into the chamber 24. Opening the valve 26, periodically, allows the debris to discharge from the chamber 24. Downstream of the first separation stage 18, a second separation stage 28 is located. The second separation stage 28 comprises a filter 30 connected by means of a manual valve 32 to a disposal chamber 34 which receives separated debris when the valve 32 is opened periodically. The chamber 34 is vented to the atmosphere via a further manual valve 36 when opened periodically. The filter 30 is a coarse filter, which may be made of wire mesh. Downstream of the second separation stage 28, a fine filter 38 is located. The filter 38 is a fine filter, which may be made of paper. Downstream of the filter 38, the pipe 2 divides into two branches, a first branch 2' leading to a Roots blower 40. The blower 40 is driven by a diesel powered engine 42, to which it is connected by means of a safety coupling 44. Diesel fuel is supplied to the engine 42 by 6 means of a fuel valve 46. The second branch 2" leads via a second automatic valve 48 back to the first branch 2', downstream of the blower 40. The function of the second automatic valve 48, which as will be explained later, is spring-loaded 'fail-open' is to protect the blower 40 from damage due to build-up of excess pressure downstream of the blower 40. The pipe 2 then returns via a third automatic valve 50, a non-return valve 52 and a manual valve 54 to the second connection point 6 where it is connected to the gas main 8. The function of the non-return valve 52 is to ensure that the gas flow cannot reverse. A plurality of sensors S 1 to S 5 are positioned along the pipe 2 to sense the pressure at the points where they are connected. A first sensor S 1 is positioned between the first automatic valve 16 and the first separation stage 18, a second sensor S 2 is positioned between the first separation stage 18 and the second separation stage 28, a third sensor S 3 is positioned between the second separation stage 28 and the filter 38, a fourth sensor S 4 is positioned between the filter 38 and the blower 40 and a fifth sensor S 5 is positioned between the blower 40 and the third automatic valve 50. The sensors S 1 to S 5 are connected to a central control and monitoring unit (not shown). As can be seen more clearly in Figure 2, a suction head shown generally at 56 and mounted on an inner tube (not shown) is introduced into the gas main 8 at the first connection point 4. The inner tube on which the suction head 56 is mounted is controlled 7 by means of a jack 58. For ease of transport, the cleaning unit 10 is preferably mounted on a trailer 60 within a housing 62. Preferably debris from a length of the main 8 between the access points 4 and 6 is scraped or otherwise suitably propelled by appropriate means towards the access point 4, whilst the main is live, so this debris is gathered at a single place in the main at or adjacent to the access point 4 for extraction by the suction head 56. In operation, prior to start-up of the cleaning process, the first and second manual valves 14 and 54 are closed, as are the first and third automatic valves 16 and 50. The first and third automatic valves 16 and 50 are spring loaded 'fail-shut', i.e. in the closed position when the system is not in operation. The second automatic valve 48 is open when the system is not in operation and closed when it is in operation; i.e. it is spring loaded 'fail-open'. As the cleaning process is started, the cleaning unit 10 is initially purged with gas which is injected into the pipe 2 via the inlet 12, so that the whole system is filled with gas and there is no air present. The manual valves 14 and 54 are then opened and the control unit opens the automatic valves 16 and 50, the fuel valve 56 and shuts the automatic valve 48 and then the diesel 8 engine 42 is started, to operate the blower 40. The engine 42 is hand-cranked, for safety reasons, as an electric starter might produce sparks which could ignite the gas. The fuel valve 46 is a solenoid operated valve which is linked to the control system, so that the control system can shut-down the diesel engine 42 in an emergency, by closing down the fuel supply to the engine. While the cleaning system is in operation, the sensors S 1 to S 5 continually monitor the gas pressure to ensure that it is above atmospheric pressure and below a maximum set operating pressure, which is substantially equal to the pressure in the gas main. Any loss in pressure below atmospheric pressure or increase above the set operating pressure indicates to the control system that there is an emergency, caused for example by a blockage in the system and the control system shuts down the cleaning process. In the event of an emergency, the following close down sequence is followed; (i) the diesel supply to the diesel engine 42 is shut down; (ii) the second automatic valve 48 is opened to bypass and thus protect the blower 40 by allowing gas pumped thereby to circulate through the pipe branch 2" and valve 48 and back to the blower to ensure there is no excessive pressure build-up whilst the system is in the process of shutting down: (iii) after a set time, typically 5 seconds, the control system closes the first and third automatic valves 1 and 3 and the cleaning system stops operation. 9 By monitoring the outputs of the sensors S 1 to S 5 , the control system is able, in an emergency shut-down as described above, to indicate to the operator where the problem has arisen, which is helpful in achieving a more rapid solution to the problem. The control system is further designed not to allow the cleaning system to operate outside of the system set parameters. For example, the control system can be set to allow the cleaning system to operate with a maximum pressure differential across each of the filters 30,38, thus detecting when a filter is blocked or becoming blocked. Either access point 4 or 6 may be specially drilled or may be a known access point normally provided to a gas main. The access points 4 and 6 are sealed after the cleaning procedure is completed and the pipe 2 is detached from the access points.

Claims: 10 CLAIMS A method of cleaning a pipeline (2) for transporting a fluid, which method comprises removing debris from the pipeline (2) by means of a collecting device and a removal unit (56), characterised in that the pipeline (2) is cleaned in a commissioned state, without interrupting the flow of fluid through the pipeline, by removing a mixture of fluid and debris from the pipeline (2) by means of suction, separating the debris from the fluid and re-injecting the cleaned fluid into the pipeline (2). A method according to claim 1 characterised in that the fluid is a gas. A method according to claim 2 characterised in that the gas is a gas which forms an explosive mixture when mixed with air A method according to any of claims 1 to 3 characterised in that debris from a length of the pipeline is gathered therein at a single place from which the gathered debris is removed by said suction. A method of cleaning a pipeline (2) as claimed in any of claims 1 to 3, which method comprises the steps of (i) inserting into the pipeline (2) to be cleaned a device for scraping the internal wall of the pipe and collecting the debris deposited by this scraping, together with loose debris in the pipe; 1 1 (ii) propelling the collecting device, together with the collected debris, along the pipeline to a collection point; (iii) introducing a removal unit (56) into the pipeline (2) for location close to the collecting point and (iv) removing debris from the pipeline (2) by means of this removal unit (56) characterised in that the pipeline (2) is cleaned in a commissioned state, without interrupting the flow of fluid through the pipeline (2), and the removal unit (56) comprises a suction head (56) which is powered by a vacuum unit located in a cleaning unit (10) , which cleaning unit (10) is connected to the pipeline (2) to be cleaned at a first connection point (4), close to the collection point for debris, and at a second connection point (6) downstream (with respect to the direction of fluid flow) of the first connection point (4), and a mixture of gas and debris is removed by suction from the pipeline at point (4), passed through the cleaning unit (10), the debris is separated out from the gas/debris mixture as it is passed through the cleaning unit (10) and the cleaned gas is returned to the pipeline (2) at the second connection point (6). A method according to claim 5 characterised in that the cleaning unit (10) is provided, close to its connection point (4), with an inlet (12) for purging gas, and purging gas is supplied to the cleaning unit (10) at the start of the cleaning process. 12 A cleaning unit (10) for use in a cleaning method according to any of claims 1 to 3, 5 or 6 characterised in that the cleaning unit (10) comprises, connected in series, first means for connecting the cleaning unit to the pipeline, first valve means (14), (16), one or more separation stages (18), (28), (38) for mechanical separation of debris from the gas/debris mixture, a blower (40) for creating suction, second valve means (48) connected in parallel with the blower (40), third valve means (50), (54), and second means for connecting the cleaning unit to the pipeline. A cleaning unit (10) according to claim 7 characterised in that it further comprises a non-return valve (52) positioned between the valve means (50) and the second means for connecting the cleaning unit (10) to the pipeline (2). A cleaning unit (10) according to claim 7 or claim 8 characterised in that it comprises a first separation stage (18) which comprises a cyclone separator (20). A cleaning unit (10) according to any of claims 7 to 9 characterised in that it comprises a second separation stage (18) which comprises a coarse filter (30). A cleaning unit (10) according to any of claims 7 to 10 characterised in that it comprises a third separation stage (38) which comprises a fine filter (38). A cleaning unit (10) according to any of claims 7 to 1 1 characterised in that it further comprises a plurality of sensors ( S' to S 5 ) for measuring the pressure at a 13 plurality of points in the cleaning unit (10), and control means for registering the output of the sensors ( S 1 to S 5 ), determining whether a hazard condition exists and taking appropriate action. A cleaning unit ( 10) according to claim 12 characterised in that the control system further comprises means for indicating to the operator of the system the location of a fault which has arisen. A cleaning unit (10) according to claim 12 or claim 13 characterised in that the control system can be set to ensure that the cleaning system only operates within pre-set system parameters. A cleaning unit (10) according to any of claims 7 to 14 characterised in that the cleaning unit (10) comprises said first means for connecting the cleaning unit to the pipeline connected in series with an inlet (12) for purging gas connected in series with said first valve means. A trailer unit which comprises a cleaning unit ( 10) as claimed in any of claims 7 to 15 mounted on a trailer (60) , within a housing (62).

Inventors: ROSE MICHAEL, ROSE, MICHAEL
Applicants: BRITISH GAS PLC, ROSE MICHAEL, BG PLC, ROSE, MICHAEL
Application year: 1998
Main classification: B08B9
IPC codes: B08B9