PIPELINE

The present invention relates to a device for use in deployment of a pipeline pig into a pipeline, and to a method of deploying a pipeline pig into a pipeline. In particular, but not exclusively, the present invention relates to a device for use in deployment of a pipeline pig into a pipeline, the device cooperating with a pig launcher coupled to the pipeline.

Pipelines are used in many industries in order to transport fluids, including the oil and gas exploration and production industry, where they are used to transport hydrocarbon containing fluids (oil and/or gas) from one location to another, such as from an offshore to an onshore location, or between different onshore locations.

It is well known that pipelines require periodic maintenance to be carried out, in order to maintain the integrity of the pipeline and continued flow of fluid. For example, pipelines experience corrosion over time, which can impair flow and potentially lead to the integrity of the pipeline being compromised. Deposits can build-up on the internal surface of the pipeline, disrupting and potentially blocking flow. These problems can be exacerbated by the fluids which are transported along the pipeline, particularly in the case of hydrocarbon containing fluids, which can be corrosive to the pipeline material. Also, deposits including waxes, condensates and scale can form on the internal surface of the pipeline, and other deposits including sulphate reducing bacteria (microbes found in oil) can damage the pipeline wall. In some industries, there is a requirement for a pipeline to be cleaned before a different fluid is transported along it, to remove residual traces of any fluid that has previously been contained in the pipeline.

A pipeline pig is a maintenance tool which is used to carry out maintenance on a pipeline. A pig is introduced into a pipeline via a pig launcher and is forced along the pipeline by the product flowing through the line, without interrupting flow. Various different types of pig are known, including scraper-type pigs, which include scrapers for physically removing deposits and corroded material from the internal surface of the pipeline as the pig travels along it; cleaning pigs, which include brushes and/or deformable wiper elements which wipe the internal surface clean and can remove deposits and corroded material; inspection pigs, which include inspection equipment such as one or more of a camera, an ultrasonic inspection tool and/or magnetic flux leakage inspection tool for inspecting the internal surface, pressure and temperature sensors; and multi-purpose pigs which are capable of carrying out two or more of these functions.

Pig launchers typically comprise a minor tubular barrel having an internal diameter which corresponds to that of the pipeline which the launcher is coupled to, a major tubular barrel having a larger internal diameter than that of the minor barrel, a tubular reducer extending between the major and minor barrels and which progressively decreases in internal diameter from that of the major barrel to that of the minor barrel, and a closure door mounted on an end of the major barrel, through which pipeline pigs can be inserted into the launcher. A pig receiver (or pig trap) of similar construction is provided at a distal end of the pipeline, for recovering the pig following its passage along the line.

Historically, it has been standard practice to load and launch pipeline pigs into a pig launcher one at a time, as and when required. The pigs are dimensioned so that they are a close fit in the pipeline, often carrying a deformable wiper element which has an outer diameter that is slightly larger than the inner diameter of the minor barrel (and so of the pipeline). For example, the wiper element may have an outer diameter which is around 105% to 106% of the minor barrel inner diameter, in an undeformed state. The pigs are, however, of a smaller outer diameter than the inner diameter of the major barrel, to facilitate insertion of the pig into the barrel. The pig is inserted into the major barrel and translated along it into the reducer, typically using a hydraulic ramrod, until the pig/pig wiper comes into contact with the internal surface of the reducer. At this point, the pig launcher door can be closed, and a portion of the product in the pipeline diverted behind the pig, to force the pig along the reducer into the minor barrel, for deployment into the pipeline.

Whilst this procedure is an effective method of launching a pig into a pipeline, it can be relatively time consuming and costly where multiple pigs are required over a period of time, since the procedure must be repeated each time a pig is launched. Pipeline pigging is a specialist procedure requiring suitably skilled technicians. Accordingly, pigging is only carried out as-and-when required, by deploying a team of technicians and the required pigging equipment on site when a pigging operation is to be performed. Single loading and launching creates more wear and tear on moving parts of the launcher, such as valves and the closure door. This increases the maintenance requirement on the pig launcher.

The frequency of pigging may be dictated by a remote or long-distance location, as in the case of remote un-manned platforms, or very long pipelines, where it is costly and time consuming to deploy a number of technicians to carry out the operation.

According to a first aspect of the present invention, there is provided a device for use in deployment of a pipeline pig into a pipeline, the device comprising: an elongate tubular pig housing having an outer wall and a bore extending along a length of the housing, the bore adapted to receive a plurality of pipeline pigs, the pig housing adapted to be located in a barrel of a pig launcher coupled to a pipeline; and at least one fluid injection port extending through the outer wall of the pig housing, the at least one fluid injection port communicating with the bore of the pig housing so that fluid can be injected through the at least one fluid injection port and into the bore of the pig housing, for translating at least one of the pipeline pigs out of the pig housing and into the pig launcher barrel.

According to a second aspect of the present invention, there is provided a pipeline pig deployment assembly comprising: a plurality of pipeline pigs; and a device for use in deployment of at least one of the pipeline pigs into a pipeline, the device comprising: an elongate tubular pig housing having an outer wall and a bore extending along a length of the housing, the bore adapted to receive the plurality of pipeline pigs, the pig housing adapted to be located in a barrel of a pig launcher coupled to the pipeline; and at least one fluid injection port extending through the outer wall of the pig housing, the at least one fluid injection port communicating with the bore of the pig housing so that fluid can be injected through the at least one fluid injection port and into the bore of the pig housing, for translating at least one of the pipeline pigs out of the pig housing and into the pig launcher barrel. According to a third aspect of the present invention, there is provided a pig launcher comprising a pig launcher barrel and a pipeline pig deployment assembly according to the second aspect of the invention.

The provision of a device having an elongate tubular pig housing which can receive a plurality of pipeline pigs may provide the advantage that a plurality of pigs can be loaded into a pig launcher at the same time. The required number of pigs can be positioned within the housing prior to the housing being located in the barrel of the pig launcher. This may provide the advantage that multiple pigs can be directed out of the housing and into the pig launcher barrel (and so into the pipeline) without requiring that the pigs be separately loaded into the pig launcher. A single pig can be deployed from the housing when desired, the remaining pig or pigs residing in the housing until such time as a requirement for a further pig or pigs to be discharged into the pipeline exists. The further pig or pigs can thus be deployed when desired, and without requiring that the further pig be separately transported on site and loaded into the pig launcher barrel. This may not only reduce costs associated with carrying out a pigging operation, but may also reduce wear and tear on equipment, including the pig launcher. This in turn may promote more frequent pigging of a pipeline, which may be of particular benefit in relatively mature pipeline installations, which can experience greater deterioration and deposit of materials on the inner surface of the pipeline wall. In addition, the invention may provide the advantage that deployment of pigs into the pipeline can be automated from a remote location, without requiring the presence of skilled technicians on site during each deployment. This may promote more frequent pigging, which can be beneficial in mature pipeline installations.

The device may comprise at least one seal element for sealing between the at least one fluid injection port and a port extending through a wall of the pig launcher barrel. The at least one seal element may facilitate injection of fluid into the bore of the pig housing through the fluid injection port. The device may comprise a plurality of fluid injection ports. A corresponding plurality of ports may extend through the wall of the pig launcher barrel. A seal element may be provided for each fluid injection port of the housing. A fluid injection port may be provided for each pig which is to be received in the housing. The fluid injection ports may be spaced apart along a length of the housing. The number of housing fluid injection ports may correspond to the number of pigs which can be received in the housing. The at least one fluid injection port may extend through the wall of the housing, which may be a side wall, and may extend between an outer surface of the housing and an inner surface of the housing. In use, when the housing is located in the pig launcher barrel, the or each fluid injection port may be adapted to overlap a respective port in the barrel, and may be adapted to substantially align with a respective port in the barrel. This may facilitate injection of fluid into the housing bore. The injection fluid may be a dedicated fluid, and may be a gas, optionally an inert gas such as Nitrogen.

The at least one seal element may be hollow and/or generally tubular. The at least one seal element may comprise a side wall, an inlet at one end of the seal element, an outlet at a second end (which may be an opposite end) of the seal element, and a passage extending along the seal element between the inlet and the outlet. In use, fluid may be supplied along the seal element passage and through the fluid injection port into the bore of the housing. The at least one seal element, in particular its side wall, may be deformable and may be expandable. The pressure of fluid supplied into the seal element passage may cause the seal element to expand to seal between the housing and the pig launcher barrel, and/or to enhance a seal between the housing and the pig launcher barrel. The at least one seal element may define a first seal face surrounding the inlet for sealing contact with the pig launcher barrel, and a second seal face surrounding the outlet for sealing contact with the pig housing. The inlet of the seal element may be adapted to surround the port in the wall of the pig launcher barrel. The outlet of the seal element may surround the fluid injection port of the housing. The at least one seal element may be a bellows-type seal. The at least one seal element may be a mushroom -type seal. The at least one seal element may be mounted on or to the housing, and adapted to slide relative to an inner surface of the pig launcher barrel during insertion of the housing into the barrel.

The pigs may each comprise at least one seal element for sealing the pig relative to an inner surface of the housing. The at least one seal element may be a wiping seal that provides a wiping seal with the housing surface when the pig is translated relative to it (as well as surfaces of part of the pig launcher barrel and of the pipeline). In use, when the pigs are located in the housing, the or each fluid injection port may be arranged to inject fluid into the bore of the housing at a location which is downstream of the pig seal element, relative to a direction of flow of fluid out of the housing and into the pig launcher barrel.

In this way, the injection fluid may serve to impart a fluid pressure force on the pig seal element, to urge the pig out of the housing.

The at least one fluid injection port may extend through a wall of the housing, which may be a side or end wall, and may extend between an outer surface of the housing and an inner surface of the housing. In use, when the pigs are located in the housing, the at least one fluid injection port may be located so that it is downstream of the pig which is furthest away from a pig deployment outlet of the housing (which may be a trailing pig), optionally downstream of a wiper element of said pig, relative to a direction of flow of fluid out of the housing and into the pig launcher barrel.

The injection fluid may be a product contained within the pipeline, at least a portion of which may be diverted into the housing bore to translate the pig out of the housing. The fluid may be directed through a main inlet port in the pig launcher barrel, which may be a kicker port. The main inlet port may communicate with an annular region disposed between an inner surface of the barrel and an outer surface of the pig housing. The at least one fluid injection port of the pig housing may communicate with the annular region.

The pigs may each comprise a pig body and at least one functional element extending in a generally radially outward direction from the pig body. The functional element may be selected from the group comprising: a scraper element for scraping an inner surface of the pipeline wall; a wiping element for wiping an inner surface of the pipeline wall; a cleaning element for cleaning an inner surface of the pipeline wall; and a seal element for sealing the pig relative to an inner surface of the pipeline wall.

At least the trailing pig or pigs, and optionally each of the pigs, may comprise at least one bypass aperture for bypass flow of fluid past said pig. Optionally a plurality of bypass apertures are provided. The bypass aperture may facilitate a bypass flow of fluid past (or around) a trailing pig (or pigs) in the housing, to translate a pig which is closer to a pig deployment outlet of the housing out of the housing and into the pig launcher barrel. Said pig may comprise at least one bypass member defining the at least one bypass aperture, and a cover which is movable relative to the bypass member between an open position in which the aperture is at least partly open, and a closed position in which the aperture is at least partly occluded. Said pig may comprise a substantially hollow pig body. A passage may extend along a length of the pig body, through which fluid may flow to bypass said pig. A trailing bypass member may be provided at or proximate a trailing end of the pig.

A leading bypass member may be provided at or proximate a leading end of the pig.

Where there are trailing and leading bypass members, the bypass apertures of each bypass member may be opened to allow flow through the pig. The cover may comprise a bypass aperture or apertures which corresponds to the aperture of the bypass member. In the open position, the bypass aperture of the bypass member may be completely open and so not occluded by the cover. In the closed position, the bypass aperture of the bypass member may be completely closed, and so completely occluded by the cover. In the open position, the bypass apertures of the bypass member and of the cover may be substantially aligned.

In the closed position, the bypass apertures of the bypass member and the cover may be substantially misaligned. The cover may be locatable in an intermediate position (or positions) between the open and closed positions, in which the at least one bypass aperture is partially occluded. The cover may be rotatable between the open and closed positions, and may be rotatably mounted relative to the bypass member. Said pig may comprise a receiver which is adapted to receive a signal transmitted by a transmitter in an external location (which may be external to the housing and suitably external to the pig launcher), to move one of the cover and the bypass member relative to the other, between the open and closed positions. The receiver may be associated with an actuator coupled to one of the cover and the bypass member, for moving the cover relative to the bypass member (or vice versa). Receipt of an actuating signal by the receiver, transmitted by the transmitter, may cause the receiver to operate the actuator. The actuator may be a motor.

The pigs may be selected from the group comprising: a scraper-type pig, including one or more scraper which may be for physically removing deposits and/or corroded material from the internal surface of the pipeline as the pig travels along it; a cleaning pig, including one or more brush and/or deformable wiper element, which may be for wiping the internal surface of the pipeline to remove deposits and/or corroded material; an inspection pig, including inspection equipment such as one or more of a camera, an ultrasonic inspection tool and/or magnetic flux leakage inspection tool for inspecting the internal surface of the pipeline, pressure and temperature sensors; and a multi-purpose pig capable of carrying a plurality of these functions.

The device may comprise at least one support for supporting the housing within the pig launcher barrel. The at least one support may provide a spacing between the housing, in particular an outer surface of the housing, and the pig launcher barrel.

The device may comprise a housing seal for sealing the housing relative to an inner surface of the pig launcher barrel. The housing seal may define one of said supports. The housing seal may provide a barrier to fluid flow along the barrel past the housing, when the housing is located in the barrel. This may facilitate injection of fluid into the bore of the housing through the at least one housing fluid injection port, the housing seal serving to ensure such fluid is directed into the housing fluid injection port. The housing seal may extend around an outer surface of the housing, and may be generally annular in shape. The housing seal may be provided at or proximate a leading end of the housing, taken relative to a direction of travel of the pigs into the pig launcher barrel. The housing seal may be shaped to engage a reducer of the pig launcher, the reducer having a tapering internal diameter. The housing seal may taper in a direction towards the leading end of the housing.

The pig launcher may comprise a minor tubular barrel portion having an internal diameter which corresponds to that of the pipeline which the launcher is coupled to, a major tubular barrel portion having a larger internal diameter than that of the minor barrel portion, a tubular reducer extending between the major and minor barrel portions and which progressively decreases in internal diameter from that of the major barrel portion to that of the minor barrel portion, and a closure door mounted on an end of the major barrel portion, through which pipeline pigs can be inserted into the launcher.

The device may comprise an adjustment mechanism for adjusting a position of the housing within the pig launcher barrel. The adjustment mechanism may define one or more of said supports. The adjustment mechanism may comprise at least one jack for adjusting a vertical position of the housing within the pig launcher barrel. The device may comprise one or more guide such as a roller, wheel or slider, which may facilitate adjustment of a position of the housing along a length of the pig launcher barrel.

The housing may comprise a leading end and a trailing end, taken relative to a direction of travel of the pigs into the pig launcher barrel. The housing may be open at the leading end, which may define a pig deployment outlet of the housing. The housing may be closed at a trailing end. The housing may be adapted to receive pigs (which are to be deployed into the pig launcher) through the open leading end. The pigs may be inserted into the open leading end and translated towards the closed trailing end. The pigs may be arranged in series, aligned one behind the other, along the length of the housing.

According to a fourth aspect of the present invention, there is provided a method of deploying a pipeline pig into a pipeline, the method comprising the steps of: locating a plurality of pipeline pigs in a bore of an elongate tubular pig housing, the bore extending along a length of the housing, the housing having an outer wall and at least one fluid injection port extending through the outer wall so that it communicates with the bore of the pig housing; locating the pig housing including the pipeline pigs within a barrel of a pig launcher coupled to a pipeline; and injecting a fluid into the bore of the pig housing through the at least one fluid injection port, to translate at least one of the pipeline pigs out of the pig housing and into the pig launcher barrel.

The method may comprise translating a single pig, from the group of pigs located in the housing, out of the housing and into the pig launcher barrel. The method may comprise translating the pig which is disposed towards a leading end of the housing out of the housing and into the pig launcher barrel, leaving a trailing pig or pigs in the housing.

The method may comprise directing fluid into the housing bore through a fluid injection port to a location which is upstream of a pig that is behind (i.e. trailing) a leading pig. A fluid injection port may be provided which is associated with each pig, and the method may comprise selectively injecting fluid through the fluid injection port associated with the pig which is to be translated.

The method may comprise sealing the at least one fluid injection port relative to the pig launcher barrel using a hollow/tubular seal element, and injecting fluid into the housing bore through a port of the pig launcher barrel, the seal element and the fluid injection port of the housing.

The method may comprise directing fluid into the housing bore through the at least one fluid injection port to a location which is downstream of a trailing pig in the housing, or which is downstream of at least a leading end of a trailing pig. The method may comprise bypassing the fluid around or through the trailing pig towards a leading pig which is to be deployed from the housing and into the pig launcher barrel. Where there is a leading pig, and two or more trailing pigs, the method may comprise bypassing the fluid around or through each of the trailing pigs to the leading pig. The method may comprise selectively arranging the trailing pig or pigs to permit such fluid bypass to the leading pig.

The method may comprise sealing the housing relative to the pig launcher barrel, optionally at or proximate a leading end of the housing. The method may comprise injecting fluid into an annular region disposed between an inner surface of the barrel and an outer surface of the pig housing, optionally through a port of the pig launcher barrel.

The method may comprise placing the at least one fluid injection port of the pig housing in communication with the annular region, so that fluid injected into the annular region through the barrel port passes through the at least one fluid injection port of the pig housing and into the housing bore.

The method may comprise locating the pigs in series within the pig housing, one behind the other. Further features of the method of the fourth aspect of the invention may be derived from the text set out elsewhere in this document, particularly in or with reference to the first, second and/or third aspects of the invention.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. l is a highly schematic cross-sectional side view of a pig launcher of a conventional type, with a pipeline pig located in the barrel in preparation for deployment into a pipeline;

Fig. 2 is a partial longitudinal cross-sectional view of a device for use in deployment of a pipeline pig into a pipeline in accordance with an embodiment of the present invention;

Figs. 2A and 2B are longitudinal sectional side and end views, respectively, of a housing forming part of the device of Fig. 2;

Fig. 2C is an enlarged detail view of part of the housing shown in Figs. 2A and B;

Fig. 3 is an enlarged view of a seal element forming part of the device shown in Fig. 2;

Fig. 4 is a longitudinal sectional side view of an alternative housing forming part of a variation of the device shown in Fig. 2;

Fig. 5 is a cross-sectional view of the housing taken along the line C-C in Fig. 4;

Figs. 6 and 7 are perspective and side views, respectively, of part of a pipeline pig which is a variation on the pipeline pig shown in Fig. 2, the variation including a bypass aperture arrangement;

Figs. 8 and 9 are rear views of the bypass aperture arrangement shown in Figs. 6 and 7, showing the bypass apertures in an open position (Fig. 8) and a closed position (Fig. 9), respectively; and Fig. 10 is a rear view of the bypass aperture arrangement shown in Figs. 6 and 7, showing the bypass apertures in an intermediate position.

Turning firstly to Fig. 1, there is shown a highly schematic cross-sectional side view of a pig launcher of a conventional type, indicated generally by reference numeral 10, shown coupled to a pipeline 12. In the illustrated example, the pipeline 12 is employed to transport hydrocarbon fluids (oil and / or gas) in the oil and gas exploration and production industry, such as from an offshore location to an onshore location, or between different onshore locations.

As is well known, the pig launcher 10 comprises a barrel 16 having a major barrel portion 18, a minor barrel portion 20, and a tapered reducer 22 which extends between the main and minor barrel portions. The major barrel portion 18 has an internal diameter which is greater than that of the minor barrel portion 20, and the reducer 22 tapers from a diameter which corresponds to that of the major barrel portion 18, to a diameter which corresponds to that of the smaller dimension minor barrel portion 20. As will be understood by persons skilled in the art, this provides a transition pathway for a pipeline pig from the pig launcher 10 into the pipeline 12. The minor barrel portion 20 internal diameter corresponds to that of the pipeline 12, for ease of insertion of a pig into the pipeline 12.

Fig. 1 shows a pipeline pig 24 of a conventional type which has been located within the major barrel portion 18 of the pig launcher 10, in preparation for translation of the pig out of the pig launcher and into the pipeline 12. The launcher 10 also includes a closure door 26, which can be opened so that the pig 24 can be inserted into the main barrel portion 18 of the pig launcher 10, suitably using a hydraulic ramrod (not shown). The closure door 26 is then closed and sealed relative to the main barrel portion 18.

The pipeline 12 includes a T-junction 28 having a branch 30 by which the pig launcher 10 can be coupled to the pipeline, and a branch 35 which is coupled to a main portion 36 of the pipeline 12. A main line isolation valve 32 is provided which controls the flow of fluid from a supply side portion 34 of the pipeline 12 through the T-junction 28 into the branch 35 and hence into the main portion 36 of the pipeline 12. A bypass line known as a ‘kicker line’ 38 extends between the supply side portion 34 of the pipeline 12 and the major barrel portion 18 of the pig launcher 10. The kicker line 38 includes a kicker line valve 40, which controls the flow of fluid along the kicker line into the pig launcher 10. The pig launcher 10 also includes an isolation valve 42, which isolates the pig launcher from fluid in the pipeline 12.

A conventional procedure to insert the pig 24 into the pipeline 12 is as follows. The pig 24 is inserted into the major barrel portion 18 of the pig launcher 10 and is advanced until it comes into contact with an internal surface 44 of the reducer 22. Typically, the pig 24 comprises a number of functional elements 46, 48, 50 and 52, and at least the functional element 46, provided towards a leading end 54 of the pig 24, takes the form of a wiping seal element. The wiping seal element 46 is suitably of an elastomeric material, and provides a wiping seal with the internal surface 44 of the reducer 22, and indeed with an internal surface 56 of the minor barrel portion 20 and an internal surface 58 of the pipeline 12

The kicker line valve 40 and the isolation valve 42 are both closed prior to opening of the launcher closure door 26, for insertion of the pig 24. A vent line 60 includes a vent valve 62, which is opened in order to vent any residual pressure present in the pig launcher 10 before the closure door 26 is opened. As is well-known, insertion of the pig 24 can be carried out on a live pipeline, without interrupting the flow of product along the line.

Once the pig 24 has been inserted and brought into contact with the reducer 22, the kicker line valve 40 can be opened to direct a portion of the pipeline product into the major barrel portion 18 of the pig launcher 10, as indicated by the arrows 64 in the drawing. The main line isolation valve 32 can then be closed, and the launcher isolation valve 42 opened, so that all product flow is directed through the kicker line 38 and into the major barrel portion 18. The fluid imparts a fluid pressure force on the pig, in particular upon the wiper seal element 46, translating it through the reducer 22 into the minor barrel portion 20, through the isolation valve 42 and into the pipeline 12. A pig signaller 66 is provided on the pipeline 12 which provides an indication that the pig 24 has passed the signaller and entered the pipeline. The isolation valve 42 can then be closed, the kicker line valve 40 closed, and the main line isolation valve 32 reopened. Fluid is then once again directed from the supply side portion 34 into the branch 35, and hence into the main part 36 of the pipeline 12. This acts to translate the pig 24 along the pipeline 12 to a pig trap (not shown), which is typically located at or towards a distal end of the pipeline.

Turning now to Fig. 2, there is shown a partial longitudinal cross-sectional view of a device for use in deployment of a pipeline pig into a pipeline, the device indicated generally by reference numeral 68. The device is shown located in a pig launcher 10 of the type shown in Fig. 1 and described above. The same reference numerals will be employed for the pig launcher shown in Fig. 2 as for the pig launcher shown in Fig. 1. The pig launcher 10 is shown coupled to the pipeline 12, with two pig signallers 66 provided at spaced locations along the length of the pipeline. Flanges 70 and 72 are shown, by which sections of the pipeline are coupled together. Advantageously, and as will be appreciated from the following description, the device 68 of the present invention can be used as a retrofit device which can be located in a pre-existing pig launcher 10 on a pipeline 12, without requiring any modification to the structure of the pig launcher.

The device 68 generally comprises an elongate tubular pig housing, cassette or canister 74 having an outer wall 76 and a bore 78 extending along a length of the housing. The housing 74 is shown separately and in more detail in the longitudinal sectional side view of Fig. 2A, the end view of Fig. 2B, and the enlarged detail view of Fig. 2C. As shown in Fig. 1, the bore 78 is adapted to receive a plurality of pipeline pigs, two of which are shown and indicated by the numerals 24a and 24b. It will be understood that more than two pigs may be located in the housing 74, depending on factors including the length of the housing and of the pigs.

The pig housing 74 is locatable within the barrel 16 of the pig launcher 10, in particular within the major barrel portion 18, as shown in the drawings. At least one fluid injection port is provided which extends through the outer wall 76 of the pig housing 74, and in the illustrated embodiment two such fluid injection ports are provided, indicated by the reference numerals 80a and 80b. The fluid injection ports 80a and 80b communicate with the bore 78 of the pig housing 74, so that fluid can be injected through the injection ports and into the bore of the pig housing, for translating the pigs 24a and 24b out of the housing 76 and into the pig launcher barrel 16 (specifically into the minor barrel portion 20). In the illustrated embodiment, a fluid injection port 80a, b is provided for each pipeline pig 24a, b, fluid being selectively injected through the port that is associated with the pig that is to be launched.

As shown in the drawing, the pigs 24a and 24b are located in series within the pig housing 74. The pig housing 74 comprises a leading end 82 and a trailing end 84, considered relative to a direction of flow of fluid out of the housing 74 and into the pig launcher barrel 16, and/or a direction of translation of a pig out of the housing and into the barrel (as indicated by the arrow A). The leading end 82 is open, and the trailing end 84 is closed by a closure plate 86 which is secured to a flange 88 carried by the housing 74. The pigs 24a and 24b are typically inserted through the open leading end 82 of the housing 74, suitably using a hydraulic ramrod (not shown).

The fluid injection ports 80a and 80b are each coupled to a source of fluid which is used to translate the pigs 24a and 24b out of the housing 74, typically an inert gas such as Nitrogen. When it is desired to carry out a pigging procedure on the pipeline 12, the housing 74 containing the pigs 24a and 24b is loaded into the major barrel portion 18 of the pig launcher 10. The procedure associated with isolating the pig launcher in order to insert the housing 74 is substantially the same as that described above in relation to Fig. 1, concerning the insertion of a conventional pig.

The pig 24a is deployed independently of the pig 24b, to perform a first pigging operation. This involves injecting fluid through the injection port 80a and into an annular region 90 of the housing bore 78. Suitable valving is provided (not shown) in order to isolate the second fluid injection port 80b, so that fluid is only directed through the first port 80a. The pig 28a includes functional elements 46a, 48a, 50a, 52a, 53a and 55a which extend radially outwardly from a body 92 of the pig. At least the element 46a takes the form of a wiper seal element which seals the pig 24a relative to an inner surface 94 of the pig housing 74. It will be understood that each of the functional elements typically describe an outer diameter which is greater than an internal diameter of the pig housing 74 (which corresponds to that of the minor barrel portion 20). As a result, the functional elements will typically be deflected and so deformed when the pigs 24a and 24b are located in the housing 74 as shown in the drawing. However, the functional elements have been shown undeflected for ease of illustration. The pigs 24a and 24b are pulled back a short distance following insertion into the housing 74, in order that the functional elements are deflected backwards, relative to a desired direction of travel of the pigs out of the housing and into the launcher.

Injection of fluid into the annular region 90 imparts a fluid pressure force on the wiper seal element 46a, which acts to translate the pig 24a out of the pig housing 74 and into the reducer 22 of the pig launcher 10. The functional elements 48a or 50a may also be wiper seal elements, in which case the fluid pressure force will act upon that element in order to translate the pigs. However, the functional elements 48a and 50a may take the form of cleaning elements such as brushes, through which the injected fluid can flow in order to impart the fluid pressure force on the wiper seal element 46a.

Fluid may continue to be injected through the injection port 80a in order to translate the pig 24a out of the reducer 22 and into the minor barrel portion 20. Once the pig 24a has passed a T-junction (28 in Fig. 1, but not shown in Fig. 2), as indicated by the pig signallers 66, the pipeline product may be employed to translate the pig along the pipeline. A kicker line port 138 is provided in the major barrel portion 18, extending through the wall 102 of the major barrel portion. A nozzle 140 connects the kicker port 138 to a kicker line, such as the line 38 shown in Fig. 1. In this way and as described above, the pipeline product can be diverted into the pig launcher through the kicker line port 138. Fluid which is supplied through the kicker line port 138 flows into an annular region 136 located between an internal surface 126 of the major barrel portion 18 and an outer surface 98 of the pig housing 74. This fluid can communicate with the housing bore 78 through flow ports 134 (shown in Fig. 2A) which extend through the housing wall 76. This fluid can act upon the pig 24a to translate it out of the pig launcher 10 and along the pipeline 12. It will be understood that the ports 134 will typically be located downstream of the wiper seal element 46a, so as to avoid providing a bypass flow path around the seal element.

When a need arises to carry out a further pigging operation, the second pig 24b can be deployed into the pipeline 12, following a similar procedure to that described above in relation to the pig 24a. In this instance, fluid is injected through the fluid injection port 80b and into an annular region 96 of the pig housing 74, this fluid acting on a wiper seal element 46b of the second pig 24b. During translation of the first pig 24a out of the housing 74, the fluid injection port 80b remains closed. Similarly, during translation of the second pig 24b, the port 80b is open whilst the port 80a remains closed.

The fluid injection ports 80a and 80b are spaced apart along a length of the pig housing 74, and each extend through the housing wall 76 between the inner surface 94 of the housing 74 and an outer surface 98 of the housing. A corresponding plurality of ports 100a and 100b are provided which extend through the wall 102 of the pig launcher major barrel portion 18. A nozzle 104a, 104b is provided which communicates with the barrel ports 100a, 100b respectively, through which fluid to be injected can be supplied through the barrel ports and housing ports 80a, 80b into the housing bore 78.

A seal element is provided for sealing between each of the housing fluid injection ports 80a and 80b and the barrel ports 100a, 100b. The seal elements are indicated by the reference numerals 106a and 106b, and each have the same structure. The seal element 106a is shown in more detail in the enlarged view of Fig. 3, and will now be described. In use, when the pig housing 74 is located in the main barrel portion 18, the housing fluid injection ports 80a and 80b overlap with the respective barrel port 100a and 100b, and are suitably aligned as best shown in the enlarged view of Fig. 3. The seal elements 106a and 106b are hollow, being generally tubular, and each comprise a sidewall 108, an inlet 110 at one end of the seal element, an outlet 112 at a second opposite end, and a passage 114 extending along the seal element between the inlet and the outlet. In use, fluid is supplied from the barrel port 100a, along the seal passage 114 and through the housing fluid injection port 80a into the housing bore 78. It will be understood that the seal element 106b is similarly arranged in relation to the ports 80b and 104b. The side wall 108 of the seal element 106a is deformable, and is suitably expandable under the pressure of fluid supplied into the seal element passage 114. This causes the seal element 106a to expand to seal between the housing 74 and the major barrel portion 18, and/or to enhance a seal between the housing and the pig launcher barrel. The seal element 106a defines a first seal face 116 which surrounds the seal inlet 110, and a second seal face 118, which surrounds the seal outlet 112. The seal inlet 110 suitably surrounds the barrel port 100a, whilst the outlet 112 suitably surrounds the housing fluid injection port 80a.

The seal element 106 is secured to the pig housing 74 via a clamping assembly, which includes a mounting plate 120 that is secured to the pig housing 74, a clamping ring 122 and a number of fixings such as bolts 124. The bolts 124 pass through the clamping ring 122 and into the mounting plate 120. Part of the wall 108 of the seal element 106a is located between the clamping ring 122 and the mounting plate 120, and is clamped in place when the bolts 124 are tightened.

The seal elements 106a and 106b come into contact with an internal surface 126 of the major barrel portion wall 102 when the housing 74 is inserted. This requires that the seal elements 106a and 106b slide over the internal surface 126 to their positions shown in Figs. 2 and 3, in which the housing fluid injection ports 80a and 80b are aligned with the barrel ports 100a and 100b. A suitable low friction coating may be applied to an outer surface of the seal element walls 108, and/or to the barrel internal surface 126, to ease passage of the seal elements along the surface. Selection of a suitable material for the seal elements 106a and 106b, such as an elastomeric material, may also facilitate such movement.

As mentioned above, when fluid is injected through the seal elements 106a and 106b into the pig housing bore 78, the seal elements are caused to expand. Suitably the seal elements take the form of bellows-type or mushroom-type seals, which may facilitate this. The seal elements 106a and 106b have both been shown mounted to the pig housing 74. It will be understood however that the seal elements may alternatively be mounted to the main barrel portion 18 of the pig launcher 10. However, it may generally be preferred to avoid this as such could require a modification to the pig launcher 10, with a consequent impact upon relevant certification of the launcher.

The device 68 includes a housing seal 128 for sealing the pig housing 74 relative to the inner surface 126 of the pig launcher barrel 16, which is best shown in the enlarged detail view of Fig. 2C. The housing seal 128 provides a barrier to fluid flow along the barrel 16 past the housing 74, when the housing is located in the barrel as shown in Fig. 2. The housing seal 128 extends around the outer surface 98 of the pig housing 74, and is located proximate the leading end 82 of the housing. The housing seal 128 is shaped to engage the reducer 22 of the pig launcher, which has the tapering internal diameter. To this end, and as shown in Fig. 2C, the housing seal 128 tapers in a direction towards the leading end 82 of the housing 74.

The pigs 24a and 24b are of a relatively conventional type, including the various functional elements. The functional elements may be arranged to perform one or more of a scraping, cleaning or wiping function. Also, inspection equipment may be provided for inspecting the internal surface 58 of the pipeline 12, including for example a camera, an ultrasonic inspection tool, a magnetic flux leakage inspection tool, pressure and/or temperature sensors.

The device 68 also comprises at least one support for supporting the pig housing 74 within the major barrel portion 18 of the pig launcher 10. The housing seal 128 forms one such support, spacing the housing 74 relative to the main barrel portion 18. The tapered shape of the housing seal 128 may facilitate passage of the housing 74 along the major barrel portion 18 during insertion, resisting damage through contact with edge surfaces of the barrel ports 100a and 100b. A further support is provided by a wheel or roller 130 which is mounted on the pig housing 74 towards its trailing end 84. The housing seal 128 and wheel 130 together provide the required spacing relative to the major barrel portion 18, this spacing being bridged by the seal elements 106a and 106b, which place the housing fluid injection ports 80a, 80b and barrel ports 100a, 100b in fluid communication, as discussed above. An adjustment mechanism is also provided for adjusting a position of the housing 74 within the major barrel portion 18 of the launcher 10. The adjustment mechanism includes the wheel 130 and a jack 132 coupled to the wheel 130, which is adjustable to vary a height of the housing 74 within the main barrel portion 18. If desired, more than one such adjustment mechanism may be provided.

A variation on the device 68 will now be described, with reference again to Figs. 1 to 3, as well as to Fig. 4 which is a longitudinal sectional side view of a variation on the housing 74 (indicated by reference numeral 74’), and the cross-sectional view of the housing 74’ of Fig. 5 which is taken along the line C-C in Fig. 4. Like components of the housing 74’ with the housing 74 of Figs. 1 to 2C share the same reference numerals with the addition of the suffix’. In the variation housing 74’, the fluid injection ports 80a and 80b have been dispensed with, but may remain and be closed via suitable valving or plugs. Fluid injection ports 134’ extend through an outer wall 76’ of the housing 74’, between an outer surface 98’ of the housing and an inner surface 94’. The fluid injection ports 134’ are located downstream of the pig 24b which is furthest away from an open leading end 82’ of the pig housing 74’, relative to the direction of flow of fluid out of the housing and into the pig launcher barrel 16. Suitably, the fluid injection ports 134’ are provided proximate a trailing end 84’ of the pig housing 74’. However, any location which is downstream of a leading end of the trailing pig 76b, in particular downstream of/behind its wiper element 46b (or any trailing wiping elements located further down the pig body) may be a suitable location for the fluid injection ports 134’.

The fluid injection ports 134’ communicate both with a housing bore 78’ and the annular region 136 (Fig. 1) located between the internal surface 126 of the major barrel portion 18 and the outer surface 98’ of the pig housing 74’. Pipeline product can be diverted into the pig launcher through the kicker line port 138 when it is desired to launch a pig. Fluid which is supplied into the annular region 136 through the kicker line port 138 can communicate with the housing bore 78’ through the fluid injection ports 134’. This fluid can act upon the pigs 24a and 24b to translate them out of the pig housing 74’ and into the pig launcher barrel 16. To facilitate selective deployment of the leading pig 24a, leaving the trailing pig 24b within the housing 74’, it is necessary for the pipeline product which has been injected into the pig housing bore 78’ through the fluid injection ports 134 to bypass the trailing pig 24b. This is achieved by providing the trailing pig 24b with bypass apertures which facilitate a bypass flow of fluid past the pig. It will be understood that, where more than two pigs are located in the housing 74’, each pig which trails the leading pig would require such bypass apertures.

One suitable bypass arrangement 141 is shown in the perspective view of Fig. 6 and the side view of Fig. 7. In the illustrated embodiment, the bypass arrangement 141 comprises a bypass member in the form of a circular plate 146, the bypass plate including four bypass apertures 142 which are spaced apart around a circumference of the bypass plate.

However, any suitable number of bypass apertures 142 may be provided. The bypass plate 146 includes an outer rim 144, and the bypass apertures 142 are located radially inwardly of the rim.

A cover is provided, in the form of a generally circular plate 148, which is moveable relative to the bypass plate 146 between an open position shown in the rear view of Fig. 8 (in which the apertures 142 are completely open), and a closed position shown in the rear view of Fig. 9 (in which the bypass apertures 142 are completely occluded by the cover plate, and so completely closed). The cover plate 148 includes apertures 149 which align with the apertures 142 in the bypass plate 146 in the open position.

The cover plate 148 is movable between the open and closed positions, and is suitably rotatable between the positions. This is achieved by rotatably mounting the cover plate 148 to the bypass plate 146, an actuator in the form of a motor 150 being coupled to the cover plate 148 for rotating it between its different positions. The pig 24b comprises a receiver 152 which is associated with the motor 150, for triggering the motor to rotate the cover plate 148 between its open and closed positions. A transmitter (not shown) provided externally of the pig launcher 10 serves for sending a signal (e.g. a radio frequency or ultrasonic signal) to the receiver 152 to cause it to trigger the motor 150 to rotate the cover plate 148. The cover plate 148 may be locatable in intermediate positions between the fully open and fully closed positions of Fig. 8 and 9, this being shown in Fig. 10. In the intermediate position shown in the drawing, the bypass apertures 142 are partially occluded.

The pig body 92 is hollow, defining an internal passage 154 (see Fig. 2) through which a bypass flow of fluid can flow through the pig 24a/b. The bypass arrangement 141 is provided on a leading end 95 of the pigs 24a/b, as shown in Fig. 2, so that the bypass flow of fluid can flow along the internal passage 154 and out of the pigs when the bypass apertures 142 are open. A corresponding bypass arrangement 141 can be provided on a trailing end 93 of the pig, and both the leading and trailing bypass arrangements actuated to open positions so that fluid can flow into and out of the pig bodies 92 through the bypass apertures 142 and the internal passages 154. The trailing and leading bypass arrangements 141 would both be triggered to move between their open and closed positions by the signal sent to receivers 152 of the arrangements. In a further variation, only a trailing bypass arrangement 141 may be provided on the pigs 24a/b, located towards their trailing ends 93.

It will be understood that launching of the leading pig 24a requires that the bypass arrangement 141 of the trailing pig 24b be open, and that the bypass arrangement 141 of the leading pig 24a be closed. In this way, fluid can bypass through the internal passage 154 of the trailing pig 24b to the leading pig 24a, for imparting a fluid pressure force on the leading pig to translate it out of the housing 74’ and into the launcher 10. This is achieved without imparting a fluid pressure force on the trailing pig 24b sufficient to move it, so that the trailing pig remains in its position within the housing 74.

It will also be understood that the leading pig 24a could conceivably be provided without such a bypass arrangement 141, since it will be the first pig to be launched and so does not require to have fluid bypassed through it to another pig. However, in practice the positions of the pigs 24a/b within the housing 74’ during a subsequent deployment may be varied, and so the pigs will typically all include bypass arrangements 141. Different signals may be issued to trigger the bypass arrangements 141 of different pigs, particularly the leading pig 24a. The housing 74’ includes supports 130’ in place of the wheel 130, which take the form of elongate skids mounted to the outer surface 98’ of the housing 74’, and which extend part way along the length of the housing. The supports 130’ may be of a low friction material, for example a polymeric material such as PTFE. Fig. 5 illustrates an optional loading tray 158 by which the pigs 24a, b can be loaded into the major barrel portion 18 of the pig launcher 10. The loading tray 156 is curved and includes elongate restraints 158 against which the supports 130’ are seated, so as to control a rotational position of the housing 74’ during insertion into the launcher 10. This may be applied to the housing 74 of Fig. 2, to assist in correct orientation of the seal elements 80a, b with the barrel ports 100a, b.

In the variation described above, the fluid injection ports 134’ are provided in place of the housing injection ports 80a and 80b, and pipeline product is employed to translate the pigs 24a and 24b out of the housing 74’ . It will be understood however that in a further variation, both the fluid injection ports 80a and 80b, and the ports 134’ may be provided.

A dedicated fluid such as Nitrogen may be employed to translate the pigs 24a and 24b out of the housing 74’ in the fashion described above (injected through the portions 80a and 80b), and pipeline product then employed to transport the pigs out of the launcher 10 and into the pipeline 12, the pipeline product injected through the ports 134’.

Operation of the device 68 of the present invention to launch a pig may be achieved remotely, once the housing 74/74’ containing the pigs 24a and 24b has been located in the pig launcher 10. This may avoid a requirement to maintain a skilled technical team on site during deployment of the pig. For example, a signal may be issued from a control site at a distant location from the pig launcher, which will operate valves etc. associated with the launcher 10 in order to launch the pigs 24a, 24b from the launcher as and when required. Such can include triggering the transmitter to issue a signal causing bypass apertures on the pig or pigs to be opened.

The device of the present invention provides numerous advantages over prior pig launching equipment. These include that the provision of a device having an elongate tubular pig housing which can receive a plurality of pipeline pigs may provide the advantage that a plurality of pigs can be loaded into a pig launcher at the same time. The required number of pigs can be positioned within the housing prior to the housing being located in the barrel of the pig launcher. This may provide the advantage that multiple pigs can be directed out of the housing and into the pig launcher barrel (and so into the pipeline) without requiring that the pigs be separately loaded into the pig launcher. A single pig can be deployed from the housing when desired, the remaining pig or pigs residing in the housing until such time as a requirement for a further pig or pigs to be discharged into the pipeline exists. The further pig or pigs can thus be deployed when desired, and without requiring that the further pig be separately transported on site and loaded into the pig launcher barrel. This may not only reduce costs associated with carrying out a pigging operation, but may also reduce wear and tear on equipment, including the pig launcher.

This in turn may promote more frequent pigging of a pipeline, which may be of particular benefit in relatively mature pipeline installations, which can experience greater deterioration and deposit of materials on the inner surface of the pipeline wall. In addition, the invention may provide the advantage that deployment of pigs into the pipeline can be automated from a remote location, without requiring the presence of skilled technicians on site. This may promote more frequent pigging, which can be beneficial in mature pipeline installations.

Various modifications may be made to the foregoing without departing from the spirit or scope of the present invention.