Abstract:
A sampling device ( 10 ) includes a sample extraction portion ( 28 ) which reciprocates within a cylindrical sample housing portion ( 26 ). The sample housing portion is axially moveable through a gate valve ( 22 ) to permit removal and maintenance of the sample extractor.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a sampling device such as one for use in process sampling, including the sampling of fluids, slurries, and powders 
     BACKGROUND TO THE INVENTION 
     It is known to require the extraction of sample quanta from pipelines and other process flow operations. Such sampling is required in many types of operations, including oil and gas processing, mineral processing, chemical processing, food preparation and pharmaceutical preparation. 
     A known type of sampling device is bolted to the side of a pipeline, and comprises a rod which slides through a cylindrical tube aligned radially to the pipeline. The rod includes two sets of axially separated circumferential seals which engage with inner walls of the tube, and a sample spool piece located between the two sets of seals. In order to acquire a sample, an end of the rod including an outer circumferential seal set and the sample spool piece are moved axially from the tube into the pipeline. Product from within the pipeline thus flows about the sample spool piece, up to the second, inner circumferential seal set. The rod is then withdrawn into the tube, with a sample being held in the sample spool piece between the two seals. The rod is withdrawn a sufficient distance that the inner seal passes over an aperture, through which the sample is extracted for testing. 
     There are several drawbacks to use of such a device. Principal amongst these is that the outer circumferential seal set slides within the tube, and is thus subject to wear. During normal product flow within the pipeline, when sampling is not occurring, this outer seal set is required to prevent leakage from the pipeline. As such, should wear occur, the pipeline must be shut down and emptied in order for the seal set to be replaced. 
     The present invention attempts to overcome at least in part some of the aforementioned disadvantages of previous sampling devices. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention there is provided a sampling device for extracting a sample from a pipe, the sampling device comprising a sample housing portion and a sample extracting portion, the sample extracting portion being moveable relative to the sample housing portion, characterised in that the sample housing portion is movable relative to the pipe. Advantageously, this permits separate seals to be employed between the sample extracting portion and the sample housing portion, and the sample housing portion and the pipe. 
     Preferably, the sample housing portion is operatively associated with a primary valve means, such that the sample housing portion may be fluidly connected to the pipe when the primary valve means is in an open configuration, and the primary valve means seals the pipe against the sample housing portion when the primary valve means is in a closed configuration. This permits the sample housing portion to be removed for maintenance or other reasons whilst maintaining the integrity of the pipe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an isometric view of a sampling device in accordance with the present invention; and 
         FIG. 2  is a cross sectional view of the sampling device of  FIG. 1 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the Figures, there is shown a sampling device  10 . 
     The sampling device  10  extends from a first or inner end  12  adjacent, in use, a pipe (not shown) to a second or outer end  14  remote from the pipe. The first end  12  includes a connecting flange  16  which may be connected to the pipe. A pair of side rails  18  extend from the connecting flange  16  to the second end  14 . At the second end  14  the side rails are connected to an endplate  20 . 
     The sampling device  10  includes a primary valve means located adjacent the first end  12 . In a preferred embodiment, as shown in the drawings, the primary valve means is a knife gate valve  22 . The knife gate valve  22  is bolted to the side rails  18 . 
     The knife gate valve  22  has a central bore  24 . The central bore extends through the knife gate valve  22 , and the connecting flange  16  and into the pipe, and is substantially cylindrical. 
     The sampling device  10  further comprises a sample housing portion  26 . The sample housing portion  26  is substantially cylindrical, with an external diameter sized to be in sliding, sealed relationship with the central bore  24 . The sample housing portion  26  is moveable relative to the pipe, between an active position wherein the sample housing portion  26  extends through the knife gate valve  22  (as shown in  FIG. 2 ) and the connecting flange  16  and an inactive position wherein the sample housing portion  26  locates outside the knife gate valve  22 . The sample housing portion  26  is fluidly connected to the pipe when in the active position. 
     A sample extracting means is actively associated with, and moveable relative to, the sample housing portion  26 . The sample extracting means comprises a sample extracting portion  28 , a first activating rod  30  and a first piston  32 . 
     The sample extracting portion  28  includes a spool  34  fixed between disc-like seals  36 . The disc-like seals  36  are in sliding, sealing engagement with an internal bore of the sample housing portion  26 . An annular space  38  of defined volume is located between the spool  34  and the internal bore of the sample housing portion  26 . 
     The first activating rod  30  is coaxial with, and of slightly smaller diameter than, the disc-like seals  36 . The first activating rod  30  is mounted at an inner end thereof to a rearmost of the disc-like seals  36 . Axial movement of the first activating rod  30  thus causes the sample extracting portion  28  to slide along and within the sample housing portion  26 . 
     The first piston  32  is mounted to an outer end of the first activating rod  30 . The first piston  32  is in sliding engagement with the interior of a first cylinder  40 . The first cylinder  40  is mounted on the side rails  18  so as to be axially movable along the side rails  18 . The first cylinder  40  is fixed at an inner end thereof to the sample housing portion  26 , such that axial movement of the first cylinder  40  along the side rails  18  causes axial movement of the sample housing portion  26  within the central bore  24 . The stroke of the first piston  32  within the first cylinder  40  is sufficiently long that when the first piston  32  is at an outer end of the first cylinder  40  the spool  34  is adjacent an outer end of the sample housing portion  26  (as shown in  FIG. 2 ), and when the first piston  32  is at an inner end of the first cylinder  40  the spool  34  extends beyond the first end  12  of the sampling device  10  into the pipe. 
     The first cylinder  40  is fixed at an outer end thereof to a second cylinder  42 . The second cylinder  42  is mounted to the side rails  18  so as to be axially moveable along the side rails  18  in unison with the first cylinder  40 . 
     The second cylinder  42  has a second piston  44  in sliding engagement with its interior, and a second activating rod  46  associated with the second piston  44 . The second activating rod  46  pushes against the first piston  32 , such that when the second piston  44  moves towards the first end  12  the first piston  32  is caused to move in unison. The second activating rod  46  is not coupled to the first piston  32 , so movement of the second piston  44  towards the second end  14  does not cause movement of the first piston  32 . 
     The stroke of the second piston  44  is smaller than that of the first piston  32 . It is sufficiently long to move the sample extracting portion  28  to a location adjacent the first end  12  of the sampling device  10 , and the inner end of the sample housing portion  26 , but not sufficiently long to move the extracting portion  28  into the pipe. The second cylinder  42  is sealed at an outer end thereof by a cylinder end cap  48 . 
     A threaded rod  50  extends between the end plate  20  and the cylinder end cap  48 . The threaded rod  50  is connected centrally of the cylinder end cap  48  in such a manner that it can rotate freely whilst remaining connected. The threaded rod  50  passes through a centrally located, threaded aperture  52  in the end plate  20  and is fixed to a handle  54 . 
     Rotation of the handle  54  causes the rod to move in an axial direction though the aperture  52 . In turn, this causes the second cylinder  42 , the first cylinder  40  and the sample housing portion  26  to move along the side rails  18  in an axial direction. 
     The knife gate valve  22  is preferably a double knife gate valve, with bleed points located behind each of the knives. 
     The first and second pistons  32 , 44  are preferably pneumatically controlled, with air supply points within the first and second cylinders  40 ,  42  at either end. 
     In the embodiment shown in the drawings, the sampling device  10  is associated with a weld-on adaptor  56 . The weld-on adaptor  56  is arranged to be welded onto the wall of the pipe, and provide a housing against which the connection flange  16  can be bolted. In this embodiment the sampling device includes a forwardly projecting portion  58  which is arranged to locate within the weld-on adaptor  56 . 
     In use, the knife gate valve  22  is moveable between an open configuration and a closed configuration. In the open configuration, the sample housing portion  26  is able to move in an axial direction within the central bore  24  into the active position. 
     When the sample housing portion  26  is in the active position, sampling can take place. 
     When the sample housing portion  26  is in the active position, the sample extending portion  28  can move between three positions: a collecting position, a neutral position and an emptying position. 
     In the collecting position, the spool  34  is located beyond the first end  12  of the sampling device  10 , in other words the spool  34  is within the pipe. As the spool  34  is withdrawn into the sample housing portion  26 , the annular space  38  is filled with a defined volume of sample being collected. 
     In the emptying position, as shown in  FIG. 2 , the sample extracting portion  28  is located towards an outer end of the sample housing portion  26 . The sample housing portion  26  includes at least one aperture (not shown) which fluidly connects with the annular space  38  when the sample extracting portion  28  is in the emptying position. This permits the sample contained in the annular space  38  to be removed by suitable means, such as the action of gravity. 
     In the neutral position, the sample extracting portion  28  is located adjacent the inner end of the sample housing portion  26 , such that it is adjacent the pipe without being in the pipe flow path. 
     The supply of air into the first cylinder  40  causes the first piston  32  to move between inner and outer ends of the first cylinder  40 , thus causing the sample extracting portion to move between the collecting and emptying positions. 
     The supply of air into the outer end of the second cylinder  42  causes the second piston  44  to move to the inner end of the second cylinder  42 , thus causing the first piston  32  to move partially along the first cylinder  40  and the sample extracting portion to move from the emptying position to the neutral position. 
     In use, it is envisaged that the sample extracting portion  28  will normally be maintained in the neutral position. Supply of air into the outer end of the first cylinder  40  will cause it to move into the collecting position for a predetermined period of time. Supply of air into the inner ends of both first and second cylinders will then move the sample extracting portion  28  into the emptying position for a predetermined period of time. Finally supply of air into the outer end of the second cylinder  42  will cause the sample extracting portion to return to the neutral position. 
     When maintenance is required on the sampling device, it will be necessary to move the sample housing portion  26  into the inactive position. This is achieved by turning of the handle  54 , which moves the rod  50 , the first and second cylinders  40 ,  42  and the sample housing portion  26  along the side rails  18  in an axial direction towards the second end  14 . This movement is effected until the sample housing portion  26  is clear of the knife gate valve  22 . The knife gate valve  22  is then moved into the closed configuration, sealing the pipe against the sample housing portion  26 . The sample housing portion  26  may then be extracted for maintenance. 
     Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. For instance, it will be appreciated that the present invention can be performed with only one cylinder, and not using the neutral position.