Abstract:
A pig for evacuating pipelines is disclosed. The pig includes a body of a deformable material having an outer surface configured to contour to a pipeline to be evacuated. At least a portion of the deformable material is impregnated with a quantity of magnetic or magnetizable metallic particals.

Description:
This is a continuation of application(s) Ser. No. 09/007,639 filed on Jan. 15, 1998 now U.S. Pat. No. 6,176,938. 
    
    
     FIELD OF THE INVENTION 
     The present invention concerns the evacuation of pipelines and particularly but not exclusively to the cleaning of pipelines by removal of material from therewithin. 
     DESCRIPTION OF THE PRIOR ART 
     Pipelines are used to convey fluid materials in many industrial environments. The production of many liquid products especially on an industrial scale, including chemicals, foodstuffs, beverages, pharmaceuticals, oils, cosmetics to name but a few, involves conveying product and/or substrate/ingredients for the product along pipelines. 
     Often it is required to clean the inside of such pipelines or at least to remove most of the material from therewithin. Cleaning is important for example when a different material is to be conveyed through a pipeline and contamination must be avoided. In many situations it is imperative that the pipeline is emptied completely of one material before another material can be conveyed therealong. It is also often desirable to recover material remaining in a pipeline, for example after a production run, to mitigate problems of wastage. The term “evacuated” is used in this specification to refer to the removal of material from a pipeline, and particularly to the removal of all or substantially all product from a pipeline or section of pipeline. 
     One known method of evacuating pipelines is to force a device, often termed “a pig” through the pipeline under pressure from a propellant liquid or gas. Known pigs push material along a pipeline and out through a designated outlet in the pipeline, in many instances for collection for use or disposal. However, known designs of pig comprise a quite rigid and hard body. This means that the pig has to be diametrically significantly smaller than the inside diameter of a pipeline for it to be able to move around bends in the pipeline during use. Therefore with such known designs of pig, material is often left lining the inside of a pipeline thereby providing incomplete and often unsatisfactory evacuation of material. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to obviate or mitigate the aforesaid disadvantage of the prior art. 
     According to the present invention there is provided a pipeline evacuating device comprising a first relatively rigid portion and a second relatively deformable portion arranged to be compressable against the rigid portion when the device is forced through a pipeline containing material to be removed by the reaction of the material in the pipeline against the force of movement of the device, the compression causing the second portion to deform to at least substantially slidingly seal against the inside of the pipeline whereby to provide efficient evacuation of material from the pipeline as the device is forced therealong. 
     Preferably the second portion is resiliently deformable such that upon removal from pressurized conditions the pig returns to a non-compressed, relaxed condition. Preferably the second portion is arranged to be compressable to increase the relaxed width of the second portion in a direction generally perpendicular to the intended direction of movement of the device in use along a pipeline. Preferably the second portion is deformable desirably generally symmetrically, to form a seal, desirably in the form of a sealing collar, around the device to provide for substantially complete slidable sealing around the device in a pipeline. Preferably the force(s) exerted onto the pipeline by the second portion is/are greater than those exerted by the first portion. Preferably the second portion extends substantially across the width of the first portion, to provide for a sealing collar generally at one end of the first portion. Preferably the second, deformable portion is located on the one end which in use leads the device to provide for compression of the second portion between the fluid in the pipeline to be removed and the first rigid portion. 
     Preferably the device is generally elongate, and operable in the longitudinal direction. The device may taper at said one leading end but desirably comprises a surface generally perpendicular to the direction of movement of the device on which the reactive forces of the material act in use. 
     Preferably the first rigid portion is magnetic and/or magnetizable to facilitate detection of the location of the device in a pipeline. The rigid portion may comprise the same or similar material, desirably plastics material, as the second deformable portion, and with magnetic or magnetizable additive(s) therein which additive(s) may contribute to the relative rigidity of the first portion. The additive(s) may be metallic or metal compounds perhaps in powder and/or granular form. The first portion may be of greater diameter than the second portion when the device is in the relaxed condition. 
     Preferably the second portion is firmly attached to the first relatively rigid portion, and may be fused, and/or chemically bonded, thereto. 
     The first and second portions may be encased in a flexible outer sheath which sheath is preferably relative tough to provide protection of the first and second portions. 
     The device may comprise a further deformable portion which further portion is desirably arranged to be compressable along with the said deformable portion to provide a second slidable seal. Preferably the further second portion is provided at the other, rear end of the device to be deformable through compression between the means providing the force for movement of the device and the relatively rigid portion. Preferably the further second portion is similar to the said first second portion. The device may be generally symmetrical and preferably bidirectionally operable. 
     According to a further aspect of the present invention there is provided a method of evacuating material, such as fluid from a pipeline, the method comprising driving an evacuating device substantially as described in any of the preceding seven paragraphs down a pipeline containing material to be removed, the driving force being sufficient to cause the second, deformable portion of the device to be compressed between said driving force and the reactive force of the material in the pipeline to deform to form a substantially sliding seal on the inside of the pipeline and move the device along the pipeline to force fluid before the device along the pipeline for removal. 
     The driving force may be provided by pressurised air supplied into the pipeline behind the device. Alternatively or additionally the driving force may be provided by pressurised liquid, such as a cleaning liquid. 
     According to a still further aspect of the present invention there is provided a method of manufacture of a pipeline evacuating device substantially as hereinbefore described, the method comprising moulding a first rigid portion adjacent a second relatively deformable portion, curing the portions together, encasing the portions in a protective sheath and curing the sheath on the portions. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Curing may be effected by heat treatment. Magnetic and/or magnetizable additive(s) may be added to the first portion when in a pre-moulded liquid state, which additive(s) at least contribute to the relative rigidity of the first portion. 
    
    
     An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which: 
     FIG. 1 is a diagrammatic cross-section of a pipeline evacuating device according to the present invention; 
     FIG. 2 is a diagrammatic cross-section of the device of FIG. 1 in use in a pipeline in accordance with the present invention; and 
     FIG. 3 is a diagrammatic representation of a pipeline system being evacuated by the device of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     With reference to the drawings a pipeline evacuating device  10 , hereinafter termed a pig, comprises a first relatively rigid portion  12  and a second relatively deformable portion  14  arranged to be compressable against the rigid portion  12  when the device  10  is forced through a pipeline  16  containing fluid F (FIGS. 2 and 3) to be removed, by the reaction of the fluid F against the forced movement of the device  10  along the pipeline  16 , the compression causing the second portion  14  to deform to at least substantially slidingly seal against the inside of the pipeline  16  whereby to provide efficient evacuation of the fluid F from the pipeline as the device  10  is forced therealong. 
     In more detail, the rigid portion  12  is located generally centrally in the generally elongate pig  10 . The relatively rigid portion  12  comprises a plastics material in which is dispersed a magnetic or magnetizable material, such as strontium ferrate. At either end  18 , 20  of the rigid portion  12  is a relatively deformable portion  14 . Each deformable portion  14  comprises the same or similar plastics material to that of the rigid portion  12 , but does not comprise any magnetic or magnetizable additives. Upon curing (as described later) the rigid portion  12  and the respective deformable portions  14  bond together. 
     A generally cylindrical outer protective sheath  22  encases the portions  12 , 14 , and is of plastics material again the same or similar to that of the portions  12 , 14 , such that upon curing, the device is essentially as integral unit. 
     In its natural, relaxed condition, the pig  10  is of generally cylindrical configuration, as shown in FIG. 1, having a substantially straight longitudinal cylindrical portion  24  principally defined by the rigid portion  12  but which is defined at its ends by a part  25  of the respective deformable portions  14 . The parts  25  are slightly tapered to give the device a slightly belled shape. The pig  10  tapers at each end  26 , 28  along a respective frusto conical surface  30 , 32  extending from the ends of the cylindrical portion  24  toward a respective end surface  34 , 36  which surfaces are both generally perpendicular to the longitudinal axis of the pig  10 . 
     It is important that the cylindrical portion  24  of the pig  10  is defined at its ends by a part  25  of the respective deformable portions  14  for efficient function of the pig  10  as these parts  25  form, in use, the seal against the inside of a pipeline as will be described. 
     As mentioned above, the material of manufacture of the portions  12 , 14  and the outer sheath  22  are the same or of the same chemical family. The plastics material for the rigid portion  12  is mixed with a magnetic or magnetizable additive such as strontium ferrate. The plastics material making up the respective deformable portions  14  does not comprising any such additive. The respective portions  12 , 14  are moulded and cured by heating. The curing process bonds the portions  12 , 14  together. The flexible outer sheath  22  which may comprise additives to increase its protective qualities is then located around the portions  12 , 14 . The pig  10  is then further heated to bond the sheath  22  and portions  12 , 14  together. 
     Once the pig  10  has been moulded, it is placed in a magnetic field, such as that produced by an electrical coil (not shown). The magnetic field is of sufficient strength to induce the desired permanent magnetic characteristics in the rigid portion  12  of the pig which magnetic characteristics enable detection of the location of the pig  10  in a pipeline  16  with appropriate detecting apparatus. Of course the deformable portions  12 , 14  comprise no magnetic additives and are therefore non-magnetic and remain relatively soft and deformable. 
     In use, a pig  10  according to the present invention is used to evacuate fluid, and usually liquid, from within a pipeline  16 . The material evacuated is often a product of an industrial process, and efficient removal of residual product in a pipeline provides for more economical industrial processes. Further, efficient evacuation of product from pipelines provides for more efficient cleaning of that pipeline for subsequent use. 
     Referring to FIG. 3 in particular, a pig  10  is shown in use evacuating a pipeline  16  of liquid material F. The pipeline  16  is normally used to convey liquid material F (which for the purpose of illustration only will be considered to be a liquid product that is being heat treated in the pipeline  16 ) from an inlet conduit  38  which supplies the product F from downstream, to a receptacle  40 . A valve arrangement  42  is provided at the intersection of the inlet conduit  38 , the entrance to the pipeline  16  and a pig storage housing  44 . Pig detecting means  46 , 48  are provided to detect the presence or absence of a pig  10  in the storage housing  44  and at the output end  50  of the pipeline  16 , respectively. Heating means (not shown) is provided to heat treat the liquid F in the pipeline, for example to pasteurise it. 
     A propellant fluid source  52 , such as a compressed air generator or pressurised cleaning liquid source, is connected via a conduit  54  to the storage housing  44  for selective supply of propellant fluid thereto to drive a pig  10  located in the housing  44  down the pipeline  16  as will be described. 
     During normal operation of the pipeline  16 , the valve arrangement  42  connects the inlet conduit  38  to the pipeline  16  to allow the flow of liquid F pumped by the pump  56  from the conduit  38  along the pipeline  16 . With the valve arrangement  42  in this condition (as shown in dotted outline in FIG.  3 ), the storage housing  44  comprising a pig  10  (as shown in dotted outline) is isolated from the pipeline  16  and the propellant fluid source is de-activated. 
     In this example, the liquid F is pasteurised and it is pumped along the pipeline. Of course it is not relevant to the present invention what treatment, if any, is given to fluid in the pipeline prior to evacuation. 
     Upon completion of a production run for the liquid F, the pump  56  is deactivated and the valve arrangement  42  turned to the position shown in FIG. 3 wherein the conduit  38  is isolated from the pipeline  16 , and the storage housing  44  is placed in communication with the pipeline  16 . 
     The propellant fluid source  52  is then activated, and pressurised propellant fluid (indicated by the arrows X) is forced down the conduit  54  into the housing  44  wherein it acts upon the pig  10  to drive it down, through the valve arrangement  42  and along the pipeline  16 . 
     As the force of the propellant fluid acts on the pig  10  (as shown diagrammatically in FIG. 2) to force it along the pipeline  16  to thereby drive the fluid F in the pipeline out through the output end  50 , the reaction or resistance of the fluid F to such movement acts on the leading end  26 , and particularly against the surface  34  and thereby compresses the relatively soft leading deformable portion  14  against the relatively rigid portion  12 , to cause the deformable portion  14  to bell out or expand particularly in the region of the parts  25  in a lateral direction to form a sealing collar  37  that presses against the inside surface of the pipeline  16  to provide a slidable seal thereagainst. The sealing collar  37  presses against the inside of the surface harder than the relatively non-deformable parts of the device  10 . 
     Similarly at the rear end  28 , the force of the propellant fluid on the end  28  and particularly the surface  36  compresses the deformable portion  14  against the rigid portion  12  to cause the rear deformable portion  14  to bell out to form a sealing collar  37  which presses against the inner surface of the pipeline  16  to provide a second, slidable seal against the inside of the inside of the pipeline  16 . The force of the propellant fluid F is sufficient to drive the pig  10  in this deformed condition along the pipeline  16 , with the respective compressed portions  12  dragging along the inner surface of the pipeline  16 , thereby ensuring that little or no residue of liquid F is left behind the pig  10  and hence providing efficient evacuation of fluid F from the pipeline  16 . The propellant fluid F may be cleaning fluid which further cleans, particularly on a microbial level, the inside of the pipeline  12  following the movement of the pig  10  along the pipeline. 
     It will be appreciated that the relative softness of the deformable portions  14  allows the respective portions  14  to further deform to enable the pig  10  to move around bends and the like in the pipeline  16 . The rigid portion  12  is necessarily spaced from the inside of the pipeline  16  sufficiently to provide movement around bends. 
     Further, because the external diameter of the pig  10  is sufficiently less than the internal diameter of the pipeline in which it is intended for use, the pig  10  is readily launched into a pipeline for use. 
     As mentioned above, the magnetic characteristics of the rigid portion  12  enable the position of the pig  12  in the pipeline  16  to be determined, and once the pig  10  reaches the end  50  of the pipeline  16 , the second detector  48  signals this, and the propellant fluid source can be de-activated. The fluid F evacuated from the pipeline  16  is collected in the receptacle  40  for use or disposal as appropriate. 
     It will be appreciated that the pig  10  according to the present invention provides for more efficient evacuation and cleaning of pipelines  16  than is provided by conventional designs of pig, and the pig  10  could be used to evacuate gases from pipelines  16  as well liquids under appropriate conditions. 
     Various modifications may be made without departing from the scope of the present invention. For example the rigid portion may be non-magnetic/non-magnetizable. 
     Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.