Abstract:
This invention relates to a pipeline inspection apparatus and to a method of inspecting the internal surfaces of a pipeline using a pipeline inspection apparatus. A pipeline inspection apparatus comprises a main body having a front end and a rear end relative to a direction of travel of the apparatus along a pipeline in use; sealing means for sealing against an internal surface of the pipeline, the sealing means being attached to the main body; an imaging module mounted proximate the front end of the main body, the imaging module comprising a camera and a light source, the light source being arranged to emit light in a direction towards the internal surface of the pipeline, and the camera being arranged such that, in use, the camera captures image data of the internal surface of the pipeline; and control circuitry located within the main body, the control circuitry including a power supply and memory means for storing data captured by said camera, wherein the sealing means forms a seal against the internal surface of the pipeline such that, in use, a fluid flowing along the pipeline applies a driving force to the pipeline inspection apparatus to propel the apparatus along the pipeline.

Description:
BACKGROUND 
     a. Field of the Invention 
     This invention relates to a pipeline inspection apparatus and to a method of inspecting the internal surfaces of a pipeline using a pipeline inspection apparatus. 
     b. Related Art 
     Pipeline Inspection Gauges (Pigs) are known for use in pipeline cleaning and inspection. Typically a Pig is inserted into a pipeline at a particular point (a launching station), is propelled along the pipeline by the flow of fluid through the pipeline and is then removed from the pipeline at a specific point further downstream (a receiving station). 
     The use of Pigs allows pipes to be cleaned and the condition of the pipes to be inspected without stopping the flow of fluid through the pipe. 
     An intelligent Pig, or Smart Pig, can be used to collect data, typically about the condition of the pipeline, while it is travelling along the pipeline. Some prior art devices, for example, have incorporated sensors to detect pipe defects and corrosion. Data from these sensors are then analysed once the Pig has been retrieved from the pipeline. In order to determine the position of any defect within the pipeline, Pigs often also incorporate some form of location monitoring system, or the location of the Pig is monitored by sensors located above-ground. 
     Pipelines often contain fluids at a high temperature, and the fluids may be highly acidic or basic. For these reasons it is necessary to carefully protect any sensors and electronics that are contained within the Pig. 
     It some circumstances it is desirable to capture images of the internal wall of a pipeline. Prior art systems have been developed that can travel along a length of pipeline and which incorporate a video camera. These systems mount the camera on a wheeled apparatus, or tractor, to enable the speed of passage of the camera through the pipeline to be controlled to capture images of sufficient quality for subsequent analysis. 
     Additionally, these systems incorporate a line or tether linking the camera tractor back to a base station. The tether permits a user to control movement of the camera tractor, permits video images to be streamed back to the base station for observation and permits the camera tractor to be retrieved from the pipeline after use. 
     It is an object of the present invention to provide an improved pipeline inspection apparatus that overcomes some of the problems with prior art devices. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a pipeline inspection apparatus comprising:
         a main body having a front end and a rear end relative to a direction of travel of the apparatus along a pipeline in use;   sealing means for sealing against an internal surface of the pipeline, the sealing means being attached to the main body;   an imaging module mounted proximate the front end of the main body, the imaging module comprising a camera and a light source, the light source being arranged to illuminate the internal surface of the pipeline, and the camera being arranged such that, in use, the camera captures image data of the internal surface of said pipeline; and   control circuitry located within the main body, the control circuitry including a power supply and memory means for storing data captured by the camera,   wherein the sealing means forms a seal against the internal surface of the pipeline such that, in use, a fluid flowing along the pipeline applies a driving force to the pipeline inspection apparatus to propel the apparatus along the pipeline.       

     Preferably the light source surrounds said camera to more evenly illuminate the area to be imaged. 
     In preferred embodiments the camera is forward-facing, relative to a direction of travel of the apparatus along a pipeline, and the light source emits light in a direction forwards and outwards, such that the camera captures image data of the internal surface of the pipeline at a distance in front of the apparatus. 
     Preferably the camera is located along a central longitudinal axis of the apparatus. 
     To aid propulsion of the inspection apparatus along the pipeline the sealing means preferably forms a fluid tight seal against the internal surface of the pipeline. 
     The apparatus preferably comprises first and second sealing means spaced apart along the length of the main body between the front and rear ends. 
     The camera is preferably a video camera. Additionally, the light source typically comprises an array of light sources spaced apart around the camera. These light sources are preferably light emitting diodes due to their low power consumption. 
     A face plate is preferably used to seal the main body at the front end, the face plate comprising an inner portion and an outer portion surrounding the inner portion. The inner portion preferably includes a transparent window through which, in use, images are captured by the camera, and the outer portion preferably includes a transparent window through which, in use, light is emitted by the light source. To permit the light to be emitted in a direction forwards and outwards towards the internal surface of the pipeline, the outer portion is preferably sloped relative to the longitudinal axis of the apparatus. 
     The outer portion is preferably sloped at an angle of between 5° and 85° to the longitudinal axis, and is more preferably sloped at an angle between 30° and 80° to the longitudinal axis. 
     In a preferred embodiment of the invention the outer portion is annular and is sloped such that radially inner parts of the outer portion are further forward, relative to a direction of travel of the apparatus along a pipeline in use, than radially outer parts of the outer portion. 
     The inner portion may comprise a side wall that projects forward from the outer portion. A lens of the camera may then be located within this side wall such that the camera is mounted further forward than the light source. 
     The inspection apparatus preferably comprises a capping piece seated around the inner portion. Preferably the capping piece surrounds the side wall of the inner portion. 
     The capping piece preferably has a sloped outer surface such that a first, furthest forward, end of the capping piece has a larger circumference than a second, rear end of the capping piece. In this way the capping piece forms a flared nose of the apparatus. 
     The sloped outer surface of the capping piece assists in deflecting the emitted light outwards, towards the internal walls of the pipeline and away from the centrally located camera lens. The flared capping piece additionally forms a protective member that prevents the face plate from being damaged if the front of the inspection apparatus collides with or scrapes against the internal surface of the pipeline and, similarly, protects any coating on the internal surface of the pipeline from damage caused by contact with the front of the inspection apparatus, especially as the apparatus passes around bends in the pipeline. 
     To further protect the front end of the inspection apparatus and the internal surfaces of the pipeline, the apparatus preferably comprises a guard member surrounding the front end of the main body, the guard member being made from a resilient material. 
     It is advantageous if the inspection apparatus is autonomous and does not require a link or tether back to a base station. For this reason it is preferable if the power supply comprises a battery. The battery may be rechargeable. 
     Additionally it is desirable if the inspection apparatus can be pre-programmed so that a permanent communication link does not need to be maintained between the apparatus and a base station in order to control the apparatus during deployment. As such, it is preferably if the control circuitry comprises means for switching the camera and lights on and off at pre-programmed time points after the apparatus is switched on. 
     Preferably the apparatus comprises means for measuring the speed of the apparatus through the pipeline in use. The measured speed may then be used to control a frame rate of the camera, such that the frame rate may be increased as the speed of the apparatus increases. 
     The apparatus may comprise means for determining the orientation of the apparatus within a pipeline. 
     In some embodiments of the inspection apparatus the sealing means comprises a sealing disc. Preferably the sealing means comprises two or more sealing discs spaced apart along the length of the apparatus. In order to accommodate varying diameters along the length of the pipeline through which the inspection apparatus travels it is desirable for at least one of the sealing discs to have a different diameter to the other sealing discs, such that a seal is maintained between the inspection apparatus and the internal surface of the pipeline. 
     In other embodiments the sealing means may comprise a cup-shaped sealing member having a sloped side wall. 
     Preferably the main body comprises a flange and the sealing means is clamped to the flange. This arrangement enables the sealing means to be easily changed or replaced as required. 
     The length of the inspection apparatus, between the front end and the rear end of the main body, is preferably between 300 mm and 400 mm, to enable the apparatus to pass around tight bends in the pipeline. 
     The invention also provides a method of inspecting the internal surfaces of a pipeline using an inspection apparatus according to the invention, the method comprising:
         pre-programming the control circuitry with a recording schedule;   initiating the inspection apparatus;   deploying the inspection apparatus within a pipeline to be inspected;   retrieving the inspection apparatus from the pipeline; and   downloading image data from the memory means,   wherein, the recording schedule comprises time points, after initiation of the apparatus, at which image data captured by the camera is recorded to the memory means.       

     Preferably the apparatus comprises means for switching the camera on and off and the recording schedule comprises time points after initiation of the apparatus at which the camera is switched on and off. 
     Preferably the apparatus comprises means for switching the light source on and off and for adjusting the intensity of the light source, and the recording schedule comprises data specifying a light intensity at specific time points after initiation of the apparatus. 
     Switching off the camera and light source, or decreasing the intensity of the light source, during deployment of the inspection apparatus allows the power consumption to be minimised. Additionally, the intensity of the light source may be adjusted depending on the type of fluid through which the apparatus moving. 
     In preferred embodiments the inspection apparatus comprises means for measuring the speed of the apparatus through a pipeline, and the method comprises adjusting a frame rate of the camera based on the measured speed of the apparatus. 
     In some embodiments the inspection apparatus may be deployed within a relatively complex network of pipelines. In these situations it is desirable if the inspection apparatus comprises means to log its position within the pipeline. The inspection method then preferably comprises the steps of logging the position of the inspection apparatus during deployment, creating a graphical representation of the geometry of the pipeline, and linking the graphical representation to the image data. This enables the exact location of any regions of interest identified by the image data to be determined. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be further described by way of example only and with reference to the following drawings, in which: 
         FIG. 1  is a perspective view from the front of a pipeline inspection apparatus according to a first preferred embodiment of the present invention; 
         FIG. 2  is a perspective view from the rear of the pipeline inspection apparatus of  FIG. 1 ; 
         FIG. 3  is a plan view from the side of the pipeline inspection apparatus of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the pipeline inspection apparatus of  FIG. 3  along the line IV-IV; 
         FIG. 5  is a perspective view from the front of a pipeline inspection apparatus according to a second preferred embodiment of the present invention; 
         FIG. 6  is a perspective view from the rear of the pipeline inspection apparatus of  FIG. 5 ; 
         FIG. 7  is a plan view from the side of the pipeline inspection apparatus of  FIG. 5 ; and 
         FIG. 8  is a cross-sectional view of the pipeline inspection apparatus of  FIG. 7  along the line VIII-VIII. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 4  show a pipeline inspection apparatus  10  according to a first preferred embodiment of the present invention. The pipeline inspection apparatus  10  comprises a substantially cylindrical main body  12 , sealing means  14  and an imaging module comprising a camera and light sources (not shown in  FIGS. 1 to 4 ). 
     The sealing means  14  are arranged to form a fluid tight seal against an internal surface of a pipeline (not shown) along which the apparatus  10  travels in use. In this way, a fluid, flowing along the pipeline, pushes against a rear surface of the sealing means  14  and main body  12  to force or propel the apparatus  10  along the pipeline. This has the advantage that the inspection apparatus  10  does not require its own drive means to provide motion through the pipeline, thereby reducing the complexity and the power requirements of the apparatus  10 . 
     The main body  12  comprises a tubular housing  22  having a front end  24  and a rear end  26  relative to the direction of travel of the apparatus  10  through a pipeline in use. The main body  12  is preferably made from stainless steel, but may be made from any suitable material able to withstand the high pressures and temperatures encountered in a pipeline. 
     The rear end  26  of the housing  22  is sealed by a cover  28  having a circular end plate  30  and a tubular side wall  32  extending perpendicularly from the perimeter of the end plate  30 . The internal diameter of the cover side wall  32  is substantially equal to the external diameter of the housing  22  such that the rear end  26  of the housing  22  is received within the side wall  32  of the cover  28 . Suitable sealing means such as O-rings may be used to provide a fluid-tight seal between the cover  28  and the housing  22 . 
     The cover  28  is, preferably, removable from the rear end  26  of the housing  22  to permit access to an internal space  23  of the housing  22 , as further described below. 
     The sealing means  14  comprises a first sealing means  14   a  and a second sealing means  14   b  spaced apart along the length of the main body  12 . In particular, the first sealing means  14   a  is located proximate the front end  24  of the housing  22  and the second sealing means  14   b  is located proximate the rear end  26  of the housing  22 . In this embodiment each of the sealing means  14   a ,  14   b  are identical and will be referred to generally in the following description as the sealing means  14 . 
     The sealing means  14  comprises a guiding or alignment disc  33  and a plurality of sealing discs  34 ; each disc  33 ,  34  extending radially outwards around the complete circumference of the housing  22 . The alignment disc  33  and the sealing discs  34  are preferably made from a resilient material, for example a rubber or plastics material, such as polyurethane. The diameter of the alignment disc  33  is slightly less than the diameter of the smallest sealing disc  34  and the thickness of the alignment disc  33  is greater than the thickness of the sealing discs  34 . The function of the alignment disc  33  is to maintain the alignment of the inspection apparatus  10  within a pipeline such that a longitudinal axis  35  of the inspection apparatus  10  remains substantially parallel to a longitudinal axis of the pipeline in the region of the apparatus  10 . 
     In this embodiment the sealing means  14  comprises three sealing discs  34  held apart from each other along the length of the housing  22  by two spacer discs  36  located between the sealing discs  34 . Preferably the thickness of the spacer discs  36  is one to two times the thickness of the sealing discs  34 . In other embodiments any suitable number of sealing discs  34  may be included, together with a corresponding number of spacer discs  36 . 
     In the specific arrangement shown, first and second sealing discs  34   a ,  34   b  nearest the front end  24  of the housing  22  are of a first diameter. The third sealing disc  34   c  in each group of three, furthest from the front end  24 , is of a second, larger diameter than the first and second discs  34   a ,  34   b . The differences in the diameters of the sealing discs  34  allows changes in the internal dimensions of the pipeline to be accommodated, while still maintaining an adequate fluid-tight seal between the sealing discs  34  and internal surfaces of the pipeline to enable propulsion of the inspection apparatus  10  along the pipeline. 
     Preferably the sealing discs  34  are interchangeable such that discs  34  having different diameters may be secured to the main body  12  depending on the internal diameter of the pipeline through which the inspection apparatus  10  will travel. In particular, the diameters of the sealing discs  34  are chosen to provide a close fit between the outer edge of the sealing disc  34  and an internal surface of a pipeline, such that a fluid tight seal is formed between the inspection apparatus  10  and the pipeline. 
     The sealing means  14  are secured to the housing  22  by mechanical fastening means  38 . In this embodiment the housing  22  includes two flanges  40  that are integrally formed with the housing  22  and extend radially from an external surface  42  of the housing  22 ; a first of the two flanges  40   a  being nearer the front end  24  of the housing  22  and a second of the two flanges  40   b  being nearer the rear end  26  of the housing  22 . In a preferred embodiment the first flange  40   a  is located about one third of way along the length of the housing  22  from the front end  24  and the second flange  40   b  is located about two thirds of the way along the length of the housing  22 . 
     Each flange  40  includes a plurality of holes  44  spaced equally apart around the flange  40 , and through which a plurality of bolts  46  extend. The bolts  46  pass through corresponding holes  48  in each of the sealing discs  34  and spacer discs  36  to secure the sealing means  14  to the housing  22 . A ring-shaped clamping plate  49  is positioned on the opposite side of the sealing means  14  from the flange  40  such that the sealing discs  34  and spacer discs  36  are clamped between a respective flange  40  and clamping disc  49  by means of the bolts  46 . Securing the sealing discs  34  to the main body  12  in this way allows the sealing discs  34  to be changed easily to attach sealing discs  34  of a different diameter or to replace worn discs  34 , or for more or fewer discs  34  to be secured to the housing  22  depending on the type of pipeline being inspected. 
     As shown most clearly in  FIGS. 3 and 4 , the first sealing means  14   a  are secured to a front face  50  of the first flange  40   a  and the second sealing means  14   b  are secured to a rear face  52  of the second flange  40   b , such that an elongate central section of the housing  22  without sealing means extends between the first and second flanges  40   a ,  40   b.    
     The front end  24  of the housing  22  is sealed by a face plate  54  having a sloped outer portion  56  and a projecting inner portion  58 . In this example and as shown in  FIG. 4 , the face plate  54  comprises a ring-shaped outer portion  56  that is integral with the tubular side wall  20  of the housing  22  at the outer edge of the outer portion  56 . The outer portion  56  is sloped relative to the longitudinal axis  35  such that radially inner parts of the outer portion  56  are located further forward than radially outer parts, with respect to the direction of travel of the inspection apparatus  10  in use. A circular inner portion  58  is located in the centre of the ring-shaped outer portion  56  and comprises a tubular side wall  60  that is integrally formed with an inner edge of the outer portion  56 . The tubular side wall  60  extends forward of the outer portion  56  substantially parallel to the longitudinal axis  35  of the inspection apparatus  10 . 
     The inner portion  58  of the face plate  54  is sealed by means of an optically transparent window  62 , which is received within the tubular side wall  60 . Typically the window  62  is made from sapphire or another suitable material that is optically transparent and able to withstand the high pressures and temperatures that may be encountered within a pipeline. The window  62 , in this example, is substantially disc-shaped and is co-axial with the main body  12  of the inspection apparatus  10 . 
     A plurality of apertures  64  are formed spaced apart around the outer portion  56  of the face plate  54 . Each of these apertures  64  is also sealed by means of an optically transparent window  66 , preferably made of sapphire or a similar material. Due to the slope of the outer portion  56  of the face plate  54 , an axis of each of the windows  66  in this portion  56  is at an angle to the longitudinal axis  35  of the apparatus  10 . 
     An imaging module is located within a front portion of the internal space  23  of the housing  22  behind the face plate  54 . The imaging module comprises a camera and an array of light sources. The camera is located centrally with respect to the longitudinal axis  35  of the apparatus  10  such that the camera lens  68  is aligned with the transparent window  62  in the inner portion  58  of the face plate  54 . In particular the camera is arranged such that the camera lens  68  locates within the side wall  60  of the inner portion  58 , directly behind the transparent window  62 . 
     The camera&#39;s image sensor (not shown) is then located behind the lens  68  within the tubular housing  22 . 
     The camera is preferably a video camera that is able to capture high definition colour images at a high frame rate. In a preferred embodiment the camera has a resolution of 1280×720 pixels and a frame rate of 30 frames per second. 
     The array of light sources, which in preferred embodiments are light emitting diodes (LEDs), are arranged around the camera. In this embodiment a plurality of LEDs are arranged in a ring surrounding the camera, each of the LEDs being aligned with one of the transparent windows  66  in the outer portion  56  of the face plate  54 . In this way, in use, the LEDs emit light through the transparent windows  66  to illuminate the internal surfaces of the pipeline in front of the inspection apparatus  10 . 
     The light sources and the corresponding transparent windows  66  are preferably formed as close to the outer edge of the face plate  54  as possible to maximise the amount of light illuminating the internal surfaces of the pipeline. Furthermore, the slope of the outer portion  56  of the face plate  54  is such that the light is emitted generally in a direction outwards towards the internal surfaces of the pipeline. This minimises the amount of light that is reflected from materials flowing through the pipeline directly in front of the camera, thereby improving image quality. 
     The inspection apparatus  10  further comprises a capping piece  70  that is seated around the inner portion  58  of the face plate  54 . 
     The capping piece  70  is ring-shaped and has an internal diameter substantially equal to the external diameter of the tubular side wall  60  of the inner portion  58 . In preferred embodiments the capping piece  70  is screwed onto the side wall  60 , so that the capping piece  70  is interchangeable and replaceable. The capping piece  70  is preferably made from a plastics material or aluminium. 
     An outer surface  72  of the capping piece  70  is sloped so that an outer diameter of the capping piece  70  at a first end  74  is smaller than the outer diameter of the capping piece  70  at a second end  76 . The capping piece  70  is secured to the inner portion  58  of the face plate  54  such that the first end  74  of the capping piece  70  is in contact with the outer portion  56  of the face plate  54  and the second end  76  of the capping piece  70  forms a furthest forward face of the inspection apparatus  10 , with respect to a direction of travel in use. In this way, the capping piece  70  forms a flared nose  70  of the inspection apparatus  10 . 
     The capping piece  70  performs two primary functions in use. Firstly, the sloped outer surface  72  deflects light emitted through the transparent windows  66  in the outer portion  56  of the face plate  54  outwards, towards the internal walls of the pipeline and away from the camera lens  68 . Secondly, the flared capping piece  70  forms a protective member or bumper around the projecting inner portion  58  of the face plate  54 . In use, as the inspection apparatus  10  travels around bends in the pipeline, the capping piece  70  prevents the face plate  54  and the transparent windows  62 ,  66  from being damaged if the front of the inspection apparatus  10  collides with or scrapes against the internal surface of the pipeline. Additionally, the capping piece also protects any coating on the internal surface of the pipeline from damage caused by the front of the inspection apparatus  10 , especially as the apparatus  10  passes around bends in the pipeline. 
     For additional protection at the front of the inspection apparatus  10 , a protective guard member or cuff  78  is located around the front end  24  of the housing  22 . The guard member  78  is in the shape of a truncated dome having a central bore  80  within which the front end  24  of the housing  22  is received. In this way, the guard member  78  is ring-shaped having a cylindrical inner surface and a convex curved outer surface. The guard member  78  is secured to the housing  22  such that the base  82  of the truncated dome, which forms the rear face  82  of the guard member  78 , is seated against a front face  84  of the first sealing means  14   a  and is, in particular, in contact with the clamping plate  49 . A plurality of holes  86  are formed through the guard member  78 , aligned with each of the bolts  46  of the first sealing means  14   a  thereby providing access to one end of these bolts  46 . The front end or face  88  of the guard member  78  is substantially aligned with a front edge of the housing  22 . 
     The guard member  78  is preferably made from a resilient material, for example a rubber or plastics material, such as polyurethane. 
     A power supply (not shown in  FIGS. 1 to 4 ) for the camera and light sources is housed within the main body  12  of the inspection apparatus  10 . In a preferred embodiment the power source comprises one or more batteries. 
     The main body  12  also houses programmable control circuitry (not shown in  FIGS. 1 to 4 ) for the camera and light sources, together with memory means. The memory means is used to store image data captured by the camera, which is retained on board the inspection apparatus  10 . In preferred embodiments the apparatus  10  does not transmit the collected image data to a base station or similar during deployment of the apparatus  10 , as this transmission requires additional power resources. 
     The on-board power supply and programmable control circuitry, together with the means to store image data on the memory means within the apparatus  10 , means that the inspection apparatus  10  is effectively autonomous and does not need to be tethered. 
     Before deployment of the inspection apparatus  10  through a pipeline, the control circuitry is pre-programmed with an image recording schedule. The recording schedule comprises a series of time points, from when the inspection apparatus  10  is initiated, at which, for example, the camera will switch on and off, the light sources will switch on and off, and the memory means will start and stop recording and storing the collected image data. The recording schedule may also include time points at which the brightness of the light sources is increased or decreased and, in these embodiments, the control circuitry also includes means for adjusting the brightness of the light sources. 
     The removable cover  28  at the rear end  26  of the housing  22  provides access to the power supply, control circuitry and the memory means. This permits connections to be made to recharge the power supply, program the control circuitry and download data from the memory means. In a preferred embodiment it is desirable if a connection may be made directly between the control circuitry and memory means and a computer, for example by means of a USB connection. 
     In use, before deployment, the inspection apparatus  10  is pre-programmed with a recording schedule. For example, the schedule may comprise the following information: 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Time from 
                   
                   
               
               
                 initiation 
                 Camera 
                 Light 
               
               
                 (minutes) 
                 State 
                 Level 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2 
                 ON 
                 100% 
               
               
                 20 
                 OFF 
                  0% 
               
               
                 60 
                 ON 
                  50% 
               
               
                 70 
                 OFF 
                  0% 
               
               
                 120 
                 ON 
                  35% 
               
               
                 150 
                 OFF 
                  0% 
               
               
                   
               
             
          
         
       
     
     The inspection apparatus  10  is then switched on or initiated just before it is deployed within the pipeline to be inspected. The inspection apparatus  10  then travels along the pipeline due to a flow of fluid through the pipeline. 
     While the inspection apparatus  10  is travelling through the pipeline the control circuitry operates the camera, light sources and memory means according to the recording schedule. 
     Because the speed of movement of the inspection apparatus  10  through the pipeline is determined solely by the speed of flow of the fluid through the pipeline, the time at which the inspection apparatus  10  is passing certain points in the pipeline can be easily determined before the inspection apparatus  10  is deployed. As such, the recording schedule based simply on a time-since-initiation may be used to activate the camera and light sources only when the inspection apparatus  10  is passing known points of interest. In this way it is not necessary to keep the camera and lights switched on for the whole time that the inspection apparatus  10  is deployed, which reduces power consumption. Additionally, it is not necessary to constantly monitor the location of the inspection apparatus  10  and manually activate the camera and light sources when the inspection apparatus  10  passes points of interest, by means of transmissions to and from the apparatus  10 . 
     The inspection apparatus  10  may, however, include a tracking system that enables the apparatus  10  to be located in the pipeline. This tracking system may emit tracker signals intermittently. In other embodiments the inspection apparatus  10  may be tracked by sensors positioned above-ground that detect the position of the apparatus  10  within the pipeline. 
     In preferred embodiments of the apparatus  10  the control circuitry includes a sensor for monitoring the speed at which the apparatus  10  is travelling through the pipeline and means for adjusting the camera frame rate based on the measured speed. In this way the frame rate of the camera may be increased when the apparatus  10  is travelling at higher speeds to reduce blurring of the captured images. 
     At the end of the deployment, the inspection apparatus  10  is retrieved from the pipeline. Image and other data, for example positional data, is then downloaded from the memory means of the apparatus  10  to a suitable computer. The video or still images captured by the camera can then be analysed to identify areas of concern or points of interest within the pipeline. If positional data is also recorded by the inspection apparatus  10 , for example by an on-board odometer, this can be used to determine the exact location of these areas of concern or points of interest. Alternatively, the location of these areas may be determined based on the time after deployment at which the image was captured. 
     In some embodiments it is also desirable if the inspection apparatus  10  comprises means to detect its orientation within a pipeline. This orientation data is then, preferably, linked to the recorded image data such that, during analysis of the image data, the exact position of an area of interest may be determined within a pipeline. For example, the location of an area of corrosion may be determined not only in terms of its location along the length of the pipeline, but also whether the area of corrosion is at the top or bottom of the pipeline or a side of the pipeline. This information allows any remedial action that is subsequently taken to be more precisely tailored to minimise expense and disruption to the pipeline operations. 
     The inspection apparatus  10  may also include electronic accelerometers and gyroscopes to log the position of the inspection apparatus  10  during deployment. Data collected by the accelerometers and gyroscopes can then be used to create a graphical representation of the geometry of the pipeline. This representation may then be linked to the video images of the internal surface of the pipeline. 
       FIGS. 5 to 8  show a pipeline inspection apparatus  110  according to a second preferred embodiment of the present invention. The pipeline inspection apparatus  110  is substantially the same as the inspection apparatus  10  of the first embodiment and corresponding features have been indicated by reference numerals incremented by 100. 
     All of the components of the inspection apparatus  110  are identical to those of the first embodiment, except for the sealing means  114 . 
     In this embodiment, the sealing means  114  comprises a first sealing means  114   a  and a second sealing means  114   b  spaced apart along the length of the main body  112 , as in the previous embodiment. In this example, however, each sealing means  114  comprises a single cup-shaped sealing member  134 . 
     The sealing member  134  comprises a substantially flat ring-shaped base portion  90  and a sloped side wall  92  extending from and integral with an outer edge of the base portion  90 . The side wall  92  extends completely around the base portion  90  so as to define a central recess  94  in the sealing member  134 . The side wall  92  is sloped such that an outer diameter of the sealing member  134  is smallest at the base portion  90  and increases towards a free edge  96  of the side wall  92  furthest from the base portion  90 . Furthermore, the thickness of the side wall  92  decreases from a base of the side wall  92  proximate the base portion  90  towards the free edge  96  of the side wall  92 . 
     The sealing member  134  is preferably made from a resilient and flexible material, for example a rubber or plastics material, such as polyurethane. 
     The sealing means  114  are secured to the housing  122  by mechanical fastening means  138 . As in the first embodiment, the housing  122  includes two flanges  140  that extend radially from an external surface  142  of the housing  122 ; a first of the two flanges  140   a  being nearer a front end  124  of the housing  122  and a second of the two flanges  140   b  being nearer a rear end  126  of the housing  122 . 
     Each flange  140  includes a plurality of holes  144  spaced equally apart around the flange  140 , and through which a plurality of bolts  146  extend. The bolts  146  pass through corresponding holes  148  in each of the base portions  90  of the sealing members  134 , to secure the sealing members  134  to the housing  122 . 
     The orientation of the sealing members  134  when secured to the housing  122  is such that the base portions  90  are substantially perpendicular to the longitudinal axis  135  of the housing  122 , and the side walls  92  extend outwards and rearwards with respect to the housing  122  and the direction of travel of the inspection apparatus  110  in use. 
     The size and shape of the sealing members  134  is designed such that the free edge  96  of the side walls  92  makes contact with the internal surfaces of the pipeline during deployment of the inspection apparatus  10  to provide a fluid-tight seal. The shape of the side walls  92  and the material from which they are made enables the side walls  92  to flex to accommodate irregularities and changes in diameter of the pipeline. 
     The sealing means  114  further comprise ring-shaped spacer discs  136 . In the first sealing means  114   a , the spacer discs  136  are located between the flange  140   a  and the base portion  90  of the first sealing member  134   a , within the recess  94 . The spacer discs  136  and sealing member  134   a  are secured to the flange  140   a  in front of the flange  140   a , such that the spacer discs  136  are in contact with a front face  150  of the flange  140   a . The bolts  146  pass through the flange  140   a , the spacer discs  136 , the sealing member  134   a  and a clamping plate  149 , which is in contact with a face  98  of the base portion  90  of the sealing member  134   a , to clamp the sealing means  114   a  to the flange  140   a . In this embodiment, the thickness of the spacer discs  136  is such that the flange  140   a  lies substantially in the same plane as the free edge  96  of the side wall  92  of the sealing member  134   a.    
     In the second sealing means  114   b , the spacer discs  136  are also located in contact with the base portion  90  of the sealing member  134   b  within the recess  94 . The spacer discs  136  and sealing member  134   b  are secured to the flange  140   b  behind the flange  140   b , relative to a direction of travel of the inspection apparatus  110  in use, such that a face  98  of the base portion  90  of the sealing member  134   b  is in contact with a rear face  152  of the flange  140   b . The bolts  146  pass through the flange  140   b , the sealing member  134   b , the spacer discs  136  and a clamping plate  149 , which is in contact with the spacer discs  136 , to clamp the sealing means  114   b  to the flange  140   b.    
     In this way, the sealing members  134  of this embodiment are secured to the housing  122  in substantially the same way as the sealing discs  34  are secured to the housing  22  in the first embodiment. In particular, the use of spacer discs  36 ,  136  means that the cup-shaped sealing members  134  are completely interchangeable with the sealing discs  34 , and either may be chosen depending on the circumstances in which the inspection apparatus  10 ,  110  is being deployed. 
       FIG. 8  shows the location of the imaging module  2 , power supply  4  and control circuitry  6  within the housing  122 . As can be seen, the imaging module  2  is located at the front of the housing  122  behind the face plate  154 , the power supply  4  is in the form of a plurality of batteries  4  that are positioned along the length of the housing  122 , and the control circuitry  6  is located towards the rear of the housing  122 . 
     In some embodiments of the present invention, the inspection apparatus  10 ,  110  includes one or more side view cameras for capturing additional high resolution images of the internal surfaces of the pipeline. In embodiments in which two or more side view cameras are included, the images captured by these cameras may be ‘stitched’ together during subsequent post-processing and analysis of the images to create a complete 360° view of the surface of the pipeline. These images may be used for corrosion analysis for example. 
     The length of the inspection apparatus  10 ,  110  is preferably between 300 mm and 400 mm, and more preferably between 300 mm and 350 mm. The relatively short length of the inspection apparatus  10 ,  110  compared to known inspection devices enables the apparatus to negotiate tight bends in the pipeline. In particular the inspection apparatus  10 ,  110  is designed to be able to pass around 1.5 D bends (1.5 D means that the centreline radius of the bend is 1.5 times the nominal pipe diameter). In a particular embodiment of the invention, the inspection apparatus  10 ,  110  is designed to pass through 1.5 D bends in a 6″ (15 cm) diameter pipe. 
     The inspection apparatus of the present invention, therefore, provides an improved pipeline inspection apparatus that overcomes some of the problems with prior art devices.