Abstract:
The invention relates to a machine for coating the interior of a pipe. The machine can be pulled through and positioned within a pipe or pipeline by a internal pipe tractor, and can be used to apply viscous liquids, including two part epoxies and urethanes, to the interior wall of the pipe. The machine is typically used for the overcoating of portions of pipe having defects in their internal coatings, for example, at their girth welds.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/367,652 filed Jul. 26, 2010 under the title INTERNAL GIRTH WELD LIQUID COATING CART. 
         [0002]    The content of the above patent application is hereby expressly incorporated by reference into the detailed description hereof. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The invention relates to a machine for coating the interior of a pipe. The machine can be pulled through and positioned within a pipe or pipeline by a internal pipe tractor, and can be used to apply viscous liquids, including two part epoxies and urethanes, to the interior wall of the pipe. The machine is typically used for the overcoating of portions of pipe having defects in their internal coatings, for example, at their girth welds. 
       BACKGROUND OF THE INVENTION 
       [0004]    Metal pipelines, for example, oil or gas pipelines, are typically coated, both on the interior and the exterior, to protect the metal surface from corrosion or other undesirable effects. Coatings can include a wide variety of plastics, including polyethylene, polyurethane, or epoxy coatings. The exterior surface is typically coated to prevent corrosion due to contact with air or water, including salt water, for example, in transatlantic pipelines. The interior surface can also be coated, since contact with liquid material, for example, gas condensate, inside the pipeline can promote corrosion from within. 
         [0005]    Typically, pipes used in pipelines are coated at the factory with a protective coating. The coating typically does not extend to the very ends of the pipes, since the metal must be exposed for attachment in the field. The pipes are then welded together at their ends, in the field, using girth welds; because these girth welds, and the surrounding surfaces, are typically exposed metal surfaces, they must then be coated, again, in the field. Exterior coatings are often in the form of a shrink wrap sleeve which is applied to the exterior surface of the exposed pipe, and shrunk into place using the application of heat. The interior surface of the exposed portion of the pipe surrounding (and including) the girth weld is often coated utilizing a preheated, liquid state plastic, utilizing a brush, or the application of a powder onto a pre-heated surface, said powder then melting to form a generally uniform coating. 
         [0006]    As can be readily appreciated, once a pipeline is in place, access to the girth welds interspersed along its length can be problematic, especially on the interior of the pipe. Accordingly, internal pipe tractors have been developed, which can run along the inside of a pipe. The internal pipe tractors have wheels that run along the inside wall of the pipe, and can be controlled remotely, by an operator outside of the pipe. These internal pipe tractors can perform a variety of functions. For example, an internal pipe tractor can be hitched to an inspection cart, having lights and cameras for the visual inspection of the interior surface of a pipe. The inspection cart can identify minute defects in the pipe coating (known as holidays), for example, along the girth weld. Often these holidays are as small as a pin prick, but can be the point at which corrosion occurs. 
         [0007]    Liquid coating carts are known in the art. For example, U.S. Pat. No. 5,181,962 describes a cart having an air compressor, a liquid coating material reservoir, and a rotating spray gun. The cart can be wheeled to a holiday/defect location using a standard internal pipe tractor. Then the rotating spray nozzle can be activated, such that liquid is sprayed through the spray gun utilizing the force of the compressed air, while the spray gun rotates. This coats the interior of the pipe with the liquid coating material. However, this type of liquid coating cart can only be used with liquid coating materials of low viscosity, and suffers from issues related to the clogging of the spray gun, which can be extremely inconvenient when the machine is several hundred feet away from the nearest operator. 
       SUMMARY OF THE INVENTION 
       [0008]    According to one embodiment of the present invention is provided a liquid coating cart for coating an inside surface of a pipe, comprising: (a) a frame, having a rear end and a front end, and wheels capable of displacing the frame along the inside surface of the pipe; (b) a controller, capable of receiving instructions from a remote interface; (c) a cartridge containment block, capable of housing at least two fluid cartridge, each of said fluid cartridges containing fluid for coating the inside surface of the pipe; (d) a housing for a static mixer, located in or proximal to the cartridge containment block, and situated such that when fitted with a static mixer having a feeding end and a nozzle end, a channel is formed between the fluid cartridges and the feeding end of the static mixer, through which the fluid can be displaced; (e) a ram system capable of displacing said fluid out of said fluid cartridges and into said static mixer, and then through said static mixer and out of said nozzle end, said ram system controlled through the controller; (f) a fluid dispensing unit, comprising a cup having an interior bottom and an interior sidewall, said cup connected to a cup drive motor capable of rotating said cup around an axle connected to its interior bottom, said cup drive motor controlled through the controller; (g) said fluid dispensing unit capable of displacement between two positions, an operating position wherein the cup is proximal to the nozzle end of the static mixer such that fluid displaced from the static mixer enters the cup, and a transport position wherein the cup is further from the nozzle end of the static mixer such that fluid displaced from the static mixer does not enter the cup; said displacement controlled through the controller. 
         [0009]    In certain embodiments, the liquid coating cart further comprises a waste catch situated below the nozzle end of the static mixer such that, when the fluid dispensing unit is in the transport position, fluid displaced from the nozzle end of the static mixer falls into said waste catch. 
         [0010]    In certain embodiments, the liquid coating cart further comprises a platform, capable of linear displacement along the frame by means of a motor controlled by the controller, said platform housing the cartridge containment block, the ram system, and the fluid dispensing unit, which extends therefrom. 
         [0011]    In certain embodiments, the liquid coating cart further comprises a solvent containment area within or proximal to the cartridge containment block, and capable of cleaning the static mixer nozzle by dispensing solvent through said static mixer and out of said nozzle end, said dispensing of solvent controlled by the controller. 
         [0012]    In certain embodiments, the controller is a programmable logic controller or a personal computer based controller. 
         [0013]    In certain embodiments the liquid coating cart further comprises a coupling at or near the rear end, for providing mechanical and electrical connection to a tractor cart. 
         [0014]    In certain embodiments, the liquid coating cart further comprises an air blowoff unit capable of blowing air to displace dust or debris from the inside surface of the pipe, said air blowoff unit controlled by the controller. 
         [0015]    In certain embodiments, the liquid coating cart further comprises a camera and a light source, mounted onto the frame and capable of transmitting images of the interior surface of the pipe, said camera and light source controlled by the controller. 
         [0016]    In certain embodiments, images are transmitted to the remote interface via the controller. 
         [0017]    In certain embodiments, the wheels are adjustable for fitting the liquid coating cart into pipes of different diameters. 
         [0018]    In certain embodiments, the liquid coating cart further comprises a distance measuring encoder wheel capable of measuring a distance travelled along the pipe, and sending information relating to said distance travelled through the controller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a top view of a liquid coating cart made in accordance with an embodiment of the invention. 
           [0020]      FIG. 2  is a side view of the liquid coating cart of  FIG. 1 . 
           [0021]      FIG. 3  is a section view of the section B-B as shown in  FIG. 2 . 
           [0022]      FIG. 4  is an auxiliary view of the liquid coating cart of  FIG. 1 . 
           [0023]      FIG. 5  is a front view of the liquid coating cart of  FIG. 1 , shown within a pipe. 
           [0024]      FIG. 6  is a schematic view of the components of the liquid coating cart. 
           [0025]      FIG. 7  is a photograph of the cup and other elements of a liquid coating cart according to the invention. 
           [0026]      FIGS. 8A and 8B  are schematic representations of two possible control systems for the liquid coating cart. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    Referring now to  FIGS. 1-4 , a liquid coating cart  28  has a frame  30  for containing many of its components. Attached to the frame  30  at a rear end  31  are rear wheels  34 , which are capable of resting on the inside surface of a pipe  70 . Attached proximal to a front end  33  are front wheels (not shown, but placed at or near front wheel placement  32 ). The front wheels are far enough back from the front end  33  so that they are not sprayed by fluid leaving cup  54  (described further, below). 
         [0028]    Also at rear end  31  is coupling  36  for mechanically and electrically connecting the liquid coating cart  28  to a tractor cart used in the field (not shown), for example, a battery powered tractor cart. Typically, the tractor cart has a control system and communications antenna, and the electrical connection at coupling  36  between the liquid coating cart  28  and the tractor cart provides a common network between the tractor cart, the liquid coating cart, and a remote control unit (not shown) on which an operator can control the operations of the carts. Optionally (not shown), the liquid coating cart  28  may be mechanically and electrically connected but have its own, separate, control system and communications antenna (not shown), with the electrical connection simply used to provide power to the components of the liquid coating cart  28 . Alternatively, but not shown, the coupling may be optional, with the liquid coating cart having its own power supply, control system, and communications antenna, and not relying on a tractor cart. 
         [0029]    The liquid coating cart  28  is equipped with a controller  38 , such as a programmable logic controller, capable of controlling the various motors and elements of the liquid coating cart  28 , as described further below. The controller  38  can receive instructions from the remote control unit (not shown) via the tractor cart communications antenna, and can send information received from the various elements of the liquid coating cart  28  (for example, the camera  42 , described further below) in the same manner. Alternatively, the controller  38  can receive instructions from the remote control unit (not shown) via its own communications antenna (not shown), on the liquid coating cart  28 . 
         [0030]    The frame  30  also houses camera  42  and lights  44 , which can be used to locate holidays or defects in the pipe coating. Camera  42  can send image signals to a user through the programmable logic controller  38 , and the communications antenna of the tractor cart. Camera  42  can be used to confirm that the liquid coating cart  28  is working properly, and can ensure that sufficient coating of the pipe has occurred. 
         [0031]    Frame  30  also houses platform  41  which can be displaced laterally in relation to frame  30  by electric linear activator  40 . Attached to platform  41  is a heated cartridge containment block  50 , which houses one or more (as shown, two) optionally disposable, fluid cartridges (not shown). The fluid cartridges contain the fluid that is to coat the inside of the pipe. The cartridge containment block  50  is capable of heating the fluid contained in the fluid cartridges. Fluid contained in the fluid cartridges is forced out by rams  46  which are displaced using linear stepper drive  48 . Optionally, there are multiple rams  46  which allow displacement of fluid from multiple fluid cartridges. As shown, there are two rams  46 , which allow displacement of two different fluids from the fluid cartridges into static mixer  52 . For example, and as shown, each fluid cartridge hold one part of a two part epoxy. The rams  46  displace the fluid from the fluid cartridges, and the two parts of the epoxy are mixed in static mixer  52 . The mixed two part epoxy solution exits static mixer  52  through nozzle  53  and onto the inner surface of cup  54 . Cup  54  rotates around axle  56  at high speed, driven by cup drive motor  58 , as shown being a direct connect motor. Centrifugal force forces the solution to the side wall  60  of the cup  54 , which is angled to facilitate expulsion of liquid out of the top of the cup  54 . 
         [0032]    Optionally (not shown), the fluid containment block  50  can hold an additional fluid cartridge for solvent or other cleaning fluid, which can be used to clean the static mixer  52 , nozzle  53 , and/or cup  54  in situ. Displacement of fluid from this cartridge would be performed in a manner similar to that described above. 
         [0033]    Also optionally (not shown), instead of or in addition to having a platform  41  laterally displaceable on frame  30 , the entire liquid coating cart  28  can be laterally displaced along the pipe when coating, either utilizing the power of the tractor cart or under its own power. 
         [0034]    Cup  54  location relative to nozzles  53  can be adjusted through cup and motor slide axis  62 . Frame  30  also comprises a distance measuring encoder wheel  66  to help determine the approximate location of the liquid coating cart  28  within the pipe. 
         [0035]      FIG. 5  shows a front view of the liquid coating cart  28  within the environment of a pipe  70 . Pipe  70  is a 16″ pipe. Preferably, and as shown, the liquid coating cart  28  is located such that the axel  56  and cup  54  are located at or around the center of the pipe  70 . This allows for even coating of the pipe by liquid expulsed from the top of cup  54 . 
         [0036]    Not shown, but as would be evident to a person of skill in the art, the liquid coating cart  28  could also be used within a larger pipe, for example, a 20″ pipe  72  or a 24″ pipe  74  simply by replacing or adjusting the length of the axles of rear wheels  34  and front wheels (not shown). The wheels  34  themselves may also be replaced in order to have the desired angle of contact between the wheels  34  and the pipe  72  or  74 . For example, the liquid coating cart  28  can come equipped with three sets of wheel  34 , each having axles of different lengths and different angles of contact between the wheel  34  and the pipe  70 ,  72 ,  74 , to optimize fitting the liquid coating cart  28  in pipes of different diameters. Other pipe widths, for example pipes of 4 or 6 feet in diameter can also be coated, using a similar device to that shown, but made to a larger scale. 
         [0037]      FIG. 6  shows a schematic view of the liquid coating cart  28 , showing aspects not shown in  FIGS. 1-5 . Here, one can see rams  46  which are capable of lateral displacement. Rams  46  can enter fluid containers  51 , forcing fluid out of the opposing end of fluid containers  51  (for example a fluid cartridge) and into static mixer  52 . Using this same force (the lateral displacement of rams  46 ) the mixed fluid is then forced out of the nozzle  53  of static mixer  52  and into cup  54 , which is rotating along axle  56  powered by cup drive motor  58 . Not shown in  FIGS. 1-5  is waste catch  67 . When spraying fluid, nozzle  53  is at the location shown in the figures, and proximal to cup  54 . However, when the liquid coating cart  28  is being transported from one location to another, or when it is not desired to spray fluid, platform  41  is displaced relative to cup  54 , and the nozzle  53  is positioned to be directly above waste catch  67 . During transport or otherwise when the liquid spray cart  28  is not spraying liquid, rams  46  continue to push fluid through static mixer  52 , and out of nozzle  53 , but at a reduced rate. This prevents fluid from curing or hardening within static mixer  52 , since the fluid in the static mixer  52  is constantly in a state of motion. 
         [0038]    Also shown in  FIG. 6  is heating element  64 , which, in  FIGS. 1-5 , is present, but incorporated within heated cartridge containment block  50 . This heating element  64  serves to heat the fluid within fluid container  51 . 
         [0039]      FIG. 6  also shows air blowoff  76  which is capable of blasting air against the interior pipe wall, clearing it of debris or dust before application of the fluid coating. 
         [0040]      FIG. 7  is a photograph showing the cup  54  and other aspects of the liquid coating cart  28 . 
         [0041]      FIG. 8A  is a schematic of a liquid coating cart  28  control system. An alternative liquid coating cart  28  control system is shown in  FIG. 8B . 
         [0042]    As shown in  FIG. 8A , a user operates control panel  78 , which has a screen  80  (for example, an LCD panel), and a variety of controls  82 ,  84 . Through the control panel  78 , the user can view what is being seen by camera  42 , as well as operate the various elements of the liquid control cart  28 . The control panel  78  is connected, through a computer  86 , to a telecommunications antenna  88 , capable of sending and receiving signal to the liquid coating cart  28 , through tractor cart  90 . An antenna  92  on the tractor cart  90  receives and sends this signal to telecommunications antenna  88 . Antenna  92  is connected to a controller  94  which operates the tractor cart  90  functions, for example, the activation of motor  96  for operating the wheels of the tractor cart  90 . Controller  94  is also connected, through connector  98  and through coupling  36  to controller  38  on the liquid coating cart  28 . Through the controller  38 , a user operating the control panel  78  is able to control various aspects of the liquid coating cart  28 , such as camera  42 , lights  44 , activation and speed of linear stepper drive  48 , activation of the electric linear activator  40 , activation and speed of cup drive motor  58 , heating element  64 , and activation of air blowoff  76 . 
         [0043]    As shown in  FIG. 8B , the user operates control panel  78  in a manner similar to that shown in  FIG. 8A . However, the telecommunications antenna  88  is capable of sending and receiving signal to the liquid coating cart  28  directly, instead of through tractor cart  90 . An antenna  93  on the liquid coating cart receives and sends this signal to telecommunications antenna  88 . Antenna  93  is connected to controller  38  on the liquid coating cart  28 ; through the controller  38 , the user operating the control panel  78  is able to control various aspects of the liquid coating cart  28 , in a manner similar to that shown in  FIG. 8A . 
         [0044]    The liquid coating cart  28  is used in the following manner. A holiday/defect location is identified with other, known, inspection equipment. The liquid coating cart  28  is mechanically and electrically connected to a battery powered tractor cart through coupling  36 . The tractor cart has a control system and a communications antenna attached, and communicates via said communications antenna with a mobile control unit which is operated by a user. Once the liquid coating cart  28  is thus connected, communications are established between the liquid coating cart  28  and the mobile user interface via the wireless communications system. 
         [0045]    Fluid containers  51 , which may be in the form of a disposable, proprietary cartridge, containing fluid, are loaded onto the liquid coating cart  28 , within the cartridge containment block  50 . Optionally, static mixers  52  are also loaded, in the case (as shown) where static mixers  52  are a disposable consumable. Optionally, depending on what kind of liquid is contained within the fluid containers  52 , the liquid in the fluid containers  51 , and, again optionally, the static mixers  52  and the cup  54 , are heated by activation of the heating element  64 . 
         [0046]    The liquid coating cart  28  is placed into an open end, or an access panel, of a pipeline. The liquid coating cart  28  is then driven to the defect furthest from the insertion point in the particular string of pipe, optionally using distance measuring encoder wheel  66  to track the distance. In some cases tractor cart  90  may also have a distance measuring system, such as an electronic encoder, in which case, this may be used instead of distance measuring encoder wheel  66 . 
         [0047]    The precise defect location is then optionally located and verified manually by way of visual confirmation utilizing camera  42 , in conjunction with distance measuring encoder wheel  66 . An air blast against the base of the pipe is provided to move any large debris or dust from the coating area, through the activation of air blowoff  76 . 
         [0048]    The coating procedure is then initiated, as follows. The dispensing cup  54  is retracted to the operating position, proximal to mixer nozzle  53 . This allows the mixer nozzle  53  to deposit material within the cup  54 . The cup is then spun at high speed through the activation of cup drive motor  58 . The platform  41  which holds the cartridge containment block  50 , the mixer  52 , and the cup  54  is then moved in a reciprocating fashion by way of electric linear activator  40 . The total stroke of travel is approximately 10″ or less; the rate of travel is adjustable and based on the viscocity and other characteristics of the fluid, and can be approximately 1″ per second. This allows the cup  54  to coat/overcoat a section of pipe approximately 10″ in length, more than sufficient for covering any coating defect. The user then activates the linear stepper drive  48 , a mechanical screw mechanism driven by a motor, which moves rams  46 , which are moved forward at a controlled rate. The rams  46  force liquid out of fluid container  51  and into mixer  52 , and then out of mixer  52  through nozzle  53  and into cup  54 , which expels the mixed liquid onto the interior wall of the pipe. The rams  46  can be moved separately or independently, for example, where it is desired to use more fluid from one fluid container  51  than the other (for a specific fluid ratio mix), this can be done. Based on feedback from an linear variable differential transformer sensor (not shown), the rams  46  are stopped after the desired distance of travel has been achieved, said distance relating to the total volume of epoxy dispensed. Optionally, instead of stopping completely, the rams  46  are slowed down to a much slower speed. Cup  54  continues to rotate for a period of time, to ensure the fluid dose is fully dispensed; the cup  54  is then stopped, as is the platform travel. The platform is then moved back to a retracted position, and the cup  54  is moved to the extended position, approximately 3″ from the retracted position. This enables the mixer nozzle  53  to overhang waste catch  67 , for collection of leakage and purged epoxy. 
         [0049]    The static mixer  52  is periodically purged, through motion of rams  46  a small, measured amount, or, as described above, through the continual motion of rams  46  at a much slower than standard operational speed. This prevents the fluid in the static mixer from curing, hardening, or otherwise thickening to the point where it no longer dispenses satisfactorily. Accordingly, small volumes of fluid are dispensed through nozzle  53  and into waste catch  67 . 
         [0050]    Once coating has been achieved, the user can perform a visual verification of overcoat utilizing camera  42 . A photo of the joint is taken for the data log. The liquid coating cart  28  is then driven to the defect location second furthest from the insertion point, and the process repeated. The process is repeated again for each defect, until all defects are repaired or resources are depleted. 
       ELEMENT LIST 
       [0000]    
       
           28  liquid coating cart 
           30  frame 
           31  rear end 
           32  front wheel placement 
           33  front end 
           34  rear wheels 
           36  coupling 
           38  programmable logic controller 
           40  electric linear activator 
           41  platform 
           42  camera 
           44  lights 
           46  rams 
           48  linear stepper drive 
           50  cartridge containment block 
           51  fluid container 
           52  static mixer 
           53  nozzle 
           54  cup 
           56  axle 
           58  cup drive motor 
           60  side wall 
           62  cup and motor slide axis 
           64  heating element 
           66  distance measuring encoder wheel 
           67  waste catch 
           70  pipe 
           72  20″ pipe 
           74  24″ pipe 
           76  air blowoff 
           78  control panel 
           80  screen 
           82 ,  84  controls 
           86  computer 
           88  telecommunications antenna 
           90  tractor cart 
           92  antenna 
           93  antenna 
           94  controller 
           96  motor 
           98  connector