Patent Application
20130269812
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.
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.
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.
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.
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.
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.
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.
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.
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.
In certain embodiments, the controller is a programmable logic controller or a personal computer based controller.
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.
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.
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.
In certain embodiments, images are transmitted to the remote interface via the controller.
In certain embodiments, the wheels are adjustable for fitting the liquid coating cart into pipes of different diameters.
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.
Referring now to
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.
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.
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.
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.
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.
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.
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.
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.
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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.
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.
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.
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.
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.
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.
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.
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. The content of the above patent application is hereby expressly incorporated by reference into the detailed description hereof.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2011/050457 | 7/26/2011 | WO | 00 | 6/12/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61367652 | Jul 2010 | US |
