Patent Application
20230139461
The present invention relates to the preparation of pipe coatings for the subsequent application of joint coatings, for coating joints between pipe sections of pipelines. The invention has particular utility for oil or gas pipeline field joints.
Pipelines in the oil and gas industry are typically formed from multiple lengths of steel pipe sections that are welded together end-to-end as they are being laid. To prevent corrosion of the steel pipe sections and to reduce heat loss of fluids transported by the pipelines, the pipe sections are coated with one or more protective and/or insulative layers, typically a multi-layer coating comprising, for example, an epoxy bottom layer (especially fusion-bonded epoxy, FBE) followed by one or more polyethylene (e.g. polypropylene and/or modified polypropylene) outer layer(s). The pipe sections are usually coated at a factory remote from the location in which they are to be laid. This is often referred to as factory-applied coating and it is generally more cost effective than coating pipe sections on site where they are laid. (“On site”, generally known as “in the field”, may be on land, or at sea from a pipe-laying ship.) At the factory, the coating is applied to the outside of the pipe sections and a short length (known as a “cutback” region) is left uncoated at each end of the pipe section. The uncoated ends are necessary to enable the steel pipe sections to be welded together to form the pipeline in the field. The welded uncoated ends, known as field joints, must be coated in order to provide the necessary protection and/or insulation, and such coating is known as the field joint coating.
To prepare a field joint region of the pipeline for the field joint coating, each end region of the factory coating is typically machined by hand using power tools to remove a thin top layer, so that any dirt and grease is removed, and so that there will be good adhesion between the factory coating material and the field joint coating material. Additionally, unless already present, chamfers or bevels are hand machined into the polyethylene layer(s) to provide a gradual decrease in thickness of the factory coating material in a direction towards the uncoated lengths of pipe sections. Furthermore, a short length, known as a “toe”, of the FBE material extending from each end portion of the polyethylene material is typically abraded to clean the external surface of the FBE material and to ensure good adhesion to the field joint coating material.
Field joints are commonly coated by means of an injection-moulded polypropylene (“IMPP”) coating process. The exposed steel pipe section ends are heated, e.g. by induction heating. A layer of powdered fusion-bonded epoxy primer is then typically applied to the heated pipe section ends, and a thin layer of polypropylene is typically applied to the FBE primer during the FBE curing time. The end regions of the factory-applied coating, including the chamfers, are then heated, e.g. by means of radiant (infrared) heating. The field joint is then completely enclosed in a heavy-duty mould that defines a cavity around the welded pipe joint, the uncoated ends of the pipe sections, and the end regions of the factory-applied coating. Heated molten polypropylene (or modified polypropylene) is then injected into the mould cavity, to fill the cavity, and is allowed to cool. Once the injection-moulded polypropylene has cooled and solidified, the mould is removed from the field joint, leaving the solidified polypropylene field joint coating in place. Other types of field joint coating processes are also known. For example, the injection-moulded polyurethane (IMPU) coating process uses a chemically curable urethane material instead of injecting polypropylene as the mould-infill material around the field joint.
Australian Patent No. AU 2012204047 B2 discloses an underwater pipeline coating removal apparatus for enabling a section of an underwater pipeline to be repaired or replaced. The apparatus comprises a rotating cutting tool for removal of an outer reinforced-concrete layer of the underwater pipe, a rotating milling tool for removal of polymer coating from the pipe, and a rotating brushing tool for removing a residual polymer coating layer. All three tools are arranged to move radially towards and away from the pipe, and each of them has an axis of rotation that is parallel to the longitudinal axis of the pipe.
German Patent No. DE 102004031756 B4 discloses an apparatus for applying a bevel or chamfer to the polymer coating of a pipe in preparation for a field joint coating. In use, the apparatus is fixed to the exterior surface of a pipe by means of a link chain and a tensioning helical spring, and the apparatus also includes wheels which allow rotation of the apparatus around the pipe circumference. The apparatus may be guided around the pipe by hand or by means of a drive arrangement. The apparatus includes a drive with a working head to produce the chamfer, and the drive is supported by a holding means which enables its height and degree of inclination relative to the pipe to be adjusted, so that the desired inclination angle of the chamfer, within a range of approximately 15 to 25 degrees to the pipe axis, can be produced.
There is a need to improve the process of preparing a pipeline field joint for the field joint coating.
In a first aspect, the present invention provides a pipe coating material removal apparatus according to claim 1 of the appended claims.
A second aspect of the invention provides a method of preparing a pipe coating in readiness for receiving a field-applied coating, according to claim 20 of the appended claims.
Preferred, and other optional, features of the invention are defined and described in the dependent claims.
Accordingly, a first aspect of the invention provides a pipe coating material removal apparatus, comprising: a support frame; a subframe supported by the support frame and configured to rotate relative to the support frame at least partially around a subframe rotation axis, the subframe rotation axis configured to be substantially coaxial with a longitudinal axis of a pipe to which the apparatus may be applied in use; and one or more coating material removal members rotatably mounted to the subframe to remove part of an exterior coating of a said pipe; wherein the apparatus is configured such that the one or more coating material removal members enable the removal of pipe coating material at orientations substantially parallel to, and inclined with respect to, the longitudinal axis of the pipe.
A second aspect of the invention provides a method of preparing a pipe coating in readiness for receiving a field-applied coating, comprising removing pipe coating material using an apparatus according to the first aspect of the invention.
It is to be understood that any feature, including any preferred feature, of any aspect of the invention may be a feature, including a preferred feature, of any other aspect of the invention.
The pipe preferably comprises a joint region, e.g. a field joint, between two pipe sections of a pipeline.
Preferably, the removal of pipe coating material at an orientation inclined with respect to the longitudinal axis of the pipe provides part of the pipe coating with a chamfered or bevelled external surface, or provides a clean new external surface of a pre-existing chamfered or bevelled section of the pipe coating material.
The one or more coating material removal members preferably is adjustable to enable the removal of pipe coating material at an orientation substantially parallel to, and inclined with respect to, the longitudinal axis of the pipe.
Advantageously, the one or more coating material removal members may be adjustable to enable the orientation of pipe coating material removal to be varied throughout a range or series of orientation angles and/or to enable a depth of pipe coating material removal to be varied. The range or series of orientation angles preferably has a lower limit of no more than 0 degrees and preferably has an upper limit of at least 20 degrees, more preferably at least 30 degrees, with respect to the longitudinal axis of the pipe.
Preferably, the one or more rotatable coating material removal members each comprise a rotatable milling cutter (e.g. a generally or substantially cylindrical milling cutter) or a rotatable grinding member or abrasive member. The, or each, grinding member or abrasive member preferably comprises a grinding wheel, or a flap wheel, e.g. a ceramic flap wheel, or a wire brush wheel. The, or each, coating material removal member preferably is rotatable by means of a motor, e.g. a pneumatic motor.
The pipe coating removal apparatus may further comprise a feed plate located on one side, or on each of two opposite sides, of the, or each, rotatable coating material removal member, preferably arranged to control or determine a depth of coating removed from the pipe by the coating material removal member in use. In some preferred embodiments, the, or each, feed plate is movably, preferably rotatably, mounted with respect to the rotatable coating material removal member, to accommodate misalignments between the coating material removal member and the pipe, in use.
An angle of orientation of a rotation axis of one or more coating material removal members (especially the, or each, milling cutter, where present) with respect to the subframe rotation axis preferably is adjustable to enable the orientation of pipe coating material removal to be varied. The angle of orientation of the rotation axis of the, or each, coating material removal member preferably is adjustable by means of an air-hydro cylinder, for example.
The depth of coating material removal by one or more coating material removal members (especially the, or each, milling cutter, where present) may advantageously be adjustable by means of a servo motor or actuator, for example. Preferably, the depth of coating material removal is settable with the aid of a mechanical contact member, preferably comprising one or more feed plates and/or one or more ball transfer units, arranged to contact an exterior surface of the pipe coating, in use.
The pipe coating material removal apparatus of the invention preferably further comprises one or more distance measuring sensors configured to enable the apparatus to control an operating position of one or more said coating material removal members relative to the external surface of the pipe or pipe coating in use. The, or each, distance measuring sensor may advantageously comprise, for example, at least one of: an inductive sensor; an eddy current sensor; an optical sensor; a laser sensor; a mechanical sensor; an ultrasonic sensor; and a capacitive sensor.
The pipe coating material removal apparatus of the invention preferably further comprises a longitudinally movable member, preferably a plate member, movably mounted on the subframe, and to which the, or each, coating material removal member is mounted for longitudinal positioning with respect to a said pipe. The movable member (e.g. plate member) preferably is longitudinally movable (e.g. slidable) with respect to the subframe by means of a linear servo motor or actuator mounted on the subframe.
The pipe coating material removal apparatus of the invention preferably includes a plurality of coating material removal members mounted on the subframe in one or more coating material removal subassemblies. Preferably, there may be a plurality of coating material removal subassemblies rotatably mounted to the subframe in one or more opposing pairs of coating material removal subassemblies, for example. Advantageously, the, or each, coating material removal subassembly may be movable relative to the subframe by means of a pneumatic cylinder, for example.
In some preferred embodiments of the invention, the pipe coating removal apparatus includes one or more laser sensors, preferably one or more 2-dimensional profile laser sensors, configured to locate profile features of the pipe coating. Preferably, the, or each, laser sensor is configured to locate profile features of the pipe coating, which profile feature locations are used to axially position the coating material removal members with respect to the pipe coating.
A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:
Referring to
The illustrated support frame 3 comprises an outer steel frame of the apparatus 1, which supports the rest of the apparatus, including the subframe 5. The support frame 3 and the subframe 5 include wide slot-like openings 7 and 9 respectively, in respective opposite end wall parts 11 and 13 of each of the support frame 3 and the subframe 5, to allow the pipe section 2 to extend through the apparatus 1 with the longitudinal axis of the pipe section substantially coaxial with the subframe rotation axis A. The subframe 5 is mounted on the support frame 3 by means of a gear and drive system, comprising a large partial ring gear 15 (see
As shown in
In use, an opposing pair of coating material removal subassemblies 29 may be moved to the correct longitudinal position along the pipe section 2 to carry out the particular required coating material removal operation at that longitudinal position, by longitudinal movement (e.g. sliding) of the plate member 23 caused by control of the linear servo motor 25, for example by computer (e.g. utilizing an optical or laser sensor for longitudinal positioning) and/or human operator control via a control panel (not shown). Then, each coating material removal subassembly 29 of the longitudinally positioned opposing pair may be rotated towards the pipe section 2 about its hinge 31 on its gullwing arm 33 by means of its respective pneumatic cylinder 35, again by computer and/or human operator control, for example. For speed of operation, and also for balance and close positional control, both coating material removal subassemblies 29 of an opposing pair preferably are rotated into position to operate substantially at the same time at different circumferential locations on the pipe section 2, preferably substantially diametrically opposite locations.
In use, the subframe 5 is rotated relative to the support frame 3, at least partially around the pipe section 2, by the electric motor and the chain or belt, e.g. by computer and/or human operator control, so that each of the currently operating coating material removal subassemblies 29 removes the required coating from a respective circumferential region of the pipe section 2. Once the particular coating material removal operation required at that longitudinal position around the entire circumference of the pipe section 2 has been completed, the coating material removal subassemblies 29 may be rotated away from the pipe section 2 about their hinge 31 by their pneumatic cylinders 35, and any required further coating removal operations at different locations on the pipe section 2 may be carried out in a similar way.
As shown in
Each mounting frame 37 also supports a mechanical contact member 51, e.g. in the form of one or more ball transfer units, arranged to contact the exterior surface of the factory-applied pipe coating 6 to limit the radially-inward travel of the gullwing arms 33 and to assist in setting the depth of coating material removal by each milling cutter 41. For parallel coating material removal (i.e. parallel to the pipe axis A) the cutting edge(s) of each milling cutter 41 are typically set at a position (equating to a coating material removal depth) approximately 0.5 mm radially inward of the radially inwardmost part(s) of the mechanical contact member 51. Preferably, as little coating material as possible is removed from the surface of the pipe section 2. The depth of coating material removal, by each milling cutter 41, is adjustable by means of a linear servo motor or actuator 53, preferably a high precision linear servo motor, supported by each mounting frame 37, which is configured to adjust the position of the mechanical contact member 51 relative to the milling cutter 41. This is achieved by each mechanical contact member 51 being mounted on a respective pivot arm 55 (in the form of a “quadrant arm” in the illustrated exemplary embodiment) which is pivotably mounted via a pivot 57 to its respective mounting frame 37, and a movable actuator arm 59 of the linear servo motor 53 being connected to the pivot arm 55 at a position spaced from the pivot 57. Each linear servo motor 53 is controllable by computer and/or human operator control, for example.
In the illustrated embodiment, each mechanical contact member 51 comprises a plurality of ball transfer units which can be kept automatically in contact with the exterior surface of the factory-applied pipe coating 6 by being mounted on a pivoting support 61 which itself is pivotally mounted to the respective pivot arm 55. The pivoting movement of each pivot arm 55 is guided by means of guide wheels 63 rotationally mounted on the respective mounting frame 37, and the pivoting movement of each pivoting support 61 is guided by means of projections 65 on the pivot arm 55 movably located in part-circular slots 67 on the pivoting support 61. (Other mechanical arrangements may additionally or alternatively be used, as will be understood by the skilled person.)
Each subassembly frame 39 is rotatably mounted on its mounting frame 37 by means of hinges 69, to enable the angle of orientation of the subassembly frame, with respect to the longitudinal axis of the pipe section 2, to be varied, thereby enabling the angle of orientation of each coating removal member 41, 47, with respect to the longitudinal axis of the pipe section 2, to be varied. The angle of orientation of each subassembly frame 39 is adjustable by means of an air-hydro cylinder 71 which extends between an attachment pivot 72 on each mounting frame 37 and an attachment pivot 74 on each respective subassembly frame 39. Air-hydro cylinders 71 are preferred for this purpose because of their rigidity once the orientation has been set. The operation of each air-hydro cylinder 71 is controllable by computer and/or human operator control, for example. The angle of orientation of each milling cutter 41 determines the chamfer or bevel angle of each chamfer or bevel 10 which is formed in the factory-applied coating 6 by the apparatus 1, this preferably being in the range of 20 to 35 degrees, e.g. substantially 30 degrees, for example. However, the operating orientation of each milling cutter 41 preferably is continuously variable through an entire range of angles elative to the subframe rotation axis A (which is substantially coaxial with the longitudinal axis of the pipe section, during operation of the apparatus 1). The range of angles preferably has a lower limit of no more than 0 degrees (i.e. at least parallel to axis A, and possibly including “negative” inclined angles). An upper limit of the range of angles may be at least 20 degrees, and preferably at least 30 degrees, for example. The ability to operate the milling cutters 41 at substantially any angle within a range of angles enables different chamfer/bevel angles to be used (e.g. depending on specific requirements), and may also enable the provision of a smooth (rather than stepped) transition between milled and nonmilled coating regions, for example.
As mentioned above, and as best shown in
The rotational abrasive member 47 is powered by a pneumatic motor 75, and preferably is brought into operation to abrade and clean the external surface of the “toe” of fusion-bonded epoxy (FBE) material 12 and to ensure good adhesion to the subsequently-applied field joint coating material, preferably after the chamfers or bevels 10 have been formed in the polyethylene layer 8 of the factory coating 6. The correct radial positioning of the rotational abrasive member 47 relative to the exterior surface of the steel pipe section 2 is controlled by means of the distance measuring sensor 49 and a computer controller (not shown). Advantageously, the sensor-computer system may determine the distance between the sensor 49 and the pipe surface, and make any necessary distance corrections, several times per second during operation. In some preferred implementations of the invention, the depth of coating material removal by the milling cutter 41 is also controlled with reference to distance measurements made by the distance measuring sensor 49, e.g. using proportionality parameters to set the correct material removal depth(s).
When not in operation, the rotational abrasive member 47 is held in an extended “parked” position as shown in
As described above, when the pipe coating removal operation(s) required at a particular longitudinal position of the pipe section 2 has/have been completed, the plate member 23 is moved longitudinally by the linear servo motor 25 with respect to the substructure 21 so that the appropriate coating removal subassemblies 29 may carry out any required further pipe coating removal operation(s) at one or more different longitudinal positions on the pipe section 2. Once all of the necessary pipe coating removal operations have been completed, the apparatus 1 may be removed from the pipe section 2 and the field joint coating operations may commence.
The feed plates 79 are rigidly mounted relative to the axis of rotation of the milling cutter 41 such that the distance from the surface of the cutter to the running surface on the feed plates is constant. The feed plates act to passively control the depth of cut without the need for sophisticated controls. The feed plates 79 are configured to ensure a minimum amount of material is always removed from the factory coating 6 to present a clean “virgin” surface for the application of the field joint coating (injection moulded polypropylene), while accommodating variations in diameter, ovality and alignment, for example. Additionally, the feed plates 79 are configured to prevent the milling cutter 41 from removing an excessive amount of factory coating material 6, which can cause the cutter to stall and disrupt the coating preparation procedure. A further benefit of the feed plates 79 is to help with chip extraction. The feed plates 79 create a narrow channel to direct airflow and contain chips being thrown from the cutter 41. An extraction port 81 on the back of the cutter box can allow for the connection of dust extraction equipment and removal of the chips from the cutter assembly, for example.
A detail of factory coating material removal utilising feed plates 79a and 79b is shown in
The factory coating surface 6 to be prepared by the apparatus 1 according to the invention is generally not perfectly round, and its thickness generally varies along with the dimensions of the pipe 2 beneath. In addition to this, the pipe 2 may not be positioned in the exact centre of the apparatus corresponding to the axis of rotation of the subframe 5. These factors combined mean that as the, or each, coating material removal subassembly 29 rotates around the pipe 2, the location of the surface of the coating changes. As described above, each coating material subassembly 29 is mounted to a pneumatically actuated gullwing arm 33, which moves the subassembly 29 towards or away from the pipe and factory coating. With the embodiments of
In the embodiment shown in
The chamfering pivot point preferably is substantially in-line with the chamfer coating surface from the reference point of the line of action of the swing arm. The force imparted by the air-hydro cylinder 71 to extend the milling cutter subassembly 39 to the initial chamfer angle against the first stop 91 must be light enough to be overcome by the force from the pneumatic cylinder 35, so that the piston 76 of the air-hydro cylinder 71 can be compressed to allow the milling cutter 41 to sit “flat” against the chamfer surface, thereby providing a passive system that matches the angle of the cutter to the angle of the chamfer without the need for sophisticated controls.
In some preferred embodiments of the invention, a first step in the method of preparing a pipe coating using the apparatus of the invention is to scan, e.g. laser scan, the factory coating and determine the location of the critical inflection points on the factory coating. The position of the pipe within the apparatus can vary along with the dimensions of the factory coating and the apparatus preferably is able to accommodate these variations automatically, without any operator input. Accordingly, in some preferred embodiments of the invention, and as shown in
The, or each, laser sensor 97 may be selected such that its field of view is sufficient to detect all of the critical points across the acceptable range of pipe locations without the need to move or reposition the laser. Once the apparatus has been moved to the pipe, and the pipe is at a suitable position within the apparatus, the, or each, laser sensor 97 preferably scans the factory coating and using software and computer control determines X (pipe axial) and Y (pipe radial) coordinates for each of the inflection points 99, 101, 103, and 105, of the coating (see
It will be understood that the above description and the drawings are of particular example embodiments of the invention, but that other implementations and embodiments of the invention are included in the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2114073.6 | Oct 2021 | GB | national |
