METHOD AND APPARATUS FOR COATING PIPES

Abstract: A method of coating pipes with concrete comprises conveying a series of pipe sections to a concrete coating station, rotating a pipe section about its longitudinal axis at the station and applying concrete to the outside of the pipe (1) during rotation whilst continuously feeding a line (3) to the rotating pipe to form a winding of line around the leading end of the pipe, subsequently feeding a wire (5) together with the line to the rotating pipe to form a winding of wire overlaid with line around the pipe during the application of concrete, and cutting the wire at a predetermined time prior to completion of the concrete coating whilst the pipe is still rotating whereby the wire is wound within the concrete coating, and continuing to feed the guide line to the rotating pipe after cutting of the wire to wind the line around the tail end of the pipe. Apparatus comprises a plurality of rollers (6, 7, 9, 10, 11, 12) including cutting elements (8) on rollers (7) and drive means to feed wire and a further series of rollers (4) for feeding line in a controlled manner.

Description: Method and Apparatus for Coating Pipes. This invention is concerned with coating of pipes of the type used in subterranean or submerged pipelines for recovery of oil, gas, slurries or the like pipeable materials from a subterranean well. In particular it is concerned with pipes in which a steel pipe section is coated with an anti-corrosion coating and then a concrete aggregate antibuoyancy coating (hereinafter concrete coating). Such pipes normally include a mechanical shear transfer device in the form of wire windings or caging applied around the anti- corrosion coating prior to application of the concrete coating. This opposes the tendency of the concrete coating to slip or jump off the anti-corrosion coated pipe during laying operations which can impose considerable bending stresses upon the pipe. Reference may be made to the following patents US 3 955 600 and GB 1 504 051/2 which are representative of the known art. Typically, each pipe section is caused to rotate about its longitudinal ax s and passed longitudinally past a concrete coating station wherein concrete/aggregate is caused to impinge upon the rotating pipe thereby building up a thickness of concrete on the pipe to form a coating. Normally where a wire mesh (hereinafter referred to as wire) winding is used, it is necessary to lash an end of the wire to the front end of the pipe before it is rotated and advanced past the concrete coating station. As the pipe is so advanced, the wire is fed in a continuous manner at an appropriate angle to allow the rotation of the pipe to cause winding of wire throughout its length. Once that section has passed by that station, the wire must be cut and lashed at the tail end of the pipe section. This has several disadvantages which include a less than desirable rate of production because of the need to stop the pipe before and after the concrete coating station to secure the wire which would otherwise simply exhibit a "clock-spring effect" and release itself, during coating, to a loose non-uniform relaxed winding without the desired function. Further, the process cannot readily be automated due to the need to have personnel attending to fastening of the wire at both ends of the pipe. Additionally it is undesirable to have a free end of wire directly contacting the anti-corrosion coating on the steel pipe since it is liable to penetrate that coating through abrasive contact and cause corrosion attack points which could weaken and ultimately cause premature failure and the need for replacement of that section. Therefore it is an object of this invention to obviate or mitigate the aforementioned disadvantages by providing a coating method and apparatus for carrying out the method offering several advantages over the known art including the capability of improving production rate, allowing the possibility of automating the coating station, reducing the personnel demands and minimising wire contact with the anti- corrosion coating. Accordingly this invention provides in its broadest aspect a method of coating pipe sections which comprises conveying a series of pipe sections past a concrete coating station having means for advancing and rotating the sections longitudinally, characterised by providing at that station means for continuously feeding a line to the rotating sections, means for continually feeding a wire to the rotating sections in a manner such that the line fed to the sections brings the wire into position for winding around the section and overlies the wound wire throughout its length, and cutter means, cooperating with the wire-feed means, for automatically cutting the wire at predetermined time intervals whereby in carrying out the method, the line is first fed to the leading end of the rotating pipe and wound around same for sufficient turns to secure same, then wire is drawn in to begin the winding around the pipe during the application of concrete coating in the station, and the wire is subsequently cut as it is fed to prevent the winding extending beyond the concrete coated length of the pipe section whilst the line continues to be wound around the tail end of the pipe. Thus the objects of the invention are achieved in that the line acts to secure the front and tail ends of the wire winding to avoid the need to manually lash the wire to the pipe, wire cutting is achieved automatically without the need to stop the advance of the pipe sections and the method readily lends itself to automation whereby the feed rate of wire together with the cutting intervals may be calculated and the station set to repeatedly wind wire within the concrete coating step. This has the advantage that the wire follows in the line during the initial stage of concrete coating whereby the wire itself never actually contacts the pipe section but becomes embedded within the concrete accumulating upon the pipe to form the weight coating. Preferably, the method includes the provision of wire shaping means to allow pre-shaping of the wire to introduce curvature enabling the wire to readily conform to the circumference of the pipe section. This facilitates winding and allows the use of inexpensive line since it requires less force to secure the wire on to the pipe so that it is possible to use a variety of synthetic fibre or relatively fine wire filaments for this purpose. Advantageously, each pipe section is conveyed away from the coating station at an accelerated rate in comparison with the throughput rate at the coating station whereby the line is snapped between sections. The apparatus to be included in a station for coating rotating pipe sections with concrete according to this invention comprises a first feed mechanism for delivering a line from an appropriate renewable supply of same sufficient to obtain a substantially continuous feed of wire to the pipes to be coated at that station; a second feed mechanism located in close proximity to the first and arranged to feed wire from an appropriate renewable supply of same sufficient to secure a continual feed of wire in a manner such that it comes into contact with the line whereby it is subsequently caused to contact and form a winding around the rotating pipe section as concrete is applied thereto; and a cutter assembly for limiting the length of wire to be wound around the pipe section. The cutter assembly may be a guillotine arrangement. Preferably the wire feed mechanism cooperates with wire shaping means which preforms the wire in a curved configuration sympathetic to the circumference of the pipe. Preferably also, the first feed mechanism comprises a plurality of rollers mounted in series through which the line is passed in a serpentine manner and at least one of said rollers is movable relative to the others to increase or decrease tension applied to the line. The second feed mechanism preferably comprises a pair of counter-rotating rollers mounted in parallel and mutually spaced apart so as to allow contiguous passage of wire therebetween, at least one of which is driven by a motor tc provide a means of advancing wire through the feed mechanism; a further pair of cooperating counter-rotating rollers having cutting elements on the surfaces thereof enabling wire passing between the rollers to be cut between the cutting elements at predetermined intervals; and a plurality of rollers located such that there is provided at least one reaction surface below the advancing wire against which the wire may be formed into a curved shape by controlled pressure exerted from at least one further roller located on the other side of the wire. At least one roller in each pair may be provided with means for adjusting mutual spacing of the paired rollers to accomodate different thicknesses of wire and alter the pressure applied by the rollers. It is preferred that the rollers are driven through chain and sprocket transmission by electric motors. In the case of the cutter roller drive it is necessary to include a clutch to disengage these rollers during winding of wire over the length of the pipe section and limit cutting operations to shortly before complete winding of wire over the pipe section. Also, in the case of the cutter rollers at least, it is preferred that the drive to one roller is transmitted to the other through engagement of gears at the ends of the rollers in order to synchronise the operation of the cutting elements thereon. The cutting elements are preferably formed and arranged on the roller surfaces so as to provide a guillotine cutting action. The invention will now be further described by way of example with reference to the accompanying drawings in which:- Fig. 1 is a schematic side elevational view of the apparatus for winding wire on a pipe at a concrete coating station omitting drive transmission and support structure for ease of identification of major components of the feed mechanisms; Fig. 2 is a plan view of the apparatus showing detail of drive mechanisms for the apparatus; Fig. 3 is a schematic view of one end of a pipe coated in accordance with the method of the invention; and Fig. 4 is a plan view of a section of the wire mesh which may be applied by the method of the invention. Referring primarily to Figs. 1 and 2 of the drawings, a wire winding apparatus will now be described for use at a station for coating pipe sections (1) which have already received an anti-corrosion coating (such as an epoxy resin) with concrete, in which said sections are fed^in series past a concrete throwing device (not shown) on a driven roller conveyor device illustrated schematically only by the rollers (2). Above the said throwing device there is located a wire mesh spool and a nylon line spool neither of which is illustrated since their precise location is not important. A line feed mechanism including a plurality of rollers (4) at least some of which are movable relative to each other to enable control of tension in a line (3) is situated above the intended path of the pipes and feeds line (3) to the side of the pipes opposite to the concrete throwing device. Adjacent to the line feed mechanism is a wire feed mechanism comprising a pair of rubber coated rollers (6) mounted in parallel and driven in a counter rotary fashion by an electric motor (26) through a transmission including drive chain (27) and gears (28). The rollers are provided with adjuster screw means (29) for moving the rollers together or apart to adjust the pressure exerted upon wire passing between them and to accomodate differing thicknesses of wire. The wire feed mechanism is intended to provide a continual delivery of sections of wire of a length appropriate to provide a winding around a pipe section which is wholly confined within the concrete coating applied to the pipe. To this end there is a roller cutter assembly in the wire feed mechanism directly in the path of the wire (5) as it exits from the driven rollers (6). This cutter assembly comprises a pair of rollers (7) each having a cutter blade (8) extending longitudinally across the roller surface. These rollers are mounted in parallel and driven by an electric motor (46) through a coupling (47) and gears (48) providing for counter-rotation of the rollers (7). The cutter drive incorporates a clutch (49) enabling the cutter assembly to be disengaged to allow free passage of a length of wire between the rollers (7). This embodiment also includes in the wire feed mechanism a wire forming assembly comprising a plurality of rollers (9, 10, 11, 12), two of which (11, 12) are mounted as a pair in parallel and driven by electric motor (36) through chain (37) and gears (39) counter to each other to cause advancement of wire between them. The other two rollers (9, 12) are free running on bearings (54) so mounted as to provide independently adjustable means of bringing pressure onto the wire as it is fed through the rollers (10, 11) whereby it may be shaped into a curve which facilitates winding thereof around the pipe (1). In use of the apparatus in carrying out the method of the invention, as a start up procedure, the line (3) is drawn in a serpentine path through the rollers (4) and passed around the leading end of the first pipe (1) in the series which, because it is revolving, causes the line (3) to be wound around that end for a number of turns which has been found sufficient to secure it to that end. Thereafter, the line (3) need not be touched and it will continue to be drawn through the feed mechanism in an uninterrupted continuous manner for as long as there remains line on the spool and will thus be continuously wound round all pipes conveyed in series past the coating station. At a predetermined time after feeding the line through the apparatus onto the pipe (1), the wire mesh feed is started, whereupon the wire advances into contact with the line and becomes directed thus onto the pipe section. At this time also the concrete throwing device is operated causing a concrete layer to begin to build up on the revolving pipe before the wire comes into contact with it. Thereafter, the line and wire are fed together so that the line overlies the wound wire until the concrete coating has been applied. At a predetermined instance prior to complete coating of the pipe, the cutter assembly is operated to cut the wire and the drive rollers (6) are momentarily stopped to provide a gap between the end of one wire winding and the start of the next. In this way the wire is wound wholly within the length of the concrete coating, and is embedded therein without coming into direct contact with the anti-corrosion coating on the pipe. Additionally because the line is not cut it is still wound for several turns on after the cut end of wire is wound onto the pipe to provide a means which has been found sufficient to counter any "clock spring" effect of the wire within the still hardening concrete coating. This line is easily severed by the action of the accelerated conveyance of the coated pipe away from the station in a manner known in the art.

Claims: Claims 1. A method of coating pipes with concrete which comprises conveying a series of pipe sections past a concrete coating station, rotating a pipe section about its longitudinal axis at the station, winding wire about said section and applying concrete to the outside of the pipe section during rotation thereof characterised by feeding a line to the rotating pipe prior to the application of concrete to form a secured winding of line around the leading end of the pipe, subsequently feeding a wire together with the line continuously to the rotating pipe in order to form a winding of wire overlaid by a winding of line on the pipe during the application of concrete to the rotating pipe, and cutting the wire at a predetermined time prior to completion of, and during the application of, the concrete coating whilst the pipe is still rotating whereby the wire is embedded in the concrete coating, and continuing to feed the line to the rotating pipe after cutting of the wire to wind the line around the tail end of the pipe. 2. A method according to claim 1 wherein the wire is formed into a curve prior to winding upon the pipe. 3. A method according to claim 1 wherein the line is made of a synthetic fibre material or a wire filament. 4. Apparatus for coating pipes with concrete comprising means for conveying a series of pipe sections past a concrete coating station, means for rotating a pipe section about its longitudinal axis at the station, means for feeding wire to said section and means for applying concrete to the outside of the pipe section during rotation thereof characterised in that a line feed mechanism for continuously feeding a line to the rotating pipe is provided adjacent to a wire feed mechanism for continually feeding a length of wire to the rotating pipe section during coating with concrete, said wire feed mechanism including a cutter assembly for limiting the length of wire to be wound around the pipe section during coating of the rotating pipe section. 5. Apparatus according to claim 4 wherein the wire feed mechanism further comprises a wire shaping assembly for preforming the wire in a curved shape to facilitate winding thereof about a pipe section. 6. Apparatus according to claim 5 wherein the wire shaping assembly comprises a plurality of rollers at least one of which provides a reaction surface over which wire is passed and against which wire may be shaped by the application of pressure from at least one other roller beneath which the wire is passed. 7. Apparatus according to claim 4 wherein the cutter assembly comprises a pair of rollers each having a cutter blade extending longitudinally across the roller surface and being mounted in parallel and driven by an electric motor through a transmission system providing for counter-rotation of the rollers and interruption of the cutting action to allow passage of wire therebetween. 8. Apparatus according to claim 4 wherein the line feed mechanism comprises a plurality of rollers mounted in series through which line is fed in a serpentine fashion, at least one of which rollers is movable relative to the others to provide for alteration of tension applied to the line. 9. Apparatus according to claim 4 wherein the wire feed mechanism comprises a pair of rubber coated rollers mounted in parallel and driven in a counter rotary fashion by an electric motor through a mechanical transmission to advance wire through the mechanism, said rollers having screw adjuster means for moving the rollers together or apart; a roller cutter assembly directly in the path of the wire as it exits from the driven rubber rollers, and having a pair of rollers each having a cutter blade extending longitudinally across the cutter roller surface, said cutter rollers being mounted in parallel and driven by an electric motor through a mechanical transmission providing for counter-rotation of the cutter rollers, which transmission incorporates a clutch enabling the cutter assembly to be disengaged to allow free passage of a length of wire between the cutter rollers; a wire shaping assembly comprising a plurality of rollers, including a pair mounted in parallel and driven by an electric motor through a mechanical transmission system counter to each other to cause advancement of wire between them and other rollers so mounted as to provide independently adjustable means of bringing pressure onto the wire as it is fed through said pair of rollers whereby it may be shaped into a curve which facilitates winding thereof around a pipe section.

Inventors: BUTTIMORE WAYNE KEITH, MULLEN DOUGLAS THOMAS, BUTTIMORE, WAYNE, KEITH, MULLEN, DOUGLAS, THOMAS
Applicants: BREDERO PRICE SERVICES, BRITISH PIPE COATERS, BREDERO PRICE SERVICES LIMITED, BRITISH PIPE COATERS LIMITED
Application year: 1987
Main classification: B28B21
IPC codes: B28B21, B65H81