GB2313805A

GB2313805A - Coating elongate members

Info

Publication number: GB2313805A
Application number: GB9711639A
Authority: GB
Inventors: Robert Kenneth Oram
Original assignee: Balmoral Group Ltd
Current assignee: Balmoral Group Ltd
Priority date: 1996-06-05
Filing date: 1997-06-05
Publication date: 1997-12-10
Also published as: GB9611668D0; NO972560D0; GB9711639D0

Abstract

A coating device 4 coats an elongate member 10, such as a pipe for subsea use, by continuous casting of a material onto the external surface of the member. The method involves providing the coating device 4 with two or more flexible bands which are carried on rollers, the bands serving to define a cavity (8, Fig 2) between them, feeding the elongate member 10 into the cavity, injecting an unhardened coating material into the cavity so as to coat the member as it is fed through the cavity and hardening the coating. The cavity may be circular or hexagonal in cross-section. The apparatus may also comprise straightening rollers 2, positioning rollers 3 and haul-off rollers 5 for the elongate member. The coating material may be polyurethane, silicone, rubber, or cementitious material and may include fillers such as gas bubbles, glass microspheres, fibres and weighting materials.

Description

COATING OF PIPES AND OTHER ELONGATE MEMBERS This invention relates to the coating of elongate members such as marine tethers and subsea pipes for example with anticorrosion or insulating or buoyancy coatings.

Much piping for subsea use is manufactured or supplied in lengths typically 6-24 metres long. Each length is then coated and shipped. Prior to laying the lengths are field jointed which is to say that exposed pipe ends are welded together and insulating material used to cover the joint. This process can be difficult to perform well.

It may be desirable to provide extended lengths of marine tethers with uniform coatings and this has hitherto been difficult.

The invention seeks to reduce the difficulties associated with the prior art.

According to the invention there is provided a method of applying a coating of hardened material to an elongate member for subsea use, the method comprising the steps of providing a plurality of continuous flexible bands carried on rollers for rotational movement said plurality of continuous flexible bands defining a cavity, ii receiving a portion of said elongate member to be coated in said cavity, iii injecting unhardened coating material into said cavity while rotating said bands and traversing said elongate member through said cavity, and iv hardening said unhardened coating material.

According to the invention there is further provided apparatus for applying a coating of hardened material to an elongate member for subsea use, the apparatus comprising a a plurality of continuous flexible bands carried on rollers for rotational movement said plurality of continuous flexible bands defining a cavity, ii means for rotating said bands, iii means for traversing said elongate member through said cavity iv means for injecting unhardened coating material into said cavity while rotating said bands and traversing said elongate member through said cavity, and iv means for hardening said unhardened coating material.

According to the invention there is still further provided an elongate member for subsea use having a coating layer said coating layer being applied to said elongate member by continuously casting said coating material about said elongate member.

The invention will now be described by way of non-limiting example by reference to the figures of which Figure 1 is a schematic plan view of apparatus for coating pipe, Figure 2 is an enlarged cross-sectional view of the apparatus of Figure 1 and Figure 3 is a scrap view of a band.

The invention will first be described by way of non-limiting example by reference to an embodiment in which steel pipe is provided with an insulating coating.

Relativelv small pipe for example 100-150 mm (4-6") OD is obtainable on reels of continuous length up to several kilometres.

The length of this pipe is such that the need for field jointing is substantially reduced or even eliminated provided that a usable insulated pipe could be obtained. Prior to final spooling on to the reels a thin coating may have been applied to the pipe. Examples might include fusion bonded epoxy or cross-head extruded polyethylene. These coatings are very thin and while they may protect against corrosion have very limited insulating ability.

The invention allows an insulating coating to be applied to a continuous length of pipe 10. Reel 1 with the pipe 10 to be coated is conveniently braked by a brake (not shown) and drawn-off using a haul-off device. The pipe 10 may be straightened by passage through straightening rollers 2. Optionally the pipe 10 may be accurately positioned for example by positioning rollers 3. The pipe then passes through coating device 4 to be described hereinafter in greater detail. Coated pipe 10 emerges from the coating device 4 and may be wound under tension for example using haul-off rollers 5 onto take-up reel 6 for shipment.

The coating device 4 comprises a plurality of flexible bands 7 which surround the pipe 10 to be coated defining a cavity 8 into which coating material is cast. The bands 7 move at about the same speed as the pipe. The bands 7 may be continuous as shown in the Figures and at the end of the downstream travel are returned to the start position away from the pipe 10. The bands are thus endless. As can be seen from Figure 1 the bands 7 are carried on rollers 20. Cavity 8 as defined by the bands is in this embodiment a right cylinder but the invention is not to be regarded as so restricted. In particular corrugations may be provided in the bands or the cavity may be a section of a torus. In some embodiments of the invention the cavity is polygonal for example hexagonal in cross-section to provide a polygonal product. A convenient form for the bands may be broadly similar to a CAThRPILLARTM track with a plurality of articulated sections 9,9a joined to form an endless belt and driven by a capstan. As can be seen from Figure 2 the pipe 10 and working faces 11 of the articulated sections 9 may define an annular cavity 8 or mould space. In the embodiment of Figure 2 two bands are provided. The invention is not to be regarded as so restncted and greater numbers may be used. Large numbers of bands may result in unnecessary complication are should generally be avoided.

Coating material is introduced into the coating device 4 conveniently at or near the upstream end so as to completely fill the mould space 8. Clearly the required feed rate will depend on the pipe throughput and coating thickness.

The axis of the pipe 10 may have a vertical component and indeed the axis may be substantially vertical so as to facilitate fillwsg.

The coating material cures, optionally aided by catalyst, or freezes while the coating device 4 surrounds the pipe 10. At the point the pipe 10 leaves the coating device 4 the coating should have sufficient strength to maintain itself on the pipe 10 without fitnher support although those skilled will be able to devise embodiments with additional support stages separated from the coating device 4.

A dam ring (not shown) of outside diameter corresponding to the mould inside diameter may be placed on the pipe 10 prior to tirst starting to coat the pipe 10 to allow the process to be started by staining the coating in the mould space 8.

Those skilled will have little difficulty in selecting coating r.laterials which harden, for example by curing, rapidly enough to he used and are also flexible enough to allow the coated pipe to be spooled. Examples include polyurethanes, silicones, synthetic rubbers, flexible cementitious materials and so forth. Fixers such as gas bubbles, glass or polymer microspheres, fibres. weighting materials, aggregates can be incorporated in the coating.

Multiple layer coatings can be obtained by providing multiple coating devices not all of which need be of the invention.

In a further embodiment the invention is used to coat marine tethers with buoyancy material. For example the tether may be made of pultruded carbon-fibre rods twisted into u ire The buoyancy material could be applied to substantially the whole tether or just to a portion for example the upper 5-600m in a tether intended for use in water 1400m deep. Typical carbon fibre tether density is of the order of 1 .57m and it is possible to reduce the bulk density of such a tether using syntactic polyurethane especially HGMS syntactic polyurethane to obtain a neutrally buoyant 150250mm diameter product which is reelable to a radius ot about 7.5m. In essence the process is that hereinbefore described except that a reel of composite tether is traversed through the apparatus rather than a pipe.

Those skilled will have little difficulty in devising modifications.

Claims

1. A method of applying a coating of hardened material to an elongate member for subsea use, the method comprising the steps of providing a plurality of continuous flexible bands carried on rollers for rotational movement said plurality of continuous flexible bands defining a cavity, ii receiving a portion of said elongate member to be coated in said cavity, iii injecting unhardened coating material into said cavity while rotating said bands and traversing said elongate member through said cavity, and iv hardening said unhardened coating material.

2. The method of claim 1 wherein said elongate member is selected from the group consisting of pipes and tethers.

3. The method of claim 1 wherein said hardened coating is selected from the group consisting of polyolefins, polyurethanes, silicones, synthetic rubbers, syntactic foams and flexible cementitious materials.

4. The method of claim 3 wherein said hardened coating includes a filler selected from the group consisting of gas bubbles, glass microspheres, polymer macrospheres, fibres, weighting materials, and aggregates.

5. Apparatus for applying a coating of hardened material to an elongate member for subsea use, the apparatus comprising a a plurality of continuous flexible bands carried on rollers for rotational movement said plurality of continuous flexible bands defining a cavity, ii means for rotating said bands, iii means for traversing said elongate member through said cavity iv means for injecting unhardened coating material into said cavity while rotating said bands and traversing said elongate member through said cavity, and iv means for hardening said unhardened coating material.

6. The apparatus of claim 5 wherein said belts comprise a plurality of articulated sections.

7. The apparatus of claim 5 wherein said cavity is hexagonal in cross-section.

8. The apparatus of claim 5 further comprising a a reel upstream of said cavity for reeling said uncoated elongate member, b draw off means for drawing said elongate member off said reel, c straightening rollers for straightening said elongate member and positioning rollers for positioning said elongate member intermediate said reel and said cavity, d haul off rollers for hauling said coated elongate member onto a take off roller downstream of said cavity.

9. An elongate member for subsea use having a coating layer said coating layer being applied to said elongate member by continuously casting said coating material about said elongate member.