GB2516296A

GB2516296A - Cutting apparatus

Info

Publication number: GB2516296A
Application number: GB1312885.5A
Authority: GB
Inventors: Ronald Wraith
Original assignee: UNDERWATER CUTTINGS SOLUTIONS Ltd
Current assignee: UNDERWATER CUTTINGS SOLUTIONS Ltd
Priority date: 2013-07-18
Filing date: 2013-07-18
Publication date: 2015-01-21
Anticipated expiration: 2033-07-18
Also published as: GB2516296B; GB201312885D0

Abstract

An apparatus for cutting an object, such as a pipe, using a flexible cutting member, preferably a diamond wire, comprising clamping legs 16 that grip an object to be cut, and a frame 22 with guide members 30 (which may be pulley wheels) that carry and drive the sawing wire. The frame is moved relative to the clamping legs by a hydraulic motor (26 of figure 5) and a tension control device 34 ensures the tension in the wire does not get too great. The tension control device includes a valve (figures 14-15) that varies the flow of hydraulic fluid through the motor. If the tension in the wire gets too high guide member 30b moves against a biasing spring (42 figure 12) causing the valve to reduce the fluid flow to the hydraulic motor. This valve may comprise one inlet and one outlet and a linear actuator, preferably with a tapered portion, that controls the flow of hydraulic fluid between the inlet and outlet in response to linear movement of the spring. The frame moving means may comprise a worm screw 28 which the motor drives along. Preferably this apparatus is included in a remotely operated vehicle (ROV) for use underwater.

Description

Cutting Apparatus The present invention relates to a cutting apparatus and relates particularly, but not exclusively, to a diamond wire cutting apparatus for cutting subsea gas, oil pipe lines and subsea structures during decommissioning.

The use of diamond wire, that is a wire impregnated with diamond dust, as a cutting tool is well known. It is also known for such diamond wire cutting tools to be used in deep subsea decommissioning work such as the cutting and removal of oil, gas pipes and subsea structures from the sea bed. Such cutting tools are either attached to a remotely operated vehicle (ROY) or handled by a diver. When working at significant depths it is particularly important that wires are not broken since changing a wire requires the tool to be returned to the surface, the wire changed and the tool returned to its cutting location which takes a significant amount of time.

These tools are typically formed having a clamping portion that attaches to the pipe to fix the tool relative to the pipe it is going to cut. The clamping portion has a U-shaped frame attached to it which is sized to fit the pipe into the open portion of the U-shaped frame. A diamond wire, formed as a continuous loop, runs around the periphery of the frame and is driven to circulate around the frame with a cutting portion extending across the open section of the U-shaped frame. A drive mechanism moves the frame relative to the clamping portion, thereby slowly moving the wire to cut through the pipe in question. The rate of movement of the frame relative to the clamping portion is under operator control and this is generally done by a judgement and interpretation of the pressure gauges for the wire and feed motors made by eye depending upon how bent the wire becomes at the point it is pressing against and cutting the pipe.

Such operator judgement can be inconsistent and can lead to excess pressure being placed on the diamond wire or the opposite and not enough pressure resulting in time wasting. Furthermore, the judgement using the deflection of the wire is inconsistent since the deflection of the wire varies as it passes through the varying thickness of the circular pipe when cutting tangentially to the circumference of the pipe.

Preferred embodiments of the present invention seek to overcome the above described disadvantages of the prior art.

According to an aspect of the present invention, there is provided an apparatus for cutting an object using a flexible cutting member, the apparatus comprising:-fixing means for fixing the apparatus relative to an object to be cut; a frame for carrying at least one flexible cutting member; frame moving means for moving, under hydraulic control, the frame relative to the fixing means; a plurality of guide members for guiding the flexible cutting member around said frame; drive means for driving the flexible cutting member around said guide members; and tension control means for controlling the tension in the flexible cutting member, said tension control means including at least one of said guide members being movable relative to said frame, biasing means for biasing the movement of said moveable guide member, and hydraulic fluid flow control means for controlling the flow of hydraulic fluid to said frame moving means in response to movement of said movable guide member.

By providing a cutting apparatus including tension control means having a movable guide member that is biased relative to the frame and a hydraulic fluid flow control means for controlling the flow of hydraulic fluid to the hydraulically controlled frame moving means, the advantage is provided that a consistent pressure can be applied to the article being cut through the cutting wire. As a result, the cutting device is able to cut at an optimal efficiency, with minimal operator judgement required and at minimal risk of the wire being damaged through the application of too much pressure on the article being cut. In particular, operator judgement is removed. For example, the operator's need to judge the strain being placed on the cutting wire at different points through the cutting of a pipe is removed.

This is important because at the start of a cutting operation as the diamond wire begins to cut into the top of the pipe, the diamond wire is cutting through the maximum thickness of pipe as it is cutting into the whole length of the portion of wire that is in engagement with the pipe. This is in contrast to the position when the wire is halfway through cutting the pipe and is therefore cutting two portions of pipe wall at their minimum thickness. If the frame was to be moved at a consistent speed relative to the clamping device, this would mean that the speed throughout the cut would have to be the minimum speed required to cut through the thickest portion of the pipe at the top and would therefore be very inefficient during the middle of the cut where the thickness of wall being cut is at its lowest. By maintaining a constant pressure on the wire, the speed of the cut self regulates with the frame moving relative to the gripping means slowly at the start of the cut, speeding up during the middle of the cut and then slowing down again at the very end of the cut where the position returns to being similar to the start of the cutting operation.

The control mechanism described above for the cutting apparatus is able to operate entirely under hydraulic control and does not require any electrical sensor apparatus. As a result, in a sub-sea decommissioning operation, the apparatus is able to operate, without the need for any addition to the hydraulic umbilical that is used in similar diamond wire

cutting devices of the prior art.

In a preferred embodiment, the fixing means comprises at least one clamp for clamping the apparatus to the object being cut.

By clamping the cutting apparatus to the pipe, the advantage is provided that the movement of the frame relative to the clamp is easily to consistently control.

In another preferred embodiment, the frame moving means comprises a hydraulic motor and worm screw.

By using a hydraulic motor and worm screw, the advantage is provided that the slow movement of the frame relative to the fixing means is easily controlled.

In another preferred embodiment, at least one said guide member comprises at least one pulley wheel rotatably fixed to said frame.

In a preferred embodiment, the drive means comprises at least one said pulley wheel being driven.

In another preferred embodiment, the driven pulley wheel is driven by a hydraulic motor.

In a further preferred embodiment, the biasing means comprises at least one spring fixed at one end to said frame and at the other end to said movable guide member.

In a preferred embodiment, the hydraulic fluid flow control means comprises at least one valve.

In another preferred embodiment, the valve comprises at least one inlet, at least one outlet and at least one linear actuator that controls the flow of hydraulic fluid between said inlet and outlet in response to linear movement of an engaging portion of said actuator.

By using a valve with an inlet and an outlet and a linear actuator for controlling the flow of hydraulic fluid between the inlet and the outlet, the advantage is provided that the actuator can be controlled by movement of the pulley wheel relative to the frame.

In a further preferred embodiment, the linear actuator comprises at least one tapered portion.

By having a tapered portion to the linear actuator, the advantage is provided that the flow of hydraulic fluid can be gradually altered as the pulley moves relative to the frame.

As a result, a small movement of the pulley causes a small reduction in the flow of fluid to the hydraulic motor thereby causing a small slowdown in the rate of movement of the frame relative to the fixing means. With increasing pressure on the wire, the pulley moves further and if the diamond wire is unable to cut the article at all, and the wire does not move through the article, the continued movement of the frame relative to the fixing means will all be taken up by the movable pulley which will eventually close the valve and prevent any further movement of the frame.

According to another aspect of the present invention there is provided a remotely operated vehicle for use underwater, the vehicle comprising:-a vehicle body, propulsion means for moving the vehicle in the water, and an apparatus for cutting an object using a flexible cutting member as set out above.

Preferred embodiments of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:-

S

Figure 1 is a front view of an apparatus of the present invention before a cut to an article is made and with a protective cover plate removed; Figure 2 is a side view of the apparatus of Figure 1 with the protective cover replaced; Figure 3 is a side view of the apparatus of Figure 2 after a cut has been made; Figures 4, 5, 6 and 7 are front, side, top and perspective views of the apparatus of Figures 2 and 3 in a transportation condition; Figure 8 is a close-up of a portion of the apparatus of Figure 1; Figures 9 and 10 are views of the reverse side of the close-up portion shown in Figure 8 with a valve in a closed and an open condition respectively; Figures 11 and 12 are front and rear views of a portion of the apparatus of Figure 1; Figure 13 is an exploded view of the portion shown in Figures 11 and 12; Figures 14 and 15 are sectional views of a valve used in the apparatus of Figure 1 in a closed and an open condition respectively; and Figure 16 is an exploded perspective view of the valve shown in Figures 14 and 15.

Referring initially to Figures 1 to 7, an apparatus, in the form of diamond wire cutting machine 10 is provided for cutting an object, for example a pipe 12 using a flexible cutting member, in this example, a diamond wire 14. The diamond wire 14 is formed as a continuous loop and is a metal wire impregnated with diamond dust of a type that is familiar to persons skilled in the art. For example, a Diamond wire, sometimes referred to as a "blade", can be made from a metal stranded core coated in synthetic rubber, on this coating diamond-impregnated beads are bonded at a set spacing usually between 38 & 52 beads per meter. These beads are commonly formed by electroplating, vacuum brazing or sintering.

Machine 10 has a fixing means in the form of gripping legs 16, that, under the control of hydraulic rams 18 clasp and grip on to pipe 12. Gripping legs 16 are attached to and fixed relative to a body 20 onto which is movably mounted a frame 22 that carries the diamond wire 14. The frame 22 moves relative to the body 20 and gripping legs 16 under the control of frame moving means 24 which includes a hydraulic motor 26 and a worm drive 28.

Mounted to frame 22 are a plurality of, and in the embodiments shown five, guide members, in the form of pulley wheels 30, that guide the diamond wire 14 around the frame 22+ The frame 22 is U-shaped and two of the pulley wheels 30 are located at the distal ends of the frame so that the diamond wire 14 is stretched across the open end of the U-shaped frame. This portion stretched across the open end of the frame forms the cutting section and the pipe 12 to be cut will pass between these distal ends of the frame.

One of the pulley wheels 30, indicated at 30a, provides a drive means for driving the diamond wire 14 around the other guide members 30. Drive wheel 30a is larger than the other pulley wheels 30 so as to provide a groater contact surface with diamond wire 14. Drive wheel 30a is driven by a hydraulic motor 32.

With additional reference to Figures 8 to 13, cutting machine 10 also includes a tension control means, indicated generally at 34, for controlling the tension in diamond wire 14 by controlling the frame moving means 24 that moves the frame 22 relative to the pipe 12 being cut. The tension control means 34 utilises one of the pulley wheels 30 that is indicated as 30b. This pulley wheel 30b is able to slide relative to frame 22, Pulley 30b (not shown in Figures 11 and 12) is mounted on an axle 36 that is in turn attached to a mounting block 38 that is able to slide within guides 40.

Mounting block 38 is pushed outwards by a biasing means, in the form of spring 42, that is attached at one end to block 38 and at the other end to an adjustable stopping member 44.

The position of adjustable stopping member 44 can be altered by movement of nuts 46 and 48 that can be adjusted along threaded rod 50 that is fixed to end piece 52 which is in turn fixed to frame 22. As a result, as diamond wire 14 is cutting into pipe 12 and the tension in the wire increases, movable pulley wheel 30b is able to move inwards by compressing spring 42 thereby ensuring that the tension in diamond wire 14 does not increase too much.

To ensure the free movement of block 38 within guides 40, a U-shaped extension 54 extends from the block 38 providing a pair of arms 56 that extend along the length of guides 40. As a result, when the spring is compressed, the bottom portion, indicated at 58, of U-shaped extension 52 extends out further beyond end piece 52.

With further reference to Figures 14 to 16, also forming part of the tension control means 34 is hydraulic fluid flow control means, in the form of valve 60, which controls the flow of hydraulic fluid to hydraulic motor 26.

Because valve 60 controls hydraulic motor 26 it in turn controls the movement of the frame 22, and therefore the cutting wire 14, relative to the gripping legs 16 and body 20. If valve 60 slowè the flow of hydraulic fluid to hydraulic motor 26 the speed of rotation of the hydraulic motor is slowed, thereby slowing the drive to worm drive 28.

Valve 60 has an inlet 62 and an outlet 64 which are connected by a hydraulic fluid pathway 66. valve 60 has two further openings 68 and 70 that are sealed by plugs 72 and are connected by a reverse flow pathway 74. Opening 70, which extends down to outlet 64 contains a reverse flow control ball valve 76. Flow within valve 60 is controlled by a linear actuator in the form of flow control pin 78 that has a tapered body 80 and a non-tapered end 82 that extends through an aperture 84 and is sealed by an 0 ring 86. End portion 82 also has an engaging surface 88.

Returning to Figure 12, the tension control means 34 further includes an adjustable valve engaging member, generally indicated at 90. The valve engaging member includes a bracket 92, which is attached to mounting block 38. Extending though bracket 92 is a bolt 94 that is fixed in position by a pair of nuts 96. The head 98 of bolt 94 is for engaging the engaging surface 88 of pin 78 of valve 60.

The movement of mounting block 38 causes movement head 98 of bolt 94 which in turn moves pin 78 varying the flow of hydraulic fluid through valve 60.

Operation of the cutting machine 10 will now be described. In Figure 1 the diamond wire 14 is shown in two different positions in the cutting region between the distal ends of U-shaped frame. 22. In one position the wire 14 extends lineally between the pulley wheels 30 at the distal ends of frame 22 and this represents the cutting wire 14 in a non-working condition and not under full working tension. In the other position the wire is slightly bent between the pulley wheels 30 at the distal end of frame 22 and in this condition the wire would be pressed into engagement with the pipe 12 that it is cutting, the wire 14 is under full working tension and spring 42 would be slightly compressed with pulley wheel 30b moved slightly inwards.

Referring to Figures 14 and 15, Figure 14 shows the valve 60 in a closed condition and Figure 15 shows the closed in a fully opened condition in which the hydraulic fluid can flow from inlet 62 to outlet 64 with the pin 78 pushed into the valve. As a result of the shape of tapered body 80, as the flow control pin 78 moves from the fully in and open position shown in Figure 15 to the fully closed and out position shown in Figure 14, the rate of flow of hydraulic fluid through valve 60 decreases. The speed of rotation of the hydraulic motor 26 is therefore variably controlled by the position of engaging surface 88 of flow control pin 78.

Engaging surface 88 of pin 78 is designed to engage the head 98 of the bolt 94 that forms axle 36. As a result, the movement of movable pulley wheel 30b moves flow control pin 78 and controls the flow of hydraulic fluid through valve 60.

In order to set up cutting machine 10, the ideal tension for cutting the pipe in question using the diamond wire in question is determined or estimated. For example, a tension equivalent to a pull of 40 kilograms might be the ideal tension in wire 14. In this case, a weight measuring hang balance is attached to wire 14 in the centre of the cutting portion, between the distal ends of frame 22, and the balance is pulled until the weight of approximately 40 kilograms is measured on the balance. This will result in the wire 14 being bent into working condition position in Figure 1. When this tension is achieved, the nuts 96 are adjusted so that head 98 of bolt 94 just or almost touches engaging surface 88 of flow control pin 78 when valve 60 is in the closed position, as shown in Figure 14 where the end portion 82 of pin 78 extends as far out as possible through aperture 84. As a result, when the tension in cable 14 reaohes or exceeds a point that is equivalent to pulling with a force of 40 kilograms, the valve 60 becomes fully closed, thereby preventing any further movement of the frame relative to the gripping legs 16 and body 20.

However, when the tension in wire 14 is less than the point that is equivalent to pulling with a force of kilograms, the spring 42 pushes the pulley wheel outwards and the head 98 of bolt 94, engaging with surface 88 of pin 78, pushes the pin 78 inwards opening the valve and allowing hydraulic fluid to flow through valve 60 thereby driving the hydraulic motor 26 and moving the frame 22 down to cut through the pipe. As the tension in wire 14 increases, spring 42 becomes slightly compressed and the head 98 of bolt 94 causes pin 78 to move downwards slightly which in turn causes the tapered body 80 to enter aperture 84 and slow the flow of hydraulic fluid to outlet 64.

In the event that the diamond wire becomes jammed, it is necessary to be able to reverse the movement of the frame.

This is achieved by reversing the flow of hydraulic fluid to the hydraulic motor 26 and reverse control ball valve 76 allows a reverse flow from outlet 64 through valve 76 and reverse flow pathway 74 to inlet 62. As a result, the position of flow control pins 78 (which would normally be in the fully closed position in the event of the wire becoming jamnied) does not matter in order to obtain a reverse flow through valve 60.

When cutting machine 10 is used to cut a pipe 12 it is moved into position relative to the pipe 12 and the gripping legs, under the control of hydraulic rams 18 are used to clasp and grip the pipes 12. The drive when 30a, under the control of hydraulic motor 32, is then used to drive the diamond cutting wire 14 around the pulley wheels 30.

Hydraulic motor 26 is then used to start movement of frame 22 relative to the pipe 12 and the cutting of the pipe is started. Once the wire has started cutting into pipe 12, it will slowly cut through the uppermost portion of the pipe where it is cutting through the longest portion of the outer surface of pipe 12 at one time. At this point it is likely that the flow of hydraulic fluid through valve 60 will be slowed in order to allow the diamond wire 14 to cut into this thickest portion of the wall. Once the cut has been completed, the frame 22 can be reversed from the position shown in Figure 3 and back to the starting position shown in Figure 1 and the gripping legs can be removed from gripping the pipe 12.

It will be approciatcd by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that the various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, the apparatus described above can be used under water but is equally applicable to being used in any location. The apparatus can be used with any form of suitable abrasive wire and can be used to cut other articles than pipe. The wire described above is in the form of a continuous loop, although any other arrangement of wire can be used. For example, the wire may be a single length that is run from one spool to another and then the direction revered. The wire can equally be any suitable flexible cutting member where the tension in the cutting member is an import factor.

The gripping legs could be used by any suitable stabilising means, for example if the object to be cut is to be located on a stable surface, non-gripping legs that simply straddle the article to be cut and engage the surface on which it is located can be used. The apparatus of the present invention can be attached to any suitable manoeuvring device or operated by hand. Such suitable manoeuvring devices include a remotely operated vehicle and in such circumstances, the apparatus is manoeuvred with the gripping legs 16 in a retracted position, as shown in Figures 4 to 7.

It should be noted that in Figures 2 to 7 the apparatus is shown with a protective casing 90 that cover the pulley wheels 30 and the portion of the diamond wire 14 that is not extending between the distal ends of frame 22. In Figure 1, this casing 100 has been removed.

Claims

Claims 1. An apparatus for cutting an object using a flexible cutting member, the apparatus comprising:-fixing means for fixing the apparatus relative to an object to be cut; a frame for carrying at least one flexible cutting member; frame moving means for moving, under hydraulic control, the frame relative to the fixing means; a plurality of guide members for guiding the flexible cutting member around said frame; drive means for driving the flexible cutting member around said guide members; and tension control means for controlling the tension in the flexible cutting member, said tension control means including at least one of said guide members being movable relative to said frame, biasing means for biasing the movement of said moveable guide member, and hydraulic fluid flow control means for controlling the flow of hydraulic fluid to said frame moving means in response to movement of said movable guide member.
2. An apparatus according to claim 1, wherein said fixing means comprises at least one clamp for clamping the apparatus to the object being cut.
3. An apparatus according to claim 1 or 2, wherein said frame moving means comprises a hydraulic motor and worm screw.
4. An apparatus according to any of the preceding claims, wherein at least one said guide member comprises at least one pulley wheel rotatably fixed to said frame.
5. An apparatus according to claim 4, wherein said drive means comprises at least one said pulley wheel being driven.
6. An apparatus according to claim 5, wherein said driven pulley wheel is driven by a hydraulic motor.
7. An apparatus according to any of the preceding claims, wherein said biasing means comprises at least one spring fixed at one end to said frame and at the other end to said movable guide member.
8. An apparatus according to any of the preceding claims, wherein said hydraulic fluid flow control means comprises at least one valve.
9. An apparatus according to claim 8, wherein said valve comprises at least one inlet, at least one outlet and at least one linear actuator that controls the flow of hydraulic fluid between said inlet and outlet in response to linear movement of an engaging portion of said actuator.
10. An apparatus according to claim 9, wherein said linear actuator comprises at least one tapered portion.
11. An apparatus for cutting an object using a flexible cutting member substantially as hereinbefore described with reference to the accompanying drawings.
12. A remotely operated vehicle for use underwater, the vehicle comprising: -a vehicle body, propulsion means for moving the vehicle in the water, and an apparatus for cutting an object using a flexible cutting member according to any of the preceding claims.