GB2430399A

GB2430399A - Cutting Apparatus

Info

Publication number: GB2430399A
Application number: GB0519289A
Authority: GB
Inventors: Stephen Mckelvey; Robert Biggs
Original assignee: UWG Ltd
Current assignee: UWG Ltd
Priority date: 2005-09-22
Filing date: 2005-09-22
Publication date: 2007-03-28
Also published as: GB0519289D0

Abstract

A cutting apparatus comprises a plurality of rotary cutting means mounted on a first plate 6. The first plate is mounted on a second plate 7 both the first and second plates having a C-shape. The first plate is rotated relative to the second plate to enclose a tubular member 200 which is then engaged by the plurality of rotary cutting means. The member can be severed by rotating the plurality of rotary cutting means around the member.

Description

CUTTING APPARATUS

BACKGROUND

a. Field of the Invention

The present invention relates to apparatuses for cutting and in particular to apparatuses that can be used to cut underwater members, such as the tubular members that are commonly found on structures used in the extraction of oil and gas.

b. Related Art The decommissioning of offshore oil and gas platforms is required once the resource of oil or gas has been depleted or if the platform has passed its operating lifetime. A number of different approaches have been contemplated, such as bandsaws and the strategic placement of explosives.

Two approaches that have been used are the use of large hydraulic shears to sever a tubular member (see, for example, US 5 245 982 and US 5 413 086) and the use if diamond wire cutters (see, for example, EP 1 373 645). However, neither of these approaches are without disadvantages: the shears and the hydraulic rams that are required to power them are large, heavy and expensive and the first two factors make underwater deployment difficult. It has also been observed that bandsaws and diamond wire cutters are prone to becoming trapped when cutting and can also take a long time to sever a tubular member.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an apparatus for cutting a tubular member, the apparatus comprising: a first plate and a second plate, the first plate and the second plate both comprising an aperture for receiving In a tubular member and the first plate being rotatably mounted on the second plate; rotating means for, in use, rotating the first plate relative to the second plate; a plurality of rotating cutting means mounted on the first plate and coupled to respective positioning means; wherein, in use, the first plate is rotated relative to the second plate to receive a tubular member within the aperture of the first and second plates and the positioning means move one or more of the plurality of rotating cutting means into contact with the received tubular member.

According to a second aspect of the present invention there is provided a method of cutting a tubular member, the member comprising the steps of: a) aligning a first plate with a second plate such that a tubular member can be received in an aperture formed in the first plate and the second plate; b) rotating the first plate relative to the second plate such that the tubular member is enclosed within an aperture defined the first plate and the second plate; c) moving a plurality of rotary cutting means into contact with the outer surface of the tubular member; and d) activating the plurality of rotary cutting means in order to form a plurality of cuts in the tubular member. Preferably the method comprises the further step of e) moving the plurality of rotary cutting means around the outer surface of the tubular member to sever the tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the following Figures in which: Figure 1 shows a first schematic depiction of a cutting apparatus according to the present invention; and Figure 2 shows a second schematic depiction of a cutting apparatus according to the present invention shown in Figure 1 when the apparatus is engaged with a tubular member. n

DETAILED DESCRIPTION

Figure 1 shows a first schematic depiction of a cutting apparatus 100 according to the present invention. The cutting apparatus 100 comprises a plurality of rotary cutters I that are mounted on a first plate 6. The first plate is substantially C- shaped and is received upon a second plate 7, the second plate having an identical shape to that of the first plate 6. Each of the rotary cutters I is connected to a cutting drive means 2, which preferably comprise a hydraulic motor. Each of the rotary cutters I is also connected to a feed mechanism that enables the rotary cutters to be moved radially towards or away from the centre of the apparatus.

The feed mechanism comprises a sliding means 3 and an actuator 4, such as a hydraulic cylinder, that can be used to move the sliding means and thus vary the position of the rotary cutter. Alternatively, the feed mechanism may comprise a pivot and an actuator such that the position of the rotary cutter can be varied by pivoting the cutter. The first plate is supported by a bearing (not shown) on the second plate and a sector or a ring gear 8 and one or more rotary motors 9 are provided in order to allow the first plate to be rotated relative to the second plate.

Preferably the one or more motor(s) are secured to the second plate.

In use the apparatus is moved relative to a tubular member 200 to be cut such that the tubular member is received within the open region of the first and second plates. Figure 2 shows a second schematic depiction of the cutting apparatus 100 as described above with reference to Figure 1 when the apparatus is engaged with a tubular member. The tubular member is engaged by the rotation of the first plate such that the tubular member is encircled by the apparatus. This is achieved by the activation of the rotary motor(s) such that the first plate is rotated relative to the second plate. The apparatus further comprises a plurality of clamping mechanisms 10 that are extended to clamp the tubular member in position in the centre of the substantially circular region formed when the first plate is rotated.

Once the tubular member has been secured by the plurality of clamping mechanisms the rotary cutters are advanced radially and are rotated by their respective cutting drive means such that the rotary cutters begin to cut into the tubular member. Once the rotary cutters have made the initial cut, the rotary motor(s) may be activated further in order to rotate first plate such that the rotary cutters are moved around the outer surface of the tubular member 20 in order to complete the severance of the member. Preferably, the cutters will initially be advanced at a low speed in order to allow cuttings to be removed until the cutters have passed through the surface of the member. It will be understood that all of the rotary cutters may be activated together or that one or more of the cutters may be activated at different times. In the event that one of the cutters fails then it may be retracted and the cutting may continue with the remaining rotary cutters. Blade members 5 may be provided, these blade members having the same width as the rotary cutters, in order to remove the blade of a rotary cutter from the member if the blade becomes stuck.

Preferably the feed mechanism comprises a tracking system that enables the penetration of each cutter through the wall of the tubular member to be controlled.

The tracking system may be passive, for example a stop or pin that prevents the cutter from being advanced beyond a predetermined distance,. Alternatively an active tracking system may be used, with sensors monitoring the speed and displacement of each rotary cutter and feeding this data back to the control unit for the cutting drive means or to an operator. This assists in the use of the apparatus to cut members of differing sizes or tubular members that are distorted and if the member is received eccentrically in the apparatus.

One of the advantages of the present invention is that it may be used where there is only access to the member to be cut from one side (as long as there is sufficient clearance for the first plate to be rotated around the member). In use the apparatus is positioned around the member with the assistance of a crane, driver or remotely operated vehicle (ROy). Buoyancy may be added to the apparatus in order to facilitate the installation and operation of the device, particularly in use with an ROy. One or more cameras may also be mounted on the apparatus to assist in the installation of the apparatus and/or to enable the progress of the cutting operation to be monitored.

The present invention provides an increased performance when compared with a bandsaw as the member is cut in a number of different locations around the circumference of the member rather than at a single location. As these regions are equally spaced around the member, this reduces the chances that the loads generated by the member causes the kerf to close, which can lead to the blade being jammed in the pipe.

It will be readily understood that a number of variations may be made to the above apparatus without departing from the scope of the present application. For example, more than three rotary cutters may be used and this will lead to a decrease in the time taken to sever a member each of the cutters need only cut a smaller arc of the member. Increasing the number of rotary cutters will of course increase the weight of the apparatus and it is believed that three rotary cutters is an adequate compromise for most applications.

Claims

1. An apparatus for cutting a tubular member, the apparatus comprising: a first plate and a second plate, the first plate and the second plate both comprising an aperture for receiving a tubular member and the first plate being rotatably mounted on the second plate; rotating means for, in use, rotating the first plate relative to the second plate; a plurality of rotating cutting means mounted on the first plate and coupled to respective positioning means; wherein, in use, the first plate is rotated relative to the second plate to receive a tubular member within the aperture of the first and second plates and the positioning means move one or more of the plurality of rotating cutting means into contact with the received tubular member.

2. An apparatus according to claim 1, wherein the apparatus further comprises a plurality of clamping means received upon the second plate, the plurality of clamping means acting, in use, to clamp a tubular member to be cut such that the tubular member is securely received within the aperture of the first and second plates.

3. An apparatus according to claim I or claim 2, wherein both the first and second plates are substantially C-shaped and the plurality of rotating cutting means are mounted on the first plate with substantially equal rotational offsets.

4. An apparatus according to any preceding claim wherein, in use, the first plate is rotated relative to the second plate in order to sever a tubular member.

5. A method of cutting a tubular member, the member comprising the steps of: a) aligning a first plate with a second plate such that a tubular member can be received in an aperture formed in the first plate and the second plate; b) rotating the first plate relative to the second plate such that the tubular member is enclosed within an aperture defined the first plate and the second plate; c) moving a plurality of rotary cutting means into contact with the outer surface of the tubular member; and d) activating the plurality of rotary cuffing means in order to form a plurality of cuts in the tubular member.

6. A method according to claim 5 further comprising the step of; e) moving the plurality of rotary cutting means around the outer surface of the tubular member to sever the tubular member.

7. A method according to claim 5 or claim 6, further comprising the step of; f) securing the tubular member using a plurality of clamping means, wherein step f) is carried out after step b) but before step c).