GB2386856A

GB2386856A - Monitoring of a pipe cutting mechanism

Info

Publication number: GB2386856A
Application number: GB0207210A
Authority: GB
Inventors: Laurie Todd; Alfred Rhodes; Brendan Larkin
Original assignee: MOS COLD CUTTING SYSTEMS Ltd
Current assignee: MOS COLD CUTTING SYSTEMS Ltd
Priority date: 2002-03-27
Filing date: 2002-03-27
Publication date: 2003-10-01
Also published as: GB0207210D0

Abstract

The invention relates to cutting mechanism 22 for cutting the interior of an oil or gas well pipe 16 or oil/gas well support pile 14a/b. The cutting mechanism 22 is suspended by means of a wire 24 inside the pipe 16 or pile 14a/b. Services to the cutting mechanism 22 are via umbilical cords 26, 28 and 30 which provide electricity, a water slurry mix of the cutting operation and pneumatic power. The cutting mechanism 22 also incorporates a motor 32 which is arranged to drive the cutting mechanism.

Description

À. À a..

J e À À. 1 2386856 e Monitoring of a Pipe Cutting Mechanism This invention relates to a monitoring system for a remote controlled cutting machine and a method of monitoring a 5 remote cutting machine.

Figure 2 shows schematically a well head 10 sunk into a seabed 12 and supporting piles 14a and 14b extending down from an oil rig or the like. The well head 10 consists of 10 a pipe 16 (or multiple pipes) which extends up to an oil rig at the sea surface or other suitable installation for removing oil from the well head 10. The piles 14a and 14b are formed by hollow tubular structures.

15 When decommissioning an oil well the pipe 16 and well head 10, as well as the piles 14a and 14b must be removed by cutting the pipes. A cutter 18 is shown suspended on a wire 20 which extends down from the oil rig at the sea surface. The cutter 18 is used to cut the well head 10 20 below the surface of the seabed 12 by moving around the interior of the well head 10 and cutting the pipe material as it moves. A similar technique is used for removal of the piles 14a and 14b.

25 Disadvantages arise with this prior art set up in that

there is no means by which the progress of the cutting operation by the cutting mechanism 18 can be ascertained.

Visual inspection beneath the seabed 12 is not possible.

30 It is an object of the present invention to address the above stated problem.

tc e À According to a first aspect of the present invention a method of monitoring a remote controlled cutting mechanism comprises: obtaining signals from a sensor of a cutting 5 mechanism, which cutting mechanism is remote from a control means of the cutting mechanism, the sensor being operable to detect rotation of a part of the cutting mechanism relative to a member to be cut, said signals from the sensor corresponding to rotational information 10 for the cutting mechanism; passing said signals to the control means; translating said signals into rotational information for the cutting mechanism using information pre-programmed into the control means.

The sensor may be a proximity sensor, which preferably provides a signal for each rotation thereof with respect to the member to be cut. - - -

20 The cutting mechanism is preferably an underwater cutting mechanism. Preferably the member to be cut is a pipe, which may be an oil/gas well pipe or a supporting pile for said pipe.

25 Preferably the cutting mechanism operates beneath the sea bed. The control means may be a computer and may include a programmable logic circuit (PLC). The information pre 30 programmed into the control means may include: the number of signals from the proximity sensor that corresponds to the number of turns of a cutting head of the cutting mechanism, the number of turns of the cutting head

- D. At'. À À required to cut a given member to be cut and/or the time elapsed since a cutting operation commenced.

The control means may use the signals from the proximity 5 sensor and the pre-programmed information to derive a value for the speed of a cutting operation, the time taken for a given cutting operation, the proportion of a cutting operation completed and/or the angle through which the cutting mechanism has already cut.

The derived values are preferably displayed on display means, preferably connected to the control means.

The pre-programmed information may include information 15 relating to a number of different sizes of member, or pipe, to be cut. Size information for a member to be cut may be entered into the control means before commencement of a cutting operation.

20 The speed of a motor driving the cutting mechanism is preferably variable, preferably to prevent excessive wear of the cutting mechanism and/or allow for environmental or other factors affecting a desired cutting speed.

25 A motor of the cutting mechanism is preferably located in a first section of the cutting mechanism. A cutting head of the cutting mechanism may be located in a second section. An intermediate section may be located between the first and second sections. The motor may drive the 30 intermediate section via reduction gearing. The intermediate section may drive the second section via reduction gearing. The ratio between rotation of a motor drive shaft and the cutting head may be approximately in

-. -. À-.:e À A-: the region of between 50 and 150 to 1, preferably between approximately 75 and 125 to 1, most preferably between approximately 90 and 110 to 1.

5 The intermediate section may also incorporate a proximity sensor. According to a second aspect of the invention a monitoring system for a remote controlled cutting mechanism comprises 10 at least one sensor arranged to be attached to a remote controlled cutting mechanism; and control means operable to receive signals from said sensor; wherein the sensor is operable to detect rotation of a 15 part of the cutting mechanism relative to a member to be cut, and pass said signals to the control means; and wherein the control means is operable to translate said signals from the sensor into rotational information relating to a cutting head of the cutting mechanism using 20 information pre-programmed into the control means.

The control means may include display means. The control means may include, or be, a computer, which may be a Siemens Step 7 processor, programmed in Siemens Step 7.

The invention extends to a cutting mechanism incorporating said at least one sensor.

The invention extends to a computer operable to perform 30 the method of the first aspect.

À À À -

À À -

À d The invention extends to a recordable medium carrying a computer program operable to perform the method of the first aspect.

5 All of the features described herein may be combined with any of the above aspects in any combination.

For a better understanding of the invention and to show how the same may be brought into effect, a specific 10 embodiment of the invention will now be described, by way of example, and with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a cutting mechanism; 15 and Figure 2 is a schematic view of a prior art set up for

decommissioning an oil well.

20 Figure 1 shows a cutting mechanism 22 for cutting the interior of an oil or gas well pipe 16 or oil/gas well support pile 14a/b. The cutting mechanism 22 is suspended by means of a wire 24 inside the pipe 16 or pile 14a/b shown in Figure 2. Services to the cutting mechanism 22 25 are provided via umbilical cords 26, 28 and 30 which provide electricity, a water slurry mix for the cutting operation and pneumatic power. The cutting mechanism 22 also incorporates a motor 32 which is arranged to drive the cutting mechanism.

The cutting mechanism 22 is divided into a number of sections, with three being shown as an example in Figure 1. An upper section 34 incorporates the motor 32. A

_, -a- e r À À À middle section 36 is driven by the motor 32. A lower section 38 incorporates a cutting head 40 and is caused to rotate by means of coupling with the middle section 36.

The arrow B in Figure 1 indicates the rotation of the 5 cutting head 40. The cutting mechanism 22 also incorporates at least one stabilizing arm 42 to brace the cutting mechanism 22 against the pipe which is to be cut.

The upper section 34 of the cutting mechanism 22 10 incorporates a proximity sensor 44 and the middle section 36 incorporates a proximity sensor 46.

The middle section 36 rotates with respect to the upper section 34 when the motor 32 is turned.

The proximity sensor 44 in the upper section 34 detects rotation of the upper section 34 relative to the well head 10 which is to be cut. The proximity sensor 46 attached to the middle section 36 detects the rotation of the 20 middle section 36 relative to the well head 10.

In addition to relative rotation of the upper section 34 with respect to the middle section 36, the lower section 38 also rotates with respect to the middle section 36 by 25 means of gearing (not shown) between the two sections.

Signals from the proximity sensors 44 and 46 are transmitted by the electrical umbilical cord 26 to computing means and control means (not shown) mounted at 30 the sea surface where the cutting mechanism 22 is controlled. By taking a difference between the proximity sensor 44 and proximity sensor 46 rotation of the upper section 34 with respect to the well head 10 can be removed

À (e cat À À:: from the figure for rotation of the middle section 36 with respect to the well head 10. Thus the number of turns of the motor 32 (a known figure) can be related to the movement of the middle section 36. The rotational speed 5 of the cutting head 40 can be determined using the known gear,ratio between the middle section 36 and the lower section 38 using the data from the proximity sensor 46.

The gearing of the cutting mechanism 22 is typically such 10 that 100 turns of the motor 32 result in a single turn of the cutting head 40, although different ratios could be used. One entire cutting operation to sever the well head 10 may require approximately 72,000 revolutions of the cutting head 40.

A programmable logic circuit PLC (not shown) in the control means is programmed with the number of revolutions of the cutting head 40 which equates to the number of revolutions with respect to the well head 10 of the 20 proximity switch 46. Thus by using the output of the proximity switch 46 a readout of a speed of cut value can be provided.

Knowledge of the number of turns required to cut a given 25 pipe is also programmed into the PLC to allow a time taken for a cut to be generated and the progress through a particular cut to be given as an output based on the number of revolutions required for a cut and the number of revolutions already achieved.

In addition, the PLC can be programmed to use the information from the proximity sensors 44 and 46 to determine an angle of cut, which gives the progress

- - through the 360 angle of a complete cut. Thus if half the required 72,000 revolutions have been completed the angle of cut will be half the complete 360 , i.e. 180 .

5 The information as to the speed of the cut is particularly useful because it is often necessary to regulate the speed of the cut depending on the qualities of the slurry used and also the pressure of the slurry. Pressure sensing for the slurry mixture is already a known feature in this type 10 of cutting mechanism 22.

The system disclosed above is advantageously programmed using the Siemens Step 7 processor using the Step 7 language. The programming of such a machine to make use 15 of the information from the proximity sensors 44 and 46 provides particular advantages which allow monitoring of the cutting head 40 in an underwater cutting operation.

Such monitoring has not previously been attainable. The cutting operation will typically be conducted 20 approximately 200 metres beneath the surface of the water and cutting is carried out beneath the seabed 12 for minimization of environmental impact.

The reader's attention is directed to all papers and 25 documents which are filed concurrently with or previous to this specification in connection with this application and

which are open to public inspection with this specification, and the contents of all such papers and

documents are incorporated herein by reference.

All of the features disclosed in this specification

(including any accompanying claims, abstract and drawings), and/or all of the steps of any method or

I:.. process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

5 Each feature disclosed in this specification (including

any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each 10 feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any 15 novel one, or any novel combination, of the features disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

be----::;--:. CLAIMS:

1. A method of monitoring a remote controlled cutting mechanism comprises: 5 obtaining signals from a sensor of a cutting mechanism, which cutting mechanism is remote from a control means of the cutting mechanism, the sensor being operable to detect rotation of a part of the cutting mechanism relative to a member to be cut, said signals 10 from the sensor corresponding to rotational information for the cutting mechanism) passing said signals to the control means; translating said signals into rotational information for the cutting mechanism using information pre-programmed 15 into the control means.

2. A method as claimed in claim 1, in which the sensor is a proximity sensor.

20 3. A method as claimed in claim 2, in which the proximity sensor provides a signal for each rotation of the proximity sensor with respect to the member to be cut.

4. A method as claimed in any preceding claim, in which 25 the cutting mechanism is an underwater cutting mechanism.

5. A method as claimed in any preceding claim, in which the member to be cut is a pipe.

30 6. A method as claimed in any preceding claim, in which the control means is a computer and includes a programmable logic circuit (PLC).

À c -:'... -:e 7. A method as claimed in any preceding claim, in which the information pre-programmed into the control means includes: the number of signals from the proximity sensor that corresponds to the number of turns of a cutting head 5 of the cutting mechanism, the number of turns of the cutting head required to cut a given member to be cut and/or the time elapsed since a cutting operation commenced. 10 8. A method as claimed in any preceding claim, in which the control means uses the signals from the proximity centre and the pre-programmed information to derive a value for the speed of a cutting operation, the time taken for a given cutting operation, the proportion of a cutting 15 operation completed and/or the angle through which the cutting mechanism has already cut.

9. A method as claimed in claim 8, in which the derived values are displayed on display means.

10. A method as claimed in any preceding claim, in which the preprogrammed information includes information relating to a number of different sizes of member, or pipe, to be cut.

11. A method as claimed in any preceding claim, in which the speed of a motor driving the cutting mechanism is variable. 30 12. A method as claimed in any preceding claim, in which a motor of the cutting mechanism is located in a first section of the cutting mechanism.

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13. A method as claimed in claim 12, in which a cutting head of the cutting mechanism is located in a second section. 5 14. A method as claimed in claim 13, in which an intermediate section is located between the first and second sections.

15. A method as claimed in claim 14, in which the motor 10 drives the intermediate section via reduction gearing.

16. A method as claimed in either claim 14 or claim 15, in which the intermediate section drives the second section via reduction gearing.

17. A method as claimed in any preceding claim, in which the ratio between rotation of a motor drive shaft and a cutting head is approximately in the region of between 50 and 150 to 1.

18. A method as claimed in any one of claims 14 to 17, in which the intermediate section also incorporates a proximity sensor.

25 19. A monitoring system for a remote controlled cutting mechanism comprises at least one sensor arranged to be attached to a remote controlled cutting mechanism; and control means operable to receive signals from said sensor) 30 wherein the sensor is operable to detect rotation of a part of the cutting mechanism relative to a member to be cut, and pass said signals to the control means; and wherein the control means is operable to translate said

- À À

signals from the sensor into rotational information relating to a cutting head of the cutting mechanism using information pre-programmed into the control means.

5 20. A monitoring system as claimed in claim 19, in which the control means includes display means, 21. A monitoring system as claimed in either claim 19 or claim 20, in which the control means includes, or is, a 10 computer.

22. A cutting mechanism incorporating a sensor as described in claim 19.

15 23. A computer operable to perform the method of any one of claims 1 to 18.

24. A recordable medium carrying a computerprogram operable to perform the method of any one of claims 1 to 20 18.

25. A method substantially as described herein with reference to the accompanying drawings.

25 26. A system substantially as described herein with reference to the accompanying drawings.