GB2386853A

GB2386853A - A feeder device for a high pressure hydraulic cutting system pressure vessel

Info

Publication number: GB2386853A
Application number: GB0207211A
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: GB0207211D0

Abstract

A feeder device or outlet valve 28 for a high pressure cutting system pressure vessel 1 includes a high pressure fluid inlet 30, means in the form of spaced channels 34 to distribute the fluid around the pressure vessel and outlet means comprising multiple inlet openings or channels 42 from the interior of the vessel to the feeder device and an outlet 46. The feeder device may be used to ensure a slurry of garnet and water is mixed in and supplied from the pressure vessel.

Description

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A Feeder Device for a High Pressure Hydraulic Cutting System Pressure Vessel This invention relates to a feeder device for a high 5 pressure cutting system pressure vessel.

High pressure hydraulic cutting systems typically use minerals, such as garnet, in a water suspension which are kept in pressurized pressure vessels and fed along a pipe 10 to a cutting head through which a fine jet of the mineral suspension is ejected in order to cut material, such as a metal pipe. The abrasive action of the minerals in suspension is the primary agent by which the cutting is achieved. The use of a cold cutting technique which uses a mineral/water suspension is particularly advantageous in underwater environments and also in underwater environments having a fire risk, such as in oil and gas 20 fields. A cold cutting system is particularly

advantageous for the decommissioning of oil/gas wells, during which decommissioning a well head pipe and supporting piles must be severed and removed. The use of a garnet/water suspension is particularly advantageous.

The pressurised water/mineral mix is stored in a pressure vessel and added to a pressurised water stream. A prior art arrangement to allow the exit of the water/mineral mix from the pressure vessel is to use a ball valve. When 30 high pressures are used or are needed a ball valve functions poorly and typically would block, with obvious disadvantages resulting. Also, the garnet must be kept in

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e t À suspension otherwise damage to the pipes supplying the cutting head will result.

It is an object of the present invention to address the 5 above mentioned disadvantages.

According to a first aspect of the present invention a feeder device for a high pressure cutting system pressure vessel comprises: 10 inlet means for an input fluid supply; distribution means for directing said fluid around said pressure vessel; and outlet means comprising multiple inlet openings and an outlet. Preferably, the feeder device is for an underwater high pressure cutting system pressure vessel.

Preferably, the feeder device is adapted to mix a slurry 20 in the pressure vessel and supply that mixture to a cutting mechanism of said cutting system. The slurry may be a water/mineral mixture, which may be a water/garnet mixture. 25 The inlet means may be a conduit, which may be a pipe.

The inlet means may be arranged to extend substantially from a first side of the pressure vessel to a second side thereof. 30 A main body of the feeder device may be adapted to be secured to a wall of said pressure valve, and to provide an outlet therefrom.

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:: o r The distribution means may comprise a plurality of channels, which may lead from the inlet means to an exterior of the feeder device. The channels preferably exit at spaced locations around the exterior of the feeder 5 device. Preferably, there are six channels. The channels are preferably inclined downwards, preferably at an angle of more than approximately 45 from the horizontal. The channels preferably extend radially from the inlet means.

10 The channels are preferably arranged to cause material ejected therefrom to issue downwards and to collide with walls of the pressure vessel to be directed upwards by said walls.

15 The inlet openings of the outlet means may form channels extending from exterior of said feeder device to the outlet. The outlet may extend from an interior of the feeder device to an exterior thereof.

20 The channels of the outlet means may be formed between upper and lower parts of the feeder device. The upper part may form a distribution section incorporating the inlet means and distribution means. The lower part may form the outlet means. The upper and lower parts may be 25 secured together by a friction fit, which may be assisted with fixing means.

The channels of the outlet means may be evenly spaced around the feeder device. There may be six channels. An 30 opening of each said channels may face downwards. The channels may have a vertical section, which may lead into a generally horizontal section, which may lead into the

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r., r it outlet. The outlet may extend substantially vertically downwards towards an exterior of the pressure vessel.

The invention extends to a pressure vessel incorporating 5 the feeder device of the first aspect.

The pressure vessel may be adapted to hold a slurry mixture in suspension at greater than approximately 500 bar, preferably greater than about 750 bar, more 10 preferably more than about 850 bar, most preferably more than about 1200 bar. The pressure vessel is preferably adapted to maintain the slurry mixture in suspension at or above said pressures stated above.

15 All of the features described herein may be combined with the above aspect in any combination.

A specific embodiment of the invention will now be described, and by way of example with reference to the 20 accompanying drawings, in which: Figure 1 is a schematic cross-sectional side view of a pressure vessel for a hydraulic cold cutting system; 25 Figure la is a schematic crosssectional enlarged view of a feeder device of the pressure vessel shown in Figure 1; Figure 2 is a schematic hydraulic circuit of the cold cutting system; Figure 3 is a schematic view from the side of the cold cutting system; and

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Figure 4 is a schematic view from above of the cold cutting system.

A cold cutting system 20 comprises two pressure vessels 1 5 located in a framework 22 which secures the pressure vessels 1 in position. The pressure vessels have on/off valves 24 which regulate an input of water pressurized to approximately 1,000 bar (and possibly up to 1400 bar) by a two stage compressor (not shown). Needle valves 3 are 10 used to regulate the filling of the pressure vessels 1.

Pressure gauges 8 are located between the needle valves 3 and the pressure vessels 1.

15 Each pressure vessel comprises a drain/reverse flush needle valve 4 located at the base of each pressure vessel 1. A hydraulic cylinder operated trunnion ball valve 2 for 20 each pressure vessel 1 is used as a regulator to regulate the input of slurry at a pressure of 1,000 bar to an output 54 pipe of the system 20.

As shown in Figure 2 a plugged opening 11 allows the 25 addition of a slurry component into the pressure vessel, which slurry component comprises garnet.

Each pressure vessel incorporates a safety head 6 and rupture disc 7 to prevent dangerously high pressures being 30 created within the pressure vessels 1.

A secondary drain 10 is also provided.

re À. en. --; r '' r r. - ? r r 6 As mentioned above, the pressure vessels 1 are supplied with water at a pressure of approximately 1,OOO bar (possibly up to 1400 bar). Garnet crystals are also introduced into the pressure vessels via the plugged 5 opening 11.

The garnet forms the basis of the abrasive slurry mixture which is to be jetted to the outlet 54 at high pressure to provide the basis of the cutting mechanism.

In order to function properly, the garnet must be kept in suspension within the water in the pressure vessels 1. If the garnet is not kept in suspension then a dry mix will be issued from a main slurry outlet 26 of the pressure 15 vessels which will cause premature degradation of hoses through which the slurry mixture is directed. The garnet used has a particle the size of approximately 850 m. The slurry mixture is directed through hoses from the main slurry outlet 26 via the pipe 54 to a cutter head (not 20 shown) having an outlet diameter of approximately lmm in order to provide a fine jet for the slurry mixture, which jet is used for cutting. This cutting system is particularly advantageous for underwater cutting, in particular the underwater cutting of pipes, such as 25 oil/gas well pipes and their supporting piles.

Figures 1 and la show a feeder device/outlet valve 28 that is primarily responsible for both ensuring that the garnet is kept in suspension in the water in the pressure vessels 30 and also regulating the flow of the water/garnet slurry mixture to the main slurry outlet 26.

or cÀ... À- of; ,. r,. r I"; a, The valve 28 incorporates an inlet pipe 30 which extends downwards from an upper region of the pressure vessel towards the base of the valve 28. The inlet pipe receives pressurized water and directs that water down to a main 5 body of the valve 28. The inlet pipe 30 has a diameter of approximately 14 mm.

Water from the inlet pipe 30 enters an upper body section 32 of the valve and is directed to channels 34 which exit 10 the upper body 32. Six channels are provided, evenly spaced around the upper body 32 so that six jets of water issue from the upper body 32 at evenly spaced locations around the upper body 32. The channels 34 point downwards and so create a flow towards the base of the pressure 15 vessels, which flow is directed upwards on reaching the walls of the pressure vessels and causes a churning motion, thus ensuring that the garnet is kept in suspension in the water. Grub screws 36 are provided to allow access to the channels 34 for maintenance purposes.

The upper body portion 32 has a interference fit, assisted by a grub screw 38 with a lower body portion 40 of the valve 28. Channels 42 are formed between a side wall of the lower body portion 40 and an inner wall of the upper 25 body portion 32 which allow a water and garnet mixture to enter from the base of the valve 28 to move upwards into openings 44 in the lower body portion 40. There are six openings 44 arranged around the lower body portion 40 at even spacings. Each of the openings 44 enters into a 30 central chamber 46 which exits the lower body portion 40 at the base thereof into an exit pipe 48 which also has a diameter of 14 mm. From the exit pipe 48 the water/garnet

e (. HA r À . C t- Cam À .. slurry mixture exits the pressure vessel 1 at the main slurry outlet 26.

From the main slurry outlet 26 the slurry mixture is added 5 at valves 52 (one for each pressure vessel) to a supply of pressurized water to be supplied down the piping 54 mentioned above towards a cutter head.

The valve 28 advantageously combines a first portion for 10 ensuring that garnet within the pressure vessel is kept in suspension in the water therein. The lower second portion provides multiple pathways through which the water/garnet suspension can exit and be added to a water flow for use as the abrasive cutting element for the cold cutting 15 system 20.

As shown in Figure 2 the hydraulic circuit shows a main inlet for the pressurised water at 50 with additional valves 52, one for each of the pressure vessels 1 for 20 adding the slurry mixture to the pressurised water supply which is then passed at 54 to a cutting tool for ejection from the cutting head described above.

Each pressure vessel is generally spherical and has a 25 diameter of approximately 700 mm. An alternative shape includes a cylindrical pressure vessel.

The cold cutting system 20 is operated at a sea surface level for underwater use. The feed pipe to the cutter 30 described above may typically be several 100 metres long, possibly 250 metres long to supply the cutting head for use in the cutting of an oil/gas well pipe and supporting piles.

- À,. t : r : .. The provision of extremely high pressure (approximately 1,000 bar) water supply with abrasive garnet allows for some pressure reduction over the great distance from the 5 cold cutting system 20 to the cutting head.

The framework 22 for the pressure vessels may advantageously be provided with slots 56 at opposite ends thereof to allow the cold cutting system 20 to be lifted 10 and manoeuvred into position. The framework 22 may also provide a protective cage for the pressure vessels 1 and associated valve work and supply piping.

The valve 28 advantageously provides multiple mixing 15 outlet channels 34 to ensure even mixing of the water and garnet. Multiple inlet channels 42 for the lower part of the valve 28 are also provided to ensure even take up of the mixed water/garnet suspension. The convoluted channels through which the water/garnet suspension must 20 pass provides some pressure resistance for the mixture exiting the pressure vessels.

The extremely high pressure of the water in the pressure vessels 1 increases the need to have good mixing of the 25 water/garnet mixture which would not normally have been required with lower pressure systems previously available.

Such a previous system would be a standard ball valve to allow exit of the water and garnet suspension. However, such standard ball valve would block at the high pressures 30 used in the present system.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to

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c À À À À f 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 process so disclosed, may be combined in any combination, 10 except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including

any accompanying claims, abstract and drawings), may be 15 replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each 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 novel one, or any novel combination, of the features disclosed in this specification (including any

25 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

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1. A feeder device for a high pressure cutting system pressure vessel comprises: 5 inlet means for an input fluid supply; distribution means for directing said fluid around said pressure vessel; and outlet means comprising multiple inlet openings and an outlet.

2. A feeder device as claimed in claim 1, which is for an underwater high pressure cutting system pressure vessel.

3. A feeder device as claimed in either claim 1 or claim ski 15 2, which is adapted to mix a slurry in the pressure vessel and supply that mixture to a cutting mechanism of said cutting system.

4. A feeder device as claimed in claim 3, in which the 20 slurry is a water/mineral mixture

5. A feeder device as claimed in any preceding claim, in which the inlet means is a conduit.

25

6. A feeder device as claimed in any preceding claim, in which the inlet means is arranged to extend substantially from a first side of the pressure vessel to a second side thereof. 30

7. A feeder device as claimed in any preceding claim, in which a main body of the feeder device is adapted to be secured to a wall of said pressure vessel.

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8. A feeder device as claimed in any preceding claim, in which the distribution means comprises a plurality of channels, which lead from the inlet means to an exterior of the feeder device.

9. A feeder device as claimed in claim 8, in which the channels exit at spaced locations around the exterior of the feeder device.

10 10. A feeder device as claimed in either claim 8 or claim 9, in which the channels are inclined downwards.

11. A feeder device as claimed in claim 10, in which the channels are inclined downwards at an angle of more than 15 approximately 45 from the horizontal.

12. A feeder device as claimed in any one of claims 8 to 11, in which the channels are arranged to cause material ejected thereform to issue downwards and to collide with 20 walls of the pressure vessel to be directed upwards by said walls.

13. A feeder device as claimed in any preceding claim, in which the inlet openings of the outlet means form channels 25 extending from the exterior of said feeder device to the outlet.

14. A feeder device as claimed in claim 13, in which the outlet extends from an interior of the feeder device to an 30 exterior thereof.

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15. A feeder device as claimed in either claim 13 or claim 14, in which the channels of the outlet means are formed between upper and lower parts of the feeder device.

5

16. A feeder device as claimed in claim 15, in which the upper part forms a distribution section incorporating the inlet means and distribution means.

17. A feeder device as claimed in either claim 15 or claim 10 16, in which the lower part forms the outlet means.

18. A feeder device as claimed in any one of claims 15 to 17, in which the upper and lower parts are secured together by a friction fit.

19. A pressure vessel incorporating a feeder device as claimed in any one of claims 1 to 18.

20. A pressure vessel as claimed in claim 19, which is 20 adapted to hold a slurry mixture in suspension at greater than approximately 500 bar.

21. A feeder device substantially as described herein with reference to the accompanying drawings.