GB2369176A

GB2369176A - Gate valve

Info

Publication number: GB2369176A
Application number: GB0028149A
Authority: GB
Inventors: Neil Sutherland Duncan
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 2000-11-17
Filing date: 2000-11-17
Publication date: 2002-05-22
Anticipated expiration: 2020-11-17
Also published as: GB2369176B; GB0028149D0

Abstract

A gate valve 10 has a valve body 12 with a flow passage 14 and a cavity 16 where a gate 22 having a through bore 24 is located. Gate 22 is mounted within a carrier 26 allowing it to float axially in relation to through bore 24. A seat 18 between passage 14 and gate 22 gives sealing. An additional seat 20 on the opposite side may be used. Gate 22 is moved between open and closed positions by an actuating stem 28, which may have a piston 32 integral with or attached to its distal end and may be attached to carrier 26. Piston 32 may be received in a bonnet 36 and stem packing 58 may be provided in body 12 or bonnet 36. Piston 32 and bonnet 36 define a pair of fluid chambers 40 and 42 which can be selectively filled with pressurised fluid (e.g. from an accumulator) to open or close the valve. A similar stem 30, piston 34 , bonnet 38, and chambers 44 and 46 arrangement may be provided on the opposite side if the gate 22. The valve to be operated in a number of fail-safe modes. For use in subsea oil or gas wells, the valve will preferably pass through an aperture of 1.52m diameter.

Description

ROTARY DEPLOYABLE GATE VALVE

Field of the Invention This invention relates to gate valves suitable for use in subsea completion operations for oil and gas wells. The gate valves concerned may advantageously be deployed through the rotary table of a drilling rig or vessel. However as, in their preferred forms, they are of a compact design and employ a particularly effective sealing mechanism, they may also find uses in other applications. The preferred valve embodying the invention is suitable for FAI (Fail As Is), FSC (Fail Safe Close) or FSO (Fail Safe Open) configurations whilst using the same valve components.

Invention Background Offshore operations require the xmas tree, lower riser package and emergency disconnect package (EDP) to be stacked up and tested prior to deployment subsea. Use of a monobore riser to access a dual bore completion may require some form of isolation valve module (IVM) and bore selector device to be assembled to the top of the EDP prior to deployment.

In conventional FAI valves, the gate has limited float capability relative to the valve seats.

This can result in poor sealing characteristics, particularly at low cavity pressure. Ideally, an IVM valve should have the capability to fail as is during normal operation; but during emergency disconnect the IVM valve should have the facility to fail safe closed instead.

Conventional actuator designs do not allow the IVM valve to switch between failure modes in this way. Moreover, they are relatively bulky, and therefore cannot pass through the rotary table of the drilling rig. Such bulky components are usually positioned for connection to the running string using an overhead crane at the rig cellar deck. Some offshore rigs have very limited headroom between the cellar deck floor and the overhead crane. This makes it difficult to assemble the IVM and bore selector to the EDP.

Summary of the Invention The invention provides a gate valve comprising a body having a flow passage; a cavity in the body intersecting with the flow passage; a valve gate linearly movably received in the cavity and containing a through bore; a valve seat forming a fluid seal between the valve

gate and an end of the flow passage, and an actuator stem arranged to move the valve gate between a position in which the through bore is aligned with the flow passage to permit fluid flow through the flow passage and through bore, and a position in which the through bore and flow passage are out of alignment so that the valve gate and valve seat seal the flow passage; the valve gate being received in a carrier engaged by the actuator stem and which allows floating movement of the gate axially of the through bore. In this arrangement, the carrier retains and aligns the gate but allows it to float axially of the through bore. A particularly reliable seal can therefore be maintained, even when the pressure in the cavity is low.

The carrier may partly surround the gate with the gate being retained between the carrier and an adjacent wall of the cavity. Preferably however, the gate is received in an aperture extending through the carrier. Advantageously, the gate floats freely in the carrier and is retained in position in use by the valve seat and a further valve seat, these being on opposite sides of the valve gate.

The actuator stem may have an actuating piston integrally formed with or directly attached to its distal end. The valve and its actuator can therefore be made sufficiently compact to pass through the rotary table of a drilling rig (for example passing through a substantially circular aperture of 60 inches (1.52m) in diameter), allowing it to be easily assembled to an EDP for use in a bore selector IVM. Likewise, the actuator stem is preferably directly attached to the carrier.

The actuator stem may pass through a packing received in the valve body, so as to contain the cavity pressure. The actuating piston may be received in a bonnet attached to the valve body. In that case the stem packing may be received in the bonnet.

The actuating piston and bonnet may define a pair of opposed chambers to which pressurised fluid may be selectively supplied, for moving the stem between valve open and valve closed positions.

A further valve stem having a further actuating piston received in a further bonnet to define a further pair of opposed chambers may be provided, arranged to act upon the gate carrier opposite to the other actuator stem.

One of the chambers may be connected to a store of pressurised fluid, such as a hydraulic accumulator, so that, on removal of fluid pressure from the other chamber (s), the actuator stem (s) move (s) the gate to the closed position. If the pressurised fluid store is selectively connectable to that chamber (e. g. by a suitable valving arrangement), the same gate valve may be operated in FAI or FSC modes at will. For other applications, the pressurised fluid store and chambers can even be connectable so that, on removal of fluid pressure, the valve gate is moved to the open position, to provide a fail safe open (FSO) operating mode.

The invention and its preferred features and advantages are further described below with reference to an illustrative embodiment shown in the drawings.

Brief Description of the Drawings Fig. 1 is a schematic cross-sectional view of an IVM incorporating a gate valve embodying the invention and Fig. 2 is a perspective view of certain components of the gate valve of Fig. 1.

Description of the Preferred Embodiment The illustrated valve can be configured for either FAI, FSC or FSO operating modes, although only FAI and FSC modes are normally required in the case of IVM valves. The IVM gate valve shown is hydraulically actuated and provides a substantially more compact design over conventional valves. Even with a large flow passage, the preferred IVM incorporating a gate valve embodying the invention can pass through a conventional 60 inch (1. 52m) maximum diameter rotary table. Conventional FAI valves can suffer from poor sealing integrity due to insufficient gate float. In the IVM 10 shown, this deficiency is eliminated by using a fully floating valve gate.

The illustrated IVM consists of valve block or body 12 having a vertical flow passage 14 that intersects with a valve cavity 16. The body 12 may be connected between a bore

selector and an EDP (not shown) by connectors such as"Speedlok"TM connectors schematically indicated at 11. Each end of the flow passage 14 where it meets the cavity 16 is counterbored to receive and make a circumferential sliding seal with a valve seat 18,20.

A valve gate 22 consists of a rectangular metal slab having a through bore 24. The valve gate 22 is contained within a corresponding rectangular aperture in the centre of a gate carrier 26. The valve gate 24 is completely free to float (vertically as shown) within the gate carrier 26 in order to effect a reliable seal with the seats 18,20. Pressure from above the valve gate 22 when closed will cause it to be pressed into sealing engagement with the seat 18. Similarly, pressure from below will effect a seal between the gate 22 and the seat 20. The sealing faces of the gate 22 stand slightly proud of the carrier 26, to make contact with the seats 18, 20.

A pair of actuating stems 28,30 engage and support opposite sides of the carrier 26. The distal ends of the stems 28,30 carry pistons 32,34 that are either integrally formed with the stems 28,30 or are rigidly connected to them, e. g. by screw threads. The pistons 32,34 are received in respective bonnets 36,38, bolted and sealed to the IVM body 12. The pistons 32,34 co-operate with the bonnets to define chambers 40,42, 44,46, to or from which hydraulic fluid may be supplied or drained via respective ports 48,50, 52,54.

To move the valve from the closed position as shown towards the open position, pressurised hydraulic fluid is supplied to the port 54, thus shifting the piston 34, stem 30 and carrier 26 to the left. The through bore 24 in the valve gate 22 is thereby brought into alignment with the flow passage 14. The actuator stem 28 and piston 32 are also shifted to the left, displacing hydraulic fluid from the chamber 40 into a hydraulic accumulator circuit 56 attached to the port 48 and located in, on or in close proximity to the IVM. If the stem 28 is connected to the carrier 26 in tension as well as in compression (e. g. by a screw threaded connection), pressurised hydraulic fluid may also be supplied to the chamber 42 via the port 50 to assist in opening the valve.

To close the valve, hydraulic pressure is supplied to the port 48 from the accumulator circuit 56. Thus, if pressure is lost at the port 54, the valve closes. The IVM therefore operates in

FSC mode. As it is local to the IVM, the accumulator circuit is kept short and the risk of damage to it is minimised. During closure, hydraulic fluid is drained from the port 54. If the stem 30 is connected to the carrier 26 in tension, to assist valve closure pressurised hydraulic fluid may also be supplied to the port 52.

To operate the valve in FAI mode, the hydraulic accumulator circuit 56 is disconnected from the port 48. The valve must then be closed by connecting another source of hydraulic pressure to the port 48 and/or the port 52. To operate the valve in FSO mode, the hydraulic accumulator circuit 56 may be connected to the port 50. It is also possible to operate the IVM with the hydraulic accumulator circuit connected to the ports 52 or 54. The various port connections and corresponding modes of operation are tabulated below, where S denotes that the port concerned is connected to a source of pressurised hydraulic fluid, R denotes connection to a return line and A connection to the accumulator circuit. It will also be apparent that one of the bonnets and the corresponding actuator stem and piston is in fact redundant and may be omitted. However, duplication is preferred, for improved reliability, as well as catering for the case in which the stems 28,30 contact the carrier 26 in compression only: i. e. they act as push rods. The hydraulic connections may be exchanged as required by suitable valving in the control circuitry.

Mode Ports To IVM 54 52 50 48 54 52 50 48 FSC S R R A R S R A S R S A S A R R R A R S S A S R FAI S R R R R S R R S R S R R S R S R R S R R R R S FSO S R A R R S A R R S A S A R S R A R R S A S R S Pressure in the valve cavity 16 is isolated from the bonnets 36,38 by stem packings 58 and 60, provided in the block 12 and bonnet 38 respectively. Alternatively the packing 58 could be provided in the bonnet 36 and the packing 60 in the block 12, or both packings in the block, or both packings in their respective bonnets. Each packing is retained and energised by a respective adjustment nut 62,64, as is conventional.

Claims

CLAIMS 1. A gate valve comprising a body having a flow passage ; a cavity in the body intersecting with the flow passage; a valve gate linearly movably received in the cavity and containing a through bore; a valve seat forming a fluid seal between the valve gate and an end of the flow passage, and an actuator stem arranged to move the valve gate between a position in which the through bore is aligned with the flow passage to permit fluid flow through the flow passage and through bore, and a position in which the through bore and flow passage are out of alignment so that the valve gate and valve seat seal the flow passage; the valve gate being received in a carrier engaged by the actuator stem and which allows floating movement of the gate axially of the through bore.
2. A gate valve as defined in claim 1, in which the gate is received in an aperture extending through the carrier.
3. A gate valve as defined in claim I or 2, in which the gate floats freely in the carrier and is retained in position in use by the valve seat and a further valve seat, these being on opposite sides of the valve gate.
4. A gate valve as defined in any preceding claim in which the actuator stem has an actuating piston integrally formed with or directly attached to its distal end.
5. A gate valve as defined in any preceding claim in which the actuator stem is directly attached to the carrier.
6. A gate valve as defined in claims 4 or 5 and which will pass through a substantially circular aperture of60 inches (1.52m) in diameter.
7. A gate valve as defined in any preceding claim in which the actuating piston is received in a bonnet attached to the valve body.
8. A gate valve as defined in claim 6 in which the actuator stem passes through a packing received in the bonnet.
9. A gate valve substantially as described with reference to or as shown in the drawings.

9. A gate valve as defined in any of claims 1-7 in which the actuator stem passes through a packing received in the valve body.

10. A gate valve as defined in claim 7 in which the actuating piston and bonnet define a pair of opposed chambers to which pressurised fluid may be selectively supplied, for moving the stem between valve open and valve closed positions.

11. A gate valve as defined in any of claims 7 or 10 comprising a further actuator stem having a further actuating piston received in a further bonnet to define a further pair of opposed chambers, arranged to act upon the gate carrier opposite to the other actuator stem.

12. A gate valve as defined in claim 10 or 11 in which one of the chambers may be connected to a store of pressurised fluid.

13. A gate valve as defined in claim 12 in which the pressurised fluid store is selectively connectable to the chambers so that the gate valve may be operated in fail as is, fail safe close or fail safe open modes.

14. A gate valve substantially as described with reference to or as shown in the drawings.

CLAIMS 1. A gate valve comprising a body having a flow passage ; a cavity in the body intersecting with the flow passage; a valve gate linearly movably received in the cavity and containing a through bore; a valve seat forming a fluid seal between the valve gate and an end of the flow passage, and an actuator stem arranged to move the valve gate between a position in which the through bore is aligned with the flow passage to permit fluid flow through the flow passage and through bore, and a position in which the through bore and flow passage are out of alignment so that the valve gate and valve seat seal the flow passage; the valve gate being received in a carrier engaged by the actuator stem and which allows floating movement of the gate axially of the through bore, the actuator stem comprising an actuating piston integrally formed with or directly attached to its distal end, the actuating piston being received in a bonnet attached to the valve body, whereby the actuating piston and bonnet define a pair of opposed chambers to which pressurised fluid may be selectively supplied, for moving the stem between valve open and valve closed positions, and in which one of the chambers is selectively connectable to a pressurised fluid store, so that the gate valve can be operated in each of fail as is, fail safe close or fail safe open modes.

2. A gate valve as defined in claim 1, in which the gate is received in an aperture extending through the carrier.

3. A gate valve as defined in claim 1 or 2, in which the gate floats freely in the carrier and is retained in position in use by the valve seat and a further valve seat, these being on opposite sides of the valve gate.

4. A gate valve as defined in any preceding claim in which the actuator stem is directly attached to the carrier.

S. A gate valve as defined in any preceding claim and which will pass through a substantially circular aperture of 60 inches (1. 52m) in diameter.

6. A gate valve as defined in any preceding claim in which the actuator stem passes through a packing received in the bonnet.

7. A gate valve as defined in any of claims 1-6 in which the actuator stem passes through a packing received in the valve body.

8. A gate valve as defined in any preceding claim comprising a further actuator stem having a further actuating piston received in a further bonnet to define a further pair of opposed chambers, arranged to act upon the gate carrier opposite to the other actuator stem.