GB2112109A

GB2112109A - Multi-way valve

Info

Publication number: GB2112109A
Application number: GB08138471A
Authority: GB
Inventors: Michael Thomas Dennis
Original assignee: BRISCO ENG Ltd
Current assignee: BRISCO ENG Ltd
Priority date: 1981-12-22
Filing date: 1981-12-22
Publication date: 1983-07-13
Also published as: DE3244986A1; GB2112109B

Abstract

A slide valve which comprises a housing (10) having a longitudinal passage fitted with bushings (12, 14, 16, 17, 18, 19) defining a cylindrical bore within which a valve member (20) is longitudinally slidable, said valve member being a solid bar blind bored from both ends with aperture means (52, 54, 56, 58) in its tubular wall for providing selective communication between ports (28, 30, 32) defined by annular, outward recesses at selected bushings, wherein the valve member and ports are arranged so that on a forward stroke the reservoir port (32) is isolated before the load port (30) is connected to the pressure port (28) and on a return stroke the pressure port is isolated before the load port is connected to the reservoir port. <IMAGE>

Description

SPECIFICATION Improvements in slide valves This invention relates to a slide valve and more especially but not exclusively to a slide valve for alternatively connecting a high pressure working fluid, e.g. fluid at a working pressure of up to 10000 p.s.i., to a load or connecting the load to a reservoir or tank in order to dump the load pressurising fluid at high speed.

Valves for the above-mentioned purpose are commonly employed in oil installations, for example for controlling wellhead wing, master and sub-surface safety valves and other hydraulically actuated valves and safety devices. Existing twoposition, three-port valves for the purpose include metal to metal poppet valves, with the disadvantage that during stroking all the ports are open simultaneously. Metal to metal spool valves are also known, which avoid unwanted communication between ports during stroking, but have the alternative disadvantage of permitting continuous leakage from the supply to the tank, which is especially unacceptable when the possibility exists of long periods of non-use.

Furthermore, metal to metal seal, rotating or linear, sliding face valves are susceptibie to damage in the presence of particle contamination in the working fluid. Also known are '0' ring sealed spool valves, which avoid both disadvantages of the previously described valves, but are operable only at limited working pressures and have a short seal life.

It is an object of this invention to provide a slide valve which can overcome the disadvantages of known valves intended for the above-described usage.

According to the present invention, a slide valve comprises a housing and a valve member longitudinally slidable therein to control opening and closure of at least three ports which comprise or include a pressure port, a load port and a reservoir port, wherein the valve member and the ports are so arranged that, on a forward stroke of the valve member the reservoir port is isolated before the load port is connected to the pressure port and on a return stroke the pressure port is isolated before the load port is connected to the reservoir port.

Preferably, the housing has a bore provided with ports in the form of annular, outwardlyrecessed lands communicating with respective pressure, load and tank (reservoir) connections, and the valve member is a hollow tube closed at both ends and with an intermediate barrier, in practice being a solid bar blind bored from both ends, with aperture means in its tubular wall, on both sides of the intermediate barrier, enabling the respective lands to be selectively communicated through the interior of the valve member. The apertures are so positioned that, during stroking, either the tank port or the pressure port is isolated before the other two ports are in communication.

Sealing between the slidable valve member and the bore in the housing in which it slides is preferably effected by means of cup seals with lips spread by a ring-shaped spring seated in the cup and O-rings fitted to bushings. The cup seals are located at the internal diameter of the bushings and O-rings on the outside diameter of the bushings. The cup seals are located so that, in use, when an aperture in the tubular valve member crosses a seal, the pressure of the working fluid is balanced on the lip of the seal, which seals against the valve member. In this way it is ensured that the seals are not damaged during stroking.

Efficiency and long life is also ensured by the use of sealing materials of fluoro-elastomers or specially formulated PTFE compounds, which effect a particularly efficient sealing function in relation to stainless steel (preferably 316 S16 or 316 S12 stainless steel) or aluminium bronze alloy (preferably CA104 alloy).

In connection with the above-described manner of sealing, an important feature of the invention concerns the pressure balancing function provided in association with the isolatable ports, especially the tank port.

In a preferred arrangement, in relation to the pressure port, pressure across the associated cup seals is balanced through a pair of aperture means in the wall of the tubular valve member which, in one operative position of the valve member, effect communication between the pressure and load ports, and which at the same time ensure that the supply pressure exists in the valve member, on the one side of the barrier therein, when any aperture in the valve member on that side of the barrier is traversing a seal.

The pressure balancing function for the tank port in the preferred arrangement is particularly unique. When the working fluid which has been previously employed to pressurise the load has been dumped to the tank, the next stroke of the valve member would normally occur with a low pressure within the valve member on the one side of the barrier, and at least one of the spring biassed cup seals associated with the tankconnected land would be liable to damage. For this reason, an additional aperture is provided in the wall of the valve member, in this instance to communicate the annular space between the two cup seals nearest the one end of the valve member with a fluid reservoir chamber in the housing.This chamber, which would otherwise remain pressurised after the load is dumped thereby to cause pressure imbalance on one seal at the next stroke, is, therefore, depressurised through this additional aperture.

The pilot drive for the slidable valve member may be mechanical or electrical, but is preferably pneumatic or hydraulic with a spring return action, employing a minimum pilot operator pressure of the order of 50 p.s.i. Maximum pilot operator pressures may be up to 10000 p.s.i.

A typical working fluid will be mineral oil, water/glycol fluid mixture, water, crude oil or gases; the pilot operator fluid may be any of these same fluids.

The slide valve of the invention is not necessarily a two-position, three port valve; the same "block before bleed" functions can be achieved in a multi-position, multi-port valve.

Furthermore, the spool may be designed for either normally closed (load pressurising fluid dumped) or normally open (load pressurised) configuration when in the spring returned position.

Further features of the slide valve according to the invention will be apparent from the following description referring to the accompanying drawing, in which: the single figure is a longitudinal crosssectional view through a practical embodiment of slide valve.

This valve comprises a composite main valve housing 10 which includes internal bushings, such as those referenced 12, 14, 16, 17, 18, 19, defining a cylindrical bore within which is a valve member 20 which is longitudinally slidable. The housing 10 has fluid connections 22, 24 and 26 respectively for pressurising fluid from a working fluid pressure source, for supply of said working fluid to a load, e.g. an hydraulic ram, and for dumping working fluid from the load to a reservoir or tank.

Bushings 12, 14, 16, 17, 18, 19 etc. are fixed within the housing 10 and sealed in relation thereto, and together provide for communication from the fluid connections 22, 24, 26 to respective ports 28, 30, 32 open to the valve bore.

The pressure port 28 comprises an annular outwardly-recessed land longitudinally extended along the bore, the load port 30 is similar and the tank port 32 is similarly formed but of reduced longitudinal extent.

At one end, the valve member 20 extends out of the valve housing 10 into a composite pilot drive housing 34 secured to said valve housing.

The pilot drive for effecting a longitudinal stroking of the valve member 20 forms no part of the present invention and will not be described in detail. As illustrated, it comprises a piston plate 36 acting on a closure plate 38 at one end of the valve member 20, whereby said valve member can be forwardly stroked under the drive of a pilot operator fluid supplied through connection 40.

Return stroking of the valve member 20 is by means of a spring 42 acting on the closure plate 38.

The pilot drive could, however, be mechanical (possibly manual), or electrical.

The present invention is more especially concerned with the relative configurations of the ports and the valve member whereby a "block before bleed" function is achieved.

The slidable valve member 20, which comprises a solid bar blind bored from both ends, in addition to the closure plate 38 at one end, is closed at the other end by a plug 44.

The wall of the valve member is formed with aperture means, respectively 52 to 60, apertures 52, 54 opening to the internal space 48, which is associated with the pressure port 28, and apertures 56, 58, 60 opening to the internal space, which is associated with the tank port 32.

More particularly, in one operative position of the valve member 20, apertures 52 communicate with the pressure port 28 and supply pressurised fluid through the internal space 48, via apertures 54, to the load port 30; in another operative position of the valve member 20 (which is illustrated), apertures 56 communicate with the load port 30 and dump pressurised fluid through the internal space 50, via apertures 58, to the tank port 32.

The relative positions of the ports 28, 30, 32 and aperture means 52 to 58 ensure firstly that, during a forward stroke of the valve member 20, the tank port 32 becomes isolated from the load port 30 before communication is established between the pressure port 28 and the load port 30; and secondly that, during a return stroke, the pressure port 28 becomes isolated from the load port 30 before the latter port is communicated to the tank port 32.

Another unique feature of the invention concerns the sealing means provided between the valve member and the bore in which it slides, which seals eliminate internal leakage even under high working pressures.

Five annular cup seals 62 to 70 are provided, as illustrated. Each contains a ring-shaped spring (not shown) which urges the lips of the cup apart. Cup seals 62, 64 isolate the pressure port 28; cup seals 66, 68, 70 isolate the tank port 32.

During stroking, it is essential that the inner lip of a cup seal should not be drawn into an aperture in the wall of the cup member and be rendered liable to damage or even shearing off. It is therefore necessary to ensure that, when an aperture is crossing a seal, fluid pressure is not acting inwardly on this lip of the seal.

The pair of aperture means 52, 54 automatically ensure that the pressure of the working fluid is balanced at the vulnerable seal 64.

On the side of the tank port 32 however, assuming the load pressurising fluid has been dumped, a further stroke of the valve member 20 would be liable to damage the vulnerable seal 68.

It is for this reason that the aperture means 60 is provided; it communicates with a reservoir chamber 72 in the form of an annular recessed land, in the bore fitting 18, which chamber 72 is closed at the rearmost end by the additional cup seal 70.

When fluid is directed to the load port during a forward stroke, the chamber 72 between the cup seals 68 and 70 is pressurised to balance the pressure on the lip of the cup seal 68 during a subsequent rearward stroke of the valve member 20. Aperture 60 then dissipates pressure of fluid trapped between cup seals 68 and 70 after a rearward stroke to ensure that the lip of the cup seal 68 is pressure balanced on the next forward stroke.

In the embodiment above-described, the metal housings and associated parts are preferably made of 316 S 16 or 316 S 12 stainless steeí or of CA104 aluminium bronze alloy, whilst all sealing materials are preferably fluoro-elastomers or special PTFE compounds.

The described example is especially suitable for use at high working pressures in oil installations, where it is anticipated that only occasional stroking will be required, but long life without maintenance is an essential requirement. Equally, in an emergency situation, for example, the described valve is capable of dumping many litres of working fluid from the load in only a few seconds.

Various modifications are possible within the scope of the invention as hereinbefore defined; in particular it is to be noted that the same "block before bleed" action can be provided in a three position slide valve having more than three ports.

Finally, it is to be noted that the slide valve of this invention is not restricted to use in the oil industry, but finds industrial application in various other fields.

Claims

1. A slide valve comprising a housing and a valve member longitudinally slidable therein to control opening and closure of at least three ports which comprise or include a pressure port, a load port and a reservoir port, wherein the valve member and the ports are so arranged that, on a stroke of the valve member in one direction the reservoir port is isolated before the load port is connected to the pressure port and on a stroke of the valve member in the opposite direction the pressure port is isolated before the load port is connected to the reservoir port.

2. A slide valve according to claim 1, wherein the housing has a longitudinal cylindrical passage provided with ports in the form of annular outwardly-recessed lands communicating with respective pressure, load and reservoir connections.

3. A slide valve according to claim 2, wherein the valve member is a hollow tube closed at both ends and with an intermediate barrier, with aperture means in its tubular wall on both sides of the intermediate barrier enabling the respective lands to be selectively communicated through the interior of the valve member.

4. A slide valve according to claim 3, wherein the valve member is a solid bar blind bored from both ends.

5. A slide valve according to claim 2 or claim 3 or claim 4, wherein the said lands and connections are formed in and between a succession of internal bushings fixedly located in the longitudinal passage and defining a bore within which the valve member is slidable.

6. A slide valve according to claim 5, wherein sealing between the bushings and the valve member, in order to isolate the respective lands one from another except through said valve member, is effected by means of seals recessed into at least some of the bushings at the internal diameter thereof.

7. A slide valve according to claim 6 when appendant to claim 3, wherein the seals are located so that, in use, when an aperture in the valve member crosses a seal, the pressure of the working fluid is balanced substantially to prevent deformation of the seal into the valve member aperture.

8. A slide valve according to claim 6 or claim 7, wherein the seals are cup seals each with lips spread by a ring-shaped spring.

9. A slide valve according to any of claims 5 to 8, wherein sealing at the external diameter of the bushings, in order to isolate the respective connections one from another except through the valve member, is effected by means of O-rings recessed into at least some of the bushings.

10. A slide valve according to any of claims 6 to 9, wherein the cup seals and/or O-rings are made of an elastomeric material.

11. A slide valve according to claim 10, wherein the elastomeric material is based on a fluoro-carbon copolymer.

12. A slide valve according to claim 3 or any claim appendant thereto, wherein, in relation to seals associated with the pressure port and located between the housing and the valve member, pressure on said seals is balanced through a pair of aperture means in the wall of the valve member which both effect communication between the pressure and load ports in one operative position of the valve member and ensure maintenance of the supply pressure on one side of the barrier in the valve member when any aperture in the wall thereof on that side of the barrier is traversing a seal.

13. A slide valve according to claim 3 or any claim appendant thereto, including a fluid storage chamber provided in the housing in association with the reservoir port, which chamber is pressurised when on a stroke of the valve member in one direction working fluid is dumped through the reservoir port, thereby to balance pressure on seals associated with the reservoir port land during a subsequent stroke in the opposite direction, and an additional aperture means in the wall of the valve member through which the pressure in said chamber is dissipated after said stroke in the opposite direction, thereby to balance pressure on said seals during the next stroke in the said one direction.

14. A slide valve according to claim 13, wherein said storage chamber is formed by an additional annular land devoid of any connection to the valve exterior, with annular seals at the ends thereof, one of which also constitutes a seal for one end of the reservoir port land.

1 5. A slide valve according to any of claims 1 to 14, being a normally closed slide valve arranged so that, on a forward stroke of the valve member, the reservoir port is isolated before the load port is connected to the pressure port, and vice versa on the return stroke.

16. A slide valve according to any of claims 1 to 14, being a normally open slide valve arranged so that, on a forward stroke of the valve member, the pressure port is isolated before the load port is connected to the reservoir port, and vice versa on the return stroke.

17. A slide valve according to any of claims 1 to 16, including an hydraulic or pneumatic pilot drive coupled with a spring return.

18. A slide valve according to any of claims 1 to 17, which is a two-position, three port valve, with the load port disposed in the longitudinal direction of the valve between the supply port and the reservoir port.

19. A slide valve substantialiy as hereinbefore described with reference to the accompanying drawings.