GB2294528A - Needle valve - Google Patents

Abstract

A needle valve has a valve stem (2) movable into and out of engagement with a valve seat (36). The valve stem (2) is biased to the closed position by disc springs (18) or other resilient means, and is driven to the open position by rotation of a drive housing (8) screw-threadedly mounted in a fixed housing (5) to compress the springs (18). Rotation of the drive housing (8) in the opposite direction allows the valve stem to re-engage the seat (36) solely under the biassing force of the springs (18). Also disclosed is a needle valve comprising a stem (51) provided with a pair of flow control surfaces (62, 63) which cooperate with respective seats (64, 65). The spindle is coupled to a cam-operated drive housing (58) through a lost-motion connection which includes sets of disc springs (70, 71). The valve is particularly for use in a subsea environment and is under reduced risk of damage resulting from the application of excessive operating force. <IMAGE>

Description

"Needle Valve" This invention relates to a needle valve and is particularly, but not exclusively, relevant to a high pressure needle valve for use in demanding environments such as in subsea use.

In a conventional needle valve, a valve stem is brought into and out of engagement with a valve seat by the action of a sleeve in screw threaded engagement with the valve body, the sleeve being fixed to the stem by another screw threaded engagement.

Out patent document GB 2,222,870A discusses certain disadvantages of the foregoing conventional valves, and discloses a needle valve in which the screw threaded engagement between the stem and the sleeve is replaced by an interference fit.

Known high pressure needle valves suffer from the disadvantage that, since a high torque must be applied to achieve secure seating of the stem on the valve seat, it is easy inadvertently to over torque the valve when closing it, resulting in a likelihood of damage to the stem and/or the seat.

According to the present invention, a needle valve comprises a body, an inlet port and an outlet port formed in the body and communicating via a valve seat formed in a bore in the body, a valve stem which is axially movable to bring an inner end of the valve stem into and out of engagement with the valve seat, resilient means urging the valve stem into engagement with the valve seat, and actuator means operable to force the valve stem away from the valve seat against the bias of the resilient means.

Preferably, the actuator means comprises a rotary member having a screw thread whereby rotation of the rotary member produces axial motion relative to the valve body.

In a particularly preferred form, the resilient means comprises a stack of disc springs trapped between a collar on the valve stem and a housing secured to the valve body; and the rotary member is a cup-shaped member in screw threaded engagement with said housing and engaging under an end cap of the valve stem.

Preferably, a high pressure axial seal is provided between the body and an inner portion of the stem.

Preferably also, ring seals are provided between the housing and the body, between the cup-shaped member and the housing, and between the end cap and the cup-shaped member.

In an alternative form of the invention, the actuator means may comprise an actuator member movable axially of the valve stem by a manually operated cam mechanism, said resilient means being interposed between the actuator member and the valve stem. Further, the valve stem may be engageable selectively with said valve seat or a second valve seat, and said actuator member is then bidirectionally engageable with the valve stem via first and second resilient means.

Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which: Fig. 1 is a plan view of a needle valve forming one embodiment of the invention; Fig. 2 is a cross-section on the line X-X of Fig. 1; Fig. 3 is a cross-section of a modified form of needle valve forming a second embodiment of the invention; and Fig. 4 is a cross-section of a further embodiment of the invention.

Referring to Figs. 1 and 2, the valve has a body 1 within which an inlet port 30 communicates with an outlet port 31 via drilled passages 33 and 34 and a central bore 35. The central bore 35 is formed with a valve seat 36 which is engaged by the end of a stem 2 to block flow through the valve.

The stem 2 is biased into the closed position by resilient means in the form of a stack of conical disc springs 18 which act between a collar 37, integrally formed on the stem 2, and a face of a housing 5.

The housing 5 has a generally cylindrical forward part in screw threaded engagement with a cylindrical cavity of the body 1 and sealed with respect to the body 1 by an O-ring 17. After being screwed into the body 1, the housing 5 is locked in position by a locking plate 4 secured in place by set screws 14.

The housing 5 further has a rearward part, also of generally cylindrical form, which is internally threaded to receive a cup-shaped drive housing 8. The drive housing 8 has an inner end portion which engages under an end cap 6 secured to the outer end of the stem 2, in the example shown by interengaging screw threads.

A stainless steel washer 13 is provided between the end face of the drive housing 8 and the end cap 6. The drive housing 8 is sealed with respect to the main housing 5 by an O-ring 11, and a seal ring 12 is provided between the end cap 6 and the drive housing 8.

A drive pin 7 extends diametrically through the drive housing 8, secured in position by a spring pin 21, and with one end extending from the drive housing 8 for engagement by an actuating device, for example a driving member mounted on a ROV in the case of subsea use. The status of the valve is indicated by the position of the extending part of the drive pin 7 in relation to a position indicator ring which is secured to the locking plate S by set screws 9.

The main fluid path is sealed with respect to the stem 2 by a high pressure axial seal 19 secured in place and energised by a seal back-up member 3 screwed into a threaded counter bore of the body 1.

For transport purposes, the ports 30, 31 may be blanked off by plastics caps 20. The ports 30, 31 are provided with weep holes 38 which may likewise be blanked off for transport by plastics plugs 22.

In use, the valve is normally closed by the action of the disc springs 18 bearing on the stem 2 via the collar 37. It should be noted that the force exerted on the valve seat by the stem in this condition is dependent only on the spring force, which is set by the springs used and the spacing of the collar 37 with respect to the face of the housing 5. To open the valve, the drive pin 7 is engaged and rotated through a predetermined angle, in the example shown 270".

Rotation of the drive pin 7 and thus of the drive housing 8 causes outward axial movement of the drive housing 8 which draws the stem 2 off the valve seat 36 to open the valve. Reverse rotation allows the disc springs 18 to return the stem 2 into engagement with the valve seat 36.

Fig. 3 shows a modified form of needle valve. This is similar in principle to the embodiment of Figs. 1 and 2, and like parts are denoted by like reference numerals. In Fig. 3, however, the inlet port 30 and outlet port 31 are formed in an outer body member la, while the valve seat 36 is formed in an inner body member lb. The inner body member 1b is received within the outer body member la and is held in position by a locking ring 4a in conjunction with a snap ring 40.

With reference to Fig. 4, there is illustrated a further embodiment illustrating a valve which employs a bi-directional or two-way stem tip. This design of valve permits flow from two separate sources to be selected for supply. A valve stem 51 has a tip formed with upper and lower sealing faces 62, 63 for sealing against upper and lower valve seats 64, 65. The valve has a common inlet 66 and first and second outlets 67, 68.

In the neutral position shown in Fig. 4, fluid can flow from the inlet 66 to both outlets 67, 68. When the valve stem 51 is urged into upper or lower positions to bring one of the sealing faces 61, 62 into engagement with the respective valve seat 64, 65 flow occurs through the other outlet only.

The arrangement of Fig. 4 uses a cam 50 to operate the valve stem 51. Actuation of the cam 51 is by a lever 52 which moves through an arc to lower or lift the stem 51 via a cup-shaped drive housing 58. The drive housing 58 engages a drive spool 59 having an upper flange 60 and a lower flange 61. A first set of disc springs 70 is interposed between the flange 60 and the interior lower face of the drive housing 58. A second set of disc springs 71 is interposed between the outer lower face of the drive housing 58 and the lower flange 61. The sets of disc springs 70 and 71 act to cushion the closing force in both directions thereby avoiding excessive loads on the valve stem.

The present invention thus provides a needle valve suitable for high pressure use and in which the closing force of the valve stem against the valve seat is independent of the torque or other actuating force applied to operate the valve.

The invention may readily be embodied in valves having a working pressure of 10,000 psi or greater, and capable of operating subsea to depths of 5,000 ft.

There is a high degree of flexibility of layout: the entry and exit ports can be positioned in any desired orientation in the main body, while providing an unrestricted flow area.

The use of conical disc springs is particularly preferred, since this facilitates the provision of a high spring force in a limited area. Belleville washers may be used in a similar way. However, other forms of resilient biasing means, for example coil springs, may be used.

Claims (8)

1. A needle valve comprising a body, an inlet port and an outlet port formed in the body and communicating via a valve seat formed in a bore in the body, a valve stem which is axially movable to bring an inner end of the valve stem into and out of engagement with the valve seat, resilient means urging the valve stem into engagement with the valve seat, and actuator means operable to force the valve stem away from the valve seat against the bias of the resilient means.

2. A needle valve according to claim 1, in which the actuator means comprises a rotary member having a screw thread whereby rotation of the rotary member produces axial motion relative to the valve body.

3. A needle valve according to claim 2, in which the resilient means comprises a stack of disc springs trapped between a collar on the valve stem and a housing secured to the valve body; and the rotary member is a cup-shaped member in screw threaded engagement with said housing and engaging under an end cap of the valve stem.

4. A needle valve according to claim 3, in which a high pressure axial seal is provided between the body and an inner portion of the stem.

5. A needle valve according to any preceding claim, in which ring seals are provided between the housing and the body, between the cup-shaped member and the housing, and between the end cap and the cup-shaped member.

6. A needle valve according to claim 1, in which the actuator means comprises an actuator member movable axially of the valve stem by a manually operated cam mechanism, said resilient means being interposed between the actuator member and the valve stem.

7. A needle valve according to claim 5, in which the valve stem is engageable selectively with said valve seat or a second valve seat, and in which said actuator member is bidirectionally engageable with the valve stem via first and second resilient means.

8. A needle valve substantially as herein described with reference to, and as shown in Figs. 1 and 2 or Fig. 3 or Fig. 4 of, the drawings.