GB2125521A - Flow control valve - Google Patents

Abstract

A choke valve for controlling the flow of fluids from a well bore comprises a body (10) having an inlet (12) and outlet (14). A disc (28) is non-rotatably mounted in the body and includes at least one non- central aperture (32). A second disc (26) also having at least one non- central aperture (30) is rotatable relative to the first disc (28) by an external handle (44) to move the apertures (30, 32) into and out of register. Spring loaded pistons (56) bias the movable disc (26) against the fixed disc (28) to provide a seal between opposing faces (50, 52) at low pressure and low flow rates. <IMAGE>

Description

SPECIFICATION Flow control valve The present invention relates to flow control valves, and in the preferred embodiment provides a multiples orifice control valves of the type employed on oil or gas wells as a drilling choke valve or as a production choke.

In drilling oil or gas wells, the control or domination of downhole pressure is critical.

The drilling fluid or mud used in drilling the well forms the first line of defense in controlling the downhole pressure. Extreme care is used in controlling the downhole pressure to prevent a well blowout.

Unfortunately, even when extreme care is exercised by the drilling crew, formation fluids, such as gas, salt water or oil, or any combination thereof, may enter the drill hole.

When a noticeable increase in the volume of the mud in the mud pit occurs, the event is known as a "kick". An uncontrolled flow of formation fluid is a "blowout". When a "kick" occurs, it is necessary to activate the second line of defense in controlling the down hole pressure to prevent a "blowout".

The second line of defense includes blowout preventers and choke valves.

The blowout preventers are used to close the top of the well. At the same time, it is necessary to circulate heavier drilling fluid into the well and then allow controlled escape of the combined formation and drilling fluids.

The choke valve is used to control the flow of fluids from the well by regulating the size of a flow opening provided beneath the top of the well. The choke valve maintains enough back pressure to allow the controlled discharge of drilling and formation fluids, but prevents further entry of formation fluid into the well.

A choke valve that has achieved wide acceptance in the drilling industry for handling deep, high pressure wells, is disclosed in United States patent 3,207,181. The choke valve illustrated in the referenced patent comprises a pair of discs having orifices therethrough, with one of the discs being rotatable relative to the other disc for selectively aligning the orifices for regulating the flow of fluid through the valve. The discs' interface is sealed closed due to the relatively high pressure fluid flowing against the upstream disc, which forces the downstream face of the upstream disc into sealing engagement with the upstream face of the downstream disc.

However, the interface of the discs will not seal until fluid pressure and/or flow reach a point at which the mass of the upstream plate is overcome. Until the necessary flow and/or pressure conditions are achieved, at least a portion of the opposed faces are in spaced relation; thereby defining a fluid flow path.

The flow of fluids through the unsealed interface during low pressure conditions may cause erosion of the discs.

Further, it is necessary to leak-test the choke valves prior to their being placed in service. The leak-testing must be accomplished at relatively high pressure conditions due to the aforedescribed problem associated with the lack of proper sealing at low pressure conditions. The foregoing requires special test procedures and equipment.

Attempts have been made to solve the low pessure seal problem by reducing the linear tolerance between the discs and the means employed to rotate the rotatable discs. Although the foregoing reduces sealing losses, the problem is not eliminated, while reducing linear tolerances increases the manufacturing cost.

According to the present invention there is provided a flow control valve comprising: a valve body having a longitudinally extending opening therein; means defining an inlet leading to said opening; means defining an outlet leading from said opening; a pair of relatively rotatable disc means disposed in continguous relation in said opening between said inlet and said outlet, with one of said disc means being positioned upstream with respect to the other of said disc means; means extending into said body for rotating one of said disc means relative to the other of said disc means; each of said disc means having openings therethrough movable into and out of alignment to control the flow of fluid from said inlet to said outlet; and force producing means connected to the upstream side of the upstream disc means for urging said disc means into sealing engagement with said downstream disc means.

The preferred embodiment of the invention achieves low pressure or static sealing of the discs' interface without significantly increasing the manufacturing costs of the valve.

The above and other features and advantages of the invention will become clear from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 is a sectional view illustrating a cross-sectional view of a prior art flow control valve highlighting the short-coming thereof; and Figure 2 is a sectional view, similar to Fig.

1, illustrating a flow control valve incorporating the present invention.

In referring now to the drawing, Fig. 1 illustrates a multiple orifice valve of the prior art and Fig. 2 illustrates the valve of Fig. 1 including the invention herein disclosed. In referring to Figs. 1 and 2 of the drawing, like numerals shall refer to like parts.

Referring first to Fig. 1, the multiple orifice valve includes a valve body generally denoted by reference numeral 10 having an inlet opening 1 2 and an outlet opening 14. Body 10 includes a main section 1 6 having longitudinally extending opening 1 8 therethrough.

Section 1 6 includes a flange-like portion 20 which is welded or otherwise secured to a corresponding flange-like portion 21 of tubular section 22. An O-ring seal 24 is provided between the opposed faces of flange-like sections 20 and 21.

A pair of relatively rotatable discs means 26 and 28 are disposed in contiguous relation in opening 1 8 between inlet 1 2 and outlet 14.

Discs means 26 and 28 respectively include orifices 30 and 32 extending therethrough. As illustrated, disc means 26 is positioned upstream with respect to disc means 28. Downstream disc means 28 is longitudinally positioned within opening 1 8 through engagement with shoulder 33.

As noted previously, each disc means 26 and 28 has at least one orifice therethrough respectively 30 and 32. The orifices are selectively brought into alignment upon relative angular movement of one of the disc means with respect to the other of the disc means. In the specific embodiment, disc means 26 is angularly movable with respect to disc means 28.

To effect such angular movement, an actuator member generally referenced 34 is rotatably mounted in end wall 35 of body section 16. Actuator member 34 includes a stem section 48 extended through an opening 37 in end wall 35 and sealed therein as by means of O-rings 36. At its inner end stem 48 carries a forked turning member 38 engageable in a notch 40 formed in disc means 26. Actuator member 34 is adapted to be rotated by an operating handle or wheel 44 formed as part of a cap 42 secured by fastener means 46 to the outer extremity of stem 48.

It should be understood that the mass of each of the discs means 26 and 28 is comparatively great. Although disc means 26 is forced towards disc means 28 by actuator member 34, there is a certain degree of linear tolerance between the end of forked turning member 38 and notch 40 of disc means 26.

Accordingly, at low pressure or static conditions, disc means 26 assumes the position with respect to disc means 28 as illustrated in Fig. 1. As readily observed, the confronting faces 52 and 50 respectively of disc means 26 and 28 are spaced apart to define a fluid flow channel. As previously discussed, the illustrated valve is primarily used as a choke valve in drilling operations. When it is desired to terminate flow of drilling fluid through the valve, orifices 30 and 32 of the disc means are angularly spaced as illustrated in Fig. 1.

However, when the valve is closed at low pressure conditions, there is insufficient force on the upstream face of disc means 26 to fully force the confronting faces 50 and 52 of the two disc means into sealing engagement.

Thus, fluid can flow around the edge of disc 26 and through orifice 30 into orifice 32.

This precludes positive closure and the undesired fluid flow may cause erosion of the disc means.

Now referring to Fig. 2, there is illustrated a valve that is identical to the valve illustrated in Fig. 1 except that the valve illustrated in Fig.

2 incorporates the present invention designed to overcome the shortcomings of the prior art valve. In particular, it will be readily observed that confronting faces 50 and 52 are in sealing engagement. The sealing engagement between the confronting faces of disc means 26 and 28 is achieved irrespective of the force produced by the upstream pressure acting against the upstream face of disc means 26.

To achieve the desired sealing engagement of faces 50 and 52, force producing means generally referenced 53 is connected to the upstream face of disc means 26 for urging the disc means into sealing engagement with the downstream disc means. In the preferred embodiment, force producing means 53 comprises a pair of retractable pistons 56 extending from cylinders 54. Each cylinder includes a spring 58 for forcing the piston outwardly from the cylinder towards disc means 26. The cylinders are connected to actuator member 34. As illustrated, the cylinders are symmetrically positioned about either side of the longitudinal axis of the disc means so that the force provided by each of the cylinders is equal so that disc means 26 is uniformly forced into sealing engagement with disc means 28.

By providing positive sealing of the confronting faces of discs means 26 and 28 fluid flow between orifices 30 and 32 at low upstream pressure conditions is prevented. The foregoing obviates the problem discussed with respect to the prior art valve whereby positive seal was not availabe at low pressure and erosion of the disc was occuring thereby increasing maintenance of the valve and decreasing its reliability.

While the preferred embodiment utilizes spring-loaded pistons 56 extending from cylinders 54, alternative means for producing the necessary force may be utilized. For example, a belleville spring may be installed between actuator member 34 and the upstream face of disc means 26. Similarly an elastomeric member may be bonded to the front face of the actuator member to apply a force on the upstream face of disc means 26, or a spring device may be suitably placed to urge the actuator member into positive engagement within notch 40.

While a perferred embodiment of the present invention has been described and illustrated, the invention should not be limited thereto but may be otherwise embodied within the scope of the following claims.

Claims (4)

1. A flow control valve comprising: a valve body having a longitudinally extending opening therein; means defining an inlet leading to said opening; means defining an outlet leading from said opening; a pair of relatively rotatable disc means disposed in contiguous relation in said opening between said inlet and said outlet, with one of said disc means being positioned upstream with respect to the other of said disc means; means extending into said body for rotating one of said disc means relative to the other of said disc means; each of said disc means having openings therethrough movable into and out of alignment to control the flow of fluid from said inlet to said outlet; and force producing means connected to the upstream side of the upstream disc means for urging said disc means into sealing engagement with said downstream disc means.

2. The flow control of claim 1 wherein said upstream disc means is rotatable and said force producing means is connected to said means for rotating said disc means.

3. The flow control valve in accordance with claims 1 or 2 wherein said force producing means comprises a pair of cylinders urged into contact with said upstream face of said upstream disc means, with the force produced by said pair of cylinders being equal.

4. A flow control valve substantially as hereinbefore described with reference to the drawings.