Device for controlling fluid flow

Abstract

A device is provided for controlling the flow of a fluid through a conduit from an upstream side to a downstream side of the device. The device includes a valve aperture, a cylindrical mounting member on the downstream side of the valve aperture, a valve member on the outside of the cylindrical mounting member that moves reciprocally to open and close the valve aperture, a control volume defined between the cylindrical mounting member and the valve member, an arrangement for introducing a control pressure into the control volume, and a seal between the outer surface of the cylindrical mounting member and the inner surface of the valve member that substantially seals the control volume. The valve member is acted on by the pressure of the upstream side (P.sub.1) and the control pressure (P.sub.4) so as to be moved by the difference between these pressures.

Claims

1. A device for controlling the flow of a fluid through a conduit from an upstream side of the device to a downstream side of the device, the device comprising: a valve aperture; a cylindrical mounting member arranged on a downstream side of the valve aperture; a valve member movably mounted on an outside of the cylindrical mounting member and arranged to move reciprocally to selectively open and close the valve aperture, thereby controlling flow of the fluid through the valve aperture; a control volume arranged to receive a control pressure for acting on the valve member, wherein the device comprises no more than one control volume for receiving the control pressure that acts on the valve member, and wherein the control volume is defined between the cylindrical mounting member and the valve member; a control conduit for introducing the control pressure into the control volume; and a flange for mounting the device within the conduit, wherein the cylindrical mounting member is attached to the flange and wherein the flange comprises one or more apertures to allow fluid to flow through the flange and into a downstream side of the conduit; wherein the valve member is acted on by a pressure of the upstream side and the control pressure so as to be moved by a difference between these pressures.

2. The device as claimed in claim 1, wherein the cylindrical mounting member, the valve member and the valve aperture are arranged coaxially with respect to each other about an axis that extends in a direction collinearly with the general direction of fluid flow through the valve aperture.

3. The device as claimed in claim 1, wherein the axis of the device is parallel to an axis of the conduit in which the device is arranged.

4. The device as claimed in claim 1, wherein the valve aperture lies in a plane perpendicular to the axis of the cylindrical mounting member.

5. The device as claimed in claim 1, wherein the device comprises a housing, wherein the housing comprises a wall in which the valve aperture is defined, and wherein the housing is attached to the cylindrical mounting member.

6. The device as claimed in claim 1, wherein the downstream side of the valve aperture has a planar face in a plane perpendicular to an axis of the device.

7. The device as claimed in claim 1, wherein the device comprises a housing attached to the cylindrical mounting member via the flange, and wherein the housing comprises a wall in which the valve aperture is defined.

8. The device as claimed in claim 1, wherein the valve member is arranged to move in a direction perpendicular to the plane of the valve aperture.

9. The device as claimed in claim 1, wherein the valve member comprises an end cap lying substantially in a plane parallel to the plane of the valve aperture, and wherein the end cap is arranged to open and close the valve aperture.

10. The device as claimed in claim 1, wherein the cylindrical mounting member comprises a central bore that forms at least part of the control volume.

11. The device as claimed in claim 10, wherein the device comprises a spring arranged in the central bore within the cylindrical mounting member and arranged to bias the valve member towards the valve aperture.

12. The device as claimed in claim 1, further comprising a seal arranged between an outer surface of the cylindrical mounting member and an inner surface of the valve member, the seal being configured for substantially sealing the control volume, wherein the cylindrical mounting member comprises a groove in the outer surface of the cylindrical mounting member, extending around the perimeter of the cylindrical mounting member, and wherein the seal is arranged in the groove.

13. The device as claimed in claim 1, further comprising a seal arranged between an outer surface of the cylindrical mounting member and an inner surface of the valve member, the seal being configured for substantially sealing the control volume, wherein the seal is resiliently biased between the outer surface of the cylindrical mounting member and the inner surface of the valve member.

14. The device as claimed in claim 1, wherein the valve member is both sealed on and guided by the outer surface of the cylindrical mounting member.

15. A device for controlling the flow of a fluid through a conduit from an upstream side of the device to a downstream side of the device, the device comprising: a cylindrical valve aperture; a cylindrical mounting member arranged on a downstream side of the cylindrical valve aperture; a valve member movably mounted on an outside of the cylindrical mounting member and arranged to move reciprocally relative to the cylindrical mounting member to selectively open and close the valve aperture, thereby controlling flow of the fluid through the valve aperture, wherein the valve member comprises a planar end that is arranged to extend fully over, and fit into, an area of the cylindrical valve aperture; a control volume defined between the cylindrical mounting member and the cylindrical valve member; and a control conduit for introducing the control pressure into the control volume; wherein the valve member is acted on by a pressure of the upstream side and the control pressure so as to be moved by a difference between these pressures.

16. A device for controlling the flow of a fluid through a conduit from an upstream side of the device to a downstream side of the device, the device comprising: a valve aperture; a cylindrical mounting member arranged on a downstream side of the valve aperture; a valve member movably mounted on an outside of the cylindrical mounting member and arranged to move reciprocally to selectively open and close the valve aperture, thereby controlling flow of the fluid through the valve aperture; a control volume arranged to receive a control pressure for acting on the valve member, wherein the device comprises no more than one control volume for receiving the control pressure that acts on the valve member, and wherein the control volume is defined between the cylindrical mounting member and the valve member; and a control conduit for introducing the control pressure into the control volume, wherein the control conduit is fluidly connected to a control pressure regulator for introducing and controlling the control pressure in the control volume; wherein the valve member is acted on by a pressure of the upstream side and the control pressure so as to be moved by a difference between these pressures, and wherein the control pressure regulator is in fluid communication with the upstream side of the device and arranged to set the control pressure dependent on the upstream pressure.

Description

(1) Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows a cross sectional view of a device, along with a schematic of a control loop, in accordance with an embodiment of the invention;

(3) FIG. 2 shows two isometric views of the device shown in FIG. 1;

(4) FIG. 3 shows a cross sectional view of a device in accordance with another embodiment of the invention;

(5) FIG. 4 shows a cross sectional view of a valve member for use with a device in accordance with another embodiment of the invention; and

(6) FIG. 5 shows an internal view of a device in accordance with another embodiment of the invention.

(7) There are many different industrial situations in which there is a desire to regulate the pressure in a fluid flow stream through a pipe or conduit. In such systems there is an input pressure that may be constant or fluctuating in time and which it is desired to control to a lower target output pressure, which also can be constant or fluctuating. As will now be described, embodiments of the present invention provide devices that are able to provide this control for the fluid flow.

(8) FIG. 1 shows a cross sectional view of a device 22, along with a schematic of a control loop 23, in accordance with an embodiment of the invention. FIG. 2 shows isometric views of the device 22 shown in FIG. 1.

(9) In FIG. 1 the fluid flow is from right to left through an upstream side 4 of the conduit, through the device 22 and into a downstream side 6 of the conduit 1. The device 22 is mounted in the conduit 1 at a flange 5 between the upstream and downstream sides 4, 6, where it is clamped in place by means of a flange bolt circle 3.

(10) The device 22 comprises three main components: a cylindrical mounting member 24, a valve member 26 and a housing 28 that defines a valve aperture 30. Each of these components is machined from a respective solid piece of acetal. The cylindrical mounting member 24 is integrally formed, and projects perpendicularly from, a flange 32 that is used to mount the device 22 in the conduit. The housing 28 is attached to and sealed against the flange 32 by means of a number of bolts 29. The housing 28 and the flange 32 are machined and attached to each other so that the valve member 26 is precisely aligned with the valve aperture 30.

(11) The device 22 is clamped between the upstream and downstream sections of the conduit 1 by means of a flange bolt circle 3, with flanges 5 on the upstream and downstream sections of the conduit 1 engaging against the flange 32 of the device 22 on the downstream side and the housing 28 on the upstream side.

(12) As can be seen more clearly in FIG. 2, apertures 31 in the flange 32 allow a flow path for fluid from the inside of the housing 28 and into the downstream side 6 of the conduit 1.

(13) The valve member 26, which has a cylindrical sheath portion 33 and an end cap 42, is mounted on the outside of the cylindrical mounting member 24 such that it is able to move reciprocally along the outer surface of the cylindrical mounting member 24. The valve member 26 can thus move between a position in which the end cap 42 is sealed against the inner face of the housing 28 to fully close the valve aperture 30, and a position in which the inner (though the spring force exerted by the spring 40 may be arranged to prevent this). The end cap 42 of the valve member 26 has a stepped outer face with a central portion 43 that is arranged to project through the valve aperture 30 when fully closed and an planar outer annulus 45 that is arranged to engage with and seal against the inner face of the housing 28 when the valve aperture 30 is fully closed.

(14) An annular seal 34 is positioned in a groove 36 in the outer surface of the cylindrical mounting member 24 so that it provides a seal between the outer surface of the cylindrical mounting member 24 and the inner surface of the valve member 26.

(15) The cylindrical mounting member 24 has a hollow central bore 38 in which a helical spring 40 is located. The spring 40 is positioned between the end of the central bore 38 against the flange 32 and the end cap 42 of the valve member 26. Between them, the valve member 26 (i.e. its cylindrical sheath portion 33 and end cap 42) and the cylindrical mounting member 24 (with its hollow central bore 38) define a control volume 44, which is sealed by the annular seal 34. The control volume 44 has a central portion within the hollow central bore 38 of the cylindrical mounting member 24 and a portion with a greater cross sectional area adjacent the end cap 42 of the valve member 26, i.e. beyond the end of the cylindrical mounting member 24.

(16) A duct 46 that is drilled through the flange 32 provides fluid communication between the control volume 44 and a pilot pressure regulator 8 to allow the pilot regulator 8 to introduce, i.e. to set, a control pressure in the control volume 44. A second duct 48 that is drilled through the housing 28 provides the pilot pressure regulator 8 with fluid communication with the upstream side 4 of the conduit 1 and a third duct 49 that is drilled through the flange 32 (though for the purposes of clarity this is shown schematically in FIG. 1 as entering directly into the downstream side 6 of the conduit 1) provides pilot pressure regulator 8 with fluid communication with the downstream side 6 of the conduit 1, so that the pilot pressure regulator 8 can use the upstream and downstream pressures to set the control pressure in the control volume 44, as will be described.

(17) As shown schematically in FIG. 1, the pilot pressure regulator 8 is arranged in a control loop 23 on the outside of the conduit 1 and is arranged to deliver a control pressure P.sub.4 to the device 22 via the duct 46 into the control volume 44. The pilot pressure regulator 8 is also in fluid communication with the upstream pressure P.sub.1 on the upstream side 4 of the conduit 1 via the duct 48 through the housing 28, and in fluid communication with the pressure P.sub.2 on the downstream side 6 of the conduit 1 via the duct 49 through the flange 32. This provides a fluid flow path through the control loop 23 that bypasses the valve aperture 30 of the device 22. The pilot pressure regulator 8 is positioned in this fluid flow path of the control loop 23, with the duct 46 into the control volume 44 branching off upstream of the pilot pressure regulator 8.

(18) The control loop 23 also includes a first orifice 50 that provides a restriction in the duct 48 between the upstream side 4 of the conduit 1 and the pilot pressure regulator 8 (such that the pressure in the control loop 23 downstream of the first orifice 50 is P.sub.3), and a second orifice 52 that provides a restriction in the duct 46 between the control volume 44 and the pilot pressure regulator 8.

(19) Operation of the device 22 will now be described with reference to FIGS. 1 and 2. In this example, the pilot pressure regulator 8 is set dependent on the pressure P.sub.2 in the downstream side 6 of the conduit 1 (though it will be appreciated that other arrangements are possible). With no flow of fluid through the conduit 1 or the device 22, i.e. a low upstream and downstream pressure in the conduit 1, the control pressure in the control volume 44 and the spring force of the spring 40 act on the end cap 42 of the valve member 26 to bias the valve member 26 into a position in which the end cap 42 is sealed against the inner face of the housing 28 to fully close the valve aperture 30.

(20) When fluid flow commences in the conduit 1, the fluid will flow in the upstream side 4 of the conduit 1 and exert a force against the end cap 42 of the valve member 26 owing to the pressure P.sub.1 in the upstream side 4 of the conduit 1. The upstream pressure P.sub.1 will also create a flow of fluid through the control loop 42, such that the flow through the first orifice 50 creates a pressure drop across it, i.e. P.sub.1-P.sub.3. This pressure drop causes the pressure P.sub.4 in the control volume 44 to be lower than the pressure P.sub.1 in the upstream side 4 of the conduit 1, which causes the valve member 26 to be pushed back from and to open the valve aperture 30, allowing flow of the fluid through the valve aperture 30, through the device 22 and into the downstream side 6 of the conduit 1 via the apertures 31 in the flange 32.

(21) While the upstream pressure maintains such a value, the valve member 26 will keep the valve aperture 30 at least partially open and thus allow fluid to flow through the device. When the upstream pressure P.sub.1 increases the effect will be two-fold. First, the increased upstream pressure will act on the end cap 42 of the valve member 26 to push it back against the control pressure in the control volume 40 and thus open the valve aperture 30 further. However, simultaneously, owing to the flow through the device, the downstream pressure P.sub.2 will also increase. This increase in the downstream pressure P.sub.2, which is used to set the pilot pressure regulator 8, causes the pilot pressure regulator 8 to close and thus to decrease the fluid flow through (and increase the pressure P.sub.3 in) the control loop 23. This causes the pressure drop across the first orifice 50 to be smaller, which will accordingly set a higher control pressure P.sub.4 (relative to the upstream pressure P.sub.1) in the control volume 44. This increased control pressure P.sub.4 will thus balance against the increased upstream pressure such that the valve member 26 settles (i.e. closes) to a position where it is pressure balanced. This will thus act to regulate the upstream pressure that is experienced in the downstream side 6 of the conduit 1.

(22) (The action of the second orifice 52 is to limit the flow rate in and out of the control volume 44 to thus regulate the change in the control pressure P.sub.4, so that the rate of the valve member 26 opening and closing may be controlled.)

(23) It will thus be appreciated that the that in this way the device acts to regulate the pressure in the downstream side 6 of the conduit 1, owing to the fact that the valve member 26 moves under a pressure difference until it settles to a position where it is pressure balanced.

(24) FIG. 3 shows a cross sectional view of a device 122 in accordance with another embodiment of the invention. The device 122 shown in FIG. 4 is almost identical to the device shown in FIGS. 1 and 2, except that the end cap 142 of the valve member 126 contains a small orifice 147 in its centre, which replaces the first orifice 50 and the duct 48 in the device 22 of FIGS. 1 and 2, and forms part of a control loop 123 with the pilot pressure regulator 108, i.e. the orifice 147 in the end cap 142 allows a small amount of fluid flow directly into the control volume 144. Furthermore, the control loop 123 of the device 122 in FIG. 3 does not include a second orifice between the pilot pressure regulator 108 and the control volume 144.

(25) Operation of the device 122 shown in FIG. 3 is almost identical to that described for FIGS. 1 and 2, except that the pressure P.sub.7 in the control volume 144 depends on the pressure drop across the orifice 147 in the end cap 142 (which depends on the upstream pressure P.sub.5) and the action of the pilot pressure regulator 108 (which depends on the downstream pressure P.sub.6). Thus, in the same manner to the operation of the device shown in FIGS. 1 and 2, when the downstream pressure P.sub.6 is low (compared to the upstream pressure P.sub.5), the valve member 126 will open, allowing more flow through the valve aperture 130 from the upstream side 104 of the conduit 101 into the downstream side 106 of conduit 101.

(26) This results in an increased downstream pressure P.sub.6, causing the pilot pressure regulator 108 to close, increasing the control pressure P.sub.7, such that the valve member 126 acts to close the valve aperture 130 and to restrict the fluid flow therethrough, thus regulating the downstream pressure P.sub.6.

(27) FIG. 4 shows a cross sectional view of a valve member 226 for use with a device in accordance with another embodiment of the invention. In this embodiment, the device has a very similar design to that shown in FIGS. 1, 2 and 3, except that its main components are made from stainless steel rather than acetal. Thus in this embodiment the valve member 226 is substantially made from stainless steel.

(28) In order to provide a compliant and thus effective seal against the valve aperture, the valve member 226 in FIG. 4 comprises an annular PTFE seal 250 arranged in a recess 252 in the end cap 242 of the valve member 226. In order to secure the seal 250 in place, a stainless steel plate 254 is attached to the end cap 242, by means of screws 256 on the side proximal to the valve aperture. The plate 254 is arranged to project through the valve aperture so that the seal 250 engages with the valve aperture when the valve aperture is closed.

(29) Operation of the device having the valve member 226 shown in FIG. 4 is almost identical to that described for FIGS. 1 to 3.

(30) It will be appreciated that the embodiment of the valve member 226 shown in FIG. 4 can equally well used in the devices shown in FIGS. 1, 2 and 3.

(31) FIG. 5 shows an internal view of a device 301 in accordance with another embodiment of the invention. In this embodiment the device 301 is arranged in a conventional cast body 302 which, by means of two flanges 304, is able to be connected to upstream and downstream sections of a conduit.

(32) In FIG. 5 the fluid flow is from left to right through an upstream side 306 of the conduit, through the device 302 and into a downstream side 308 of the cast body 302. As in the embodiments shown in FIGS. 1-4, the device 301 shown in FIG. 5 comprises three main components: a cylindrical mounting member 310, a valve member 312 and a valve aperture 314. The cylindrical mounting member 310 projects perpendicularly from a flange 316 that is used to mount the device 302 in the cast body 302. At the other end of the device, the valve aperture 314 is defined by an annulus that is held between the two sides of the cast body 302.

(33) Operation of the device 301 shown in FIG. 5 is very similar to the operation of the embodiments of the device shown in FIGS. 1-4, except that when the fluid has passed through the valve aperture 314, the flow exits perpendicularly to the cylindrical axis of the device 301 into the downstream side 308 of the cast body 302.

(34) It can be seen from the above that in at least preferred embodiments of the invention, the device provides control for the fluid flow through a conduit with a particularly simple design, having only three basic components and only a single moving part. This simplicity helps to provide a robust and reliable device, which may be manufactured inexpensively and compactly, e.g. compared to the complicated, expensive and bulky prior art pressure regulators. Also, with only three main components, the valve member and valve aperture, particularly when the valve aperture is defined in a housing, may be aligned precisely. Having a single valve aperture reduces the risk of blockages and sealing the control volume on the inside of the valve member (and thus the outside of the cylindrical mounting member) maximizes the control volume and thus the control of the device.

(35) It will be appreciated by those skilled in the art that many variations and modifications to the embodiments described above may be made within the scope of the various aspects and embodiments of the invention set out herein. For example, the control pressure may be set dependent on the upstream pressure or by a device other than the pilot pressure regulator, e.g. to deliver a fixed control pressure.