Patent ID: 12209682

DETAILED DESCRIPTION

There are many different industrial situations in which there is a desire to control the flow rate in a fluid flow stream through a conduit. In such systems, a device is required to control the output flow rate by opening and/or closing an outlet (e.g. valve) aperture. As will now be described, embodiments of the present invention provide devices that are able to provide this control for the fluid flow.

FIGS.1aand1bshow a cross-sectional view of a fluid flow device1in accordance with an embodiment of the present invention.FIG.1ashows the device1in its fully-open position andFIG.1bshows the device1in its fully-closed position. The device1comprises a valve core2, an upstream valve casing4and a downstream valve casing5, which are formed as three separate components. The device1is mounted in a pipe7that extends either side of the upstream and downstream valve casings4,5.

To assemble the device1, the valve core2is mounted and sealed between the upstream and downstream valve casings4,5and is clamped in place by means of a flange bolt circle12. This provides an advantage over one-piece cast valve bodies, in which the valve member must be smaller in diameter than the ends of the valve in order for it to be inserted through the inlet or outlet aperture. Whereas, with the present three-piece design, it is possible to accommodate a larger valve core and valve member capable of supporting higher hydraulic control pressures.

The upstream valve casing4defines an inlet aperture8and the downstream valve casing5comprises a valve seat52surrounding and defining an outlet aperture10. The flow of fluid inFIGS.1aand1bis from left to right, following a conduit6defined within the valve casings4,5.

The valve core2comprises four main components: a piston14, a closure member16, a control fluid feed18and a housing20. The piston14and the closure member16together form a valve member. The housing20and the piston14together define a control fluid pressure chamber21and a downstream pressure chamber22.

The control fluid pressure chamber21is downstream of the piston head28and is fluidly connected to the control fluid feed18for supplying a control fluid (and thus a control fluid pressure) into the control fluid pressure chamber21, such that the control fluid pressure acts on the downstream face48of the piston head28. The downstream pressure chamber22is upstream of the piston head28and is fluidly connected to the downstream side of the conduit6via an upstream piston cavity balance hole32and closure member balance holes34. This allows the fluid on the downstream side of the conduit6(and thus a downstream fluid pressure) to be supplied into the downstream pressure chamber22(via the upstream piston cavity balance hole32and the closure member balance holes34), such that the pressure in the upstream portion of the downstream pressure chamber22(and thus acting on the upstream face of the piston head28) is equal to the downstream pressure at the outlet aperture10. The housing20further defines a piston shaft aperture24and a closure member chamber25.

The control fluid feed18is connected to a source of control fluid66(e.g. hydraulic fluid, pneumatic fluid or fluid taken from within the pipe7) which is controlled by a control system70, e.g. to set the pressure of the control fluid in the control fluid pressure chamber21. The control system70may use feedback data collected by a position sensor72that determines the position of the piston14relative to the housing20and/or the outlet aperture10.

The piston14comprises a piston head28and a piston shaft30, which projects perpendicularly from the downstream surface48of the piston head28through the piston shaft aperture24into the closure member chamber25. The piston head28is sealed against the housing20by piston seals56and the piston shaft30is sealed within the piston shaft aperture24by piston shaft seals58. This prevents the control fluid from leaking into the downstream pressure chamber22and the closure member chamber25respectively.

The closure member16is attached to the downstream end of the piston shaft30such that the closure member16moves longitudinally with the piston14. The closure member16has a cylindrical sleeve portion38and an end portion36. The end portion36comprises shut off seals40, mounted on the outside surface of the closure member end portion36, and a number of closure member balance holes34that allow fluid to pass from the downstream side of the conduit6through the closure member chamber25and into the downstream pressure chamber22via the upstream piston cavity balance hole32. The closure member16is arranged to move reciprocally along the inner surface42of the housing20within the closure member chamber25.

The cylindrical sleeve portion38of the closure member16has a hollow central bore in which a helical spring54is positioned around the piston shaft30. The helical spring54is a compression spring which is held between the housing20and the closure member16to bias the closure member16to close the outlet aperture10.

The closure member16is moveable between two extreme positions: a fully-open position, as shown inFIG.1a, and a fully-closed position, as shown inFIG.1b. In the fully-open position, the upstream surface44of the piston head28abuts the upstream inner face46of the housing20and the end portion36of the closure member16is located within the closure member chamber25, leaving a flow path for the flow of fluid through the outlet aperture10from the upstream side of the device1to the downstream side. In the fully-closed position, the downstream surface48of the piston head28abuts the downstream inner surface50of the housing20and the end portion36of the closure member16is moved such that the outer surface of the end portion36of the closure member16is sealed against the valve seat52by shut off seals40. This prevents the fluid from flowing through device1via the outlet aperture10.

Operation of the fluid flow device1shown inFIGS.1aand1bwill now be described.

FIG.1bshows the device1in its fully-closed state, in which the control fluid pressure in the control fluid pressure chamber21is set to a low value by the control fluid source66(controlled by the control system70). The combined force from the downstream pressure acting on the upstream surface44of the piston head28and the spring force from the helical spring54is greater than the control fluid pressure acting on the downstream surface48of the piston head28. Thus the piston14is moved to the right ofFIG.1b, moving the end portion36of the closure member16to be sealed against the valve seat52by the shut off seals40. This prevents the fluid from flowing through the device1via the outlet aperture10.

In order to place the device1in the fully-open position, as shown inFIG.1a, the control fluid pressure is raised to a value sufficient to cause the force acting on the downstream surface48of the piston head28to be greater than the combined opposing forces caused by the helical spring54and the downstream pressure acting on the upstream surface44of the piston head28. As a result, the upstream surface44of the piston head28is moved to the position in which it abuts the upstream inner surface46of the housing20, thus moving the closure member16to be located within the closure member chamber25, leaving a flow path for the flow of fluid through the outlet aperture10.

In the event of failure of one or more of the piston seals56or piston shaft seals58, causing the pressure acting on the upstream surface44of the piston head28to become equal to the pressure acting on the downstream surface48of the piston head28, the helical spring54acts to bias the closure member16to the right ofFIGS.1aand1binto the fully-closed position. In the event of a loss of control fluid pressure (e.g. owing to a loss of power in the hydraulic and/or control systems70), the downstream pressure acting on the upstream surface44of the piston head28is greater than the control pressure acting on the downstream surface48of the piston head28. Furthermore, the helical spring54acts to bias the closure member16towards the right ofFIG.1b. Thus, in both of these failure modes of the fluid flow device1, the piston14is moved to the right ofFIG.1b, moving the end portion36of the closure member16to be sealed against the valve seat52by the shut off seals40. This prevents the fluid from flowing through device1via the outlet aperture10, thus representing a “fail closed” mode of the device.

FIGS.2aand2bshow a device101in accordance with a further embodiment of the present invention, which is a variant of the device1shown inFIGS.1aand1b.FIG.2ashows the device101in its fully-open position andFIG.2bshows the device101in its fully-closed position.

The embodiment has the same three-piece design as the embodiment shown inFIGS.1aand1b. However, the device101varies from device1in a number of ways.

First, the control fluid pressure chamber121is on the upstream side of the piston head128and the downstream pressure chamber122is on the downstream side of the piston head128. The downstream pressure chamber122in the device101is defined by the housing120, the downstream surface148of the piston head128and the inner surface of a cylindrical spring housing160. The spring housing160extends through the piston shaft aperture124from the piston chamber122to the closure member chamber125.

The spring housing160comprises a central bore162and an end aperture164, wherein the end aperture164is proportioned to accommodate the piston shaft130. A helical spring154is positioned within the central bore162such that it encompasses the piston shaft130and extends between the downstream surface148of the piston head128and the downstream inner surface of the spring housing160. The helical sprint154thus acts to bias the closure member116to open the outlet aperture110.

Second, the housing120of device101does not define an upstream cavity balance hole. Instead, the downstream pressure chamber122is fluidly connected to the outlet aperture110via the end aperture164of the spring housing160and the closure member balance holes134. The downstream pressure thus acts on the downstream face148of the piston head128.

Operation of the fluid flow device101shown inFIGS.2aand2bwill now be described.

FIG.2ashows the device101in its fully-open state, in which the control fluid pressure in the control fluid pressure chamber121is set to a low value by the hydraulic source166(controlled by the control system170). The combined force from the downstream pressure acting on the downstream surface148of the piston head128and the spring force from the helical spring154is greater than the control fluid pressure acting on the upstream surface144of the piston head128. As a result, the upstream surface144of the piston head128is moved to the position in which it abuts the upstream inner surface146of the housing120, thus moving the end portion136of the closure member116to be located within the closure member chamber125, leaving a flow path for the flow of fluid through the outlet aperture110. It will be appreciated that this arrangement is the reverse of the arrangement shown inFIG.1aand described above, where the device1is designed to fully close when the control fluid pressure is low.

In order to place the device101in the fully-closed position, as shown inFIG.2b, the control fluid pressure is raised to a value sufficient to cause the force acting on the upstream surface144of the piston head128to be greater than the combined opposing forces caused by the helical spring154and the downstream pressure acting on the downstream surface148of the piston head128. As a result, the piston114is moved to the right ofFIG.2b, moving the end portion136of the closure member116to be sealed against the valve seat152by the shut off seals140. This prevents the fluid from flowing through the device101via the outlet aperture110.

In the event of failure of one or more of the piston seals156, causing the pressure acting on the downstream surface148of the piston head128to become equal to the pressure acting on the upstream surface144of the piston head128, the helical spring154acts to bias the closure member116to the left ofFIGS.2aand2binto the fully-open position. In the event of a loss of control fluid pressure (e.g. owing to a loss of power in the hydraulic and/or control systems170), the downstream pressure acting on the downstream surface148of the piston head128is greater than the control pressure acting on the upstream surface144of the piston head128. Furthermore, the helical spring154acts to bias the closure member116towards the left ofFIG.2b. Thus, in both of these failure modes of the fluid flow device101, the piston114is moved to the left ofFIG.2b, moving the end portion136of the closure member116to be located within the closure member chamber125, leaving a flow path for the flow of fluid through the outlet aperture110, thus representing a “fail open” mode of the device.

FIGS.3aand3bshow a device201in accordance with a further embodiment of the present invention, which is a variant of the device1shown inFIGS.1aand1b.FIG.3ashows the device201in its fully-open position andFIG.3bshows the device201in its fully-closed position.

The embodiment has the same three-piece design as the embodiment shown inFIGS.1aand1b. However, the device201varies from device1in a number of ways.

The housing220of device201defines two control fluid pressure chambers: an upstream control fluid pressure chamber223, located upstream of the piston head228and a downstream control fluid pressure chamber222, located downstream of the piston head228. The upstream control fluid pressure chamber223is fluidly connected to an upstream control fluid source266via an upstream control fluid feed219for supplying a control fluid (and thus a control fluid pressure) into the upstream control fluid pressure chamber223, such that the control fluid pressure acts on the upstream face of the piston head228. The downstream control fluid pressure chamber222is fluidly connected to a downstream control fluid source268via a downstream control fluid feed218for supplying a control fluid (and thus a control fluid pressure) into the downstream control fluid pressure chamber222, such that the control fluid pressure acts on the downstream face of the piston head228.

Operation of the fluid flow device201shown inFIGS.3aand3bwill now be described.

FIG.3bshows the device201in its fully-closed state, in which the control fluid pressure in the downstream control fluid pressure chamber222is set to a low value by a downstream control fluid source268and the control fluid pressure in the upstream control fluid pressure chamber223is set to a high value by an upstream control fluid source266. Both the downstream control fluid source268and the upstream control fluid source266are controlled by a control system270.

The combined force from the control pressure acting on the upstream surface244of the piston head228and the spring force from the helical spring254(which acts to bias the closure member216towards the right ofFIG.3b) is greater than the control pressure acting on the downstream surface248of the piston head228. Thus the piston214is moved to the right ofFIG.3b, moving the end portion236of the closure member216to be sealed against the valve seat252by the shut off seals240. This prevents the fluid from flowing through the device201via the outlet aperture210.

In order to place the valve201in the fully-open position, as shown inFIG.3a, the downstream control fluid pressure is raised by the control system270to a value sufficient to cause the force acting on the downstream surface248of the piston head228to be greater than the combined opposing forces caused by the helical spring254and the downstream control pressure acting on the upstream surface244of the piston head228. As a result, the upstream surface244of the piston head228is moved to a position in which it abuts the upstream inner surface246of the housing220, thus moving the closure member216to be located within the closure member chamber225, leaving a flow path for the flow of fluid through the outlet aperture210.

In the event of failure of one or more of the piston seals256, causing the pressures in the downstream control fluid pressure chamber222and the upstream control fluid pressure chamber223to equalise, the helical spring254acts to bias the closure member216to the right ofFIGS.3aand3binto the fully-closed position. In a further failure mode, when one or more of the piston shaft seals258fail, the downstream control fluid pressure becomes equal to the downstream pressure. In this case, the helical spring254acts to bias the closure member216to the right ofFIGS.3aand3band move it in into the fully-closed position.

In the event of a loss of downstream control fluid pressure (e.g. owing to a loss of power in the hydraulic and/or control systems270), the piston head228is biased and moved towards the right ofFIGS.3aand3bby the combined force of the helical spring254and the upstream control pressure.

Thus, in all of the failure modes of the fluid flow device201described above, the piston214is forced to the right ofFIG.3b, moving the end portion236of the closure member216to be sealed against the valve seat252by the shut off seals240. This prevents the fluid from flowing through the device201via the outlet aperture210. However, it will be appreciated that the helical spring254of device201shown inFIGS.3aand3bmay be adapted to function in a manner similar to that shown inFIGS.2aand2bso that the device operates as a “fail-open” device. Furthermore, the helical spring254may be removed completely so that, in the event of seal or power failure, the valve201is designed to fail “in-place”, i.e. the valve201is not biased to either the fully-closed or the fully-open position.

FIG.4shows a device301in accordance with a further embodiment of the present invention, which is a variant of the device201shown inFIGS.3aand3b. The device301is essentially the same as the device201discussed above. However, the helical spring254has been removed and a cylindrical cage374has been centrally attached to the end portion336of the closure member316. The embodiment has the same three-piece design as the embodiment shown inFIGS.3aand3b.

The cylindrical cage374extends longitudinally through the outlet aperture310of the device301. The outer diameter of the cage374is equal to the outer diameter of the end portion336of the closure member316so that the cage374fills the outlet aperture310. The cage374comprises a plurality of apertures376which are distributed uniformly along the length and circumference of the cage374and fluidly connect inlet aperture308of the conduit306to the outlet aperture310.

As in previous embodiments, the closure member316is moveable longitudinally within the closure member chamber325between a fully-open position (shown inFIG.4) and a fully-closed position (not shown).

FIG.4shows the device301in its fully-open position, in which the downstream control fluid pressure in the downstream control fluid pressure chamber322is greater than the upstream control fluid pressure in the upstream control fluid pressure chamber323. As a result, the piston314, the closure member316and the cage374are moved to the left ofFIG.4such that the closure member316is fully located within the closure member chamber325. In this position, a maximum number of cage apertures376are opened to allow fluid to flow through the device301at a maximum flow rate.

In order to reduce the flow rate through the device301, the upstream control pressure is increased, causing the piston314, closure member316and the cage374to move to the right ofFIG.4. As the cage374is moved into the outlet aperture310, the number of cage apertures376that are closed by the valve seat352increases. This has the effect of throttling the fluid flow, as the flow rate will decrease in proportion the total area of the apertures376that remain open. Consequently, it will be appreciated that this embodiment enables more precise control of the fluid flow rate.

When the device301reaches its fully-closed position, the end portion336of the closure member316is sealed against the valve seat352by the shut off seals340and the cage374is fully encompassed by the valve seat352, thus closing all off the cage apertures376. This prevents the fluid from flowing through the device301via the outlet aperture310.

FIG.5shows a device401in accordance with a further embodiment of the present invention, which is a variant of the device301shown inFIG.4. The device401is essentially the same as the device301discussed above. However, rather than the cage374being attached to the end portion336of the closure member316, the cage474is attached to the downstream end of the closure member casing426, spanning the orifice between the closure member casing426and the valve seat452. The inner diameter of the cage474is equal to the inner diameter of the closure member casing426so that the closure member416is able to slide longitudinally within the cage474. Furthermore, the shut off seals440are mounted on the inner surface of the valve seat452rather than on the outside surface of the closure member416.

FIG.5shows the device401in its fully-open position, in which the downstream control fluid pressure in the downstream control fluid pressure chamber422is greater than the upstream control fluid pressure in the upstream control fluid pressure chamber434. As a result, the piston414and the closure member416are moved to the left ofFIG.5such that the closure member416is fully located within the closure member chamber425. In this position, none of the cage apertures476are closed by the closure member416. Therefore, fluid may flow through the device401at a maximum flow rate.

In order to reduce the flow rate through the device401, the upstream control pressure is increased, causing the piston414and the control member416to move to the right ofFIG.5. As the closure member416is moved towards the outlet aperture410, the number of cage apertures476that are closed by the closure member416increases. This has the effect of throttling the fluid flow, as the flow rate will decrease in proportion to the total area of the apertures476that remain open. Consequently, it will be appreciated that this embodiment enables more precise control of the fluid flow rate.

When the device401reaches its fully-closed position, the end portion436of the closure member416is sealed against the valve seat452by the shut off seals440and all of the cage apertures476are completely closed by the closure member416. This prevents the fluid from flowing through the device401via the outlet aperture410.

FIG.6shows a cross-sectional view of a fluid flow device501in accordance with an embodiment of the present invention, in which the device501comprises position sensing apparatus. The device501shown inFIG.6is substantially the same as the device1shown inFIG.1a, except that the device501comprises a magnet580embedded within the piston514and a magnetic field sensor582mounted within a radial hole584in the housing520.

The radial hole584extends into the valve core502from the exterior surface of the valve core502. The radial hole584is arranged in a plane perpendicular to the control fluid feed and the piston cavity balance hole (not shown). A PCB586is located within the radial hole584and comprises three magnetic field sensors (Hall effect sensors)582. Electric cables fed through radial hole584provide power to the PCB586and allow measurements of the magnetic field strength to be sent from each of the sensors582to a position sensor control unit572.

The magnet580, extending in the axial direction, is embedded centrally within the piston514. As the magnet580is rigidly embedded within the piston514, the axial displacement of the piston514corresponds exactly to the axial displacement of the magnet580. As the magnet580is located centrally within the piston514, any circumferential movement of the valve member does not cause a change in distance between the magnet514and the sensors582.

During normal operation of the device501, the flow of fluid through the device501from the inlet aperture508to the outlet aperture510is controlled by the movement of the piston514and closure member516. As the closure member516is moved towards the valve seat552, the flow through the device501is restricted. Therefore, the fluid flow may be throttled by adjusting the axial displacement of the piston514and closure member516.

The sensors582continuously measure the strength of the magnetic field of the magnet580as it moves with the piston514and closure member516. The measurements may be processed by the position sensor control unit572using an error minimisation algorithm in order to determine the axial position of the piston516and closure member516.

FIG.7shows a cross-sectional view of a fluid flow device601in accordance with an embodiment of the present invention, in which the device601comprises position sensing apparatus. The device601is essentially the same as the device501discussed above. However, the axial magnet580has been replaced by a ring magnet680that is embedded within the piston614.

A PCB686comprising three Hall effect sensors682, electrically connected to the position sensor control unit672, is located within a radial hole684. The magnet680is positioned with the piston614such that, at all axial positions of the piston614, the sensors682are positioned within the end limits of the magnet680.

Furthermore, as the ring magnet680is embedded centrally within the piston614, any circumferential movement of the closure member616does not cause a change in distance between the magnet680and the sensors682.

During normal operation of the device601, flow through the device601is throttled by the axial displacement of the piston614and closure member616. The sensors682continuously measure the strength of the magnetic field of the ring magnet680as it moves with the piston614and closure member616. In the same way as the above embodiment, the measurements may be processed by the position sensor control unit672using an error minimisation algorithm in order to determine the axial position of the piston614and closure member616.

FIG.8shows a cross-sectional view a fluid flow device701in accordance with an embodiment of the present invention, in which the device701comprises position sensing apparatus. The device701is essentially the same as the device501discussed above. However, the valve core702comprises an additional two radial holes784which extend into the valve core702from the exterior surface of the valve core702. The radial holes784are spaced axially within the valve core702. The device701further comprises an upstream pressure sensor787a, arranged to determine an upstream pressure of fluid in the conduit upstream of the device701, and a downstream pressure sensor787b, arranged to determine a downstream pressure of fluid in the conduit downstream of the device701.

A PCB786comprising a Hall effect sensor782, electrically connected to the position sensor control unit772, is located within each radial hole784. The Hall effect sensor782may be a multiple-axis magnetic field sensor782a. The magnet780is positioned with the piston714such that, at all axial positions of the piston714, the sensors782are positioned within the end limits of the magnet780.

In the same way as the above embodiments, the sensors782continuously measure the strength of the magnetic field of the magnet780as it moves with the piston714and closure member716. The measurements may be processed by the position sensor control unit772using an error minimisation algorithm in order to determine the axial position of the piston714and closure member716. For example, the measurements may be used to determine a deviation in the magnetisation of the magnet from a nominal magnetisation, and the determined axial position may be adjusted accordingly.

The fluid flow device701further comprises a cylindrical piston liner788arranged between the housing720and the piston714.

It can be seen from the above that in at least preferred embodiments of the invention, the device is a split piece design that includes three main parts: the upstream and downstream casings, and the valve core. The valve member of the device is actuated (e.g. hydraulically or pneumatically) by a control fluid. These features help to provide a fluid flow control device which is easy to manufacture and assemble, and is less likely to cause leakage of the fluid flowing through failure of the device in the manner of conventional designs.

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, even in the “fail open”, “fail closed” or “fail in position” embodiments, the device may not necessarily include a spring acting on the valve member.