Improved particle tolerant fluid flow control and isolation valve

Abstract

A flow control device (10) has at least a first sealing element (10, 13) having at least one flow opening therein and at least a second sealing element (17) having at least one flow opening therein (16, 18). The at least a first sealing element and the at least a second sealing element are in sliding, sealing contact with each other. An actuator (14) is configured for moving the at least a first sealing element relative to the second sealing element, wherein the at least one flow opening in each of the first and second sealing elements cooperate by relative movement to affect fluid flow through the first and second sealing elements. A method for controlling fluid flow includes sliding the first sealing element with respect to the second sealing element to cause the respective flow openings to control the fluid flow as desired.

Description

IMPROVED PARTICUE TOEERANT FEUID FEOW CONTROE ANDISOEATION VAEVEBACKGROUND

[0001] This disclosure relates to the field of flow controls such as valves used to control flow of fluids. More particularly, the present disclosure describes a method / solution / apparatus for a flow control having increased tolerance in handling fluids containing particles.

[0002] In process industries, as for example the oil and gas producing industry, there are needs for fluid flow control, for example, to provide pressure control, flow rate control and flow barriers such as one-way flow (e.g., check valves) and or pressure isolating barriers.

[0003] In many flow control applications there are particles and contaminated fluids in the controlled flow stream that need to be handled; this is in many cases a challenge for known fluid control devices to handle and may result in unwanted restrictions, blockage, seal / seat leakage, wear and tear which then can cause functional failures. Typical fluid and gas flow control principles involves ball and ball-seat, needle with corresponding seat and plunger with corresponding housing / seat. Particles and contaminations are a generic problem across the mentioned applications. However, particles and contaminations have become critical and well known issues, in for example, chemical injection applications for oil and gas producing wells where there are very small amounts of fluids (typical as low as 0.1 liter per hour) to be controlled, that would require small flow passages through the control device to obtain necessary controlled restriction. When controlling such small flows of fluids containing particles, particles and contaminants have become a common challenge. The challenge typical consist of partly blockage of the flow-path, lack of sealing when needed, etc.SUMMARY

[0004] One aspect of the present disclosure is a flow control device. A flow control device according to this aspect has at least a first sealing element having at least one flow openingtherein and at least a second sealing element having at least one flow opening therein. The at least a first sealing element and the at least a second sealing element are in sliding, sealing contact with each other. An actuator is configured for moving the at least a first sealing element relative to the second sealing element, wherein the at least one flow opening in each of the first and second sealing elements cooperate by relative movement to affect fluid flow through the first and second sealing elements.

[0005] In some implementations, the at least a first sealing element and the at least a second sealing element comprise disks.

[0006] In some implementations, the actuator is configured to rotate the disks with respect to each other.

[0007] In some implementations, the actuator comprises a stepper motor or a servo motor.

[0008] In some implementations, the at least a first sealing element and the at least a second sealing element comprise metal or ceramic materials.

[0009] In some implementations, the at least a first sealing element comprises full flow ports and a tortuous flow path hydraulically connected to each full flow port.

[0010] In some implementations, the at least a first sealing element comprises full flow ports and a flushing flow path hydraulically connected to each full flow port.

[0011] Some implementations further comprise a movable sealing element disposed between the at least a first sealing element and the at least a second sealing element, the movable sealing element comprising opposed, arcuate slots therein, the at least a first and a second sealing elements comprising opposed ports therein, wherein the arcuate slots and the opposed ports in the at least a first sealing element and the at least a second sealing element are arranged to reverse flow through the flow control device by reorienting the movable sealing element.

[0012] In some implementations, each of the first and second sealing elements comprises at least one flow port having shape wherein the relative movement causes a connected flow area between the respective tapered flow ports to change longitudinally and / or laterally.

[0013] In some implementations, the at least one flow port in the at least a first and the at least a second sealing element comprises at least one full flow port and a tapered flow channel fluidly connected to the at least one flow port, the tapered flow channel on the at least a first sealing element laterally offset from the tapered flow channel on the at least a second sealing element, wherein the relative movement causes a connected flow area between the respective tapered flow channels to change both longitudinally and laterally.

[0014] In some implementations, the actuator is configured to rotate the movable sealing element.

[0015] In some implementations, the opposed ports on the at least a first sealing element are angularly separated from the opposed ports on the at least a second sealing element by 90 degrees.

[0016] A method for controlling fluid flow according to another aspect of the disclosure includes moving fluid from an inlet to a fluid control device to a first slidable sealing element. The first slidable sealing element comprises at least one opening therein. The first slidable sealing element is slid with respect to a second slidable sealing element sealingly engaged with the first slidable sealing element so that at least one opening in the second slidable sealing element cooperates with the at least one opening in the first slidable sealing element to control flow of the fluid to an outlet of the fluid control device.

[0017] In some implementations, the sliding comprises rotation.

[0018] In some implementations, the at least one opening in the first slidable sealing element comprises a tortuous path.

[0019] In some implementations, the tortuous path comprises a full flow opening at an one end of the tortuous path.

[0020] In some implementations, the at least one opening in the first slidable sealing element comprises a flushing path.

[0021] In some implementations, the flushing path comprises a full flow opening at an end of the flushing path.

[0022] Some implementations further comprise moving fluid from the first slidable sealing element through a third slidable sealing element to the second slidable sealing element, wherein the first slidable sealing element and the second slidable sealing element remain in fixed position and the third slidable sealing element moves with respect to the first and second slidable sealing elements to reverse fluid flow through the fluid control device.

[0023] In some implementations, the sliding comprises rotation.

[0024] In some implementations, the first, second and third slidable sealing elements comprise disks.

[0025] In some implementations, the first slidable sealing element and the second slidable sealing element comprise opposed flow ports.

[0026] In some implementations, the third slidable sealing element comprises opposed arcuate slots.

[0027] In some implementations, the opposed ports in the first slidable sealing element are angularly separated from the opposed ports in the second slidable sealing element by 90 degrees.

[0028] In some implementations, a flow rate of moving fluid is controlled by selecting an amount of time the slidable sealing elements are arranged to allow fluid flow in a first direction and an amount of time the slidable sealing elements are arranged to allow fluid flow in an opposed direction.

[0029] In some implementations, each of the first and second sealing elements comprises at least one flow port having shape wherein the relative movement causes a connected flow area between the respective tapered flow ports to change longitudinally and / or laterally.

[0030] In some implementations, the at least one flow port in the at least a first and the at least a second sealing element comprises at least one full flow port and a tapered flow channel fluidly connected to the at least one flow port, the tapered flow channel on the at least a first sealing element laterally offset from the tapered flow channel on the at least a second sealing element, wherein the relative movement causes a connected flow area between the respective tapered flow channels to change both longitudinally and laterally

[0031] Other aspects and possible advantages will be apparent from the description and claims that follow.BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIGS. 1 and 2 illustrates example sliding sealing elements which can define a controllable flow path configuration for flow / pressure control / restriction.

[0033] FIG. 3 illustrates an example flow control assembly for flow / pressure control.

[0034] FIG. 4 illustrates an example assembly for open / close / orifice selection / one way flow functionality. The particular assembly shows an example configuration with closed and different hole / orifices that can be selected by sliding the two sealing element into the required relative positions to obtain a controlled selected range of fluid control and flow shut off, for example to control of gas flow or other fluids. The functionality as a one-way (check valve) barrier can typically be obtained by the way of configurating the sealing element(s) to open or close for the flow to pass through.

[0035] FIGS. 5 A and 5B illustrate an example flow control assembly for flow directional and or metering control. The particular assembly an example configuration where the flow direction is controlled by the relative position between the sliding sealing elements that can by the differential pressure between inlet and outlet ports operate, for example, a flow meter such as a reciprocating piston, bellow or similar device to measure the flow volume and / or rate going the flow control assembly. The flow rate can be adjusted and controlled by the time between the directional flow change, for example by utilizing a stepper motor or similar to control the speed of surface movement.

[0036] FIG. 6 shows another example implementation of a sealing element according to the present disclosure.

[0037] FIG. 7 shows an isometric view of the sealing element of FIG. 6 assembled with a second sealing element of similar configuration to illustrate cooperation of the respective flow paths in each sealing element.

[0038] FIG. 8 shows the sealing elements of FIG. 7 in plan view to illustrate certain features of the flow paths in each sealing element.

[0039] FIG. 9 shows details of another implementation of an actuator to effect relative movement between sealing elements.

[0040] FIG. 10 shows the actuator of FIG. 9 and a flow control in a flow control housing including means for moving the actuator components of FIG. 9 by differential pressure.DETAILED DESCRIPTION

[0041] A fluid flow control according to the present disclosure may comprise at least two adjacent flow control elements each having a sealing surface that can move relative to the other. The flow control may be provided with at least one fluid inlet and one fluid outlet. The two adjacent sealing surfaces may be based on a hard material, for example, metals or ceramics, and may have a very fine and accurate surface finish to provide a direct contact fluid-tight seal without needing an additional sealing element such as a resilient material, e.g., an elastomer or similar.

[0042] The configuration of fluid flow through the adjacent sealing surfaces depends on the specific control function required. The configuration could be, for example: a variable restriction flow path between the adjacent sealing surfaces to obtain a specific range of restriction for control of flow rate and / or pressure; and / or openings or holes exposed between the adjacent sealing surfaces to obtain flow shut-off, orifice selection capability, one-way flow functionality or combinations of such functionalities. By utilizing sliding adjacent sealing surfaces to control the variable restriction, open / close functionality, directionally control flow, etc., and possibly in combination with cleaning functionality, it has been demonstrated that significantly increased particle tolerance over conventional flow controls normally used for certain applications where solid particles are suspended in the fluid being controlled.

[0043] The “term sealing surface: as used herein means a surface on the sealing elements.The sealing surfaces may have the properties explained above to make a fluid tight sealwhen such sealing surfaces are adjacent to each other or to another fluid handling component of the flow control.

[0044] Several types of devices and / or methods to actuate the adjacent sealing element(s) may be used. Such devices and or methods may be, for example and without limitation, be electric, pneumatic, hydraulic, thermal, etc. The form of actuator to be connected to the flow control to slide linearly or rotate (i.e., slide rotationally) the adjacent sealing elements relative to each other may, for example, be connected directly, may be a part of or be connected indirectly thereto, and may comprise, for example and without limitation, an electric stepper motor, a piston, a bladder, a bellow, a bourdon tube, direct delta pressure driven by area design, among other possible actuation devices.

[0045] FIGS. 1 and 2 illustrate example implementations of sliding sealing elements which can define a variable restriction flow path for flow control and / or flow restriction. The illustrated examples of fluid passage shapes formed in the sliding sealing elements provide a variable restriction flow path from a fluid inlet to a fluid outlet between the adjacent sliding sealing elements (e.g., through circular disks as shown in FIG. 1 and FIG. 2) when they are adjacent in a flow control assembly, an example of which is shown at 10 in FIG. 3. The particular flow path shapes shown in FIGS. 1 and 2 are to be considered only as examples, as the actual shape, design and sizing of any particular flow path in the adjacent sliding sealing elements may be optimized for the desired flow control characteristics, flow range and functionality needed.

[0046] In FIG. 1, a first sealing element may comprise a movable (rotating) disk 11, comprises full flow orifices 11A through the rotating disk 11 at circumferential ends of tortuous flow paths 11B. When the rotating disk 11 is oriented such that the full flow orifices 11 A are respectively aligned with a fluid inlet port (16 in FIG. 3) and a fluid outlet port (18 in FIG. 3) in the flow control assembly (10 in FIG. 3), fluid flow through the flow control assembly (10 in FIG. 3) is minimally restricted. As the movable disk 11 is rotated such that greater lengths of the tortuous paths 1 IB are respectively aligned with the fluid inlet 16 and fluid outlet 18 ports, flow restriction increases.

[0047] In FIG. 2, the movable disk 13 comprises full flow orifices 13A in a manner similar to the example shown in FIG. 1. Fluid flushing paths 13B provide both variable flow restriction as the movable disk 13 is rotated as well as a mechanism to enable flushing of accumulated solid particles in the movable disk 13 and flow paths through the flow control assembly (10 in FIG. 3).

[0048] Nonetheless, the example implementations shown in FIG. 1 and FIG. 2 provide the functions of a variable restriction flow path in FIG. 1 and a flushing flow path in FIG. 2. The flushing flow path shown in FIG. 2 may be used to boost flushing efficiency, by generating speed fluctuations / turbulence across the controlled flow path to clean the controlled flow path (e.g., as in FIG. 1) of solid particles more efficiently.

[0049] FIG. 3 illustrates an example flow control assembly 10 for flow / pressure control using adjacent sliding sealing elements, for example, in the form of a disk 11 as shown in FIG. 1 and / or at 13 in FIG. 2, wherein relative movement between the movable disk 11 or13 and the remainder of the flow control assembly 10 may be effected by a rotary actuator 14. In some implementations the rotary actuator may be a stepper motor or servo motor. The inlet port 16 and an outlet port 18 are disposed in a port housing 17 forming part of the flow control assembly 10. The inlet and outlet ports 16, 18 terminate at a surface of the movable disk 11 or 13 such that the inlet and outlet ports 16, 18 are adjacent to the full flow orifices (11 A, 13 A in FIGS. 1 and 2, respectively) in one rotary orientation, and to longer portions of tortuous path (1 IB in FIG. 1 and 13B in FIG. 2) as the rotary actuator14 reorients the movable disk 11 or 13 as flow restriction is adjusted. An adjacent sliding sealing element, shown at 19, may comprise features (not shown) of any suitable type to enable flow from the inlet port 16 to the outlet port 18 having passed through selected full flow ports (11 A in FIG. 1 or 13A in FIG 2) or selected parts of the tortuous paths (1 IB in FIG. 1 or 13B in FIG. 2) on the movable disk, 11 or 13.

[0050] FIG. 4 illustrates an example flow control assembly 10 that may provide flow open and flow close functionality, variable restriction flow control selection and / or one way flow direction functionality. The example assembly in FIG. 4 may have closed surfaces, e.g., an arcuate slot at 15A on one sealing element 15 and different size holes / orifices at 17Athrough 17E on the other sealing element 17 that can be selected by sliding the two sealing elements 15, 17 (e.g., rotating) into the required relative positions to obtain a controlled or selected range of fluid flow restriction, for example, to control flow rate and / or pressure of gas or other fluid flow. The functionality as a one-way (check valve) barrier and / or as controlled opening and closing barrier can typically be obtained by way of configurating and / or controlling the actuator 14, e.g., the bellow, Bourdon tube, spring(s), stepper motor or servo motor, or combinations of such devices to open or close a path for the flow by orienting the closed surface(s) and orifices to effect the open / close or one way flow control function.

[0051] FIGS. 5 A and 5B illustrate an example flow control assembly 20 that may be used for flow direction control and / or flow metering. The actuator is omitted from FIGS. 5 A and 5B for clarity. The illustrated flow control assembly 20 in FIGS. 5 A and 5B has a rotating disk 24 disposed between two static disks 22, 26. Such configuration provides that the flow direction through the flow control assembly 20 is controlled by the relative positions of the sliding, sealing elements with respect to each other. In one implementation differential pressure between the inlet port 16 and the outlet port 18 operates, for example, a positive displacement metering device 34, such as a reciprocating piston metering device as illustrated in FIGS. 5A and 5B, a bellow, a lobed rotor metering device, a gear metering device or the like to measure the flow rate and / or fluid volume moving through the flow control assembly 20. The example flow control assembly 20 shown in FIG. 5A illustrates a first, fixed position sliding sealing element 22 and a second, fixed position sliding sealing element 26. The first fixed position, sliding sealing element 22 is in fluid communication with a main fluid inlet 16 and a main fluid outlet 18 as shown in FIG. 5 A by TO 16 and TO 18. A movable (rotating) sliding sealing element or disk 24 may have elongated, arcuate slot openings 24A, 24B thereon, wherein the movable disk 24 is disposed between the fixed position, sliding sealing elements 22, 26. The second, fixed position sliding sealing element 26 has openings, TO 30, TO 32 in fluid communication with a metering loop or other fluid device, explained below. In the present example implementation, the openings in the first, fixed position sliding sealing element 22 and the openings in the second, fixed position sliding sealing element may be oriented as shown at 90 degreesangular separation so that the arcuate slots 24A, 24B may be rotatably oriented to cause fluid flow through the sliding sealing elements to reverse between the main fluid inlets and the metering loop outlets. In FIG. 5A, the orientation of the rotating disk 24 causes arcuate slot 24A, 24B alignment such that fluid flow through the metering loop is in the direction indicated. The metering loop in the present example may comprise a fluid inlet 32 fluidly connected between one of two ports in the second, fixed position sealing element 26 and a port on one side of a flow metering device 34 which may be any of the types described above. Another port of the flow metering device 34 is fluidly connected to the other port in the second, fixed position sealing element 26. In FIG. 5B, rotating the movable 24 disk to the indicated orientation causes slot alignment to provide flow direction through the metering loop (30, 32, 34) in the opposite direction, even while flow direction with reference to the main fluid inlet 16 and the main fluid outlet 18 remains the same. The arrangement shown in FIGS. 5 A and 5B may be used, for example, to enhance removal of solids and contaminants by providing reversible flow through the metering loop or other fluid flow path as may be provided while maintaining flow direction with reference to the main fluid inlet 16 and main fluid outlet 18.

[0052] The fluid flow rate can be adjusted and controlled by the amount of time between the directional flow changes, for example by using a stepper motor, servo motor or the like to control the speed of rotating disk 24 movement (relative motion) between the adjacent sliding sealing elements 22, 26. In the present example implementation, rotation may be applied to the movable disk as shown; it is contemplated that the sealing capability of the adjacent sealing elements and their sealing surfaces as explained above will avoid the need for a rotating shaft seal where a drive shaft passes through either or both of the fixed position sealing elements 22, 26.

[0053] FIG. 6 shows another example implementation of a sealing element 111 according to the present disclosure. The sealing element 111 may be made from any material used to make sealing elements as described elsewhere herein, for example and without limitation, metal and / or ceramic. In the present example implementation, sealing surfaces 112 may be formed on raised features extending outward from the body of the sealing element 111. Flow paths extending through the sealing element 111 may comprise a full flow opening113 having connected thereto a tapered flow channel 113A that at its longitudinal end intersects the full flow opening 113. The tapered flow channel 113 A may be formed in the surface of the sealing element 111, but may not penetrate completely through the sealing element 111.

[0054] The sealing element 111 of FIG. 6 cooperates by relative movement with a corresponding sealing element 211 as shown in isometric view in FIG. 7 to affect fluid flow. The corresponding sealing element 211 may comprise flow paths including full flow openings 213 and intersecting tapered flow channels 213 A as shown in FIG. 7. In the present example implementation, the sealing elements 211, 111 may be disk shaped and rotate with respect to each other so that different portions of the respective flow paths on each sealing element 211, 111 cooperate to control flow of fluid through a flow control made using such sealing elements 211, 111.

[0055] Certain features of the flow paths in the sealing elements of FIG. 7, at 211, 111 may be better understood with reference to FIG. 8. The tapered flow channels 113A, 213A may in the present example implementation comprise generally arcuate shape, and the tapered flow channel 113 A in the first sealing element 111 may be laterally (radially in the present example) offset from the tapered flow channel 213 A in the second sealing element 211. Because the arcuate, tapered flow channels 113 A, 213 A are laterally offset, as the sealing elements 111, 211 rotate such that the flow channels 113A, 213 A overlap, the connected flow area between the flow channels 113A, 213 A increases both longitudinally (along the direction of the flow channels 113A, 213 A) and laterally. The foregoing feature may increase the responsiveness of a flow control according to the present disclosure, particularly that at the lower flow ranges of the flow control, more relative movement of the sealing elements 111, 211 may be needed to effect a certain magnitude of flow rate or pressure change, while less corresponding movement may be needed closer to the full flow position of the flow control.

[0056] The example sealing elements of FIGS. 6 through 8 provide only one example of flow ports in accordance with the present disclosure. Other implementations of flow ports may be used provided that the relative movement of one sealing element with respect tothe other sealing element provides connected flow area between them that changes both longitudinally and / or laterally (i.e. in one or two transverse directions) in order to provide increased responsiveness of flow restriction with reference to relative positions of the sealing elements with respect to each other.

[0057] FIGS. 9 and 10 show another example implementation of an actuator 114 for a flow control according to the present disclosure. The present example implementation may comprise disk shaped sealing elements, e.g., at 113 corresponding to the sealing elements shown in FIGS. 6 and 7; it should be clearly understood thar other shapes and configurations of sealing elements including those described with reference to FIGS. 1, 2, 4, 5 A and 5B may be used with such actuator 114 with equal effect. The present example actuator 114 may comprise opposed first links 115A, 115B each coupled at one longitudinal end to a movable one of the sealing elements, e.g., at 113, on opposed sides of the center line 113C of the movable sealing element 113. The opposed longitudinal end of each first link 115A, 115B is coupled to a bellcrank 117 on a respective side of the bellcrank 117 about a bellcrank pivot 117A. Thus, rotation of the bellcrank 117 about the pivot 117A results in opposed motion of the links 115 A, 115B, thus imparting rotational motion to the movable sealing element 113. Rotation of the bellcrank 117 may be effected by a second link 119 connected at one end to the bellcrank 117 on one side of the pivot 117A. The second link 119 may be connected at its other end to a linear motor 121, which will be explained with reference to FIG. 10.

[0058] FIG. 10 shows a cut away side view of a flow control device 100 including the present example implementation of the actuator 114. A flow control 10 according to any of the implementations disclosed herein may be disposed within a pressure resistant housing 101. The housing 101 may comprise s fluid inlet 101B compartment on one side. The fluid inlet compartment 101B may be connected to a fluid inlet 116. The housing 101 may comprise a fluid outlet compartment 101 A on another side, in fluid communication with a fluid outlet 118.

[0059] Fluid entering the inlet compartment 10 IB through the fluid inlet 116 may enter an inlet bellows 114A disposed in the fluid inlet compartment 101B. Fluid may leave the inletbellows 114A to fill the volume of the inlet compartment 101B outside the inlet bellows 114A as it moves toward the flow control 10. The inlet bellows 114A serve as an accumulator to maintain inlet fluid pressure. Inlet fluid pressure is also communicated to the volume inside the housing 101 in which the flow control 10 is disposed. In this way, differential pressure between the exterior an interior of the flow control 10 is minimized, thus reducing the chance for fluid leaks through the flow control 10. Fluid flowing from the fluid inlet compartment 101B may enter the flow control 10 through its fluid inlet 16, substantially as explained with reference to FIGS. 3, 5 A and 5B. Controlled fluid leaving the flow control 10 exits through a fluid outlet 18 substantially as explained with reference to FIGS. 3, 5 A and 5B. The controlled fluid may enter the outlet bellows 114B disposed in the fluid outlet compartment 101 A. The volume of the fluid outlet compartment 101 A external to the outlet bellows 114B may be filled with pressurized gas, wherein changes in fluid pressure inside the outlet bellows 114B causes expansion and contraction of the outlet bellows 114B. The second link 119 is connected at its other end to an end of the outlet bellows 114B, such that expansion and contraction of the outlet bellows 114B is communicated to the second link 119. In this way, the combination of outlet bellows 114B and second link 119 forms a linear motor 121.

[0060] A shaft 102 may be coupled to the movable sealing element 113, wherein rotation thereof is transmitted to the shaft 102. The shaft 102 may be used to operate a rotary encoder (not shown) or other device, or the shaft 102 may be coupled to a rotary actuator such as a stepper motor to operate the movable sealing element 113.

[0061] In light of the principles and example implementations described and illustrated herein, it will be recognized that the example implementations can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific implementations, but other configurations are also contemplated. In particular, even though expressions such as in “an implementation," or the like are used herein, these phrases are meant to generally reference implementation possibilities, and are not intended to limit the disclosure to particular implementation configurations. As used herein, these terms may reference the same or different implementations that are combinable into other implementations. As a rule, any implementation referenced hereinis freely combinable with any one or more of the other implementations referenced herein, and any number of features of different implementations are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A flow control device, comprising: at least a first sealing element having at least one flow opening therein; at least a second sealing element having at least one flow opening therein, the at least a first sealing element and the at least a second sealing element in sliding, sealing contact with each other; and an actuator for moving the at least a first sealing element relative to the at least a second sealing element, wherein the at least one flow opening in each of the at least a first and the at least a second sealing elements cooperate by relative movement to affect fluid flow through the at least a first and the at least a second sealing elements.

2. The flow control device of claim 1 wherein the at least a first sealing element and the at least a second sealing element comprise disks.

3. The flow control device of claim 2 wherein the actuator is configured to rotate the disks with respect to each other.

4. The flow control device of claim 1 wherein the actuator comprises a stepper motor or a servo motor.

5. The flow control device of claim 1 wherein the at least a first sealing element and the at least a second sealing element comprise metal or ceramic materials.

6. The flow control device of claim 1 wherein the at least a first sealing element comprises full flow ports and a tortuous flow path hydraulically connected to each full flow port.

7. The flow control of claim 1 wherein the at least a first and the at least a second sealing element each comprises at least one flow port having shape wherein the relative movement causes a connected flow area between the respective flow ports to change longitudinally and / or laterally.

8. The flow control of claim 7 wherein the at least one flow port in the at least a first and the at least a second sealing element comprises at least one full flow port and a tapered flow channel fluidly connected to the at least one flow port, the tapered flow channel on the at least a first sealing element laterally offset from the tapered flow channel on the at least a second sealing element, wherein the relative movement causes a connected flow area between the respective tapered flow channels to change both longitudinally and laterally.

9. The flow control device of claim 1 wherein the at least a first sealing element comprises full flow ports and a flushing flow path hydraulically connected to each full flow port.

10. The flow control device of claim 1 further comprising a movable sealing element disposed between the at least a first sealing element and the at least a second sealing element, the movable sealing element comprising opposed, arcuate slots therein, the at least a first and a second sealing elements comprising opposed ports therein, wherein the arcuate slots and the opposed ports in the at least a first sealing element and the at least a second sealing element are arranged to reverse flow through the flow control device by reorienting the movable sealing element.

11. The flow control of claim 10 wherein the actuator is configured to rotate the movable sealing element.

12. The flow control of claim 10 wherein the opposed ports on the at least a first sealing element are angularly separated from the opposed ports on the at least a second sealing element by 90 degrees.

13. A method for controlling fluid flow, comprising: moving fluid from an inlet to a fluid control device to a first slidable sealing element, the first slidable sealing element comprising at least one opening therein; sliding the first slidable sealing element with respect to a second slidable sealing element sealingly engaged with the first slidable sealing element so that at least one opening in the second slidable sealing element cooperates with the at least one opening in the first slidable sealing element to control flow of the fluid to an outlet of the fluid control device.

14. The method of claim 13 wherein the sliding comprises rotation.

15. The method of claim 13 wherein the at least one opening in the first slidable sealing element comprises a tortuous path.

16. The method of claim 15 wherein the tortuous path comprises a full flow opening at an one end of the tortuous path.

17. The method of claim 13 wherein the at least a first and the at least a second sealing element each comprises at least one flow port having shape wherein the relative movement causes a connected flow area between the respective flow ports to change longitudinally and / or laterally.

18. The method of claim 17 wherein the at least one flow port in the at least a first and the at least a second sealing element comprises at least one full flow port and a tapered flow channel fluidly connected to the at least one flow port, the tapered flow channel on the at least a first sealing element laterally offset from the tapered flow channel on the at least a second sealing element, wherein the relative movement causes a connected flow area between the respective tapered flow channels to change both longitudinally and laterally.

19. The method of claim 13 wherein the at least one opening in the first slidable sealing element comprises a flushing path.

20. The method of claim 19 wherein the flushing path comprises a full flow opening at an end of the flushing path.

21. The method of claim 13 further comprising moving fluid from the first slidable sealing element through a third slidable sealing element to the second slidable sealing element, wherein the first slidable sealing element and the second slidable sealing element remain in fixed position and the third slidable sealing element moves with respect to the first and second slidable sealing elements to reverse fluid flow through the fluid control device.

22. The method of claim 21 wherein the sliding comprises rotation.

23. The method of claim 22 wherein the first, second and third slidable sealing elements comprise disks.

24. The method of claim 22 wherein the first slidable sealing element and the second slidable sealing element comprise opposed flow ports.

25. The method of claim 24 wherein the third slidable sealing element comprises opposed arcuate slots.

26. The method of claim 24 wherein the opposed ports in the first slidable sealing element are angularly separated from the opposed ports in the second slidable sealing element by 90 degrees.

27. The method of claim 26 wherein a flow rate of moving fluid is controlled by selecting an amount of time the slidable sealing elements are arranged to allow fluid flow in a first direction and an amount of time the slidable sealing elements are arranged to allow fluid flow in an opposed direction.

28. The method of claim 13 wherein the first slidable sealing element and the second slidable sealing element are disposed in fluid having pressure equal to a fluid pressure at the inlet.

29. The method of claim 28 further comprising applying fluid pressure from the outlet to a bellows, the bellows having gas at a selected pressure on a one of the interior or exterior of the bellows not in communication with the applied fluid pressure, wherein changes in the applied fluid pressure cause expansion and / or contraction of the bellows, the expansion and / or contraction applied to one of the first or second slidable sealing elements to effect relative motion therebetween

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