A pressure actuated valve for use during installation and commission of a production string

Abstract

The present invention relates to a system and a pressure activated valve for preventing fluid from passing through an ICD during installation and commissioning of a production string in a well bore. Further the invention relates to a method for operating the pressure activated valve. The pressure activated valve can be arranged outside the production string being configured to hinder fluid from entering the ICD from a reservoir when the pressure activated valve is closed and to allow fluid from entering from the reservoir when pressure activated valve is open.

Claims

1. A pressure activated valve (1) for preventing fluid from flowing through an inflow control device (2) during installation and commissioning of a production pipe (10) of a well bore, comprising: a cylinder (102) open in both first and second longitudinal ends (102a, 102b) a cylindrical piston (104) moveably arranged within the cylinder (102), wherein the piston (104) is hollow allowing fluid to enter into a first longitudinal end section (104a) and closed at a second longitudinal end section (104b) hindering fluid from passing therethrough, wherein the piston (104) further comprises at least one radially arranged opening (112) adjacent to the second longitudinal end section (104b), a seal (113) arranged to interact with the piston (104) and the cylinder (102), wherein either the cylinder (102) comprises a slot (110) for receiving and guiding a stopper (108) which is fixed to the piston (104) or the piston (104) comprises a slot (111) for receiving and guiding a stopper (109) which is fixed to the cylinder (102) wherein the slot (110,111) is configured to guide piston (104) from i) a first position (P1), wherein the piston (104) is positioned in a pretensioned position by a spring (106), wherein the stopper (108,109) is abutting a first end (110a,111a) of the slot (110,111) and wherein the piston (104) is arranged such that the at least one radially arranged opening (112) and seal (113) are located within the cylinder (102), thereby hindering any fluid from flowing through the pressure activated valve (1); towards ii) a second position (P2) by compressing the spring (106) due to an internal pressure exerted on the piston (104), wherein the piston (104) is moved in an at least partly helical path towards the first longitudinal end (102a) of the cylinder (102), until the stopper (108,109) is abutting a second end (110b,111b) of the slot (110,111); and thereafter towards iii) a third position (P3) by releasing the internal pressure exerted on the piston (104), wherein the piston (104) is moved in a path towards the second longitudinal end (102b) of the cylinder (102) until the stopper (108,109) abuts a third end (110c,111c) of the slot (110,111) such that the seal (113) allows fluid to pass through the PAV (1).

2. The pressure activated valve (1) according to claim 1, wherein the cylinder (102) comprises the slot (110) and the stopper (108) is fixed to an outer surface of the piston (104).

3. The pressure activated valve (1) according to claim 2, wherein the cylinder (102) comprises two identical slots (110,110′) and the piston (104) comprises two stoppers (108,108′), wherein the two identical slots (110,110′) and the two stoppers (108,108′) are arranged on oppositely facing sides of the cylinder (102) and piston (104), respectively.

4. The pressure activated valve (1) according to claim 1, wherein the piston (104) comprises the slot (111) and the stopper (109) is fixed to the cylinder (102).

5. The pressure activated valve (1) according to any one of the preceding claims, wherein the at least one radially arranged opening (112) has one of an oblong, oval, and rounded corner rectangular shape extending in a longitudinal direction of the piston (104).

6. The pressure activated valve (1) according to any one of the preceding claims, wherein at least one radially arranged opening (112) has a longitudinal length extending from any one of 5% to 60% or 10% to 50% or 10% to 40% of a maximum longitudinal length of the piston (104).

7. The pressure activated valve (1) according to any one of the preceding claims, wherein the at least one radially arranged opening (112) has a circumferential extend of any one of 200 to 900 or 300 to 800 or 400 to 70°.

8. The pressure activated valve (1) according to any one of the preceding claims, wherein the piston (104) comprises at least three radially arranged openings (112).

9. The pressure activated valve (1) according to any one of the preceding claims, wherein the piston (104) has a shorter longitudinal length than the cylinder (102).

10. The pressure activated valve (1) according to any one of the preceding claims, wherein the piston (104) comprises the seal circumferentially arranged at the second longitudinal end section (104b) sealingly arranging the piston (104) within the cylinder (102) when the piston (104) is in or between the first position (P1) and second position (P2) hindering any fluid from flowing through the pressure activated valve (1).

11. A system for preventing fluid from passing through an inflow control device (2) during installation and commissioning of a production string (10) in a well bore, wherein the system comprises a production string (10) or a production string joint, an inflow control device (2) arranged within a wall of the production string (10) or the production string joint, a pressure activated valve (1) arranged outside the production string being configured to hinder fluid from entering the inflow control device (2) from a reservoir when the pressure activated valve (1) is closed and to allow fluid from entering from the reservoir when pressure activated valve (1) is open.

12. The system according to claim 11, wherein the inflow control device (2) is an autonomous inflow control device (2).

13. The system according to claim 11 or 12, wherein the pressure activated valve (1) is in accordance with any one of claims 1 to 10.

14. A method for preventing fluid flow through an inflow control device arranged within a wall of a production string (10) using a pressure activated valve (1), in accordance with the system of claim 13, wherein the method comprises the steps of: installing the piston (104) of the pressure activated valve (1) in a closed first position (P1) wherein the piston (104) is exposed to a pressure by a spring force of a set value; exerting an internal pressure above the set value, wherein the internal pressure is exerted from the production string (10) towards the pressure activated valve (1) such that the piston (104) moves into a closed second position (P2); releasing the internal pressure forcing the piston (104) to an open, third position, (P3).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] These and other characteristics of the invention will be clear from the following description of embodiments, given as non-restrictive examples, with reference to the attached sectional sketches and drawings wherein:

[0062] FIG. 1 is cross sectional view of a system having a production string, AICV, PAVs and sand screen.

[0063] FIG. 2 is an open/transparent perspective view of the system of the invention showing the sand screen, PAVs and AICV.

[0064] FIG. 3 is a perspective view of the inventive PAV according to the first example embodiment.

[0065] FIG. 4A is a cross-sectional view of the first example embodiment of the inventive PAV in the first position P1.

[0066] FIG. 4B is a cross-sectional view of the first example embodiment of the inventive PAV in the second position P2.

[0067] FIG. 4C is a cross-sectional view of the first example embodiment of the inventive PAV in the third position P3.

[0068] FIG. 5A is an open/transparent perspective view of the first example embodiment of the inventive PAV in the first position P1.

[0069] FIG. 5B is an open/transparent perspective view of the first example embodiment of the inventive PAV in the second position P2.

[0070] FIG. 5C is an open/transparent perspective view of the first example embodiment of the inventive PAV in the third position P3.

[0071] FIG. 6A to 6E are open (transparent) side-views of a PAV 1 according to a second example embodiment of the inventive PAV.

[0072] FIGS. 6F and 6G are illustrations of the path of the slot/groove of the PAV disclosed in FIGS. 6A to 6E.

[0073] FIGS. 7A to 7D are cross-sectional side views of the PAV shown in FIGS. 6A to 6D respectively.

[0074] FIG. 8A is a perspective view of the piston of the PAV shown in FIG. 6A to 6E.

[0075] FIG. 8B is a close up view of the circled area A of FIG. 8A.

[0076] In the drawings, like reference numerals have been used to indicate like parts, elements or features unless otherwise explicitly stated or implicitly understood from the context.

DETAILED DESCRIPTION

[0077] In the following, embodiments of the invention will be described in more detail with reference to the drawings. However, it is specifically intended that the invention is not limited to the embodiments and illustrations contained herein but includes modified forms of the embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.

[0078] It is appreciated that certain features of the invention, which, for clarity, have been described above in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which, for brevity, have been described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. In particular, it will be appreciated that features described in relation to one particular embodiment may be interchangeable with features described in relation to other embodiments.

[0079] FIG. 1 shows a cross section of a typical layout of a production string 10 with a sand screen 3, PAV 1 and an automated ICD, referred to as an AICV 2, mounted in series. As shown, a plurality of PAVs 1 can be circumferentially distributed around the annular production string 10.

[0080] The AICV 2 is mounted within the wall of the production string 10 to create a flow path there through, while the PAVs 1 and sand screen 3 are mounted on the outside of the production string along the outer surface thereof.

[0081] As shown in FIG. 1, the PAVs 1 do not restrict or interfere with the production string's 10 standard full internal diameter ID. During production, fluid passes through the sand screen 3, through the PAV 1, set in open position, and through the AICV 2 which will be open or closed depending on the characteristics of the fluid entering from the PAV 1.

[0082] FIG. 2 is a perspective view of how a plurality of PAVs 1 can be arranged around the production string 10 and shows how the system of the invention comprising the sand screen 3, PAVs 1 and an AICV 2 are assembled. Each PAV 1 is mounted into a ring 200. The ring can contain a single PAV 1 or a plurality of PAVs 1 as shown. The ring 200 is welded to the production string such that flow or pressure communication to the reservoir must go through the PAVs 1. The PAVs 1 are sealed against the ring 200 using seals, such as polymer, elastomer or metal seals. When internal pressure acts on the piston 104 of each PAV 1, the spring forces will open them all when the internal pressure is released.

[0083] FIG. 3 is a perspective view of a PAV 1 according to a first example embodiment of the first aspect of the PAV 1 showing the cylinder 102 having two slots 110, even if only one is visible. Further, the shown stopper 108 of the piston 104 is arranged in the first position P1 being pretensioned by the force from the spring 106 into the shown abutting position.

[0084] FIGS. 4A to 4C are cross-sectional views of the PAV 1 shown in FIG. 3 and FIGS. 5A to 5C are open transparent side views of the PAV 1 shown in FIGS. 4A to 4C. The PAV 1 is shown in the pretensioned closed position P1 in FIGS. 4A and 5A, in a closed second position P2 in FIGS. 4B and 5B and in an open third position P3 in FIGS. 4C and 5C.

[0085] With reference to FIGS. 3, 4A to 4C and 5A to 5C, the PAV 1 comprises a hollow cylinder 102 having a moveable cylindrical piston 104 arranged therein moving in the longitudinal direction L (see FIG. 3) of the cylinder 102. The piston 104 is hollow and open at the first longitudinal terminal end 104c of the first end section 104a allowing fluid to enter into the piston 104 but is closed at the second longitudinal terminal end 104d of the second end section 104b hindering fluid from passing therethrough. In the drawings the hole end section 104b is closed. The radially arranged openings 112 of the piston abut the second end section 104b of the piston 104. The radially arranged openings 112 allow fluid to pass through the PAV 1 when the seal/O-ring 113 is arranged outside the cylinder 102, i.e. when the PAV 1 is in the third (open) position P3 as shown in FIGS. 4C and 5C. The openings 112 have a longitudinal oblong shape. As shown, the second end section 104b of the piston 104 comprises the seal/O-ring 113 which sealingly arranges the piston 104 within the cylinder 102 when the PAV 1 is closed.

[0086] The spring 106 is arranged within a recess between the piston 104 and the cylinder 102 abutting a first piston rim 105 of the piston 104 at the one end which can be arranged near or approximate to the stoppers 108,108′ and a first cylinder rim 103 of the cylinder 102 at the other opposite end being arranged closer to the first longitudinal end 102a of the cylinder 102.

[0087] In other words, the piston 104 has a larger outer diameter at an area including the stoppers 108,108′ such that the outer surface of the piston 104 facing the inner surface of the cylinder 102 comprises the first piston rim 105. Further, an area of the cylinder 102 including the first end 102a of the cylinder 102 has a smaller inner diameter than the remaining part of the inner surface of the cylinder 102 such that the inner surface of the cylinder 102 comprises the first cylinder rim 103.

[0088] As seen in FIGS. 4A and 5A the spring 106 is pretensioned between the first piston rim 105 and the first cylinder rim 103 as the piston 104 is arranged in the first position P1.

[0089] In this first position P1, the spring force is directed from the cylinder rim 103 towards the piston rim 105 such that the stoppers 108,108′ are simultaneously pushed towards the first ends 110a, 110a′ of the slots 110,110′. The piston 104 is fully arranged within the cylinder 102 such that the PAV 1 is closed, thereby prohibiting fluid from passing therethrough, and hence prohibiting fluid from passing through the ICD/automated ICD. The spring force shall be chosen such that the piston 104 is not moved below a limiting design pressure which may be around 170 bars (around 2500 psi).

[0090] If the design pressure is exceeded, i.e. applying an internal activation pressure to the piston 104 in the opposite direction of the force of the spring 106, the slots 110,110′ guide the stoppers 108,108′ from the first (closed) position P1, and hence the piston 104 to the second intermediate position P2 as shown in FIGS. 4B and 5B. This occurs since the internal pressure applied on the piston 104 creates an applied force that exceeds the opposite force applied by the pretensioned spring 106. The spring 106 is hence further compressed and the stoppers 108,108′ are simultaneously guided within the paths of the slots 110,110′ in the direction circumferential and radial direction towards the first end 102a of the cylinder 102 until reaching the second ends 110b,110b′ of the slots 110,110′. The piston 104 is then arranged in the second position P2.

[0091] Further, the piston 104 may comprise a second piston rim 105′ at the first end section 104a of the piston 104 which may abut a second cylinder rim 103′ near the first end 102a of the cylinder 102. Such abutment between the piston 104 and the cylinder 102 allows the applied force to be spread over a larger area than if they were not present. Hence, the internal pressure executed on the stoppers 108,108′ of the piston 104 is spread to the cylinder 102 unloading some of the pressure executed on the stoppers 108,108′. A person skilled in the art will understand that instead of a rim 103 of the cylinder 102 the cylinder 102 may comprise any kind of resistance such as a retainer screw, retaining plug or the like.

[0092] As shown, the cylinder 102 has a smaller inner diameter at or near its first end 102a creating the second cylinder rim 103′ which abuts the second piston rim 105′ when the piston 104 is arranged in the second position P2.

[0093] The paths of the slots 110,110′ forces the stoppers 108,108′ of the piston 104 to move in a circumferential/radial path towards the first end 102a of the cylinder 102 when moving the piston from the first position P1 to the second position P2. Hence, the piston 104 is moved in the circumferential/rotational direction as well as in the longitudinal direction (i.e. in a partly helical path) until the stoppers 108,108′ reaches the second ends 110b,110b′ of the slots 110,110′. In this position the piston 104 is still fully arranged within the cylinder 102 such that the PAV 1 remains closed for fluid flow.

[0094] The activation pressure may for example be around 240 bars (3500 psi) which is the internal pressure applied to the production string for activating mechanical packers.

[0095] As the internal pressure is reduced or removed, the piston 104 is moved due to the spring force until it reaches the open third position P3, shown in FIGS. 4C and 5C. The stoppers 108,108′ of the piston 104 are moved in a straight longitudinal path of the slots 110,110′ towards second end 102b of the cylinder 102 until the stoppers 108,108′ are, due to the force exerted by the spring 106, pushed towards/abutting the third ends 110c,110c′ of the slots 110,110′. In this third position P3 of the piston 104, seal 113 of the piston 104 is extending outside the cylinder 102 such that the PAV 1 is open. Fluid is hence allowed to flow from the reservoir into the production string 10 via the PAV 1.

[0096] The spring force can be selected such that the spring 106 can be fully compressed when the piston 104 is in the second position P2 utilizing the spring 106 to a maximum. If the spring 106 is longer than the cylinder 102, the piston 104 will be tensioned in all positions after it is mounted along the production string 10. After release of the piston 104 into the third position P3, the piston 104 will still be tensioned, thereby preventing the PAV from closing due to internal pressures during operation such as backflow. However, the piston 104 may be fully extended having no tension at the third position P3 which also requires a force for moving the piston 104 back to the second position P2.

[0097] Further, the combined circumferential and longitudinal path of the slots 110,110′, which guide the piston 104 from the first position P1 to the second position P2, is hindering the stoppers 108,108′, when the piston 104 is arranged in the second position P2, to move back to the first position P1 when the internal pressure exerted on the piston 104 is released. The piston 104 will seek to move in a straight path, i.e. towards the third position P3. Hence the PAV 1 would be re-opened in the third position P3 after releasing the internal pressure and not closed in the first position, P1.

[0098] Further, the spring 106 can be free to rotate on one end so that torsional strain is not stored in the spring 106. Any torsion return motion may hence advantageously be smaller than the circumferential motion/rotation of the piston 104.

[0099] FIGS. 6A to 6E are open (transparent) side-views of a PAV 1 according to a second example embodiment which is in accordance with the second example aspect of the PAV of the present invention.

[0100] FIG. 6F discloses a first example of the path of the groove arranged on the piston, while FIG. 6G discloses a second example of a path of the groove on the piston both illustrating the full geometry of the groove when turning the piston one round i.e. 360°.

[0101] FIGS. 6F and 6G illustrate the path of the groove illustrated in FIGS. 6A to 6E and will be discussed in detail with regard to FIGS. 6A to 6E. As can be seen, the path shown in FIG. 6E differs from the path shown in FIG. 6G in that the fourth location L4 and the nineth location L9 are arranged differently. The path shown in FIG. 6G allows for less activation pressure F for moving the piston from the third location L3 to the fourth location L4 and from the eighth location L8 to the nineth location L9 than what is needed for the path shown in FIG. 6F. The direction of the activation pressure/internal pressure is indicated as arrow F while the circumferential direction of the piston is indicated by arrow R. It should be understood that the external pressure is opposite the internal pressure.

[0102] The configuration of the path illustrated in FIG. 6G is especially designed for a system comprising a plurality of PAVs 1 wherein there is a risk that the PAVs 1 operate unsynchronized. In such a system the PAVs can be forced back to being synchronized by applying an activation pressure F which is equal to or slightly larger than the pressure needed to move the piston such that the stopper engages at the fourth location L4 when moving from the third location L3 or engages at the nineth location L9 when moving from the eighth location L8, or is moved to an position between the first location L1 and second location L2 when moving from the zero location L0 or first location L1, or is moved to an position between the fifth location L5 and seventh location L7 when moving from the sixth location L6 or fifth location L5. As long as the activation pressure does not exceed the pressure needed for the piston to move the stopper of any of the PAVs 1 into the second location L2 or seventh location L7 the piston will move the stopper into the first location L1 or fifth location L5 upon releasing the activation pressure and hence all the PAVs 1 will be synchronized.

[0103] FIGS. 7A to 7D are cross-sectional views of the same illustrated PAVs 1 in FIGS. 6A to 6D, respectively.

[0104] FIGS. 6A to 6E and 7A to 7D show the cylinder 102 having a stopper 109 fixed thereto, and where the piston 104 has a slot 111 in the form of a groove 111 for guiding the stopper 109 therein.

[0105] Hence the working principle wherein the stopper 109 is arranged on the cylinder 102 and the slot/groove 111 is arranged on the piston 104 would work in the same manner as disclosed for the first example embodiment of the first aspect of the invention in FIGS. 3, 4 and 5 and is hence not shown. A person skilled in the art will understand that it is the relative movement between the piston and cylinder that is important when operating the PAV.

[0106] However, the working principle of the second example embodiment of the PAV 1 in FIGS. 6A to 6E and FIGS. 7A to 7D are different from the working principle shown for the first example embodiment in that the groove 111 has a continuous path along the circumferential direction of the piston 104. Hence, the concept of the PAV 1 differs from the previously described embodiment in that the piston 104 of the PAV 1 can be arranged in alternating positions and hence allowing for continuous open and closed cycles. Further, the PAV of the second example embodiment comprises a first spring 106 and a second spring 107 working in opposite directions, wherein the second spring 107 is a soft/less powerful spring compared to the first spring 106.

[0107] A person skilled in the art will understand that more than two full cycles can be completed by changing the design of the groove to comprise more cycles. Further, a person skilled in the art will recognize that more stoppers can be arranged on the cylinder for interacting with the groove as long all the stoppers are arranged to work in parallel.

[0108] In the following the concept of the configuration of the PAV 1 as shown in FIGS. 6A to 6E and FIGS. 7A to 7C will be disclosed in relation to the locations L0 to L9 of the groove 111 of the piston 104 as shown in FIGS. 6F and 6G.

[0109] FIGS. 6A and 7A shows the piston 104 at a position wherein the stopper 109 of the cylinder 102 is arranged at a first location L1 (see also FIGS. 6F and 6G). At this first location L1 the first spring 106 is in a relaxed unloaded state. The second spring 107 is pushing the piston 104 such that the O-ring 113 seals the piston to the cylinder 102 and no fluid can pass through the PAV 1. Further, there is no external pressure, or at least no external pressure exceeding the pressure of the second spring 107, applied to the PAV 1. However, if the PAV 1 should be subjected to internal pressure from the production string, the PAV will remain closed as will be disclosed with relation to FIGS. 6C and 7C.

[0110] Upon subjecting the PAV 1 to external pressure from the well bore, the piston 104 of the PAV 1 will be forced into the open position wherein the stopper 109 is at a so-called zero location L0 (being the same as the third position P3) where the stopper abuts a third end 111c of the groove 111 as illustrated in FIGS. 6B and 7B. In this position the PAV 1 is open allowing fluid from the bore well to pass through the PAV 1. The external pressure must however exceed the opposite force executed by the soft second spring 107. Hence the piston 104 is moved such that the O-ring 113 and the preferably also at least a part of the radially arranged holes 112 are positioned outside the cylinder 102. In this position the soft second spring 107 is compressed by the external pressure, while the first spring 106 is still in the relaxed state and as shown leaving an empty volume 114 near the first end 102a of the cylinder 102. This volume 114 could however be filled with another guided or fully compressible spring to avoid loose parts, or reengaging contact surfaces.

[0111] Upon release of the external pressure from the well bore the piston 104 will move until the stopper 109 reaches back to the first location L1 due to the force from the soft second spring 107 pushing the piston 104, and hence be closed.

[0112] If the PAV 1 is again subjected to external pressure from the bore well, the piston 104 will move such that the stopper 109 is returned to the open zero location L0 allowing fluid to pass through the PAV 1 as long as the external pressure exceeds the pressure of the soft second spring 107.

[0113] If however the PAV 1 is subjected to internal pressure from the production string, the piston 104 will be moved such that the stopper 109 is forced towards a second location L2 by compressing the first spring 106 until the piston 104 is moved such that the stopper 109 engages at the second location L2. At the second location L2 the PAV 1 is closed due to the internal pressure exceeding the pressure from the first spring 106 forcing the piston to the second location, L2. In this position the soft second spring 107 is in a relaxed state. This is illustrated in FIGS. 6C and 7C.

[0114] By releasing the internal pressure, the stopper 109 will, due to the movement of the piston 104, be forced to move into a third location L3 of the groove 111 corresponding to the first position P1 wherein the stopper 109 rests in equilibrium abutting a first end lila of the groove 111 and the first spring 106 is in a pretensioned position. The second spring 107 is still unloaded i.e. in a relaxed state. See FIGS. 6D and 7D. Also at this third location L3 of the groove 111 the PAV 1 is closed as the O-ring 113 and the openings 112 are arranged within the cylinder 102.

[0115] To move the piston 104 from where the stopper 109 is arranged in the third location L3 towards where the stopper 109 can be arranged in the fourth location L4 corresponding to the second position P2, an internal pressure exceeding the pressure from the first spring 106 must be applied to the PAV 1. Then the stopper 109 will engage at the fourth location L4 abutting a second end 111b of the groove as indicated in FIG. 6E. Hence if the PAV 1 is subjected to external pressure while the stopper 109 is arranged in the third location L3, the PAV 1 will not be able to open by moving the piston 104 such that the stopper 109 can engage at the sixth location L6 opening the PAV to allow fluid from the well bore to pass therethrough. Hence, an activation pressure being an internal pressure exceeding the pressure of the pretensioned first spring 106 must be applied for activating the PAV 1. This will activate the PAV 1 such that the piston 104 is moved until the stopper 109 reaches the fourth location L4.

[0116] By releasing the internal pressure, the piston 104 will move such that the stopper 109 engages at the fifth location L5, as shown in FIG. 6A being identical to the first location L1.

[0117] Hence upon applying external pressure the piston will move such that the stopper 109 engages at the sixth location L6 abutting the a third end 111c of the groove 111 such that the PAV 1 is open allowing fluid to pass through, being identical to the first location L1 as shown in FIGS. 6A and 7A. However, by applying internal pressure, the piston 104 will be forced to move towards the seventh location L7, i.e. such that the stopper 109 engages at the seventh location if the internal pressure exceeds the pressure applied by the first spring 106.

[0118] After the stopper has engaged at the seventh location L7, see FIGS. 6F and 6G, the piston will engage at the eighth location L8 corresponding to the third location L3 described before. Then an activation pressure must be applied to the PAV for activation thereof, hence an internal pressure exceeding the pressure of the first spring 106 must be applied for moving the piston 104 such that the stopper can engage in the nineth location L9 which in FIG. 6F corresponds to the pressure needed to move the piston to the seventh location L7, but which in FIG. 6G allows for a smaller activation pressure than the pressure to reach the seventh location L7. Upon removing the internal pressure, the piston 104 is moved back such that the stopper 109 engages the first location L1. Hence two cycles are completed when turning the piston one round i.e. 360°.

[0119] The groove 111 creates a path for the stopper 109 in both a radial direction and a longitudinal direction simultaneously when moving the piston, hence the geometry of the piston 104 can further be biased to motion in one direction via rotational locks at each extreme, especially at a second location L2, third location L3, a fourth location L4, a seventh location L7, a eighth location L8 and a nineth location L9, and/or a sustained torque can be applied by a torsional spring member, ratchet, or other similar mechanisms which can be installed for rotating the piston 104.

[0120] The PAV 1 of FIGS. 6A to 6E and 7A to 7D have a geometrical lock where the groove 111 is ramped at the second location L2, third location L3, fourth location L4, seventh location L7, eighth location L8 and nineth location L9, and the stopper 109 is spring loaded such that the stopper 109 drops into the depressions caused by the ramps at each extreme to prevent back-travel of the piston 104 as illustrated in FIGS. 8A and 8B.

[0121] FIG. 8A shows the piston of the PAV shown in FIGS. 6A to 6E and 7A to 7D. A part the path of the slot 111 configured as a groove 111 is shown on the outer surface of the piston 104.

[0122] The dashed circle A in FIG. 8A is explored in FIG. 8B illustrating that the groove 111 is ramped 111′ adjacent the second and third locations L2,L3. The same ramped structure is also arranged adjacent the fourth location L4 even if not shown.

[0123] Even if not illustrated in the FIG. 6A-6E or 7A to 7D, the cylinder 102 may comprise more than one stopper 109, which may be arranged on oppositely facing sides of the piston 104 in respective of the radial direction. The groove 111 may hence guide more than one stopper 109 parallelly.

[0124] A person skilled in the art will understand the embodiment shown in FIGS. 6A to 6E and 7A to 7D could also be working by arranging the groove on the inner surface of the cylinder and by arranging the stopper on the piston.