Valve system for controlling a liquid flushing flow through a sealing system

Abstract

The invention relates to a valve system (1) for maintaining a pressure controlled liquid flushing flow through a sealing system, the valve system comprising; a main valve body (2) forming a valve chamber (3) having a fluid input port (4) and a fluid output port (5) as well as a valve seat (6), a hollow piston valve (7) moveable arranged within the valve chamber, and a diaphragm (13) coupled with the valve body and the hollow piston valve and separating a pair of opposite pressure chambers (9, 10).

Description

[0001] Valve system for controlling a liquid flushing flow through a sealing system

[0002] BACKGROUND

[0003] The current disclosure relates to a valve system for maintaining a pressure controlled liquid flushing flow through a sealing system, the valve system comprising a main valve body forming a valve chamber having a fluid input port and a fluid output port as well as a valve seat. The valve system is particularly useful in a sealing system for sealing a marine propeller shaft or a pump shaft.

[0004] US 2007 / 0102048 Al concerns a block coaxial valve, especially for compressed air systems. The valve is not suitable for marine sealings and controlling a liquid flushing flow.

[0005] An example of a sealing with a liquid flushing flow is found in EP0679820 (Al) that relates to a sealing system for sealing a rotating shaft, such as the shaft of a pump or a similar apparatus, through a stationary wall, in which the pressure at one side of the wall differs from that at the other side of the wall, said system comprising at least two closure rings mounted around the shaft and consisting of rubber or a similar flexible material, each of said closure rings having a substantially radial collar by which the closure ring can be fixed to the wall and a lip extending from the collar and lying against the shaft.

[0006] There is a need for an improved valve in order to control a liquid flushing flow.

[0007] SUMMARY

[0008] The object of the current invention is to improve a valve system for maintaining a pressure controlled liquid flushing flow through a sealing system, in that the amount of liquid flushing flow is more precisely controlled.

[0009] Another object of the current invention is to provide an improved valve system for maintaining a pressure controlled liquid flushing flow through a sealing system wherein a known problem is at least partly solved.

[0010] Another object of the current invention is to provide an alternative valve system for maintaining a pressure controlled liquid flushing flow through a sealing system.

[0011] Therefore, the invention provides a valve system for maintaining a pressure controlled liquid flushing flow through a sealing system, the valve system comprising;- a main valve body forming a valve chamber having a fluid input port and a fluid output port as well as a valve seat,

[0012] - a hollow piston valve moveably arranged within the valve chamber and moveable between an open position spaced from the valve seat for allowing the flushing flow in a flow direction from the fluid input port to the fluid output port through the hollow piston, and a closed position against the seat for interrupting the flushing flow from the fluid input port to the fluid output port,

[0013] - a position control system for controlling a working position of the piston valve between the open position and the closed position, comprising a pair of opposite pressure chambers and a diaphragm coupled with the valve body and the hollow piston valve and separating the pair of opposite pressure chambers, as well as prestressing means for prestressing the piston valve towards the closed position and defining a threshold above which the valve opens,

[0014] wherein at least one pressure chamber of the pair of opposite pressure chambers comprises a pressure connection for a pilot line for applying a pilot pressure to the at least one pressure chamber, and wherein the prestressing means is arranged to work in parallel with the other pressure chamber of the pair of opposite pressure chambers.

[0015] The valve system according to the invention provides a reduced hysteresis, faster control, as well as enables an increased control bandwidth.

[0016] The valve body provides structural integrity to the valve system and holds the hollow piston valve within the valve chamber. Normally, the fluid input port, fluid output port, and pressure connection for the pilot line are directly provided on the valve body.

[0017] The valve seat is well known per se and cooperates with the piston valve to provide a sealing connection between the valve seat and the hollow piston valve in a manner known per se.

[0018] The hollow piston valve means that the valve does have both a function in interrupting the flushing flow as well as in allowing the flushing flow. In case of the allowed flushing flow, the flushing flow runs though the hollow piston valve.

[0019] The prestressing means can be a spiral spring, a gas spring, accumulator, or any other suitable prestressing means. In an embodiment, the prestressing means are adjustable in order to facilitate adjustment of the threshold above which the valve opens. In an alternative configuration of the valve system according to the invention, it is conceivablethat the prestressing means are configured for prestressing the hollow piston valve towards the open position and defining a threshold above which the valve closes. In other words, this valve system is a normally open type of valve.

[0020] The diaphragm, or also membrane, is known per se. It can accommodate a certain deformation in a predefined direction and therefore may comprise a number a pleats and / or folds. The diaphragm can withstand a certain pressure difference between the pair of opposite pressure chambers. The hollow piston valve is actuated by fluid pressure exerted on the diaphragm. In other words, the diaphragm is connected with the hollow piston valve such that the piston moves upon deformation of the diaphragm.

[0021] In an embodiment of the valve system according to the invention, the hollow piston valve is coaxially arranged with the fluid input port and the fluid output port, and coaxially moveable between the open position and the closed position. The coaxial arrangement provides less disturbance of the flushing flow. Coaxial means that a direction of movement is aligned with both the fluid input port and the fluid output port.

[0022] In an embodiment of the valve system according to the invention, the piston valve is slideably arranged in the valve chamber and in sliding contact with the valve body. This facilitates to align the hollow piston valve with the fluid input port and the fluid output port. This all the more makes clear that the valve body holds the hollow piston valve. Slidably is to say a loose fit between the valve body and the hollow piston valve. It will be clear that suitable sealing systems are provide between an exterior surface of the hollow piston valve and the valve body in order to force the flushing flow through the hollow of the hollow piston.

[0023] In an embodiment of the valve system according to the invention, the hollow piston valve comprises opposite ends in a direction of movement of the hollow piston valve, and wherein the valve system comprises a fluid coupling between the fluid input port and the opposite ends of the piston valve for balancing the piston valve with respect to a fluid input pressure at the fluid input port. Balancing the piston valve with respect to a fluid input pressure at the fluid input port enables faster control of the working position of the valve, as well as an increased control bandwidth. Therefore, there is no or less influence of the fluid input pressure and instead, the pilot pressure is dominant with respect to control of theworking position of the piston valve. Preferably, the projected surfaces of the opposite ends are similar or equal in the direction of movement of the hollow piston valve. Moreover, the projected surfaces of the opposite ends are minimized as much as possible. The opposite ends may be bevelled which helps in avoiding accumulation of dirt within the valve chamber.

[0024] In an embodiment of the valve system according to the invention, the valve system comprises a piston sealing system operatively connected with at least one end of the opposite ends of the hollow piston valve, the at least one end of the hollow piston facing the fluid output port and the piston sealing system isolating the at least one end of the hollow piston from the fluid output pressure at the fluid output port. The sealing system all the more enables to apply the input pressure to the at least one end.

[0025] In an embodiment of the valve system according to the invention, the valve system comprises a pressure feedback coupling between the fluid output port and the other pressure chamber of the pair of opposite pressure chambers for pressing the piston valve towards the closed position depending on a fluid output pressure at the fluid output port. The pressure feedback allows to control the working position of the piston valve both depending on the pilot line pressure as well as the resulting fluid output pressure itself. The other pressure chamber is the chamber working in parallel with the prestressing means.

[0026] In an embodiment of the valve system according to the invention, the pressure feedback coupling is arranged within the main valve body. The arrangement within the main valve body results in a compact pressure feedback coupling and a short fluid pathway that reduces hysteresis all the more.

[0027] In an embodiment of the valve system according to the invention, the pressure feedback coupling extends through an opening in the hollow piston valve, which opening extends between the hollow and the other pressure chamber. The opening in the piston valve results in an even more compact pressure feedback coupling and a shorter fluid pathway. The opening in the piston valve extends at least between the exterior surface of the hollow piston valve to the interior hollow of the hollow piston.

[0028] In an embodiment of the valve system according to the invention, the prestressing means are accommodated within the other pressure chamber of the pair of opposite pressure chambers. The other pressure chamber of the pair of opposite pressure chambersaccommodating the prestressing means provides a compact solution and all the more assures that the prestressing means and the actual pressure in the other pressure chamber work in parallel for prestressing the piston valve towards the closed position. It will be clear that any suitable arrangement of the prestressing means is conceivable as long as the prestressing means works in parallel with the other pressure chamber of the pair of opposite pressure chambers.

[0029] In an embodiment of the valve system according to the invention, the main valve body comprises a stop defining the open position of the piston valve. The stop enables a robust use of the diaphragm and limits the freedom of movement of the diaphragm and the hollow piston valve between the open position and the closed position. Therefore, damage to the diaphragm can be avoided in case of for example a pressure surge.

[0030] In an embodiment of the valve system according to the invention, at least in the open position, the diaphragm contacts the main valve body and the piston to resist the pilot pressure. The diaphragm contacting the main valve body, and the piston enables to limit the freedom of movement of the diaphragm all the more. The contact area is as large as possible to optimize support of the diaphragm.

[0031] In an embodiment of the valve system according to the invention, the diaphragm comprises a curvature having a predetermined radius over which the diaphragm rolls up and / or off. The predetermined radius enables to obtain a constant resistance against deformation of the diaphragm during a part or even all of the movement of the piston between the open position and the closed position. This constant resistance facilitates control.

[0032] In an embodiment of the valve system according to the invention, the predetermined radius is defined by a mutual spacing between the main valve body and the piston valve. This facilitates integration of the diaphragm within the valve chamber as well as support of the diaphragm.

[0033] In an embodiment of the valve system according to the invention, the at least one pressure chamber of the pair of opposite pressure chambers comprising the pressure connection for a pilot line comprises a second pressure connection enabling flushing of the at least one pressure chamber. This allows maintenance of the valve system and increases service life of the valve system.

[0034] In an embodiment of the valve system according to the invention, the second pressure connection is positioned or positionable above the pressure connection for a pilot line for allowing bleeding of air from the at least one pressure chamber. This facilitates accumulationof air close to the second pressure connection and subsequent bleeding of the accumulated air. Air in the at least one pressure chamber is detrimental to precision and speed of control of the working position of the hollow piston valve.

[0035] In an embodiment of the valve system according to the invention, the main valve body comprises two opposite body sections forming a valve chamber, and a locking system for maintaining the two opposite body sections in mutual sealing contact, wherein the locking system comprises a locking ring in threaded connection with at least one of the two opposite body sections. This allows taking the opposite body sections apart to facilitate maintenance to parts within the valve chamber.

[0036] Therefore, the invention provides a use of a valve system as defined above, in any of a pressurized supply system, a liquid flushing flow control system for a marine propeller shaft sealing, and a liquid flushing flow control system for a pump shaft sealing.

[0037] Therefore, the invention provides an assembly of valve system as defined above, and a pressurized supply system or a liquid flushing flow control system for a shaft sealing.

[0038] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached schematic drawings, in which;

[0041] figure 1 shows a perspective view of a valve system according to the invention; figure 2 shows a cross-sectional side view of the valve system of fig. 1;

[0042] figure 3 shows a top view of the valve system of fig. 1;

[0043] figure 4 shows a side view of a schematic drawing showing the functioning of the valve system of fig. 1;

[0044] figure 5 shows the valve system of fig. 1 in a pump shaft sealing system, andfigure 6 shows a side view of a schematic drawing showing the functioning of an alternative configuration of the valve system according to the invention.

[0045] DETAILED DESCRIPTION OF THE INVENTION

[0046] Figure 1 show a valve system 1. The valve system 1 functions to maintain a pressure controlled liquid flushing flow through a sealing system, for example as shown in fig. 5. The valve system 1 comprises a main valve body 2. The main valve body 2 has a substantially cylindrical shape around a central axis 16. The main valve body 2 forms a valve chamber having a fluid input port 4 and a fluid output port 5. Therefore, the main valve body 2 comprises two opposite body sections 23, 24. The two body sections 23, 24 are in mutual sealing contact and form a valve chamber 3 between them. The valve system comprises a locking system 25 for maintaining the two opposite body sections 23, 24 in mutual sealing contact. In this case, the locking system 25 comprises a locking ring 26 in threaded connection with at least one of the two opposite body sections 23, 24.

[0047] Now turning to figure 2 that shows an interior of the main valve body 2 forming the valve chamber 3. The valve chamber 3 comprises a valve seat 6. In this case, the valve seat 6 has a conical shape. Here, the valve seat 6 is made of PA 6, (Polyamide 6).

[0048] The valve system 1 comprises a hollow piston valve 7. The hollow piston valve 7 is moveable arranged within the valve chamber 3.

[0049] The hollow piston valve 7 is moveable between an open position and closed position. The hollow piston valve 7 is shown in the open position. In the open position, the hollow piston valve 7 is spaced from the valve seat 6. In the open position the flushing flow is allowed in a flow direction 36 from the fluid input port 4 to the fluid output port 5. The flushing flow flows from the fluid input port 4 through the hollow piston to the fluid output port 5.

[0050] In the closed position the hollow piston valve 7 rest against the valve seat 6. In the closed position, the hollow piston valve 7 and the valve seat 6 are in sealing contact. Therefore, in the closed position of the hollow piston valve 7, the flushing flow from the fluid input port 4 to the fluid output port 5 is interrupted.

[0051] The valve system 1 comprises a position control system 8. The position control system 8 is configured for controlling a working position of the piston valve 7. Duringoperation, the piston valve takes up a working position between the open position and the closed position. The working position depends, among other things on the actual resulting forces on the diaphragm and the hollow piston valve. The working position is highly dynamic and will vary over time. The position control system 8 comprises a pair of opposite pressure chambers 9, 10. At least one pressure chamber 9 of the pair of opposite pressure chambers comprises a pressure connection 11 for a pilot line for applying a pilot pressure to the at least one pressure chamber 9. The pilot pressure is the control pressure that functions as the control input for the position control system. The other pressure chamber 10 of the pair of opposite pressure chambers comprises prestressing means 12, in this case a spiral spring. The prestressing means 12 engage with the piston valve 7 for prestressing the piston valve towards the closed position. Therefore, the piston valve 7 is provided with a flange 27, in this case an external flange 27. Moreover, the prestressing means 12 define a threshold above which the piston valve 7 opens. The position control system 8 comprises a diaphragm 13 coupled with the valve body 2 and the hollow piston valve 7. The diaphragm 13 is coupled with the valve body 2 and the hollow piston valve 7 in a sealing manner. Therefore, the diaphragm 13 separates the pair of opposite pressure chambers 9, 10. The diaphragm 13 is coupled with the piston valve 7 by clamping between the flange 27 and a clamp ring 38. The clamp ring 38 itself is therefore clamped around the piston valve 7.

[0052] In this case, the fluid input port 4, fluid output port 5, and pressure connection 11 for the pilot line are directly provided on the main valve body 2.

[0053] The diaphragm 13 can accommodate a certain deformation in a predefine direction. Here, the diaphragm 13 can accommodate a certain deformation along the central axis 16. Therefore, the diaphragm 13 comprises a number of pleats and / or folds, in this case one fold 28. The diaphragm 13 can withstand a certain pressure difference between the pair of opposite pressure chambers 9, 10. The hollow piston valve 7 is actuated by fluid pressure exerted on the diaphragm 13. To put it differently, the diaphragm 13 is connected with the hollow piston valve 7 such that the piston 7 moves upon deformation of the diaphragm 13.

[0054] The hollow piston valve 7 is coaxially arranged with the fluid input port 4 and the fluid output port 5. In addition, the hollow piston valve 7 is coaxially moveable between the openposition and the closed position. In this case this means that the hollow piston valve 7, the fluid input port 4, and the fluid output port 5 are aligned with the central axis 16 and that the hollow piston valve 7 is moveable along the central axis 16 in a direction of movement 37.

[0055] The piston valve 7 is slideably arranged in the valve chamber 3. Therefore, the piston valve 7 is in sliding contact with the valve body 2. The sealing systems 18a, 18b are provided between an exterior surface 29 of the hollow piston valve and the main valve body 2. This will force the flushing flow all the more through the hollow 30 of the hollow piston valve 7.

[0056] The hollow piston valve 7 comprises opposite ends 14, 15 in a direction of movement of the hollow piston valve 7, meaning along the central axis 16. The valve system 1 comprises a fluid coupling 17 between the fluid input port 4 and the opposite ends 14, 15 of the piston valve 7. The fluid coupling 17 applies an input pressure to both the opposite ends. Therefore, the piston valve 7, in particular along the direction of movement, is balanced with respect to a fluid input pressure at the fluid input port 4. In this case, the projected surfaces of the opposite ends 14, 15 are similar or equal in the direction of movement 16 of the hollow piston valve 7. Moreover, the projected surfaces of the opposite ends are minimized as much as possible. The opposite ends 14, 15 are bevelled in this case, which helps in avoiding accumulation of dirt within the valve chamber 3. In this case, the piston valve 7 has a cylindrical shape and the projected surfaces of the opposite ends 14, 15 have a circular shape. Other shapes may be conceivable as long the piston valve 7 has a hollow 30.

[0057] The valve system 1 comprises a piston sealing system 18a, 18b operatively connected with at least one end 15, in this case both ends 14, 15, of the opposite ends 14, 15 of the hollow piston valve 7. The at least one end 15 of the hollow piston faces the fluid output port 5. The piston sealing system 18a isolates the one end 15 of the hollow piston 7 from the fluid output pressure at the fluid output port 5.

[0058] The valve system 1 comprises a pressure feedback coupling 19. The pressure feedback coupling 19 is arranged between the fluid output port 5 and the other pressure chamber 10 of the pair of opposite pressure chambers 9, 10. The pressure feedback coupling 19 presses the piston valve 7 towards the closed position depending on a fluid output pressure at the fluid output port 5. The other pressure chamber 10 is, here, the chamber having the prestressingmeans 12. In this case, the pressure feedback coupling 19 is arranged within the main valve body 2.

[0059] The pressure feedback coupling 19 extends through an opening 20 in the hollow piston valve 7. The opening 20 extends between the hollow 30 and the other pressure chamber 10. The opening 20 in the piston valve 7 extends at least between the exterior surface 29 of the hollow piston valve to the interior hollow 30 of the hollow piston.

[0060] Here, the main valve body 2 comprises a stop 21. The stop defines the open position of the piston valve 7. The stop 21 limits the freedom of movement of the diaphragm 13 and the hollow piston valve between the open position and the closed position.

[0061] As shown, in the open position, the diaphragm 13 contacts the main valve body 2 and the piston 7, in particular the piston flange 27. Therefore, the diaphragm can resist the pilot pressure. The contact area between the diaphragm 13 with the main valve body 2 and the piston 7 is as large as possible to optimize support of the diaphragm 13. In this case, substantially the entire diaphragm is supported. The support is provided by the clamp ring 38 as well as the body section 23.

[0062] The diaphragm 13 comprises a curvature, or also fold 28. The fold 28 has a predetermined radius over which the diaphragm rolls up and / or off. Here, the predetermined radius is defined by a mutual spacing 35 between the main valve body 2 and the piston valve 7. Therefore, the radius is very well defined because the spacing is determined by machined parts. The machined parts include the clamp ring 38 as well as the body section 23.

[0063] The at least one pressure chamber 9 of the pair of opposite pressure chambers 9, 10 comprising the pressure connection 11 for a pilot line comprises a second pressure connection 22. Therefore, flushing of the at least one pressure chamber 9 is possible between the pressure connection 11 for a pilot line and the second pressure connection 22. In this case, the second pressure connection 22 is positioned or positionable above the pressure connection 11 for a pilot line.

[0064] Figure 3 shows a top view of the valve system 1. Flushing of the at least one pressure chamber 9 is possible between the pressure connection 11 for a pilot line and the secondpressure connection 22. The valve system 1 comprises a fluid coupling 17 between the fluid input port 4 and the opposite ends 14, 15 of the piston valve 7. The fluid coupling 17 applies an input pressure to both the opposite ends 14, 15.

[0065] Figure 4 shows a schematic drawing showing the functioning of the valve system 1 of fig. 1. All equivalent parts have the same reference number. The main functioning will be summarized below. As will be immediately clear, the pressure connection 11 for a pilot line introduces a pilot pressure in the at least one pressure chamber 9. The pilot pressure applies a force to the diaphragm 13 that wants to force the hollow piston valve towards the open position. Depending on the resulting force to the diaphragm 13, the piston valve will move accordingly. The resulting force is the sum of the pilot pressure, prestressing means 12 and the feedback pressure at the fluid output port 5 that is fed back through the opening 20 of the pressure feedback coupling. The feedback pressure and the prestressing means 12 work in parallel.

[0066] Figure 5 shows the valve system of fig. 1 in a shaft sealing system 31. The shaft sealing system seals a shaft of a pump system 33 in this case. The sealing system 31 comprises a flushed sealing section 32. A liquid flushing flow runs though the flushed sealing section. The flushing flow is controlled by a pilot pressure. The pilot pressure is taken form the pump system 33 and is introduced in the valve system 1 at its pressure connection 11 for a pilot line. The shaft sealing system 31 comprises a flushing flow supply system 34. The flushing flow supply system 34 comprises a pump and a storage container for flushing medium, usually water. The flushing flow supply system 34 may be an open, or closed system that circulates the flushing flow.

[0067] Figure 6 shows a side view of a schematic drawing showing the functioning of an alternative configuration of the valve system 1 according to the invention. The only difference compared with figure 4 is that the prestressing means 12 are configured for prestressing the hollow piston valve 7 towards the open position as shown. In this case, the prestressing means 12 define a threshold above which the valve closes. In other words, this alternative valve system 1 is a normally open type of valve.

[0068] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects andfeatures described in the attached dependent claims, can be made subject of divisional patent applications.

[0069] -0-0-0-0-0-0-List of Reference numbers

[0070] 1 Valve system

[0071] 2 Main valve body

[0072] 3 Valve chamber

[0073] 4 Fluid input port

[0074] 5 Fluid output port

[0075] 6 Valve seat

[0076] 7 Hollow piston valve

[0077] 8 Position control system

[0078] 9,10 Pair of opposite pressure chambers 11 Pressure connection for a pilot line 12 Prestressing means

[0079] 13 Diaphragm

[0080] 14,15 Opposite ends of hollow piston valve 16 Central axis

[0081] 17 Fluid coupling

[0082] 18a, 18b Piston sealing systems

[0083] 19 Pressure feedback coupling

[0084] 20 Opening

[0085] 21 Stop

[0086] 22 Second pressure connection

[0087] 23, 24 two opposite body sections

[0088] 25 Locking system

[0089] 26 Locking ring

[0090] 27 Piston flange

[0091] 28 Fold of diaphragm

[0092] 29 Exterior surface of the piston

[0093] 30 Hollow

[0094] 31 Shaft sealing system

[0095] 32 Flushed sealing section

[0096] 33 Pump system

[0097] 34 Flushing flow supply system35 Spacing36 Flow direction37 Direction of movement of the hollow piston38 Clamp ring

Claims

Claims1. Valve system (1) for maintaining a pressure controlled liquid flushing flow through a sealing system, the valve system comprising;- a main valve body (2) forming a valve chamber (3) having a fluid input port (4) and a fluid output port (5) as well as a valve seat (6),- a hollow piston valve (7) moveable arranged within the valve chamber and moveable between an open position spaced from the valve seat for allowing the flushing flow in a flow direction from the fluid input port to the fluid output port through the hollow piston, and a closed position against the seat for interrupting the flushing flow from the fluid input port to the fluid output port,- a position control system (8) for controlling a working position of the piston valve between the open position and the closed position, comprising a pair of opposite pressure chambers (9, 10) and a diaphragm (13) coupled with the valve body and the hollow piston valve and separating the pair of opposite pressure chambers, as well as prestressing means (12) for prestressing the piston valve towards the closed position and defining a threshold above which the valve opens,wherein at least one pressure chamber (9) of the pair of opposite pressure chambers comprises a pressure connection (11) for a pilot line for applying a pilot pressure to the at least one pressure chamber, and wherein the prestressing means is arranged to work in parallel with the other pressure chamber (10) of the pair of opposite pressure chambers.

2. Valve system according to claim 1, wherein the hollow piston valve is coaxially arranged with the fluid input port and the fluid output port, and coaxially moveable between the open position and the closed position.

3. Valve system according to claim 1 or 2, wherein the piston valve is slideably arranged in the valve chamber and in sliding contact with the valve body.

4. Valve system according to a preceding claim, wherein the hollow piston valve comprises opposite ends (14, 15) in a direction of movement (16) of the hollow piston valve, and wherein the valve system comprises a fluid coupling (17) between the fluid input port and the opposite ends (14, 15) of the piston valve for balancing the piston valve with respect to a fluid input pressure at the fluid input port.

5. Valve system according to claim 4, comprising a piston sealing system (18) operatively connected with at least one end (15) of the opposite ends of the hollow piston valve, the at least one end (15) of the hollow piston facing the fluid output port (5) and the piston sealing system isolating the at least one end (15) of the hollow piston from the fluid output pressure at the fluid output port.

6. Valve system according to a preceding claim, comprising a pressure feedback coupling (19) between the fluid output port and the other pressure chamber of the pair of opposite pressure chambers for pressing the piston valve towards the closed position depending on a fluid output pressure at the fluid output port.

7. Valve system according to claim 6, wherein the pressure feedback coupling is arranged within the main valve body.

8. Valve system according to claim 5 or 6, wherein the pressure feedback coupling extends through an opening (20) in the hollow piston valve, which opening extends between the hollow (30) and the other pressure chamber (10).

9. Valve system according to a preceding claim, wherein the prestressing means (12) are accommodated within the other pressure chamber (10) of the pair of opposite pressure chambers.

10. Valve system according to a preceding claim, wherein the main valve body comprises a stop (21) defining the open position of the piston valve.

11. Valve system according to a preceding claim, wherein at least in the open position, the diaphragm contacts the main valve body and the piston to resist the pilot pressure.

12. Valve system according to a preceding claim, wherein the diaphragm comprises a curvature having a predetermined radius over which the diaphragm rolls up and / or off.

13. Valve system according to claim 12, wherein the predetermined radius is defined by a mutual spacing between the main valve body and the piston valve.

14. Valve system according to a preceding claim, wherein the at least one pressure chamber (9) of the pair of opposite pressure chambers comprising the pressure connection for a pilot line comprises a second pressure connection (22) enabling flushing of the at least one pressure chamber.

15. Valve system according to claim 14, wherein the second pressure connection is positioned or positionable above the pressure connection for a pilot line for allowing bleeding of air from the at least one pressure chamber.

16. Valve system according to a preceding claim, wherein the main valve body (2) comprises two opposite body sections (23, 24) forming between them the valve chamber (3), and a locking system (25) for maintaining the two opposite body sections in mutual sealing contact, wherein the locking system comprises a locking ring (26) in threaded connection with at least one of the two opposite body sections.

17. Use of valve system according to a preceding claim, in any of a pressurized supply system, a liquid flushing flow control system for a marine propeller shaft sealing, and a liquid flushing flow control system for a pump shaft sealing.

18. Assembly of valve system according to a preceding claim 1 – 16, and a pressurized supply system or a liquid flushing flow control system for a shaft sealing.-O-O-O-O-O-O-

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