Abstract:
A sanitary valve system having a sanitary valve in a valve housing with at least one inlet and at least one outlet, the sanitary valve having at least one surface formed of a hygienic material that prevents growth of bacteria or fungus and is configured to control a flow from the inlet to the outlet by means of a valve regulating element.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of application of commonly owned, co-pending U.S. patent application Ser. No. 12/680,662 which is the U.S. national phase of International Patent Application PCT/DK2008/050233 which claims priority of Danish Patent Application PA 2007 01389. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a sanitary valve system comprising a valve in a valve housing with at least one inlet and at least one outlet, which valve is a sanitary valve with at least one surface formed of a hygienic material that prevents growth of bacteria or fungus and configured to control a flow from the inlet to the outlet by means of a valve regulating element. 
         [0004]    Furthermore, the present invention also relates to a method for operating a sanitary valve primarily for fluid food, which valve at least closes or opens for a flow from an inlet towards an outlet, which valve is operated by at least one actuator, which actuator is activated by a pressurized media. 
         [0005]    2. Description of Related Art 
         [0006]    U.S. Pat. No. 6,684,897 concerns a subsea actuator and method that includes all moving components mounted in a compact, concentric configuration. The subsea actuator is highly reliable and will operate at depth even with zero valve body cavity pressure. A preferably cup-shaped spring pusher is provided in telescoping relationship to the hydraulic chamber. A piston position indicator is provided which is connected externally to the hydraulic piston cylinder to avoid the possibility of hydraulic leaks due to the piston indicator. A manual override may be provided with a manual override indicator. The manual override indicator has a shorter travel length than the manual override operating stem in order to reduce the overall length of the manual override assembly. The driving stem provides a removable connection to the hydraulic piston from the top of the actuator housing and a quick disconnect permits disconnection of the driving stem from the valve stem. In a preferred embodiment, upper and lower t-slot connections are utilized in the driving stem assembly. In a preferred embodiment, two back seat valves are removable secured to the driving stem to engage respective seats and provide additional sealing around the driving stem so as to prevent leakage between the valve chamber and actuator housing chamber. The high tension spring does not need to be removed to perform maintenance and all wear items and seals are readily accessible. Change or replacement of the stem packing is made from the top of the bonnet to avoid disassembling the bonnet to valve body connection. Pre-load bolts are used to adjustably preload the tension in the return spring. The height/weight of the actuator is significantly reduced as compared to prior art subsea valve actuators. 
         [0007]    European Patent Application EP 0 192 973 A1 describes a fail-safe valve actuator that includes a hydraulic piston and cylinder for driving the valve stem and gate member of a gate valve into a first flow control state responsive to sufficient pressure delivered by a fluid or gas supply line. Upon failure or other loss of sufficient control line pressure, a volute spring drives the cylinder, and hence the stem and gate member, axially outward resulting in the valve being moved into a second flow control state. 
         [0008]    UK Patent Application GB 2 315 114 concerns a valve actuator that includes a hydraulic cylinder and rod mounted on a housing and connected to the valve stem. Two guide rods are disposed between a fixed plate and an interface plate such that a guide plate can move along the rods. Each rod is surrounded by a spring, which has one end abutting the fixed plate while the other end abuts the guide plate to bias the guide plate away from the fixed plate. The guide plate is adapted to transmit movement of the guide plate to the valve stem, movement of the guide plate being transmitted to the valve stem only when the guide plate is moving in a direction away from the fixed plate. Movement of the rod is transmitted to the valve stem only when the rod is moving in a direction toward the cylinder. 
         [0009]    European Patent Application EP 0756118 concerns a fluid control system, and its valve assemblies, are used to control the feeding of fluids accurately by operating opening and closing valves promptly and accurately, for the manufacture of semiconductors, magnetic thin films, biotechnical products, and other products. The fluid control system comprises a principal control line (L) and plural branch control lines (L 1 , L 2 , . . . ) for feeding plural types of fluid (G 1 , G 2 , . . . ) into a processing device (C) coupled to the principal control line, and plural valve assemblies (V) incorporated in the branch control lines (L 1 , L 2 , . . . ) for switching the fluids (G 1 , G 2 , . . . ) supplied into the processing device (C). Each of the valve assemblies (V) comprises a fluid drive valve (V′) having a fluid pressure actuator ( 1 ), and an electromagnetic valve (V″) integrally attached, in single housing, substantially without hoses, to the fluid drive valve (V′) to feed a working fluid (A) into the fluid pressure actuator ( 1 ). 
         [0010]    European Patent Application EP 0136 567 relates to a seat valve ( 5 ) for a tube ( 1 ) which on the inner side has a valve seat running inclined to the tube axis, opposite and coaxially to which seat valve there is a tube connection piece ( 4 ) for the connection of the seat valve ( 5 ). This seat valve ( 5 ) contains a valve ram ( 6 ) whose projecting end carries a valve plate ( 7 ) which abuts directly in its closing direction on the valve seat ( 3 ) and in its open position is located opposite the valve seat ( 3 ) and separated there from. A control chamber in the valve housing ( 10 ,  11 ) is limited on the one hand by the control piston ( 24 ), which is connected to the valve ram ( 6 ) and can be acted upon by the medium contained in the tube against a restoring spring force. On the other hand, a control opening ( 14 ) opens into the valve chamber. The control piston ( 24 ) is guided in a cylindrical part ( 10 ) of the valve housing. A side of the piston facing the control opening ( 14 ) is split into two regions, namely into a starting region ( 28 ), which is in open connection with the control opening ( 14 ) in the open position, as a somewhat larger surface than the effective compression surface of the valve plate ( 7 ) and, when acted on by the medium, raises the control piston ( 24 ) from the cylinder cover ( 13 ) against the force of the return spring ( 26 ), and into a cut-in region ( 29 ), which is separated from the control opening ( 14 ) when it is in the open position and is likewise acted upon by the cylinder cover ( 13 ) after raising of the control piston ( 24 ). 
         [0011]    UK Patent Application GB9403879A: concerns an electro hydraulic valve actuator comprising a spring which presses the valve into a closed position. The valve is opened by hydraulic pressure. The valve actuator is pressure compensated and hermetically closed from the environment, where two bellows are used around the valve actuator to provide a hermetic seal, and to compensate the pressure. 
         [0012]    U.S. Pat. No. 4,230,299 concerns a pressure balanced gate valve mechanism wherein a closed loop fluid interchange system interconnects the valve actuator stem area of the valve mechanism with the pressure balancing stem area and functions to accommodate volumetric changes to prevent the development of a hydraulic lock that might otherwise prevent or retard opening and closing movement of the valve mechanism. Internal back-face seating arrangements with combination metal-to-metal and elastomeric sealing elements establish seals between the valve stem and bonnet at one gate position and between the pressure balancing stem and valve body structure at the opposite gate position. An externally threaded portion of the valve bonnet is receivable within internally threaded receiver openings of a plurality of different actuator systems, including manual, mechanical, hydraulic and pneumatic actuator systems. The actuator systems are field interchangeable with the valve in service and under pressure. The valve mechanism is capable of being hydraulically energized by portable hydraulic equipment for moving the valve mechanism to a predetermined position in the event the primary drive system should become inoperative for any reason. 
         [0013]    International Patent Application WO 2005/098297 concerns a valve, actuator and control system that allows minimizing the size of the actuator and operation of the control system in a manual mode that automatically prevents accidental operation by pipeline pressure is disclosed. The actuator uses gas pressure from the pipeline to power the actuator. In the event gas pressure is unavailable, a pair of manual hand pumps are incorporated to allow operation of the actuator and valve. 
       SUMMARY OF THE INVENTION 
       [0014]    It is the object of the invention to achieve actuation of valves by a non compressible media for activation of sanitary valves. A further object of the invention is to reduce the size of actuators for sanitary valves. 
         [0015]    This object may be achieved by a sanitary valve system comprising a valve in a valve housing with at least one inlet and at least one outlet, which valve is a sanitary valve with at least one surface formed of a hygienic material that prevents growth of bacteria or fungus and configured to control a flow from the inlet to the outlet by means of a valve regulating element. Such valve regulating element may be mechanically connected to a valve actuator having an actuator housing in which at least one piston separates the actuator housing in a first chamber and a second chamber. Such piston may be movable by a liquid medium being an incompressible medium primarily water in the first and second chambers, which liquid medium is regulated in the first chamber via a first line and in the second chamber via a second line by a regulator controlled by electromagnetic activation and configured to regulate pressure or flow of the liquid medium in the first and second lines to position the sanitary valve and to block the first and second lines to lock the position of the sanitary valve. 
         [0016]    Thus, it is achieved that the valve can operate over extended periods of time in sanitary environments where the valve controls precisely the flow and is capable of locking precisely even with fluctuations in the flow in a manner that is more stable and precise than known hereto. 
         [0017]    It is appreciated by a person skilled in the art that changing pressure or moving a fluid may have similar effects. In an embodiment the pressure in the chambers or cavities may be the same, but fluid is simply shifted between the chambers. In an embodiment the pressure in one chamber is changed, which will result in a movement and/or change of pressure in the other chamber. 
         [0018]    In an embodiment the regulator is a control valve such as a directional valve such as a 4/3 valve. The operation of the valve may be controlled or regulated by a motor such as a stepping motor. Thereby the sanitary valve system has shown to be very precisely controllable. Such an embodiment may be generalized to a control valve this is a directional valve with a first position, a second position and a third position. 
         [0019]    A first position may be where flow to and from the valve actuator is closed or where pressure is constant. 
         [0020]    A second position may be for increasing pressure the first chamber and decreasing the pressure in the second chamber in the valve actuator or for moving liquid medium to the first chamber and moving liquid from the second chamber. 
         [0021]    A third position may be for decreasing the pressure the first chamber and increasing the pressure in the second chamber in the valve actuator or for moving liquid medium from the first chamber and moving liquid to the second chamber. 
         [0022]    The sanitary valve may be configured for regulation of a flow of fluid Food (dairy, brewery, wine and soft drinks), fluid chemicals or fluid pharmaceuticals, which valve actuator, is activated by a liquid medium. 
         [0023]    By using a liquid medium to activate the actuator the size of the actuator will be greatly reduced in relation to traditional sanitary valve actuators, which use pressurized air. Typical valve actuators operate by pressurized air and have an actuator with a size in diameter, which extend the valve itself and where the actuators are of such a size that the valves have to be placed in some distance in order to provide sufficient room for the valve actuators. The reason why actuators by pressurized air are relatively big is that the pressure in most cases is approximately 10 Bar or below. 
         [0024]    The liquid media can be of typical hydraulic media and operate at much higher pressure. Typical pressure in hydraulic systems is 200 Bar and can be even higher. By using these extreme high pressures, extremely high forces can be achieved in an actuator. For valve actuators the pressure can be much lower and the valve will still be actuated highly effectively. Using liquid medium also leads to a situation where a return line from the valve actuator is just as necessary as the pressure line leading towards the actuator. 
         [0025]    The use of pressure line and return line leads to a situation where regulation is possible at the pressure side and the return side. It is also be possible by blocking both lines to lock the valve in a given position where the valve is locked so hard that no pressure fluctuations will be able to move the valve element in any directions. This can be achieved by a relatively simple valve arrangement where, for example, magnetic valves close when the valve has the correct opening/closing position. Thus, the valve element will be totally fixed in that position and liquid media has to be removed through the lines in order to move the valve element. 
         [0026]    Especially for sanitary valves, it is very important that no kind of pollution, such as chemicals or bacteria, is to be found in a factory where the valves operate. This is achieved when working with a liquid medium, as the medium is not in contact with the atmosphere. If by accident, the liquid medium gets into contact with Fluid food, the liquid medium can be kept chemical and neutral and be sterilised in the closed circulating system so that bacteria never will occur in the liquid. 
         [0027]    In a preferred embodiment for the invention the liquid medium comprises mostly water. Clean water is a preferred liquid for hydraulics. Water is mainly incompressible in relation to most other liquids and water is the cheapest existing hydraulic media. If by accident drops of water come into contact with Fluid food there is probably no need for destroying the products, as no actual pollution takes place. 
         [0028]    The valve actuator can operate linearly in relation to a linear operating valve closing element. When valves are linearly operated it is of course preferred to use a linear actuator placed in relation to the valve. One example is that the actuator is placed above the valve; however, the actuator can also be placed below the valve. By using a linear operation it is, for example, possible that a shaft connected to an operational distance between cavities is able to transmit the force directly to a valve closing element. By using as few mechanical elements as possible the most simple and reliable valve will be achieved. 
         [0029]    Instead the valve actuator can operate rotationally in relation to a rotationally operating valve closing element. In situations where, for example, butterfly valves are to be actuated these need rotational activation. In this situation, rotational actuators will be the most effective. By means of this, all kind of hydraulic motors can be used. Some hydraulic motors might operate together with a traditional gear mechanism to operate the valve. Thus, very small rotational hydraulic motors can be used for opening extremely big valves if there is no need for fast response. Another possibility is that the actuator itself is linear but the actual movement is transformed from linear movements into rotational movement. This is a well-known technology from valves actuated by pressurized air. 
         [0030]    Preferably, the pressure of the liquid media is below 50 Bar. The pressure has to be selected in relation to the force that is needed in order to activate a valve. Typical sufficient force is achieved by relative low pressure. A pressure twice the typical pressure of pressurized air will, for example, rapidly reduce the diameter of an actuator. Therefore, typical pressure for valve hydraulics is in the area of 20-30 Bar. 
         [0031]    The valve actuator can open the valve when a cavity is pressurized, where opening the valve also can activate a return spring for closing the valve. A typical way for operating valves is to let the hydraulic pressure open the valve and at the same time activate a return spring. If there for some reason is a pressure drop in the hydraulic system, the valve will automatically close. By means of this, a very fail safe valve is achieved, and in worst case scenarios with broken hydraulic lines it will only lead to closing of the valve. Very safe emergency closing systems can also be achieved in this way. By using water as a hydraulic medium, release valves can be used and only open in an emergency situation due to fact that water will not lead to any pollution. 
         [0032]    In a preferred embodiment, the valve can operate in relation to a first actuator for opening the valve, which valve can operate in relation to a second actuator for closing the valve. In a preferred embodiment of the invention the valve is operated by two actuators. By operating with two actuators, one actuator can perform force in the opening direction, while the other actuator can perform force in the closing direction. This is maybe the preferred embodiment where valves are used for regulation, where a valve closing element has to be placed somewhere between an opening and closing position and where regulation has to be performed. 
         [0033]    The valve actuator might comprise a first cavity for closing the valve when pressurized, which valve actuator can comprise a second cavity for closing the valve when pressurized, where a movable piston can be separating the first and second cavity. It is possible to let the valve operate by an actuator, which comprises two working cavities separated by the piston. In this way, the hydraulic pressure can be used for both opening and closing the valve. Especially when operating by using two working cavities it is possible to operate the valve with its own closed hydraulic system. Letting a pump operate in a way so the pump moves the liquid from one cavity to another, will lead to movement of the valve. If the pump is stopped, the pump might close the flow line and the valve as such is blocked in that position. Because the liquid is incompressible no movement of the valve is possible. But as soon as the pump is activated in any direction, the liquid is moved and the valve is moved from one position to another. 
         [0034]    The control valve can be electric activated, which control valve has a first position where flow to and from the valve actuator is closed, which control valve has a second position for pressurizing the first cavity and reducing the pressure in the second cavity in the valve actuator, which control valve has a third position for pressurizing the second cavity and reducing the pressure in the first cavity. If more valves are operating relatively close to each other it is possible to use a centralized pump for activating the valves. By having a pressure line and a return line, the valve regulation can be performed by electromagnetic valves that regulate the hydraulic flow. 
         [0035]    Preferably, the control valve is electric activated by pulse width modulation, One possible way of operating an electromagnetic valve is by using pulse width modulation. However, many other modulation forms are also well-known and these can also be used. 
         [0036]    Water as hydraulic media has been well-know for a very long time. Water was in fact used long before anybody started using oil as hydraulic media. The use of water hydraulic for activating sanitary valves are highly effective, as actuators will reduce in size and there will be no pollution in the room generated by the release of pressurized air. In a situation where water from the hydraulic system comes in contact with for example Fluid food, limited harm is generated to the product. However, if it had been hydraulic oil, which had come in contact with the Fluid food, a very high quantity of Fluid food would have to be destroyed due to pollution. In relation to production of drug, days of production might be destroyed. Using clear water solves the problem mainly because a small amount of water added to the product has no negative influence. Of course there are chemical products, which shall get in contact with water. In this case, other hydraulic media has to be used. 
         [0037]    It is preferred that water can be used as the form of liquid. In all situations where there are no risk of frost, which means that the production area will not be kept at a temperature below 0, there is a good argument for using absolutely clear water. The clear water is incompressible in relation to other hydraulic media and the clean water is also the cheapest hydraulic media. 
         [0038]    In cold areas the liquid can be a mixture of water and an anti freezing agent. In situations where the temperature is below  0 , such as for outdoor production systems, the water can comprise an anti-freezing agent at least in the winter period. 
         [0039]    A person skilled in the art will acknowledge the equivalence between a chamber or a cavity or similarly a space. 
         [0040]    Further details of the invention will be apparent from the following detailed description in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  shows a first possible embodiment of a valve actuator. 
           [0042]      FIG. 2  shows a valve actuator coupled to a magnetic valve. 
           [0043]      FIG. 3  shows a valve actuator operated by a motorized pump. 
           [0044]      FIG. 4  shows a valve actuator connected to a valve body. 
           [0045]      FIG. 5  shows a double acting valve. 
           [0046]      FIG. 6  shows an alternative embodiment to  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]      FIG. 1  shows a valve actuator housing  2  connected to a valve body  4 , which valve body  4  comprises an inlet  6  and an outlet  8 . Inside the valve body  4  a valve closing element  10  is shown. This valve element is connected to a shaft  12 , which shaft  12  is directly connected to a piston  14 , which piston  14  is movable inside the actuator housing  2 . A slide ring  16  tightens against the housing  2 . Below the piston  14  the cavity  18  is indicated and above this the cavity  20  is indicated. Furthermore, two lines  22  and  24  are shown, which lines are used for changing the pressure in the chambers  18  and  20 . 
         [0048]    During operation the valve actuator is able to regulate the flow from the inlet to the outlet by the valve closing element  10 . Opening of the valve takes place, if the pressure in the cavity  18  increases. If the hydraulic media can leave the cavity through line  24 , it is possible to move the piston  14  upwards. If the valve is closed the pressure increases over line  24  in the cavity  20 . If this way the flow through line  22  is open this allows the piston to move downwards, and the valve is closed. 
         [0049]      FIG. 2  shows the same valve actuator as shown in  FIG. 1 . The actuator housing  2  is connected to the valve body  4 , an inlet  6 , and an outlet  8 . The shaft  12  is connected to the piston  14 , which can be moved inside the chamber by changing the pressure in the chambers  18  and  20 . The lines  22  and  24  are connected to a hydraulic valve  30 . This valve  30  comprises a valve slider  32 , which controls the flow through the valve  30 . The slider  32  is a possible embodiment connected to a magnetic slider operated by a magnetic coil  34 . Furthermore, the hydraulic valve  30  has a pressure inlet  38  and a tank connection  36 . 
         [0050]    During operation, the hydraulic valve  30  regulates the flow in lines  22  and  24 . The slider  32  as shown allows positive flow to a cavity  20  and backwards from the cavity  18 . This allows the piston  14  to be moved downwards. If the slider  32  is moved to the middle position, there is no flow and the valve is closed. This leads to a blocking of the piston  14  in the actual position. If the piston is relatively tight and separates the cavities  18  and  20 , the piston is blocked in its actual position. This means that any pressure fluctuation in the line  6  or  8  is unable to influence the position of the actual valve in the valve housing  4 . Moving the slider  32  into its third position results in a positive flow in line  22  which flow increases the pressure in the cavity  18  and reduces the pressure in the chamber  20 . This moves the piston  14  upwards, which could lead to an opening of the valve. The slider  32  can in some situations be magnetically activated by the coil  34 . In this situation the slider could be moved very fast between the different positions. 
         [0051]    Depending on the slider  32 , the flow regulation could take place in an analogous way where there is an analogue regulation between the positions for flow and the position for closing. This way it is possible to regulate the pressure in the chamber  18  and  20  efficiently. The coil  34  could be connected to computer controlled regulation which can achieve a very precise regulation of the slider  32 . The position of the slider  32  could be indicated by indicating means which could send signals back to the computer control. 
         [0052]      FIG. 3  shows a valve actuator housing  2  during operation. The cavity is connected by a line  22  to a pump, where the cavity  20  is connected by line  24  to the pump  40 . This pump is by a rotating shaft  42  connected to a motor  44 . During operation the pump  40  could be of the gerotor type which is able to move liquid in both directions depending on the direction of the rotation. This way, very small amounts of fluid are moved by line  20  and  24 , which slightly changes the pressure in the cavities  18  and  20 . The pump  40  and the motor  44  can in fact be part of the same system and be integrated into a common housing, This way it is achieved that an actuator system is achieved, which system can operate as a stand-alone-system with electrical connection to the motor  44 , which motor could be any kind of electric motor. This way it is achieved that no pressure or return lines are necessary. Even in situations where many different valves operate very close to each other this method is highly efficient because a high number of valves can operate simultaneously. Especially when dealing with sanitary valves for food or medicine production it is very important that the valves as such operate without connection in the shape of lines. Only electrical supply is necessary. 
         [0053]      FIG. 4  shows a valve actuator  102  connected to a valve body  104 . The valve body  4  comprises an inlet  106  and an outlet  108 . The valve body  104  comprises a valve closing element  110 . The valve closing element  110  is operated by a shaft  112  which shaft is connected directly or indirectly to a piston  114  which piston  114  is movable inside the actuator housing  102 . An O-ring  116  is tied against the housing  102 . Below the piston  114  a cavity  118  is shown. A fluid connection  112  is indicated to connect the cavity  118  to a hydraulic liquid. As indicated by the arrow at the fluid connection  122 , flow can take place in both directions if connected to a control valve as shown in  FIG. 2 . Above the piston  114 , a further cavity  120  is indicated. This cavity comprises a spring  124 . 
         [0054]    In operation of a valve actuator as indicated in  FIG. 4 , the spring  124  will force the valve into a closed position. The valve will be opened if fluid is pressed into the cavity  118  and the pressure in the cavity  118  is higher than the forces acting from the spring  124 . Then the piston  114  will be moved upwards and the valve element  110  will open for a flow from the inlet  106  to the outlet  108 . Under normal working conditions, the position of the valve element  110  can be very precisely regulated by changing the pressure in the chamber  118 . In an emergency situation where, e.g., there is a power failure, the control valve could be designed to automatically enter into an open position which will reduce the pressure in the chamber  118 . The spring  124  will then automatically close the valve by pressing the valve element  110  into its closed position. The valve will then at first be opened if the pressure in the chamber  118  is increased. 
         [0055]      FIG. 5  shows a double acting valve. An actuator housing  202  is shown which actuator housing is connected to a valve housing  204 . The valve housing  204  has a first inlet  206  and a first outlet  208 . The flow between inlet  206  and outlet  208  is controlled by a valve closing element  210 . The valve element  210  is connected by means of a hollow shaft  212  which is further connected to a piston  214 . This piston  214  is movable in the actuator housing  212  and below the piston  214  is shown a first cavity  218  above the piston  214  is shown further a cavity  220 . The lower cavity  218  is connected by means of a fluid connection  222  which is connected to a control valve which is not shown. As shown in  FIG. 2 , the cavity  220  is connected by means of a fluid connection  224  also to the control valve. 
         [0056]    A further fluid inlet  236  is shown below the figure and a further fluid outlet is shown at  238 . A valve closing element is operating in the flow line between inlet  236  and  238 . The valve closing element  240  is activated by a shaft  242 . This shaft  242  is placed inside the shaft  212 . The shaft  242  is directly or indirectly connected to a piston  244  where a cavity  248  is placed below the piston  244  and a cavity  250  is placed above the piston  244 . The piston  244  comprises a tightening O-ring  246 . The cavity  248  is connected by means of a fluid connection  252  to a control valve as shown at  FIG. 2 . 
         [0057]      FIG. 6  shows an alternative embodiment to  FIG. 5  in that  FIG. 6  also describes a double acting valve, but where the actuators are operating independently in two different actuator housings from each side. 
         [0058]    The first actuator  302  is connected to the common valve housing  304 . The valve housing  304  comprises a first inlet  306  and a first outlet  308 . A valve closing element  310  is regulating the flow between  306  and  308 . The valve element  310  is connected directly or indirectly to a shaft  312  to a piston  314 . The piston  304  has an O-ring  316  to close against the housing in the valve body  302 . A cavity  318  is formed below the piston  314  and a further cavity  320  is formed above the piston  314 . The lower cavity  318  is connected by means of a fluid connection  332  to a control valve (not shown). The cavity  320  is connected by means of a fluid connection  324 . 
         [0059]    The figure further shows the second actuator housing  334  which is operation a closing element  340  which is placed between an inlet  336  and an outlet  338  of a second fluid line. The valve closing element  340  is connected by means of a shaft  342  to a piston  344 . This piston  344  comprises an O-ring  346 . A cavity has been placed above the piston and a cavity  350  is shown below the piston  344 . The upper cavity  348  is connected by means of a fluid connection  352  to a control valve as shown at the  FIG. 2 . The cavity  350  is connected to a fluid connection  354 .