Abstract:
The current invention relates to motor valves and actuators associated with such motor valves. More particularly, the current invention relates to an electro-hydraulic positioner for such actuators so that the valve can be opened, closed or partially opened. The invention also relates to a method for positioning an actuator for a motor valve. The method utilizes a hydraulic liquid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/651,965 filed May 25, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The current invention relates to motor valves and actuators associated with such motor valves. More particularly, the current invention relates to positioning such actuators so that the valve is open, closed or partially opened. 
       BACKGROUND OF THE INVENTION 
       [0003]    Motor valves are designed for use in liquid and gas control applications such as oil and water dump valves and such as burner valves. Generally, they have a valve for controlling the flow of the liquid or gas and an actuator, which controls the opening and closing of the valve based on the external input. Often the actuator has been pneumatically controlled; this involves the use of a compressed gas to position the actuator. Use of compressed gas is problematic in that a compressed gas source must be available. In field application this requires either maintaining such a compressed gas source or using locally available sources, such as gas extracted from a well. Among other difficulties, maintaining a compressed gas source is labor intensive and requires constant monitoring. Using locally available sources typically means using hydrocarbon gas; hence, there is a loss of valuable hydrocarbon gas to the atmosphere and concerns over hydrocarbon gas emissions. Additionally, the sour, wet or dirty nature of the supply gas can adversely affect the operation of the motor valve assembly and can add additional maintenance costs because of the necessity of using accessory equipment such as regulators, filters and drip pots. 
         [0004]    Accordingly, it would be desirable to have a low maintenance system for positioning the actuator, which eliminates many or all of the concerns of pneumatic systems. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with one embodiment of the invention there is provided an electro-hydraulic valve positioner comprising a first conduit, a second conduit, a pump, a check valve and an electromechanical valve. The pump has an inlet for receiving a hydraulic liquid from the first conduit and an outlet for discharging the hydraulic liquid to the second conduit. The check valve is in fluid flow communication with the outlet of the pump and the second conduit. The check valve prevents backflow from the second conduit to the first conduit. The electromechanical valve is in fluid flow communication with the first conduit and the second conduit. The electromechanical valve has a first position allowing fluid flow between the first conduit and the second conduit, and a second position preventing fluid flow between the first conduit and the second conduit. 
         [0006]    In accordance with another embodiment of the invention there is provided a process for positioning an actuator for a motor valve comprising:
       (a) receiving a first signal regarding a state of a first fluid;   (b) activating a pump in response to the first signal to thus introduce a hydraulic liquid into a second zone at a second pressure from a first zone at a first pressure wherein the second pressure is greater than the first pressure to thus produce a pressure difference;   (c) positioning the actuator in response to the pressure difference;   (d) deactivating the pump in response to a second signal wherein the deactivating occurs when the second pressure reaches a predetermined pressure set point;   (e) activating a valve in response to a third signal regarding the state of the first fluid to thus introduce the hydraulic liquid into the first zone from the second zone such that the pressure difference is reduced; and   (f) positioning the actuator in response to the thus reduced pressure difference.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a motor valve assembly incorporating one embodiment of the current invention. 
           [0014]      FIGS. 2A and 2B  are cross-sectional views with a schematic flow diagram of the electro-hydraulic valve positioner in accordance with the embodiment of  FIG. 1 .  FIG. 2A  illustrates the flow to the second side of the diaphragm.  FIG. 2B  illustrates the flow from the second side of the diaphragm. 
           [0015]      FIG. 3  is an end view of the mechanical chamber of an electro-hydraulic valve positioner in accordance with the invention. 
           [0016]      FIG. 4  is an end view of the electronics chamber of an electro-hydraulic valve positioner in accordance with the current invention. 
           [0017]      FIG. 5  is a cross-sectional view of an electro-hydraulic valve positioner taken along line  5 - 5  of  FIG. 3 . 
           [0018]      FIG. 6  is an enlargement of the check valve used in an electro-hydraulic valve positioner of  FIG. 5 . 
           [0019]      FIG. 7  is a partial cross-sectional view and partial schematic view illustrating an embodiment of the invention using a positional sensor. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0020]    The current invention is directed to an electro-hydraulic valve positioner and a process for using the same. Generally, the inventive electro-hydraulic valve positioner can be used as part of a motor valve assembly, which includes a motor valve and the electro-hydraulic valve positioner; hence, the invention also is directed to an inventive motor valve assembly and a process for using the same. The electro-hydraulic valve positioner is sometimes referred to as an actuator. In general terms, actuators are a mechanism for controlling or moving another mechanism. The inventive electro-hydraulic valve positioner is described in relation to controlling a motor valve and, thus, electro-hydraulic valve positioner is an actuator in that it moves or controls the top works of a motor valve. However, the top works move or control the valve portion of the motor works and, thus, are also an actuator. To avoid confusion the term “actuator” will only be used herein in relation to describing the top works of the motor valve. 
         [0021]      FIG. 1  shows motor valve assembly  10 , which comprises motor valve  20 , electro-hydraulic valve positioner  22  and fluid reservoir  24 . Motor valve  20  has a top portion  26 , commonly referred to as a top works  26  and a control valve  28 . Top portion  26  has diaphragm housing  27  and actuator  30 , which includes actuator stem  33 . 
         [0022]    Referring to  FIGS. 2A and 2B , a motor valve  20  is shown in cross-section and the electro-hydraulic valve is shown schematically. Motor valve  20  is of the type having a control valve  28  and a top portion  26 , which includes an actuator  30  and top portion  26 . Actuator  30  is movable with a diaphragm  32  within top portion  26 . Motor valves are well known in the art, and the interaction of the actuator and diaphragm are well known. The actuator  30  is connected at a first end to valve plug  70  and at a second end to a diaphragm plate  34 . Diaphragm plate  34  is connected around its outer circumference to diaphragm  32 . Diaphragm  32  is sandwiched around its outer circumference between upper portion  54  and lower portion  56  of diaphragm housing  27 . Thus, diaphragm  32  divides the interior portion of diaphragm housing  27  into a first zone  58  on first side  60  of diaphragm  32  and a second zone  62  on second side  64  of diaphragm  32 . First zone  58  and second zone  62  are sealed from fluid flow contact across the interior of diaphragm housing  27 ; thus, when fluid pressure is increased in one of the zones there is a pressure differential between them, the diaphragm will move towards the lower pressure zone. Spring  52  is operationally connected to diaphragm plate  34  to provide for a bias for diaphragm  32 . As illustrated in  FIGS. 2 and 3 , motor valve  20  is in a pressure-to-open configuration. Accordingly, when pressure causes diaphragm  32  to move upwardly, the actuator  30 , including actuator stem  33 , will move upwardly and will open the control valve  28 . In the pressure-to-open configuration, spring  52  provides a downward bias for diaphragm  32 . Thus, to move diaphragm  32  upward, the pressure in second zone  62  must be greater than the pressure in first zone  58  by a predetermined amount. Generally, the predetermined amount is greater than the amount overcome the bias provided by spring  52 . It is understood that for a pressure-to-close configuration, control valve  28  is normally open and pressure will be applied to the top of the diaphragm  32  to close the control valve  28  by moving diaphragm  32  downwardly and, hence, actuator  30  downwardly. In pressure-to-close configuration, spring  52  provides an upward bias for diaphragm  32 . Thus, to move diaphragm  32  downward, the pressure in first zone  58  must be greater than the pressure in second zone  62  by the predetermined amount. 
         [0023]    Control valve  28  comprises a valve housing  72 , which defines a first flow channel  74 , a second flow channel  76  and a valve seat  78 . First flow channel  74  and second flow channel  76  are in fluid flow contact across valve seat  78 ; however, when valve plug  70  is sealing engaged with valve seat  78 , first flow channel  74  and second flow channel  76  are prevented from fluid flow communication across valve seat  78 . Accordingly, when actuator  30  is in its lower most position, valve plug  70  sealing engages valve seat  78  and there is not fluid flow communication between first flow channel  74  and second flow channel  76 . As actuator  30  moves upwardly, fluid flow communication is established with maximum fluid flow when actuator  30  is in its uppermost position. 
         [0024]    Returning now to  FIG. 1 , it can be seen that electro-hydraulic valve positioner  22  is in fluid flow communication with diaphragm housing by first flow line or first conduit  44  and by second flow line or second conduit  46 . Additionally, first conduit  44  is in fluid flow communication with hydraulic liquid reservoir  24 . As shown, the motor valve  20  is configured for pressure-to-open operation and first conduit  44  is connected to upper portion  54  at port  66  and second conduit  46  is connected to lower portion  56  at port  68 . Generally, these connections will be switched for pressure-to-close configurations. During operation, diaphragm housing  27  will generally be filled with hydraulic fluid. Hydraulic liquid reservoir  24  can be any suitable container for storing additional hydraulic fluid as necessary for providing suitable hydraulic pressure to diaphragm  32 . As illustrated, hydraulic liquid reservoir  24  has transparent or translucent side wall  25  so that the amount of hydraulic liquid in the reservoir can be visually inspected. The hydraulic liquid can be any suitable liquid such as water or hydraulic oil. One type of suitable hydraulic oil is hydro-treated naphthalene oils. 
         [0025]    Turning now to  FIGS. 3 ,  4 ,  5  and  6  the components of electro-hydraulic valve positioner  22  can be seen. Electro-hydraulic valve positioner  22  has valve positioner housing  42  defining an electrical chamber  41  and a mechanical chamber  43 . Electrical chamber  41  contains electronic control unit or circuit board  36 . Mechanical chamber  43  contains pump  40 , pressure transducer  48 , check valve  50  and electromechanical valve  51 . Electrical chamber  41  and mechanical chamber  43  are isolated so that (other than connections for circuit board  36  to control the mechanical components), there is no contact between the chambers. As can best be seen from  FIGS. 2A and 2B , pump  40  has an inlet  80  in fluid flow communication with first conduit  44  so that it receives hydraulic liquid from first conduit  44 . Pump  40  has an outlet  82  for discharging the hydraulic liquid, which is at a higher pressure upon discharge than upon introduction to pump  40 . Outlet  82  is in fluid flow communication with check valve  50  and second conduit  46 . Check valve  50  is disposed so as to prevent backflow from said second conduit into outlet  82  and thus, back into first conduit  44 . Electromechanical valve  51  is in fluid flow communication with first conduit  44  and second conduit  46 . Electromechanical valve  51  has a first position, which prevents fluid flow between first conduit  44  and second conduit  46 , and a second position, which allows fluid flow between first conduit  44  and second conduit  46 . A sensor is utilized to control the positioning of actuator  30 , such as pressure transducer  48 , which senses the pressure downstream from pump  40 . As illustrated in  FIG. 2A and 2B , pressure transducer  48  senses the pressure on second zone  62 . Alternatively or in addition to pressure transducer  48 , a positional sensor  84  can be mounted as illustrated in  FIG. 7  to determine the position of actuator stem  33 , as further described below. 
         [0026]    Pump  40  can be any suitable pump that can be electronically controlled, as such pumps are known in the art. Electromechanical valve  51  can be any suitable valve, such as a solenoid valve. Pressure transducer  48  can be any suitable such pressure transducer or sensors as are known in the art. 
         [0027]    In operation, motor valve assembly  10  may be used, for example, in connection with a fluid-containing vessel to drain fluid therefrom. A liquid level controller such as, for example, an electronic liquid level controller may be connected to the fluid-containing vessel. When the fluid in the vessel reaches a level at which fluid needs to be drained therefrom, a signal will be sent to an electronic control unit or printed circuit board  36 . Operation of motor valve assembly  10  can best be seen from  FIGS. 2A and 2B , which include a schematic flow diagram portion for electro-hydraulic valve positioner  22 . 
         [0028]    Pump  40  contained in the valve positioner housing  42  is activated when the signal is sent. Valve positioner housing  42  is ported so that flow lines  44  and  46  are connected to ports in the valve positioner housing  42 . The ports are communicated with the inlet and outlet of pump  40 . 
         [0029]    Pump  40  is activated and will operate to circulate fluid from liquid reservoir  24  through line  44  and out through line  46  into the space below diaphragm  32 , that is second zone  62 . The diaphragm housing  27  of top works  26  will generally be full of hydraulic fluid, but until pump  40  is activated no pressure will be acting upward on diaphragm  32 . When the pressure in second zone  62  exceeds the pressure in first zone  58  by a predetermined amount, diaphragm  32  will lift actuator  30  to open control valve  28 . A pressure transducer  48  will sense the pressure and will shut pump  40  off when a previously determined pressure set point is reached. A check valve  50  prevents backflow and holds the diaphragm  32  in place thus holding the valve  28  open. When sufficient fluid has been drained from the fluid-containing vessel, a signal is sent to the circuit board to open the solenoid valve  51 . The solenoid valve  51  will open to allow flow therethrough back into the space above the diaphragm  32  in top works  26 ; that is, first zone  58 . A spring  52  will urge diaphragm plate  34  downwardly to push fluid outwardly through solenoid valve  50 , so that actuator  30  moves valve  28  to the closed position.  FIGS. 2 and 3  are flow diagrams showing the direction of flow to open and close valve  28 . 
         [0030]    While the description here is to a discrete, or on/off version in which the actuator moves between fully open and fully closed positions, a positional sensor, which will monitor the positions of the actuator, can be used and the actuator can be moved to desired positions that correspond to the desired position of the valve between fully open and fully closed. Position feedback may be accomplished as follows. 
         [0031]    An analog or digital signal is sent from an outside source to the printed circuit board  36  to indicate the desired position of the actuator  30  and actuator stem  33 . The position of actuator  30  and actuator stem  33  is determined through a positional sensor  84 , which is operationally connected to actuator  30  and actuator stem  33 . Positional sensor  84  can be a rotary sensor, resistive potentiometer, hall-effect sensor or any other sensor capable of detecting the position of actuator stem  33 . As shown in  FIG. 7 , positional sensor  84  is a rotational sensor that interacts with actuator stem  33  through means of grooves  86  and  88 . For a pressure-to-open valve, the electronic control unit  36  sends a signal to operate pump  40  to circulate fluid from liquid reservoir  24  through line  44  and out through line  46  into the space below diaphragm  32  to open the motor valve  20  to the desired position. Desired position feedback is accomplished through a signal from the sensor to the printed circuit board  36 . Once the desired position is reached, electronic control unit  36  sends a signal to stop pump  40 . Subsequently, if motor valve  20  needs to be further opened, a signal can be sent to start pump  40  again. Alternatively, if motor valve  20  needs to allow less flow or be closed, electronic control unit  36  sends a signal to operate electromechanical valve  51  to circulate fluid from the space below diaphragm  32  through line  46  and out through line  44  into liquid reservoir  24  to close the motor valve  20  at the desired position. Desired position feedback is accomplished through a signal from the sensor to the printed circuit board  36 . 
         [0032]    Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.