Abstract:
A valve controller configured to operate on a Foundation Fieldbus Network and including a spool valve movable between at least an opening position and a closing position, and a flapper nozzle pilot valve arranged to move the spool between the opening position and the closing position.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/935,954 filed on Feb. 5, 2014, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The invention relates generally to valve controllers for use in a plant or factory automation environment. More specifically the invention relates to solenoid piloted valve controllers used in Foundation Fieldbus (FF) networks. 
         [0003]    FF networks are commonly used in process plants to provide power and control signals to field devices that control the position of control valves. FF networks are fully digital and operate on limited power. 10-30 mA of current at between 9 to 32 Volts are typical levels. Therefore, field devices that are powered on the FF network need to function on very low power. Traditional discrete automated valve controllers use piezo pilot valves to drive a larger spool valve which shuttles air to pneumatic actuators to turn process valves. Piezo technology allows the field devices to function at the low powers provided by the FF network. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    Piezo pilot valves are limited by their ambient operating temperature range and therefore present an undesirable constraint. Piezo pilot valves provide an operating temperature range of between −20° C. to +65° C. In applications requiring an operating temperature below −20° C. or higher that +65° C. piezo pilot valves are unsuitable. 
         [0005]    In one aspect, the present invention provides a valve controller configured to operate on a Foundation Fieldbus (FF) Network and includes a spool valve movable between at least an opening position and a closing position, and a flapper nozzle pilot valve arranged to move the spool between the opening position and the closing position. 
         [0006]    In an additional aspect, the present invention provides a pilot valve for a valve controller. The pilot valve includes a flapper portion configured to transition between a rest position and a deflected position, a nozzle portion configured to receive an electrical signal, and a flow restricting orifice configured to control air flow into the pilot valve 
         [0007]    The foregoing and other aspects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]    The invention will be better understood and features, aspects and advantages other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such detailed description makes reference to the following drawings. 
           [0009]      FIG. 1A  is a schematic diagram of a valve controller showing a flapper nozzle valve in a rest position and a spool valve in an open position. 
           [0010]      FIG. 1B  is a schematic diagram of a valve controller showing the flapper nozzle pilot valve in a deflected position and the spool valve in the closed position. 
           [0011]      FIG. 2A  is a detailed view of the flapper nozzle pilot valve in the rest position. 
           [0012]      FIG. 2B  is a detailed view of the flapper nozzle pilot valve in the deflected position. 
       
    
    
       [0013]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    The invention overcomes the temperature limitation of piezo pilot valves in the valve controller field device by replacing the piezo pilot valve with a flapper nozzle valve. The flapper nozzle valve allows the operating temperature range to be extended to about −40° C. to +105° C. 
         [0015]    Unlike the piezo pilot valve function, which is a standard 3-way normally closed valve, flapper nozzle valves are traditionally used as a current-to-pressure transducer in a modulating field device. The invention reapplies the flapper nozzle valve to be used in a discrete fashion as a flapper nozzle pilot valve, The electrical power applied to the flapper nozzle pilot valve can be comparable to the electrical power of the piezo pilot valve (0 volts, +6 Volts DC). 
         [0016]      FIG. 1A  shows a valve controller  10  with no electrical power applied to a pilot  14 .  FIG. 2B  shows +6 VDC electrical power applied to the pilot  14 . The valve controller  10  may also include a spool valve  18  and a valve actuator  22 , for example a pneumatic valve actuator. 
         [0017]    With reference to  FIGS. 2A and 2B , the pilot  14  includes a solenoid  26 , a flapper nozzle valve  32  having a nozzle  30  and a flapper  34 , a flow restricting orifice  38 , a supply port  42 , an outlet port  46 , and an exhaust  50 . 
         [0018]    Turning back to  FIG. 1A , the spool valve  18  includes a spool  54  with a spool head  58 , a spring  62  that biases the spool  54 , an air supply port  1  in communication with an air supply, for example a high pressure gas supply, an open port  2 , an exhaust port  3 , a close port  4 , an exhaust port  5 , a supply port  66  in communication with the supply port  42  of the pilot  14 , and a head port  70  in communication with the outlet port  46  of the pilot  14 . 
         [0019]    The valve actuator  22  includes a cylinder  74 , a piston head  78 , an actuating rod  82 , an open port  86  in communication with the open port  2  of the spool valve  18 , and a close port  90  in communication with the close port  4  of the spool valve  18 . In other constructions, the valve actuator  22  could be designed differently. For example, a rotary actuator or other non-linear actuator may be used. The design of the linear actuator is non-limiting. 
         [0020]    In  FIG. 1A , no electrical power is provided to the pilot  14  such that the flapper  34  is in a rest position as shown in  FIG. 2A . When the flapper  34  is in the rest position, a flow path is provided from the head  58  of the spool  54  through the head port  70 , the outlet port  46 , and the nozzle  30  to vent through the exhaust  50 . High pressure air is restricted from flowing into the pilot  14  by the flow restricting orifice  38 . With the pressure vented from the head  58 , the spring  62  biases the spool  54  to an open position. When the spool  54  is in the open position, the high pressure air flows from the air supply port  1 , through the spool  54  to the open port  2  and into the open port  86  of the valve actuator  22  thereby moving the piston head  78  to an open position and actuating a process valve. 
         [0021]    Turning to  FIG. 1B , electrical power, for example +6 VDC, is provided to the pilot  14  such that the flapper  34  is in a deflected position as shown in  FIG. 2B . When the flapper  34  is in the deflected position, the exhaust  50  becomes isolated, allowing full air pressure to pass from the air supply port  1 , through the supply port  66 , the nozzle  30 , and to the outlet port  46 . High pressure air is then provided to the head  58  such that the spring  62  bias is overcome and the spool  54  is forced to a closed position. When the spool  54  is in the closed position, the high pressure air flows from the air supply port  1 , through the spool  54  to the close port  4  and into the close port  90  of the valve actuator  22  thereby moving the piston head  78  to the closed position and actuating a process valve. 
         [0022]    The above description relates to a normally open valve, although the valve controller  10  could be used for a normally closed valve. Therefore, all reference to open or closed positions is not binding and may be reversed or changed, as desired, by one skilled in the art. 
         [0023]    One application for this invention is improved valve control in gas turbine power plants which use foundation fieldbus networks and may have temperature requirements of up to 105° C. An operating current range of about 10-30 mA, together with the operating voltage range of approximately 0V to 6V provided by the foundation fieldbus network can provide the limited power used by the pilot. Foundation fieldbus networks are all-digital, bi-directional, multi-drop communication systems. Other applications of the invention may include any process control plants, including but not limited to use in the following industries: power generation, oil &amp; gas, refining, food processing, bio-pharmaceutical, and water treatment. 
         [0024]    The invention has been described in connection with what are presently considered to be the most practical and preferred embodiments. However, the present invention has been presented by way of illustration and is not intended to be limited to the disclosed embodiments. Accordingly, those skilled in the art will realize that the invention is intended to encompass all modifications and alternative arrangements within the spirit and scope of the invention.