Diagnostic apparatus and method for fluid control valves

• US 5,109,692 A
• Filed: 10/24/1990
• Issued: 05/05/1992
• Est. Priority Date: 08/25/1988
• Status: Expired due to Term

• Current Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Original Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Inventors: Fitzgerald, William V.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US07/605,130
• Time in Patent Office: 559 Days
• Field of Search: 73/168, 73/37, 73/4 R, 73/862.32, 73/9, 137/487.5, 364/558, 364/550, 364/556
• US Class Current: 73/168
• CPC Class Codes: F16K 37/0083 by measuring valve parameters
• CPC Class Codes: F16K 37/0091 by measuring fluid parameters
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

A method for diagnostically dynamic testing and determining the dynamic operating condition of a pneumatically operated fluid control valve assembly wherein a dynamic output of the valve assembly is compared in response to a dynamic input to the valve assembly. A controlled variable pneumatic pressure is supplied to the input of the valve positioner forming the dynamic input to move the flow control member. The controlled varying pressure is sensed to provide a first signal representing the dynamic input. The movement of the flow control member is sensed to obtain a second signal representing the responsive dynamic output, and the first and second signal are processed to develop valve diagnostic data, which is displayed to enable determination of the dynamic performance of the valve assembly under test.

Claims

1. A method for diagnostically dynamic testing and determining the dynamic operating condition of a pneumatically operated fluid control valve assembly having a current to pressure transducer, a valve actuator connected to a valve flow control member for movement between respective closed and open valve positions, and a valve positioner pneumatically coupled between said current to pressure transducer and said valve actuator, said method comparing a dynamic output of said valve assembly in response to a dynamic input to said valve assembly and comprising the steps of:

providing a variable control current signal input to said channel to pressure transducer and a corresponding controlled variable pneumatic pressure to the input of the valve positioner forming a dynamic input to said valve assembly to operate the valve in a dynamic test operation cycle defined by moving the flow control member between said respective closed and open valve positions;

providing a position sensor to sense movement of the flow control member;

obtaining an output signal from the position sensor corresponding to movement of the flow control member in response to said dynamic input to said valve assembly during the dynamic test operation cycle;

processing said variable control current signal and said output signal to derive valve diagnostic data representing the movement of the flow control member during the dynamic test operation cycle as a function of the variation of said variable control current signal input to said current to pressure transducer; and

displaying said valve diagnostic data for enabling determination of the dynamic performance of said valve assembly under test.

2. The method of claim 1, wherein said valve actuator includes a valve actuator spring, including the steps of:

providing a valve actuator pressure sensor to sense varying pressure at the input of the valve actuator;

obtaining a third signal from the valve actuator pressure sensor corresponding to varying pressure at the valve actuator input during the test operation cycle;

processing said output signal from the position sensor corresponding to movement of the flow control member and said third signal to derive valve diagnostic data representing the variation in pressure at the valve actuator input as a function of movement of the flow control member during the test operation cycle; and

displaying said valve diagnostic data for enabling determination of the characteristics of said valve actuator spring for said valve assembly under test.

3. The method of claim 2, including displaying said valve diagnostic data for enabling determination of the valve actuator spring adjustment values for said valve assembly under test.

4. The method of claim 3, including displaying said valve diagnostic data for enabling determination of the valve actuator spring constant values for said valve assembly under test.

5. The method of claim 1, wherein said valve flow control member is moved between respective closed and open valve positions with respect to a valve seat, including the steps of:

providing a valve actuator pressure sensor to sense varying pressure at the input of the valve actuator;

obtaining a third signal from the valve actuator pressure sensor corresponding to varying pressure at the valve actuator input during the dynamic test operation cycle for flow control member movements encompassing the fully closed valve position wherein said flow control member is seated on the valve seat;

obtaining said output signal during the dynamic test operation cycle for flow control member movements encompassing the fully closed valve positions;

processing said third signal and said output signal to derive valve diagnostic data representing the variation in pressure at the valve actuator input as a function of movement of the flow control member during the dynamic test operation cycle corresponding to flow control member movements encompassing the fully closed valve position; and

displaying said valve diagnostic data for enabling determination of the seating conditions of said flow control member on the valve seat for said valve assembly under test;

including the steps of displaying pressure values between at least two pneumatic pressure values at the end of the dynamic test operation cycle corresponding to closing of the valve as the flow control member initially contacts the valve seat and continuing until it is then totally seated against the valve seat, said two pneumatic pressure values including a pressure value (1) at the first point in flow control member travel where the pneumatic pressure initially abruptly changes in value at the end of the dynamic test operation cycle and a pressure vale (2) at the second point in the continued travel of the flow control member where the maximum pneumatic pressure value is reached and the pressure again abruptly changes as the flow control member travel direction is reversed.

6. The method of claim 7, including the steps of:

providing a pressure sensor to sense said controlled variable pneumatic pressure at the input of the valve positioner;

obtaining a third signal from the pressure sensor corresponding to said controlled varying pressure at the valve positioner input during the dynamic test operation cycle;

processing said variable control current signal and said third signal to provide valve diagnostic data corresponding to variations in the variable pneumatic pressure line connected to the valve positioner as a function of said variable control signal during said test operation cycle; and

displaying said valve diagnostic data and enabling determination of current to pressure transducer calibration values for said valve under test.