Instrument for detecting potential future failures of valves in critical control systems

• US 5,646,600 A
• Filed: 01/12/1995
• Issued: 07/08/1997
• Est. Priority Date: 01/12/1995
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hershey, John Eri, Hassan, Amer Aref, Abdel-Malek, Aiman Albert
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US08/371,716
• Time in Patent Office: 908 Days
• Field of Search: 340/679, 340/686, 364/725, 364/485, 364/487, 251/129.15-129.22
• US Class Current: 340/679
• CPC Class Codes: F16K 37/0075 For recording or indicating the functioning of a valve in combination with test equipment
• CPC Class Codes: G05B 19/4062 Monitoring servoloop, e.g. overload of servomotor, loss of feedback or reference
• CPC Class Codes: G05B 2219/42271 Monitor parameters, conditions servo for maintenance, lubrication, repair purposes
• CPC Class Codes: G05B 2219/45006 Valves

Abstract

Apparatus for monitoring the health and response of critical electromechanical control valves to detect the likelihood of future valve malfunction including the use of wavelet decomposition to selectively enhance portions of the valve response signal for comparison with a normal valve response signal.

Claims

1. Apparatus for monitoring the health and response of critical control valves by comparing an actual valve response signal with that of a normal valve response signal comprising:

a valve;

a valve actuator to actuate said valve in response to a valve control signal;

a monitor to monitor the response of said valve upon actuation of said valve to provide a valve response signal; and

means to compare said valve response signal and a normal valve response signal including

wavelet decomposition means to provide enhanced evaluation signals representing time variations in a time warped valve response signal; and

means to indicate differences between said enhanced evaluation signals and said normal valve response signal to evaluate the response and health of said valve.

2. The valve health monitoring apparatus of claim 1 wherein said valve is an electromechanical valve and said monitor is a sensor responsive to electrical input to said valve actuator.

3. The valve health monitoring apparatus of claim 2 wherein said wavelet decomposition means is a Haar wavelet decomposer.

4. The valve health monitoring apparatus of claim 3 wherein said electrical input is current flow through said valve actuator.

5. The valve health monitoring apparatus of claim 4 wherein said means to indicate differences between said enhanced evaluation signals and said normal valve response signal includes indicator signal means responsive to time varying differences of said valve response signal which exceed a predetermined amount.

6. The valve health monitoring apparatus of claim 5 wherein a visual display is provided to enable visual observation of said differences in said signals.

7. The valve health monitoring apparatus of claim 2 wherein said electrical input is the torque applied to said valve actuator in response to said valve control signal.

8. The valve health monitoring apparatus of claim 2 wherein said wavelet decomposition means comprises means for performing tiling of frequencies of the valve response signal utilizing uneven scaling to more closely examine frequencies of said valve response signal which are of interest.

9. The valve health monitoring apparatus of claim 8 wherein said tiling is dyadic tiling.

10. The valve health monitoring apparatus of claim 2 wherein said valve response signal is indicative of a malfunction and said wavelet decomposition means provides isolation of a desired spectral domain of said valve response signal indicative of said malfunction to enhance said valve response signal.

11. The valve health monitoring apparatus of claim 10 wherein said wavelet decomposition means is a Haar wavelet decomposer enabling dissection and observation of signal behavior selectively over different frequencies and different time scales.

12. The valve health monitoring apparatus of claim 11 wherein, said valve control signal provides a synchronizing signal to actuate said monitor and minimize sensitivity to time shift.

13. The valve health monitoring of claim 12 including sampler means coupling said monitor to said means to compare said valve response signal and said normal valve response signal, wherein said sampler means is selectively connected to a plurality of valves and a library of normal valve response signals is provided to provide a normal valve response signal for each of said plurality of valves.

14. The valve health monitoring apparatus of claim 1 further including switching means to selectively connect said apparatus to more than one valve for monitoring the health of said more than one valve.

15. The valve health monitoring apparatus of claim 14 further including pattern recognition means to automatically evaluate time differences between said valve response signal and a normal response of said valve response signal and to actuate an alarm when said differences exceed a predetermined amount.

16. The valve health monitoring apparatus of claim 15 wherein said valve control signal initiates the actuation of said monitor.