Title:
VALVE POSITIONER
Document Type and Number:
Japanese Patent JP3473724
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To enable any leakage from a regulating valve to the detected by outputting a diagnostic signal for increasing/decreasing an air pressure by means of a start signal, computing a quickness difference in variation between a reference signal identical to the diagnostic signal and a valve opening degree signal, and outputting an abnormal signal when the quickness difference exceeds its preset value.
SOLUTION: When air leakage takes place from an operational part 4, if pneumatic pressure is increased, any increase in output pneumatic pressure is disturbed by leakage to cause a delay in the speed and if it is decreased, any decrease in the output pneumatic pressure is made faster to cause an increase in the speed so that the quickness difference in the case of presence of leakage is larger than that in the case of absence of leakage. In the abnormality judging device 67, the quickness degree difference ΔV=V--V+ is compared between a set quickness degree reference value ΔVS and variation quickness degree V+ at the time of pneumatic pressure increase and variation quickness degree V- at the time of pneumatic pressure decrease, and if a condition like ΔV>ΔVS is observed, presence of leakage is judged to be in an operational part 4 and abnormality warning is announced. By setting the variation speed or its width of the signal from the diagnostic signal generating device 65 properly, no influence is exerted on a control system when the diagnostic operation takes place during normal operation. Therefore, leakage detection can be detected on line.
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Inventors:
Takeshi Nishijima
Application Number:
JP31525395A
Publication Date:
December 08, 2003
Filing Date:
December 04, 1995
Export Citation:
Assignee:
Yokogawa Electric Corporation
International Classes:
F15B9/09; F15B13/043; F15B20/00; (IPC1-7): F15B9/09; F15B13/043; F15B20/00
Domestic Patent References:
| JP60228775A | ||||
| JP194129A | ||||
| JP59176470A | ||||
| JP64402U |
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