Patent ID: 8606412

Claim:
A method for detecting malfunction of a first valve on a downstream side of a throttle mechanism of a pressure type flow control apparatus of a gas supply facility, wherein the method comprises the steps of: (a) adjusting fluid pressure P 1 on an upstream side of the throttle mechanism to drive a flow rate control signal Qy towards zero, by the steps of computing a flow rate Qf of fluid passing through the throttle mechanism using the fluid pressure P 1 on the upstream side of the throttle mechanism; and operating a control valve on the upstream side of the throttle mechanism by setting the flow rate control signal Qy to a difference between the computed value of the flow rate Qf of the fluid and a flow rate setting value Qe that is inputted to the pressure type flow control apparatus; (b) outputting the computed value of the flow rate Qf of the fluid as a flow rate output signal Qo; (c) outputting the flow rate output signal Qo, proportional to the fluid pressure P 1 on the upstream side of the throttle mechanism, at all times as long as the fluid pressure P 1 exists, even in a state wherein the upstream side of the throttle mechanism is closed; (d) releasing the first valve on the downstream side of the throttle mechanism of the pressure type flow control apparatus; (e) changing the flow rate setting value Qe inputted to the pressure type flow control apparatus; (f) detecting magnitude of change ΔV of the flow rate output signal Qo while the flow rate setting signal Qe changes; and (g) determining that releasing operations of the first valve on the downstream side of the throttle mechanism are functioning normally when the magnitude ΔV of change of the flow rate output signal Qo is found to be above a predetermined value, and determining that the releasing operations are malfunctioning when the magnitude ΔV of change is found to be below the predetermined value.