Patent ID: 6450190
Filing Date: 2002-09-17
Classification: G05B,G05D,Y10T

Abstract:
A method of detecting the clogging of an orifice in a pressure-type flow controller,wherein the controller has a control valve CV, the orifice, a pressure detector to detect a pressure P1 on an upstream side between the control valve CV and the orifice and a flow rate setting circuit, wherein the upstream pressure P1 is maintained about two or more times higher than a downstream pressure P2, a downstream flow rate QC is calculated by the equation QC=KP1 wherein K is a constant, and wherein the control valve CV is controlled on the basis of a difference signal QY between the calculated flow rate QC and a set flow rate QS, wherein the method comprises the steps of: providing a separate testing circuit; maintaining the control valve in a shut off state; outputting a testing signal &Dgr;QS having testing amplitude VO from the testing circuit to control valve CV; measuring a pressure amplitude V of a variable pressure &Dgr;P1 of the pressure P1 on the upstream side that arises in response to opening or closing adjustment of control valve CV; and setting off an alarm for the clogging of the orifice when the pressure amplitude V is smaller than a limit amplitude Vt.