VERFAHREN ZUR ERKENNUNG EINES ANORMALEN DURCHFLUSSES IN EINEM DURCHFLUSSREGLER FÜR EIN UNTER DRUCK STEHENDES FLUIDUM

摘要

A method checks the flow rate for abnormalities while controlling the flow rate of fluid in a pressure-type flow controller FCS using an orifice - the pressure-type flow controller wherein with the upstream pressure P1 maintained about two or more times higher than the downstream pressure P2, the downstream flow rate QC is calculated by the equation QC = KP1 (K: constant) and wherein the control valve CV is controlled on the basis of the difference signal QY between the calculated flow rate QC and the set flow rate QS. The method comprises, outputting a testing signal DELTA Qs having a testing amplitude Vo from a testing circuit provided separately or a flow rate setting circuit to the control valve CV, measuring the pressure amplitude V of the variable pressure DELTA P1 of the pressure P1 on the upstream side of the orifice that arises in response to actuation of the 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. If the testing signal DELTA Qs is superimposed on a steady-state set flow rate signal Qso and outputted to control the valve CV from the testing circuit or the flow rate setting circuit, the flow rate can be checked for abnormalities while controlling the flow rate by the steady-state set flow rate signal Qso.