METHOD AND APPARATUS FOR DETECTION OF ORIFICE CLOGGING IN PRESSURE-TYPE FLOW RATE CONTROLLERS

摘要

A method and apparatus for detection of clogging of an orifice bymeasuring the upstream side pressure without breaking up the piping system ina flow rate control unit using an orifice, so as to extend the life of the flow ratecontrol unit and enhance its safety. The apparatus of detecting clogging of anorifice in a pressure-type flow rate controller has a control valve (CV), an orifice(2), a pressure detector (14) for measuring the upstream pressure P[err]therebetween, and a flow rate setting circuit (32) wherein, with the upstreampressure P[err] maintained about two or more times higher than the downstreampressure P2, the downstream flow rate Qc is calculated with the equation Q[err] =KP[err] (K = constant) and wherein the control valve (CV) is controlled by thedifference signal Q[err] between the calculated flow rate Qc and the set flow rateQs. The apparatus comprises:a storage memory M memorizing standard pressure attenuation dataY(t) of the upstream pressure P[err] measured with the flow rate switched from thehigh set flow rate Q[err] to the low set flow rate Q[err] with the orifice (2) notclogged,a pressure detector (14) for determination of the pressure attenuationdata P(t) of the upstream pressure P[err] with the flow rate switched from the highset flow rate Q[err] to the low set flow rate Q[err] with the orifice (2) in the actualconditions,a central processing unit CPU for checking the pressure attenuationdata P(t) against standard pressure attenuation data Y(t), andan alarm circuit (46) that turns on a dogging alarm when the pressureattenuation data P(t) deviates from standard pressure attenuation data Y(t) to aspecific degree or beyond that.