Method and apparatus for detection of orifice clogging in pressure-type flow rate controllers

• Main Authors: KAGATSUME SATOSHI, HIROSE TAKASHI, HIROSE JUN, KOYOMOGI MUTSUNORI, IDETA EIJI, UNO TOMIO, IIDA SEIICHI, OHMI TADAHIRO, IKEDA NOBUKAZU, YOSHIKAWA KAZUHIRO, NISHINO KOUJI, YAMAJI MICHIO, DOHI RYOUSUKE
• Format: Patent
• Language: English
• Published: 16.10.2001
• Edition: 7
• Subjects: CONTROLLING; PHYSICS; REGULATING; SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES

A method and apparatus for detection of clogging of an orifice by measuring the upstream side pressure without breaking up the piping system in a flow rate control unit using an orifice, so as to extend the life of the flow rate control unit and enhance its safety. The apparatus of detecting clogging of an orifice in a pressure-type flow rate controller has a control valve (CV), an orifice (2), a pressure detector (14) for measuring the upstream pressure P1 therebetween, and a flow rate setting circuit (32) 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 with the equation QC=KP1 (K=constant) and wherein the control valve (CV) is controlled by the difference signal QY between the calculated flow rate QC and the set flow rate QS. The apparatus comprises:a storage memory M memorizing standard pressure attenuation data Y(t) of the upstream pressure P1 measured with the flow rate switched from the high set flow rate QSH to the low set flow rate QSL with the orifice (2) not clogged,a pressure detector (14) for determination of the pressure attenuation data P(t) of the upstream pressure P1 with the flow rate switched from the high set flow rate QSH to the low set flow rate QSL with the orifice (2) in the actual conditions,a central processing unit CPU for checking the pressure attenuation data P(t) against standard pressure attenuation data Y(t), andan alarm circuit (46) that turns on a clogging alarm when the pressure attenuation data P(t) deviates from standard pressure attenuation data Y(t) to a specific degree or beyond that.