摘要:
A construction for mounting a pressure detector prevents the detector diaphragm from being strained by stress applied to the pressure detector as the detector is mounted in a fixture main body provided in a pipe line or the like, thereby keeping the output characteristics and temperature characteristics of the detector from greatly differing before and after the mounting. The pressure detector is constructed by combining and fastening together a diaphragm base having a diaphragm and a sensor base having a sensor element therein that is activated by displacement of the diaphragm base. The pressure detector, with a gasket placed thereunder, is disposed in a mounting hole of a fixture main body that is mounted in a pipe line. The pressure detector is airtightly pressed and fastened by a presser member inserted from above in the mounting hole. The presser member is brought in contact with a block upper surface of the diaphragm base, and the gasket is also brought in contact with the block lower surface of the diaphragm base. A shallow groove is defined in the form of a ring on the lower surface of the block at a place inward of the portion contacting the metal gasket so that the shallow groove absorbs strain caused by the presser member.
摘要:
A fluid supply apparatus with a plurality of flow lines branching out from one regulator for adjustment of pressure, the flow lines being arranged in parallel, wherein a measure is taken that the operation, that is, opening or closing of one flow passage will have no transient effect on the steady flow of the other flow passages. For this purpose, each flow passage is provided with a time delay-type mass flow controller MFC so that when one closed fluid passage is opened, the mass flow controller on that flow passage reaches a set flow rate Qs in a specific delay time Δt from the starting point. Also provided are a method and an apparatus for the above in which a plurality of gas types can be controlled in flow rate with high precision by one pressure-type flow control system. To that end, a formula for calculating the flow rate of a gas is theoretically derived that flows with a pressure ratio not higher than the critical pressure ratio. From that formula, the flow factor is defined, so that the formula may be applied to a number of gas types using flow factors. The method includes calculating the flow rate Qc of a gas passing through an orifice according to formula Qc = KP 1 (K = constant) with a pressure P 1 on an upstream side of the orifice set at twice or more higher than pressure P 2 on a downstream side, wherein the flow factor FF for each kind of gas is calculated as follows: FF = (k/γs){2/(κ + 1)} 1/(κ-1) [κ/{(κ + 1)R}] 1/2 and wherein, if the calculated flow rate of gas type A is Q A , and, when gas type B is allowed to flow through the same orifice under the same pressure on the upstream side and at the same temperature on the upstream side, the flow rate Q B is calculated as follows: Q B = (FF B /FF A )Q A where
ys = concentration of gas in standard state; κ = ratio of specific heat of gas; R = constant of gas; K = proportional constant not depending on the type of gas; FF A = flow factor of gas type A; and FF B = flow factor of gas type B.
摘要:
A method for detecting abnormal flow rate by easily detecting an obstruction of an orifice while a fluid pressure flow rate controller using an orifice is controlling the flow rate. The method uses a flow rate controller (FCS) so as to calculate the flow rate Qc on the downstream side when the upstream-side pressure P1 is maintained at a value about twice or more the downstream-side pressure P2 from Qc=KP1 (K: constant) and to control the operation of a control valve (CV) according to a signal Qy representing the difference between the calculated flow rate Qc and a preset flow rate Qs. A testing circuit or flow rate setting circuit provided separately outputs a testing signal ΔQs having a testing amplitude V0 to the control valve (CV). The pressure amplitude V of a pressure variation ΔP1 of the upstream-side pressure P1 occurring in response to the opening/closing of the control valve (CV) is measured. When the pressure amplitude V decreases below a limit amplitude Vt, the obstruction of the orifice is announced, thus implementing the method. If the testing signal ΔQs is superimposed on a steady-state preset flow rate signal Qs0 and outputted together from the testing circuit or the flow rate setting circuit to the control valve (CV), an abnormal flow rate can be detected while controlling the flow rate by using the steady-state preset flow rate signal Qs0.
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 P 1 maintained about two or more times higher than the downstream pressure P 2 , the downstream flow rate Q C is calculated by the equation Q C = KP 1 (K: constant) and wherein the control valve CV is controlled on the basis of the difference signal Q Y between the calculated flow rate Q C and the set flow rate Q S . The method comprises, outputting a testing signal ΔQs 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 ΔP1 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 ΔQs 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.