Pressure type flow control system with flow monitoring

A pressure type flow control system with flow monitoring comprising:

• (a) an inlet side passage for fluid;
• (b) a control valve comprising a pressure type flow control unit that is connected to a downstream side of the inlet side passage;
• (c) a thermal type flow sensor that is connected to a downstream side of the control valve;
• (d) an orifice that is installed on a fluid passage communicatively connected to a downstream side of the thermal type flow sensor;
• (e) a temperature sensor provided near the fluid passage between the control valve and the orifice;
• a first pressure sensor provided to determine pressure off the fluid passage between the control valve and the orifice;
• (g) an outlet side passage that is communicatively connected to the orifice;
• (h) a second pressure sensor provided to determine pressure of the outlet side passage on a downstream side of the orifice;
• and
• (i) a first control unit comprising
• 1 a pressure type flow rate arithmetic and control unit to which pressure signals from the first pressure sensor and the second pressure sensor are input, and to which a temperature signal from the temperature sensor is input, and the pressure type flow rate arithmetic and control unit monitors critical expansion conditions for a fluid flowing through the orifice and computes a flow rate value Q of the fluid flowing through the orifice, and the pressure type flow rate arithmetic and control unit outputs a control signal Pd to a valve drive unit that brings the control valve into an opening or closing action in a direction in which a difference between the computed flow rate value and a set flow rate value is decreased;
• and
• 2 a flow sensor control unit to which a flow rate signal from the thermal type flow sensor input, and the flow sensor control unit computes a first flow rate of the fluid flowing through the orifice according to the flow rate signal, to indicate an actual flow rate of the fluid flowing through the orifice.