Calculation of Orifice Diameter for Flow Restrictor (OF) in a Semiconductor Vertical Furnace System

[Li Fei]

System Description:
This PID diagram is used in a vertical furnace system for semiconductor production equipment. The gas used is high-purity N₂, with an inlet pressure below 1 MPa. The system is designed to control the N₂ flow rate to 10 L/min. How can the orifice diameter of the flow restrictor (OF) be calculated?

 

[Snickster]

What is the purpose of the flow restrictor orifice? The flow controller controls the flow so why do you need a restriction orifice? Is it to limit the flow rate if the regulator fails open?