MFC Selection: Start from Process Conditions, Not a Model Table
Build a reviewable selection path from six inputs: media, range, pressure, valve state, connection and communication.
MFC selection starts from process conditions, not a model table. First record the full duty: what gas, what normal flow range, upstream and downstream pressures, whether the setpoint changes by process phase, and ambient temperature and connection type. These decide measurement principle, range, valve type, and sealing — far beyond picking a spec that looks adequate.
Range should cover normal operation without treating abnormal transients as a permanent basis. Keep typical flow within 20–80% of full scale to balance resolution and accuracy. If duty spans very different flows, consider two parallel MFCs — one carrying baseline flow, one trimming small flows — rather than compromising on a single range.
Media dictates wetted materials and sealing. Pyrophoric or toxic gases such as silane/phosphine favor all-metal sealing and explosion-proof options; fluorine-bearing gases demand corrosion-resistant sensors and flow paths; high-purity semiconductor use requires electropolished, low-particle construction. Put these requirements into the selection input up front.
Confirm connection, sealing, power, and communication at selection time: fitting type (VCR, compression, flange), supply voltage and signal format (analog 4–20 mA/0–10 V or digital DeviceNet/EtherCAT/RS-485), and whether valves should be normally open or closed to match safety logic.
Finally, document the decision: record media basis, temperature/pressure limits, flow setpoints, and accuracy requirements, and have a gas or process engineer review them at project confirmation. Return all numeric boundaries to the current controlled revision of the documentation.