Key engineering factors to consider when choosing between thermal capillary and direct Coriolis flow instruments for critical process gases.
Thermal versus Coriolis instruments
Required differential pressure limits
Gas conversion factor accuracy
Capillary thermal MFCs calculate mass through thermodynamic heat transfer for stable low-flow delivery. Direct Coriolis units measure oscillating inertia, eliminating fluid conversion factors.
Standard thermal control valves typically require 1 to 3 bar differential to maintain precise valve regulation, whereas specialized low-drop instruments operate reliably below 10 mbar.
Theoretical K-factors derive from gas density and heat capacity relative to nitrogen. For real-world mixtures and higher pressures, empirical multipoint curves avoid significant measurement skew.
Calibration and field reliability
Preventing zero-point drift, particulate obstruction in capillary sensor channels, and sustaining calibrated turndown performance over decades.
Resolving zero-point drift
Recalibration service intervals
Multi-gas switching limitations
Mechanical pipe stress, thermal cycling, and elastomer seat settling cause zero offset. Performing zero re-nulling under stabilized operating temperature and absolute shutoff restores accuracy.
We advise annual reference standard recertification. For reactive, condensable, or semiconductor process lines, semi-annual audits safeguard against residue accumulation in the bypass laminar element.
Modern microprocessors support preloaded gas property matrices. However, physical control valve orifices are optimized for specific gas densities, preventing arbitrary fluid substitution.
Have an unlisted flow challenge?
Our technical team evaluates non-standard gas tables, low-pressure drop thresholds, and recalibration needs for all major instrumentation brands.