Process applications / FLOW / ΔP
Reading a Flow Curve: Conditions Matter
Check the test assumptions
Review fluid, temperature, cartridge length, area and rating. Curves measured under different conditions cannot be compared by flow rate alone.
Separate inlet pressure from differential pressure
Inlet pressure describes system pressure. Differential pressure describes the pressure difference across the filter. They are distinct quantities and are not interchangeable.
Evaluate actual operating behavior
Feed particles, changes in viscosity and accumulated loading affect operation. Consider initial differential pressure and its development during use.
Compare clean resistance at one duty point
For curves measured with the same fluid and temperature, read differential pressure at the required flow and then verify cartridge count, length and connections. Comparing a single cartridge with a multi-cartridge housing mixes area differences with piping losses. A fair comparison needs the same measurement boundary.
- Record duty-point flow, differential pressure and total effective area.
- Establish whether housing and connection losses are included.
Control mode changes the observed trend
Under constant flow, increasing resistance commonly appears as rising pressure drop; under a fixed driving differential, it commonly appears as falling flow. State the control mode and setpoint because the same fouling process can look different under these conditions. Low starting resistance alone does not predict batch capacity or service life.
- Log control mode, setpoint and any changeover times.
- Relate flow and differential pressure to cumulative throughput, not elapsed time alone.
This general guide does not replace controlled technical documents or validation under actual process conditions.
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