Pressure drop

Illustrated explanation

Gas flow and liquid entry use different measurements

2Pressure drop
Gas flow and liquid entry use different measurementsCallout 1: Airflow capacity. Callout 2: Pressure drop. Callout 3: Water entry. Callout 4: Bubble point. Airflow, pressure loss, water entry and bubble point are measured through different setups. A single pore or flow value cannot replace the complete membrane specification. Current term: Pressure drop, callout 2. 1Flow under stated conditionsAirflow capacity 2UpstreamDownstreamPressure drop 3First defined entryWater entry 4Bubble point
  1. Airflow capacity

    The arrows show gas exchange through the device. Compare flow values only at the same pressure, gas and reference conditions.

  2. Pressure dropThis term

    A flow restriction causes a pressure difference between the stated points. Separate this loss from absolute system pressure.

  3. Water entry pressure (WEP)

    The liquid pressure is increased under the stated method until entry occurs. Surface chemistry and liquid identity matter.

  4. Bubble point

    Gas pressure drives the first defined bubble through a wetted membrane. Bubble point differs from liquid-entry pressure and requires its own method.

Airflow, pressure loss, water entry and bubble point are measured through different setups. A single pore or flow value cannot replace the complete membrane specification.

Conceptual test setups and qualitative curves. No airflow, liquid-entry pressure or pore-size calibration is implied.

ReferencesISO 80000-4:2019 — Quantities and units — MechanicsIEC 62208:2023 — Empty enclosures for low-voltage assembliesISO 19403-1:2022 — Wettability — Vocabulary and general principlesIEC 60529 — Degrees of protection provided by enclosures (IP Code)ISO 4003:1977 — Determination of bubble-test pore size