A practical procedure for identifying the pressure at which gas first passes continuously through the largest connected pore of a fully wetted filter cartridge.
The result is a pressure value observed after the cartridge has been completely wetted and gas pressure is increased slowly under controlled conditions.
Gas first displaces the wetting liquid from the largest connected pore. The pressure at which the first continuous bubble stream appears is recorded as the first bubble point pressure.
Bubble Distribution examines whether bubbles are distributed uniformly across the effective area of a porous plate or gas-distribution component. It is used to identify local blockage, cracks, weld defects, non-uniform porosity or inactive areas. See our quality inspection methods for the separate porous-plate test scope.
The sintered metal filter cartridge is filled or soaked with the specified liquid, connected to the test port and fully immersed. Sealing, test direction and the product-specific acceptance requirement must be confirmed before pressure is applied.
Pure water is generally used.
Maintain 25 ± 5 °C.
Fill or soak for 5–10 minutes.
Keep the cartridge top 1–2 cm below the liquid surface.
Increase gas pressure slowly and steadily.
Run at least twice; use the second and later values for the final result.
Use the validated machine setup and product specification for the exact fixture, gas, pressure range and acceptance limit.
Fill the cartridge with the specified test liquid and soak it for 5–10 minutes. Complete wetting is essential because trapped air can create a false early bubble path.
Drain excess liquid, connect the cartridge to the test port and secure the assembly. Check the fixture and seals before introducing gas.
Place the cartridge in the test liquid with its top 1–2 cm below the surface. Confirm that the entire effective filter area remains submerged.
Select the correct test liquid and filter-medium program on the instrument. Operate valves or levers according to the approved machine setup, then begin the controlled pressure cycle.
Raise gas pressure slowly while watching the submerged cartridge. Record the pressure when the first continuous bubble stream appears. If the agreed shop method also requires a group bubble point, continue and record the pressure when five or more continuous bubble streams are observed.
Generate, save or print the test report. Vent the system completely to zero pressure before removing the cartridge. Blow the cartridge dry, reset the machine controls and unload the test piece.
Comparable results require a controlled method and a complete test record.
| Record field | Required information |
|---|---|
| Test piece | Cartridge or batch ID, material, filter grade and dimensions |
| Test conditions | Liquid, gas, temperature, fixture and test direction |
| First bubble point | Pressure at the first continuous localized bubble stream |
| Group bubble point | Pressure at five or more continuous streams, only when required by the agreed method |
| Repeat number | Identify each run and retain the second and later values used for the final result |
| Final disposition | Compare only with the validated requirement in the applicable product specification |
The wetting liquid, temperature, filter material, test direction and method must be defined. A pressure value should not be converted into a pore-size claim or a pass/fail decision without the applicable validated correlation and product specification.
Send the filter medium, micron rating, dimensions, end fittings and acceptance requirement. FILTURE will confirm the appropriate fixture, method and report format.
