Sterilization Grade

0.22+0.22μm (2222)
0.45+0.22μm (4522)
1.2+0.45μm (1245)

CARTRIDGE FILTRATION

• 1. What is Maximum Differential Pressure?

  Maximum Differential Pressure is the highest pressure difference between the inlet and outlet of a membrane cartridge filter that the cartridge can safely withstand without damage (media collapse, pleat deformation, end-cap failure, or bypass).

  • Why it matters: Exceeding Max DP can permanently damage the membrane and compromise sterile performance.
  • How it’s applied: Max DP is typically specified for:
    • Forward flow (normal filtration direction)
    • Reverse flow (backflow during upset or incorrect installation)
    • Sometimes separately for liquid service vs gas/air service, and for operating vs cleaning/steam sterilisation conditions.
• 2. What is Bubble Point?

  Bubble Point is an integrity test concept: it is the minimum gas pressure required to force a continuous stream of bubbles through a fully wetted membrane (in contact with a wetting liquid).

  • What it indicates: Bubble Point is related to the largest pore size in the membrane. If the bubble point is too low, it can indicate:
    • membrane damage,
    • improper wetting,
    • incorrect cartridge grade, or.
    • sealing/bypass issues..
  • Why it matters for sterile filtration: It’s widely used as a quick verification that the membrane is intact and capable of achieving its rated retention (sterile performance), when performed per the manufacturer’s procedure.
• 3. What is Diffusion Flow?

  Diffusion Flow (also called diffusive flow) is the measured gas flow rate that passes through a fully wetted, intact membrane during an integrity test below the bubble point pressure.

  • What’s happening physically: Gas dissolves into the wetting liquid within the pores and migrates through the membrane—this is normal and expected at pressures below bubble point.
  • What it indicates: Diffusion flow should be within a specified limit for the filter grade and test conditions. If diffusion flow is too high, it may indicate:
    • a damaged membrane,
    • incomplete wetting,
    • wrong wetting fluid,
    • temperature effects, or
    • leakage at seals/housing.
• 4. What is Effective Filtration Area (EFA)?

  Effective Filtration Area is the usable membrane surface area inside the cartridge that is actually available for filtration (typically expressed in m² or ft²).

  • Why it matters: Higher EFA generally means:
    • a damaged membrane,
    • higher flow at a given pressure drop, and/or
    • longer service life before the filter blocks (more contaminant holding capacity).
  • Important note: Two cartridges of the same length can have different EFA depending on pleat count, pleat geometry, membrane type, and construction—so EFA is a key comparison spec for sizing and performance.