Find solutions to product related issues. For unlisted issues please contact local Cytiva service representation.
Normal Flow Filtration
Please check the following during troubleshooting:
Lower than expected flow rate or capacity
If not done previously, small scale (25- or 47-mm) testing should be performed to confirm the filter selection. Filter capacities less than 150 L/m2 generally indicate that prefiltration is required..
If previous tests have been performed and scale-up calculations have been made on a liters per square meter basis, premature plugging may indicate that fluid characteristics have changed since the initial filter sizing trials were conducted.
Ensure that the filter housing is properly vented before use. Air-locking will lead to lower than expected flow rates. This can be done via the filter vent which is present on each device.
For high viscosity streams or fluids containing a high solute concentration, prewetting the filter with purified water or formulation buffer may improve process flow rates.
Failed integrity tests
Note: Sterilizing grade and bioburden reducing membrane filters should be tested for integrity. This can be done before use, after steam-in-place and/or after use. Integrity testing assures that the filters are integral and that the proper pore size filter is installed.
Check that the filter has been properly wet with purified water and that no residual process fluids are left on the membrane. If necessary, reflush the filter following the cartridge operating instructions.
For cartridge filters, check to ensure that the filter cartridges are properly installed. Double O-ring cartridge adapters should be fully seated and locking tabs, if so equipped, should be engaged to prevent filters from being dislodged due to back pressure. If the cartridge appears to be installed correctly, inspect the O-rings for damage.
Check that the temperature of the filter is held constant during the integrity test procedure. Filters should be flushed with water that is at a temperature close to the temperature of the integrity test gas. Filter and filter housing cooling is a common cause of false integrity failures.
Check that no system leaks are present. This can be verified by removing the filter from the housing and performing a pressure-hold test on the housing and associated piping.
Cartridge deformation: Cartridge deformation includes collapse of the filter core and warping of the code-7 tabs. This is generally caused by exposure to high differential pressure at SIP temperatures.
Cartridge melting: This is an indication of excessive steam temperature and pressure.
Cartridge discoloration: Generally caused by contaminants present in the steam. Steam generators and delivery systems should be cleaned and/or sanitized. If the problem persists, a steam filter should be added to the delivery system.
Capsule deformation: Capsule deformation is generally caused by flow restrictions on the capsule inlet and outlet. Sources of flow restriction include: impermeable caps placed on the inlet & outlet fittings, crimped tubing and tubing which joins the filter inlet and outlet ports.
Fitting distortion: Especially common for sanitary (tri-clamp) connections, fitting distortion is caused:
- When capsules support excessive weight during the elevated temperature of autoclave cycles. Proper fixtures should be designed to support the weight of external fittings during autoclaving.
- By sanitary clamps which are over-tightened prior to autoclaving. Three part clamps are preferable to two part clamps because they distribute clamping forces in a more uniform fashion. Nylon clamps are preferable to stainless steel because they expand and contract in a fashion more like the capsule materials. Additionally, nylon clamps generally include a stop which prevents over tightening.