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Application Notes For MilliporeSigma Filters (continued)
Operation • Differential pressure (inlet minus outlet pressure) should be monitored regularly. Differential pressure increases as the filters plug, eventually leading to a loss of flow through the filter. Differential pressure increases exponentially. It may take many weeks to reach 80% plugged, but only a few hours for the final plugging to occur. • A common practice at breweries is to terminate the filtration and clean or change the cartridge(s) when the differential pressure reaches 30 psi. • Operate the process at the lowest, consistent flow rate to have a positive effect on filter performance. A higher face velocity leads to faster plugging. • Avoid pressure shocks and water hammer on the line. • Ensure that the top of the housing dome is periodically vented during production to remove any gas buildup that may overlap the filters. Integrity Testing • Integrity testing is only conducted on final membrane cartridges and is conducted per the recommended specifications of the manufacturer for the specific membrane used. Integrity testing is conducted after the sanitation cycle, both prior to and after the bottling run. There are a few different methods for integrity testing, of which the bubble point and pressure hold methods are the most common. The bubble point method is recommended for housings with three or less cartridges and the pressure hold method is recommended for housings with greater than three cartridges. Please consult your Gusmer representative for detailed information on integrity testing methods and specifications. • Every MilliporeSigma sterile membrane filter cartridge is integrity tested by MilliporeSigma twice prior to packaging. Damage caused to cartridges by shipping, installation or process improprieties, or housing and valve issues are usually manifested as gross integrity test failure.
Cartridge Storage • Intermediate storage (overnight or over a weekend) can be done in the filter housing. Flush the filters with warm water, sterilize the housing and pressurize with 5 psi of nitrogen. The nitrogen keeps the housing under a positive pressure. • Long-term storage is best done outside of the filter housings. Four inch PVC piping capped at both ends is frequently used to store the individual cartridges in a solution of 350 ppm sulfur dioxide that has been adjusted to a pH of 3.5 with citric acid. This solution should be tested every month and replaced as necessary. Ethanol at approximately 40% may also be used for long term storage. Remove o-rings from the cartridges prior to storage and store the o-rings in a clean and dry place. • Reinstall the o-rings, rinse, sterilize and integrity test stored cartridges prior to resuming bottling filtration.
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