Every pharmaceutical application uses tanks, containers for a storage purposes, for example storage tanks for intermediate or final products, water storage tanks, mixing tanks.
Tanks are commonly used for storing a different liquids. To protect the liquid contents from microbial or particulate contaminant, it is necessary to install a vent filter on the tank. When liquid is added or removed from a tank, air must move in or out of the tank to fill the changing airspace above the liquid. A tank vent filter allows air to flow in both directions (bia directional) and prevents possible damage to the tank that could result if air is compressed during tank filling or a vacuum is created during tank emptying. It is critical, therefore, to size for proper air flow under both normal operating conditions as well as potential CIP or steam conditions (worst condition) , taking into consideration the pressure and vacuum capasity of the vessel.
Open to the atmosphere, the air needs to filtered through a sterilizing grade vent filter to avoid any contaminations. Often enough the product fed into the tank is sterile filtered and the tank steam sterilized, therefore the vent filter needs to perform with highest level to ensure sterility. The filter needs to be and remain hydrophobic to avoid any condensate blockage and microbial growth on or within the filter layers, especially when the vent filter is used over a long period of time without steam sterilization. This is in the case on water storage tanks, which hold water of lower quality than Water for Injection (WFI), which is stored at around 90 °C. The water temperature of WFI avoids or restricts microbial growth, but has the side effect of a high condensate rate, due to the high humidity of the air overlaying the hot water.
A condensation of water on the filter cartridge can be avoided by using heat jacketed filter housings, preferably an electrical heater. Using such heat jacketed housing the filter cartridge must be visually checked on a routine basis, some manufacturers quote around every 3 months, to see whether parts of the filter are damaged by oxidization.
BEST VENT FILTER
Hydrophobic sterilizing-grade filters are commonly used as air vents on processing tanks. The goal of the application is to maintain near ambient pressure in the tank with sterility in the tank. The tank vent filter removes particles and microorganisms from the air as it flows in or out of the tank.
- Sterilizing-grade 0.2 micron PTFE membrane
- Integrity testable, bacteria retentive
- Robust construction validated for multiple SIP cycles
- High flow rate capacity.
- 100% integrity tested to ensure quality
- Repeatedly steam sterilizable hence long life.
FACTORS – LONG SERVICE LIFE
Vent filters tend to have longer service life , it remains in ser vice from 2-3 months to 1 year. The effective life will depend upon a so many of factors including environmental conditions, the operating temperature of the system as well as the choice of media of element.
As in filtration application, filter life will depend upon the load of particles the filter has to catch. Here the filter is Bi-directional it operates in both directions, there is some natural cleaning of the filter that happens as the tank fills with water and the air starts Moving out that forces in the reverse directions. Life period will be shorter in a dusty environment compared to the life period in a clean environment.
The vent filters has to withstand high temperatures will weakens the filter media and reduce the filter life. Also during steam sterilisation, steam cycles are common to remove microbial impurities. Steam will heats and cools the filter very often and cause expansion and contraction of the filter , which can damage the physical structural of the filter. In such applications use of a steam jacketed filter housings or put heat tracer on the filter housing, also constant high temperature near to 90 deg cent results in damage of the polypropylene media and supporting components .
FACTORS FOR SIZING OF VENT FILTER SYSTEM
Vent filter System sizing is a very critical process. the failure of a vent filter, not properly designed results in to the shorter service life and may result in accidental collapse of the tank. Hence , more information or technical data are requires to correct sizing of the vent filter system
- The maximum working vacuum for which the tank is designed.
- The flow rate of air through the filter in-out from the tank
- The common and maximum discharge rate of liquid from the tank.
- The air flow rate of the filter media at atmospheric conditions
- The maximum temperature of the liquid inside the tank.
- The details of safety controls installed on tank.