First of all, we need to understand the filtration mechanism of the bag filter system: the liquid flows from the inside of the filter bag to the outside of the bag, and the filtered particles are trapped in the bag. The working principle of the bag filter is pressure filtration. The bag filter system mainly comprises three parts: a filter container, a support basket and a filter bag.
1. The choice of filter bag material:
First, according to the chemical name of the fluid to be filtered, the available filter materials should be identified according to the chemical coordination, and then the filter medium temperature, operating pressure, pH value, viscosity (CPS), impurity type (hard particles, soft particles), Impurity content (PPM), operating conditions (eg, whether it is necessary to withstand steam, hot water or chemical sterilization, etc.), evaluate one by one, and remove the filter material that is not suitable. Use is also an important consideration. For example, the filter materials for pharmaceuticals, foods or cosmetics must be FDA-approved materials; for ultrapure water, the filter materials that are pure and do not contain the release materials will affect the specific impedance; Choose a hydrophobic material and whether you need a “hygienic filtration” design and more.
2. The accuracy of the filter bag:
This is one of the most troublesome issues. For example, to remove visible particles, use a 20 or 25 micron filter bag; to remove cloud in the liquid, use a 1 or 5 micron filter bag; to filter out the smallest bacteria, a 0.2 micron filter bag is required. The problem is that there are two units of filtering accuracy: absolute precision / nominal accuracy.