Absolute accuracy refers to 100% filtration of particles with marked accuracy. For any kind of filter, this is almost an impossible and impractical standard, because 100% is impossible to achieve.
Filtration mechanism
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, so that the working principle of the bag filtration is pressure filtration. The whole bag filter system consists of three parts: filter container, support basket and filter bag.
The liquid to be filtered is injected from the top of the filter bag supported by the support basket, which makes the liquid evenly distributed on the filter surface, so that the flow distribution in the whole medium is consistent, and there is no negative effect of turbulence.
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, so that the filtered liquid will not be polluted when the filter bag is replaced. The handle design in the filter bag makes the filter bag replacement fast and convenient.
The features are as follows:
High circulation capacity
Longer service life of filter bag
The uniform flowing liquid makes the particle impurities evenly distributed in the filter layer of the filter bag
High filtration efficiency, lowest cost
1. Selection of filter materials
First, according to the chemical name of the fluid to be filtered, according to the chemical cooperation taboo, find out the available filter materials, then according to the operating temperature, operating pressure, pH value, operating conditions (such as whether to withstand steam, hot water or chemical sterilization, etc.), evaluate one by one, and eliminate the unsuitable filter materials. Usage is also an important consideration. For example, the filter materials used in drugs, food or cosmetics must be FDA approved materials; For ultra pure water, it is necessary to select the filter material which is pure and does not contain the released matter and will affect the specific impedance; For filtering gas, hydrophobic materials should be selected, and “sanitary filtration” design is needed.
2. Filtration precision
This is one of the most troubling problems. For example, to remove particles visible to the naked eye, a 25 micron filter should be used; To remove cloud in liquid, 1 or 5 micron filter should be selected; A 0.2 micron filter is needed to remove the smallest bacteria. The problem is that there are two filtration accuracy units: absolute accuracy / nominal accuracy
3. Absolute accuracy / nominal accuracy
An infinite value. In the market, absolute filters, such as membrane, can only be called “close to absolute” filters, while others belong to nominal accuracy, which is the main problem: “nominal accuracy does not have a standard recognized and followed by the industry.”. In other words, company a can set the nominal accuracy at 85-95%, while company B would rather set it at 50-70%. In other words, company a’s 25 micron filtration accuracy may be equal to company B’s 5 micron, or finer. To solve this problem, experienced professional filter suppliers will help to choose the filtering accuracy, and the fundamental solution is “trial”.
4. According to the viscosity at the filtration temperature, the professional filtration equipment supplier can calculate the size of the filter, the flow rate of the filter bag and predict the initial pressure drop. If we can provide the impurity content in the fluid, we can even predict its filtration life.
5. Design of filtration system
The title covers a wide range, such as which pressure source should be selected, how much pressure is required, whether two sets of filters need to be installed in parallel to suit the continuous operation system, how to match the coarse filter and fine filter in the case of wide particle size distribution, whether check valve or other devices need to be installed in the system, etc. All these require the user to work closely with the filter supplier to find the most appropriate design.
6. How to use the filter bag
Closed filter: the filter bag and matching filter are used at the same time, and the liquid is squeezed through the filter bag by using the system fluid pressure to achieve the purpose of filtration. It has the advantages of fast flow rate, large treatment capacity and long service life of filter bag. It is especially suitable for the occasions with large flow rate requiring closed filtration. Self flow open filtration: the filter bag is directly connected with the pipeline through a suitable joint, and the fluid gravity pressure difference is used for filtration. It is especially suitable for small size, multi variety and intermittent economical liquid filtration.
Post time: Jun-08-2021