Generally, the electrophoresis tank adoptsbag filter housingto filter the electrophoresis tank liquid. Because the bag filter housing is one of many liquid filters, the bag filter housing has compact structure, high filtration precision and wide filtration range. It can filter any fine particles or suspended solids, which can be selected from 25-100 microns. Therefore, when the same filtering effect is achieved, compared with plate and frame fine filter, filter element and other equipment, it has the advantages of low investment cost, long service life, convenient management and maintenance, low replacement and filtering cost.
In order to effectively ensure the filtering effect of electrophoresis tank solution, the configuration of filter quantity needs to be determined according to the capacity of electrophoresis tank and the filtering amount of single filter at the beginning of equipment design. Otherwise, if the filter configuration is insufficient, it is not only easy to block the filter bag and affect the normal operation of tank liquid, but also may lead to large consumption of filter bag and difficult to guarantee the product quality.
After the equipment is completed and delivered for use, the key to the filtering effect depends on the front-line management. Protection is generally obtained through the following ways:
- Filtration accuracy – the filtration accuracy of electrophoresis tank is generally 25 ~ 75 μ m;
- Replace the filter bag in time according to the differential pressure. Whether the filter bag is damaged during replacement; whether the suture is firm and firm. With the extension of time, the filter bag will gradually block, so it needs to be replaced to ensure the normal circulating filtration effect. The replacement frequency of different electrophoresis lines is not the same. Poor environmental conditions, poor cleaning effect before swimming, excessive foam in the main trough and auxiliary trough in summer, and the electrophoresis line with many particles may change the filter bag every day. It is also common that some electrophoresis lines with perfect process management and good dust-proof environment do not need to replace the filter bag for a month.
- In order to ensure good appearance quality of electrophoretic coating, filter devices shall be set in the circulating pipeline of tank liquid, circulating UF liquid cleaned after swimming and circulating deionized water pipeline to filter the tank liquid and circulating cleaning liquid to a great extent.
The mechanical impurities (environmental pollution, pollution brought in by coating) and condensed particles (impurities brought in by pretreatment and dirt generated by the reaction of coating) in the tank liquid will be removed by the filter device in the circulating system. Therefore, the filtration throughput is required to be 2-4 times the tank capacity / hour.
The commonly used filter is bag filter, and thefilter bagis made of non-woven fabric or polypropylene.
The filter is driven by the main circulating pump. It is recommended to connect two bag filters in series on each main circulating pump. In this configuration, the first filter selects the filter bag with larger aperture to remove most large particle impurities, and the second filter selects the filter with smaller aperture to remove small particles.
Polypropylene filter bag can be used as cathode electrophoresis filter bag; The anode electrophoresis filter bag is non-woven.
The filtration accuracy of anode electrophoresis tank liquid generally adopts the filter bag that can pass through the filter medium of 50-75 μ M.
The filtration accuracy of cathodic electrophoresis tank liquid generally adopts the filter bag that can pass through the filter medium of 25-50 μ M.
The cleaning of the filter and the replacement of the filter bag depend on the inlet and outlet pressure on the filter. Generally, the bypass pipeline is connected in parallel on the filter pipeline (the installation form of parallel double barrel filter is recommended). The low discharge point and upper exhaust port should be set on the filter, and the filter shell should be made of stainless steel.
Practice has proved that the filtering effect depends not only on the filtering accuracy, but also on the suction position. It is generally believed that the filter suction position extracted from the bottom of the overflow tank mainly filters the particles with light specific gravity. The proportion of filtered impurities sucked from the bottom of the inclined plane at the inlet end is large.
Therefore, it is recommended to install an independent filter circuit at the front end of the electrophoresis tank, and an independent pump will deliver the tank liquid to the filter. Generally, bag filter is also selected, and the filtering accuracy is 100-150 μ M. this kind of filtration is mainly used to remove the metal debris and other impurities washed off when the coating (body and cab) is immersed in the electrophoresis tank, or precipitate at the bottom, Particulate impurities that then accumulate at the inlet.
In the new electrophoresis coating main circulation pipeline, it is suggested to design and install magnetic filter device and oil absorption filter bag.