(1) Magnetic pump
In the past, PTFE was used as the shaft seal material of centrifugal pump, and the wear resistance was not enough.It is easy to leak liquid at the shaft seal, resulting in solution loss. Therefore, the magnetic pump without shaft seal will not leak liquid.However, several problems were found after use:
① The introduction of ferromagnetic materials causes rapid wear in the pump, and the gap between the rotor and stator in the magnetic pump is small. If ferromagnetic powder slag is introduced, it will be firmly absorbed by the permanent magnet in the pump to form abrasive, which will soon wear through the injection layer outside the permanent magnet and corrode the magnet.In the electroplating solution, it is inevitable that there will be workpiece corrosion, nickel slag and chips to form ferromagnetic powder and chips, so the service life of the magnetic pump is very short.
② The magnetism of the magnet in the magnetic pump will gradually decline (especially when the magnet quality is poor), resulting in the reduction of transmission torque, the decrease of pump head and suction head, and the decrease of pressure in the filter.
Therefore, now the magnetic pump is rarely used on the filter. For the plating solution such as silver plating and gold plating, which is very expensive, but the volume of bath solution is generally small, and it is not easy to introduce ferromagnetic impurities, it is still appropriate to use the small filter with imported magnetic pump with small nominal power.Although the price is expensive, it still accounts for a small proportion of the total investment.
(2) Improved centrifugal pump
At present, the improved centrifugal pump is mostly used for the filter.The shaft seal material is made of silicon carbide material with high hardness, high wear resistance and high flatness, which is much better than the original polytetrafluoroethylene material. After normal use for several years, there is still no liquid leakage at the shaft seal.
(3) Self priming pump
The self-priming pump has strong pumping force and vacuum suction capacity in the liquid inlet pipe, but the cost is high. When the internal wear is slightly large, the self-priming capacity will be lost, so it is rarely used in practice.
(4) Submerged pump
The impeller of the submerged pump is directly immersed in the solution and can be used after startup.However, when the pump shaft is too long, it is easy to deform and damage.When the pump and the filter are integrated, it becomes an underwater pump filter.But most of them are miniaturized, otherwise the area placed on the groove is too large.After the shaft is short, the liquid can only be extracted from the middle, and the dirty liquid at the bottom is not easy to extract.Small volume tank liquid can be selected when air stirring is adopted.