First of all, it depends on what kind of acid you are conveying. The following are the common selection instructions of acid resistant vacuum pump:
1. Vacuum pump for hydrochloric acid
The highest concentration of commonly used hydrochloric acid is 38%. Therefore, the pump for hydrochloric acid basically only needs to be made of plastic. However, if the service life and cost performance are considered, fluoroalloy centrifugal pump or magnetic pump can be selected. The price and performance of these two vacuum pumps are satisfactory.
2. Selection of vacuum pump for sulfuric acid
Sulfuric acid pump is divided into dilute sulfuric acid pump and concentrated sulfuric acid pump. The former has a wide range of options. Dilute sulfuric acid pump can choose engineering plastic pump, ceramic pump and the latter (concentrated sulfuric acid pump) can only choose fluoroplastic pump, because concentrated sulfuric acid will corrode ordinary engineering plastics, while fluoroplastics will not be corroded. It should also be noted that the density of concentrated sulfuric acid is high, and the motor power should be increased when selecting pump. The simple algorithm is “shaft power” 1.84, which is the shaft power when delivering concentrated sulfuric acid.
3. Selection of vacuum pump for hydrofluoric acid
Hydrofluoric acid is very corrosive. It is recommended to use the fluoroplastic magnetic pump (and the ceramic parts of the pump must be replaced with hydrofluoric acid resistant materials)
4. Vacuum pump selected for nitric acid
Fluorine plastic magnetic pump is also recommended for nitric acid delivery pump, and the rubber sealing ring should be replaced with tetrafluorocarbon material.
5. Vacuum pump selected for acetic acid
It is one of the most corrosive substances in organic acids. Ordinary steel will be severely corroded in all concentrations and temperatures of acetic acid. Stainless steel is an excellent acetic acid resistant material. 316 stainless steel containing molybdenum can also be used in high temperature and dilute acetic acid steam. For high temperature and high concentration acetic acid or containing other corrosive media, high alloy stainless steel or fluoroplastic magnetic pump can be selected. Such as magnetic pump, stainless steel magnetic pump
6. Vacuum pump for brine (sea water)
The corrosion rate of ordinary steel in sodium chloride solution, sea water and salt water is not very high, so coating protection is generally required; all kinds of stainless steel also have very low uniform corrosion rate, but local corrosion may be caused by chloride ion, 316 stainless steel is generally better, but its price is higher, so it is recommended to select fluoroplastic centrifugal pump, such as chemical centrifugal pump.
Sealing form: the magnetic pump is static sealing form, so it is unnecessary to consider the sealing property. Generally, the centrifugal pump adopts the external bellows mechanical seal, which has good corrosion resistance and wear resistance. If the conveying medium contains particles, the hard to hard mechanical seal can be used