First, the type of water ring vacuum pump to determine the type of pump is mainly required by the work of the gas, vacuum or exhaust pressure may be. Pump work, you need to pay attention to the following two aspects: 1. Whenever possible, in the high-performance area, that is, critical vacuum or critical exhaust pressure in the region. 2. Avoid operating near maximum vacuum or maximum exhaust pressure. Operating in this area is not only inefficient but also unstable and prone to vibration and noise. Cavitation occurs frequently in vacuum applications where the vacuum is high, and the obvious hallmark of this phenomenon is noise and vibration in the pump. Cavitation can cause damage to the pump body, impeller and other parts, so that the pump can not work. According to the above principle, when the pump required vacuum or gas pressure is not high, priority can be selected in the single-stage pump. If the vacuum or exhaust pressure is high, the single-stage pump often can not meet, or require the pump at higher vacuum conditions still have a larger amount of air, which requires the performance curve at a higher degree of vacuum is flatter, the choice of two Pump. If the degree of vacuum required in -710mmHg above, the optional water ring - air pump or water ring - Roots vacuum unit as a vacuum device. If only for the vacuum pump, the single-use pump is better. Because the single-action pump is simple in construction, easy to manufacture and maintain, and has good resistance to cavitation under high vacuum conditions. If only for larger compressor use, then the choice of double-acting pump more appropriate. Because the dual-acting pump has the advantages of large gas volume, small size and light weight, the radial force can be automatically balanced, the shaft is not prone to fatigue fracture, and the pump has a longer service life. Second, according to the amount of gas required for the system to select the vacuum pump After the initial selection of the type of pump, the vacuum pump, but also according to the amount of gas required to system selection of pump models. About pumping speed selection and pumping time calculation can refer to: vacuum calculation formula.