The type of pump is mainly determined by the amount of air, vacuum or exhaust pressure required for work.
When the pump works, the following two aspects should be paid attention to:
1. As far as possible, it is required to operate in the high efficiency area, that is, in the critical vacuum or critical exhaust pressure area.
2. Avoid operating near high vacuum or exhaust pressure. Operating in this area, not only the efficiency is very low, but also the work is very unstable, easy to produce vibration and noise. For vacuum pumps with high vacuum, cavitation often occurs when they operate in this area. The obvious sign of this phenomenon is that there is noise and vibration in the pump. Cavitation will cause damage to pump body, impeller and other parts, so that the pump can not work.
According to the above principles, when the vacuum or gas pressure required by the pump is not high, it can be preferentially selected in the single-stage pump. If the vacuum or exhaust pressure is high, the single stage pump often can not meet the requirements, or, in the case of higher vacuum, the pump is required to still have a larger air volume, that is, the performance curve is required to be relatively flat at higher vacuum, two stage pump can be selected. If the vacuum requirement is above -710 mmHg, water ring-air pump or water ring-Roots vacuum unit can be selected as the vacuum pumping device.
If it is only used as a vacuum pump, it is better to choose a single-acting pump. Because the single-acting pump is simple in structure, easy to manufacture and maintain, and has good cavitation resistance in high vacuum.
If it is used only for compressors with larger air volume, it is more appropriate to select double-acting pumps. Because the double-acting pump has large air volume, small volume and light weight, the radial force can be automatically balanced, the shaft is not easy to produce fatigue fracture, and the service life of the pump is longer.
2. Selection of Vacuum Pumps Based on the Gas Volume Required by the System
After preliminary selection of the pump type, for the vacuum pump, the pump type should also be selected according to the volume of air required by the system.
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