Vacuum pump features
(1) There is a large pumping speed in a wide pressure range;
(2) The rotor has good geometric symmetry, so the vibration is small and the operation is stable. There is clearance between rotors and between rotors and shells, no lubrication, small friction loss, which can greatly reduce the driving power, so as to achieve higher speed;
(3) The vacuum pump cavity does not need oil seal and lubrication, which can reduce the pollution of oil vapor to the vacuum system;
(4) There is no compression and exhaust valve in the cavity of vacuum pump. Simple and compact structure, insensitive to dust and water vapor in the extracted gas;
(5) The compression ratio is low and the effect of hydrogen extraction is poor;
(6) The surface of rotor is curve cylinder with complex shape, so it is difficult to process and check.
Vacuum pump classification
According to its working principle, it can be divided into two types: gas delivery pump and gas capture pump.
Gas delivery pump includes: 1. Liquid ring vacuum pump (water ring vacuum pump) 2. Reciprocating vacuum pump 3. Rotary vane vacuum pump 4. Fixed vane vacuum pump 5. Slide valve vacuum pump 6. Cycloid vacuum pump 7. Dry screw vacuum pump 8. Roots vacuum pump 9. Shenhua07 molecular vacuum pump 10. Traction molecular pump 11. Compound vacuum pump 12. Water jet vacuum pump 13. Gas jet pump 14. Steam jet Injection pump 15, diffusion pump, etc.
Vacuum pump selection
The function of vacuum pump is to remove gas molecules from the vacuum chamber, reduce the gas pressure in the vacuum chamber, and make it reach the required vacuum degree. Generally speaking, there is a large range from atmosphere to extremely high vacuum. So far, no vacuum system can cover this range. Therefore, in order to meet the requirements of process index, working efficiency and equipment working life of different products, different vacuum system configuration needs to be selected for different vacuum sections. In order to achieve the best configuration, the following points should be considered when selecting the vacuum system:
1. First, the vacuum degree required by each process must be checked and determined. Because each process has its suitable vacuum range, it must be carefully studied and determined.
2. On the basis of determining the vacuum degree required by the process, check the limit vacuum degree of the vacuum pump system, because the limit vacuum degree of the system determines the best working vacuum degree of the system. Generally speaking, the limiting vacuum degree of the system is 20% lower than the working vacuum degree of the system, and 50% lower than the limiting vacuum degree of the previous stage pump.
3. Check and determine the type and volume of air extraction required by the process. Because if the kind of pumped gas reacts with the liquid in the pump, the vacuum pump system will be polluted. At the same time, it is necessary to determine the appropriate exhaust time and the amount of gas produced in the process of extraction.
4. Check and determine the time required to reach the required vacuum degree, flow resistance and leakage of vacuum pipeline. After the required vacuum degree is reached, the air extraction rate required to maintain vacuum under certain process requirements is considered.