Vacuum Pump Selection ---Guide
When choosing a vacuum pump, you need to pay attention to the following matters:
1. The working pressure of the vacuum pump should meet the ultimate vacuum and working pressure requirements of the vacuum equipment. For example: vacuum coating requires a vacuum degree of 110-5mmHg, and the vacuum degree of the selected vacuum pump must be at least 510-6mmHg. Usually the vacuum degree of the pump is selected to be half to one order of magnitude higher than the vacuum degree of the vacuum equipment.
2. Correctly select the working point of the vacuum pump. Each type of pump has a certain working pressure range, such as 10-3~10-7mmHg for a diffusion pump. Within such a wide pressure range, the pumping speed of the pump changes with the pressure, and its stable working pressure range is 510-4 ~510-6mmHg. Therefore, the working point of the pump should be selected within this range and cannot be allowed to work under 10-8mmHg for a long time. Another example is that the titanium sublimation pump can work at 10-2mmHg, but its working pressure should be less than 110-5mmHg.
3. The vacuum pump should be able to discharge all the gas generated during the vacuum equipment process under its working pressure. 4. Correctly combine the vacuum pump. Since vacuum pumps have selective pumping capabilities, sometimes one type of pump cannot meet the pumping requirements, and several pumps need to be combined to complement each other to meet the pumping requirements. For example, a titanium sublimation pump has a high pumping speed for hydrogen but cannot pump helium, while a tripole sputtering ion pump (or a diode asymmetric cathode sputtering ion pump) has a certain pumping speed for argon. Combined, the vacuum device will obtain a better vacuum degree. In addition, some vacuum pumps cannot work under atmospheric pressure and require pre-vacuum; some vacuum pumps have outlet pressures lower than atmospheric pressure and require a backing pump, so the pumps need to be combined.
5. Requirements for oil pollution in vacuum equipment. If the equipment strictly requires oil-free, various oil-free pumps should be selected, such as: water ring pumps, molecular sieve adsorption pumps, sputtering ion pumps, cryogenic pumps, etc. If the requirements are not strict, you can choose to have an oil pump and add some anti-oil pollution measures, such as adding cold traps, baffles, oil traps, etc., to achieve clean vacuum requirements.
6. Understand the composition of the pumped gas, whether it contains condensable vapor, whether there is particulate dust, whether it is corrosive, etc. When selecting a vacuum pump, you need to know the gas composition and select the corresponding pump for the gas to be pumped. If the gas contains vapor, particles, and corrosive gases, you should consider installing auxiliary equipment, such as condensers, dust collectors, etc., on the air inlet pipeline of the pump.
7. What is the impact of the oil vapor discharged from the vacuum pump on the environment? If the environment does not allow pollution, you can choose an oil-free vacuum pump or discharge the oil vapor outdoors.
8. Does the vibration generated by the vacuum pump during operation have any impact on the process and the environment? If the process does not allow it, a vibration-free pump should be selected or anti-vibration measures should be taken.
9. The price, operation and maintenance costs of vacuum pumps.