The selection of vacuum pumps should be considered in many aspects. The first is the actual working conditions, the second is the environmental requirements, the third is the equipment performance, and the fourth is the vacuum pump parameters. Only when you have more information and focus on the selection, can you choose the vacuum pump that I use.
Pay attention to the following matters when selecting the vacuum pump 1. The working pressure of the vacuum pump should meet the ultimate vacuum and working pressure requirements of the vacuum equipment. For example, the vacuum coating requires a vacuum of 1×10-5 mmHg, and the vacuum of the vacuum pump selected must be at least 5×10-6 mmHg. The vacuum of the pump is usually chosen to be half an order of magnitude higher than the vacuum of the vacuum equipment.
2. Correctly select the working point of the vacuum pump. Each pump has a certain working pressure range, such as: diffusion pump is 10-3~10-7mmHg. In such a wide pressure range, the pumping speed of the pump varies with pressure, and its stable working pressure range is 5×10. -4~5×10-6mmHg. Therefore, the working point of the pump should be selected within this range, and it should not be allowed to work for a long time at 10-8mmHg. Another example is that the titanium sublimation pump can work at 10-2mmHg, but its working pressure should be less than 1×10-5mmHg.
3. Under the working pressure, the vacuum pump should be able to remove all the gas generated during the vacuum equipment process.
4. Combine the vacuum pump correctly. Since the vacuum pump has selective pumping, sometimes a 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 it cannot be pumped, and a three-pole sputter ion pump (or a two-pole asymmetric cathode sputtering ion pump) has a certain pumping speed for argon. When combined, the vacuum device will have a better vacuum. In addition, some vacuum pumps can't work under atmospheric pressure, and need pre-vacuum; some vacuum pump outlet pressure is lower than atmospheric pressure, and the foreline pump is needed, so it is necessary to combine the pumps.
5. Requirements for oil pollution from vacuum equipment. If the equipment is strictly required to be oil-free, you should choose various oil-free pumps, such as: water ring pump, molecular sieve adsorption pump, sputter ion pump, cryopump, etc. If the requirements are not strict, you can choose to have an oil pump, plus some oil pollution measures, such as adding cold traps, baffles, oil traps, etc., can also achieve clean vacuum requirements.
6. Understand the composition of the gas to be pumped. The gas contains no condensable vapor, no particle dust, and no corrosiveness. When selecting a vacuum pump, you need to know the gas composition and select the appropriate pump for the pumped gas. If the gas contains vapors, particulates, and corrosive gases, consider installing auxiliary equipment such as condensers, precipitators, etc. on the inlet piping of the pump.
7. How does the oil vapor from the vacuum pump affect the environment? If the environment does not allow contamination, you can choose an oil-free vacuum pump or discharge the oil vapor to the outside.
8. The vibration generated when the vacuum pump works has no effect on the process and environment. If the process does not allow, choose a vibration-free pump or take anti-vibration measures.
9. The price, operation and maintenance costs of the integrated vacuum pump.
The above nine suggestions are the key points we can't ignore. Vacuum pump learning must not be arbitrary, both professional and practical.