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Precautions when selecting a vacuum pump: 1. The operating pressure of the vacuum pump should meet the requirements regarding the ultimate vacuum and operating pressure of the vacuum equipment. For example, vacuum coating requires a vacuum level of 1×10-5 mmHg; therefore, the vacuum pump used must have a vacuum level of at least 5×10-6 mmHg. Typically, the vacuum level of the pump should be half to an order of magnitude higher than that of the vacuum equipment. 2. Select the operating point of the vacuum pump correctly. Each type of pump has a certain operating pressure range; for example, the diffusion pump operates in the range of 10-3 to 10-7 mmHg. Within such a wide pressure range, the pumping speed of the pump changes with pressure, while its stable operating pressure range is 5×10-4 to 5×10-6 mmHg. Therefore, the operating point of the pump should be selected within this range, and it should not be allowed to operate at 10-8 mmHg for an extended period of time. For example, a titanium sublimation pump can operate at 10-2 mmHg, but it is preferable for its operating pressure to be less than 1×10-5 mmHg. 3. At its operating pressure, the vacuum pump should be capable of removing all the gas generated during the process in the vacuum equipment. 4. Combine the vacuum pump correctly. Since vacuum pumps have selective pumping capabilities, sometimes a single pump is not sufficient to meet the pumping requirements; it is necessary to use several pumps in combination, so that they can complement each other to fulfill those requirements. For example, a titanium sublimation pump has a high pumping speed for hydrogen but cannot pump helium, while a triode-type sputter ion pump (or a diode-type asymmetric cathode sputter ion pump) has a certain pumping speed for argon. By combining the two, a better vacuum level can be achieved in the vacuum system. Additionally, some vacuum pumps cannot operate at atmospheric pressure and require pre-evacuation ； Some vacuum pumps have an outlet pressure lower than atmospheric pressure, requiring a pre-pump; therefore, these pumps need to be used in combination. 5. Requirements of vacuum equipment regarding oil contamination. If the equipment requires absolutely oil-free operation, various oil-free pumps should be selected, such as water ring pumps, molecular sieve adsorption pumps, sputter ion pumps, cryopumps, etc. If the requirements are not strict, a model with an oil pump can be chosen, along with various oil pollution prevention measures such as cold traps, baffles, and oil traps, to meet the requirements for a clean vacuum environment. 6. Understand the composition of the gas being sampled, whether it contains condensable vapors, particulate dust, or corrosive substances. When selecting a vacuum pump, it is necessary to know the gas composition and choose an appropriate pump for the gas to be evacuated. If the gas contains vapors, particles, and corrosive gases, it is advisable to consider installing auxiliary equipment such as condensers and dust collectors on the pump’s inlet pipeline. 7. What is the impact of the oil vapor emitted by vacuum pumps on the environment? If the environment does not permit pollution, an oil-free vacuum pump can be used, or the oil vapors can be vented outside. 8. Does the vibration generated by the vacuum pump during operation have an impact on the manufacturing process and the surrounding environment? If the process does not permit it, a vibration-free pump should be selected or vibration prevention measures should be taken. 9. The price of the vacuum pump, as well as the costs associated with its operation and maintenance. 1. The operating pressure of the vacuum pump should meet the requirements for ultimate vacuum and operating pressure of the vacuum equipment. For example, vacuum coating requires a vacuum level of 1×10-5 mmHg; therefore, the vacuum pump used must have a vacuum level of at least 5×10-6 mmHg. Typically, the vacuum level of the pump should be half to an order of magnitude higher than that of the vacuum equipment. 2. Select the operating point of the vacuum pump correctly. Each type of pump has a certain operating pressure range; for example, the diffusion pump operates in the range of 10-3 to 10-7 mmHg. Within such a wide pressure range, the pumping speed of the pump changes with pressure, while its stable operating pressure range is 5×10-4 to 5×10-6 mmHg. Therefore, the operating point of the pump should be selected within this range, and it should not be allowed to operate at 10-8 mmHg for an extended period of time. For example, a titanium sublimation pump can operate at 10-2 mmHg, but it is preferable for its operating pressure to be less than 1×10-5 mmHg. 3. At its operating pressure, the vacuum pump should be capable of removing all the gas generated during the process in the vacuum equipment. 4. Combine the vacuum pump correctly. Since vacuum pumps have selective pumping capabilities, sometimes a single pump is not sufficient to meet the pumping requirements; it is necessary to use several pumps in combination, so that they can complement each other to fulfill those requirements. For example, a titanium sublimation pump has a high pumping speed for hydrogen but cannot pump helium, while a triode-type sputter ion pump (or a diode-type asymmetric cathode sputter ion pump) has a certain pumping speed for argon. By combining the two, a better vacuum level can be achieved in the vacuum system. Additionally, some vacuum pumps cannot operate at atmospheric pressure and require pre-evacuation ； Some vacuum pumps have an outlet pressure lower than atmospheric pressure, requiring a pre-pump; therefore, these pumps need to be used in combination. 5. Requirements of vacuum equipment regarding oil contamination. If the equipment requires absolutely oil-free operation, various oil-free pumps should be selected, such as water ring pumps, molecular sieve adsorption pumps, sputter ion pumps, cryopumps, etc. If the requirements are not strict, a model with an oil pump can be chosen, along with various oil pollution prevention measures such as cold traps, baffles, and oil traps, to meet the requirements for a clean vacuum environment. 6. Understand the composition of the gas being sampled, whether it contains condensable vapors, particulate dust, or corrosive substances. When selecting a vacuum pump, it is necessary to know the gas composition and choose an appropriate pump for the gas to be evacuated. If the gas contains vapors, particles, and corrosive gases, it is advisable to consider installing auxiliary equipment such as condensers and dust collectors on the pump’s inlet pipeline. 7. What is the impact of the oil vapor emitted by vacuum pumps on the environment? If the environment does not permit pollution, an oil-free vacuum pump can be used, or the oil vapors can be vented outside. 8. Does the vibration generated by the vacuum pump during operation have an impact on the manufacturing process and the surrounding environment? If the process does not permit it, a vibration-free pump should be selected or vibration prevention measures should be taken. 9. The price of the vacuum pump, as well as the costs associated with its operation and maintenance.