When we are buying vacuum pump, we should consider the following issues, and the issues are listed as follow.

1, the working pressure of vacuum pump should meet the request of maximum vacuum and working pressure of vacuum device, for example, the vacuum coating should has 1x 5mm Hg of vacuum, so when we are choosing vacuum pump, we should choose those whose vacuum is at least 5¡Á10-6mmHg. Generally, the vacuum of choosing vacuum pump should be higher than vacuum device.

2, select the right working place for vacuum pump, every vacuum pump has a range of working pressure, for example, diffusion pump whose working pressure is between 10-3 and 10-7mmHg.

3, when vacuum pump is working under its working pressure, we should discharge all gas which is produced at the process of technology.

4, combine the vacuum pump correctly, because vacuum pump exhausts selectively, so we should combine different pumps, and make them make up for each other¡¯s shortcoming.

5, vacuum device has request about oil pollution, when the device asks for working without oil, we should choose all kinds of pumps which works without oil.

6, we should know the ingredient of gas which is exhausted from vacuum pump, if gas contains vapor and corrosive gas, we should consider installing aided device at the pipe of pump, such as condenser, dust collector.

7, the influence of oil vapor which is exhausted from technology upon environment. If the environment do not allow pollution, we can choose vacuum pump which works without oil.

8, we should know whether vibration which is produced when vacuum pump is working has influence upon technology process or not. If the technology process doesn¡¯t allow it, we should choose pump which has no vibration when it is working, or we can take steps to prevent vibration.

9, the price of vacuum pump and its maintenance.