为达到最佳配置，选择真空系统时，真空泵选型应考虑下述各点：
In order to achieve the best configuration, the following points should be considered when selecting the vacuum system:
1、真空泵的极限压力应该满足该工艺的工作压力。通常选择泵的极限压力低于工艺要求约一个数量级。
1. The limit pressure of vacuum pump should meet the working pressure of the process. Generally, the limit pressure of the pump is about one order of magnitude lower than the process requirements.
2、每种泵都有一定的工作压力范围，因而，泵的工作点应该选在这个范围之内，而不能让它在允许工作压力以外长时间工作。
2. Each kind of pump has a certain working pressure range, therefore, the working point of the pump should be selected within this range, and it should not be allowed to work at the allowable working pressure for a long time.
3、真空泵在其工作压力下，应能排走真空设备工艺过程中产生的全部气体量。
3. Under its working pressure, the vacuum pump should be able to discharge all the gas produced in the process of vacuum equipment.
4、选择真空机组：
4. Select vacuum unit:
(1) 当使用一种泵不能满足抽气及真空要求时，需要几种泵组合起来，互相补充才能满足工艺要求。
(1) When using one kind of pump can not meet the requirements of air pumping and vacuum, several kinds of pumps need to be combined to complement each other to meet the process requirements.
(2) 有的真空泵不能在大气压下工作，需要预真空；有的真空泵出口压力低于大气压，需要前级泵，故都需要把泵组合起来使用。经组合使用的真空泵，我们称之为真空泵机组，它能使真空系统得到较好的真空度及排气量。我们应正确地选择组合的真空泵，由于不同的真空泵对抽除的气体要求有不同的要求，例如：在一般情况下罗茨－旋片机组不适用于含有较多可凝性气体的系统。
(2) Some vacuum pumps can not work under atmospheric pressure, need pre vacuum; some vacuum pump outlet pressure is lower than atmospheric pressure, need the front pump, so need to combine the pump. The combined vacuum pump is called vacuum pump unit, which can make the vacuum system get better vacuum degree and exhaust volume. We should choose the combined vacuum pump correctly, because different vacuum pumps have different requirements for the gas to be removed. For example, in general, roots rotary vane unit is not suitable for the system with more condensable gas.