In the production process, a vacuum pump can be selected reasonably based on the specific working pressure required by the process and the properties of the gas being pumped. Generally, the specific working pressure required by the process is determined first. Processes such as negative pressure distillation, distillation, sublimation require high vacuum degree (low working pressure), while processes such as negative pressure evaporation, drying, concentration, crystallization, dehydration, decolorization, chemical reaction absorption, and vacuum conveying require low vacuum degree (high working pressure). After determining the working pressure, a vacuum pump can be selected reasonably based on the size of the suction volume and the properties of the suction gas.

1. List the applicable ranges of various vacuum pumps based on the working pressures they can achieve.

2. Extract different gases and select different jet vacuum pumps

(1) The water jet vacuum pump is suitable for situations where the working pressure is greater than 25mmHg (3.3KPa) and various gases are suctioned, especially when suctioning condensable gases (i.e. gases that condense in water or when cooled), dust, and granular media. Its advantages are more prominent. When the working pressure requirement is relatively small and the amount of non condensable gas to be extracted is large, steam jet pumps and steam water series or steam water combination jet vacuum pumps should be selected.

(2) The working pressure of the steam water series jet vacuum pump can reach 2mmhg (267Pa), but it has a smaller pumping capacity than the new steam jet vacuum pump, steam water combination jet vacuum pump, and multi-stage steam jet vacuum pump, making it suitable for intermittent production in small and medium-sized enterprises.

(3) The working pressure of the new steam jet vacuum pump can reach 0.5mmHg (65Pa), which is suitable for processes where most of the gas being pumped is condensable and the proportion of non condensable gas is relatively small.

(4) The working pressure of the steam water combination jet vacuum pump and the multi-stage steam jet vacuum pump can reach up to 10 Pa, and they can suck various gases. The difference between them is that the steam water combination jet vacuum pump saves working steam consumption and operating costs compared to the multi-stage steam jet vacuum pump.