Because the compression ratio of vacuum pump is very limited. This compression ratio determines the capacity of the front pump, because the compression ratio is the inverse ratio of the pumping speed. Generally, the compression ratio is chosen in the range of 2 to 10. In addition, consideration should be given to the requirement of pre-sampling time. Vacuum equipment is used as auxiliary equipment in various mechanical equipment. If the normal working time is much longer than the pre-pumping time, a smaller front pump (compression ratio can be larger), if the vacuum suffocation is larger. Moreover, it is required to pre-pump quickly, using a larger front-stage pump.
Sometimes in order to better play the efficiency of the equipment, the unit is equipped with a larger pre-pumping pump in front, which is stopped after normal operation, and maintained with a smaller pre-pumping, so as to save power. The limit pressure requirement of Roots vacuum pump unit must also be considered when choosing the front stage pump. For the high limit vacuum (1 *10-3 pa~1 *10-2 Pa pressure), two-stage rotary vane oil seal mechanical pump or two-stage sliding mechanical pump are generally selected as the front stage pump.
The limit vacuum degree requires that a single-stage oil seal mechanical pump be selected as the front pump between (1*10-2Pa~1*10-1Pa) and a reciprocating vacuum pump or a liquid ring vacuum pump be selected as the front pump between 133 and 1333 PA. In order to obtain a high pumping rate at low inlet pressure (1-100pa), a Roots vacuum pump can be used as the first stage pump of another Roots vacuum pump to form a three-stage or four-stage unit. At this time, the pumping speed ratio of Roots vacuum pump is generally between 2 and 5.
Dry-Pump-Fertilizer-Industry
Vacuum-Pump-in-Vacuum-Die-Casting
Vacuum-Pump-in-Industrial-Waste-Gas-Treatment
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