How to choose Roots Vacuum Unit and the problems to be noticed? How to choose a good Roots Vacuum Unit?
The selection of pumping speed ratio between Roots pump and front pump is very important to the vacuum unit of Roots pump. Because the compression ratio of pineapple pump is very limited. The compression ratio determines the capacity of the front pump, because the compression ratio is the inverse ratio of the pump speed. Usually, the compression ratio is between 2 and 10. In addition, the requirement of pre-sampling time should also be considered. Vacuum equipment is an auxiliary equipment in various mechanical equipment. If the normal working time is much longer than the pre-pumping time, you can choose a smaller pre-pump (compression ratio can be larger), if the vacuum suffocation is larger, and requires rapid pre-pumping, then use a larger pre-pump.
The limit pressure requirement of Roots vacuum pump unit must also be considered when selecting the front pump. For high limit vacuum (1*10-3pa~1*10-2pa pressure), two-stage rotary vane oil seal mechanical pump or two-stage sliding mechanical pump are usually used in front pump. The limit vacuum degree requires that the front pump between (1*10-2pa~1*10-1pa) and (1*10-2pa~1*10-1pa) should be single-stage oil seal mechanical pump, and the front pump between 133-1333 PA should be reciprocating vacuum pump or liquid ring vacuum pump.
When the front pump of Roots vacuum pump chooses reciprocating or liquid ring rough vacuum pump, the speed of the front pump is generally 1/2-1/4 of the speed of Roots vacuum pump, which can not be too large, otherwise, the compression ratio is too large, resulting in high exhaust temperature of Roots vacuum pump and can not work normally. Y. When choosing the front pump, we should also consider whether there is corrosive medium in the pumping gas, whether there is condensable gas, size. If there is corrosive gas, oil seal mechanical pump can not be selected. Oil seal mechanical pumps are not suitable for extracting gases containing large amounts of condensable steam. Otherwise, the sealing fluid will be rapidly emulsified. When extracting gas containing a small amount of condensable steam, oil seal mechanical pump with gas ballast device must also be used as the front pump.
In order to obtain higher pumping speed under lower inlet pressure (1-100pa), 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.
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