Ordinary mechanical vacuum pumps can pump to one percent vacuum. Oil diffusion pumps can pump up to one ten thousandth or one hundred thousandth, and molecular pumps are even higher.
Low-pressure vacuum pumps:
Water ring vacuum pump 2000~4000pa
Rotary vane vacuum pump 101325~1.33×10-2 (pa)
1, water ring vacuum pump
Water ring vacuum pump (water ring pump for short) is a kind of rough vacuum pump, which can get the ultimate vacuum 2000~4000pa. 4000pa, tandem atmospheric ejector up to 270~670pa. water ring pump can also be used as
compressor
known as water ring compressor, is a low-pressure compressor, the pressure range of 1~2×105pa gauge pressure.
2, rotary vane vacuum pump (referred to as rotary vane pump) is an oil-sealed mechanical vacuum pump.
Its working pressure range is 101325~1.33×10-2 (pa) belongs to low vacuum pump. It can be used alone or as a pre-stage pump for other high vacuum pumps or ultra-high vacuum pumps. Rotary vane pumps are mostly small and medium-sized pumps. There are two kinds of rotary vane pumps: single-stage and double-stage. The so-called double-stage, is in the structure of the two single-stage pumps in series. Generally, it is made into double-stage to get higher vacuum.