single and double stage rotary vane vacuum pumps difference between
For laymen, there is no concept about single-stage rotary vane vacuum pump and double-stage rotary vane vacuum pump, and they don't understand the difference between them. The following is the difference that the vacuum pump factory will tell you:
The two-stage vane vacuum pump is based on the single-stage vane vacuum for secondary exhaust. The structure of the two stages is basically the same. The exhaust port of the first stage is connected with the air inlet of the second stage, which is discharged after secondary compression.
There are some differences between the front stage pump and the back stage pump. The pump cavity of the back stage pump is larger than that of the front stage pump, because the pumping speed of the pump is mainly determined by the effective geometric volume of the back stage pump. In addition, like the single-stage rotary vane vacuum pump, the front stage pump has oil entering the pump chamber at any time; the rear stage pump only has a small amount of oil at the beginning of operation, and after a period of operation, there is no oil entering the pump chamber, because there is no special oil circuit in the rear stage. This will not affect the performance of the rear stage pump, because the pressure at the inlet of the rear stage pump will decrease greatly with the increase of the pumping time, and the pressure difference between the inlet and outlet is small. The amount of backflow in the gap of the compressed gas stage is small. At the same time, the flow resistance in the gap is large under the condition of high vacuum degree. Although there is no oil seal, the amount of backflow is also small.
On the contrary, it has the following advantages: it can prevent the pump oil from bringing gas and steam into the inlet of the rear stage, thus greatly reducing the partial pressure of the residual gas; at the same time, because the light fraction of the oil in the rear stage pump is continuously pumped away by the front stage pump, the partial pressure of the residual oil vapor is also reduced, which improves the limit vacuum of the pump. The gas partial pressure is also reduced, and the limiting vacuum of this generation of pumps is improved.