Roots Vacuum Pump for Vacuum Drying Equipment
The selection of Roots vacuum pump of main pump mainly considers its pumping speed. Because VPD equipment does not require very strict pumping time to achieve working vacuum, the selection range of pumping speed of main pump is very wide. Generally, it can be estimated and pre-selected according to the rated pumping speed (L/s) of the main pump as about 1% of the volume of the vacuum tank (L).
Because the requirements of cold limit vacuum (1Pa) and final working vacuum (10Pa) of vacuum tank are not high, it is possible to use Roots vacuum pump to distribute the vacuum system of the front stage pump. However, in recent years, VPD equipment has adopted more two-stage Roots pump vacuum system, that is, to install an intermediate stage between the main stage Roots pump and the front stage pump. Roots pump is designed to further shorten the pumping time, improve the working vacuum and reduce the performance requirements of the main pump.
The pumping speed ratio of the primary and intermediate Roots pumps is in the range of (2:1) ~ (4:1). It can be handled according to the pumping law of the general vacuum system. The Roots pump used in VPD equipment is characterized by a small amount of kerosene vapor in the pumped gas and high temperature. When selecting pumps, it should be noted that the manufacturer should give special consideration to the determination of the rotor clearance of Roots pumps and the selection of sealing materials in pumps. In addition, Roots vacuum pump with bypass valve is usually selected.