Relationship between the pumping speed of Roots pump and fore pump

The relationship between the pumping speed of the Roots pump and the pumping speed of the front pump mainly depends on the volumetric efficiency and the permissible pressure difference of the Roots pump. If the volumetric efficiency is low, the effective pumping speed of the Roots pump unit will drop significantly. If the pressure difference of the Roots pump exceeds the permissible pressure difference, the rotor will be overheated and expanded due to the compression work, and it will be stuck. Because the pump housing is easy to dissipate heat to the surrounding environment, it is still not too hot.

The permissible pressure difference range of the Roots pump is 40-100hPa. In the higher pressure range (150hPa), the permissible pressure difference is slightly higher because the amount of gas being pumped is more, which improves the cooling of the rotor. Due to the increase in pressure difference, the required power will inevitably increase.