H Series Rotary Piston Vacuum Pumps is a sort of vacuum production equipment suitable for pumping ordinary gases and a little condensable gases (for example, water vapour) with a gas ballast used. The pump must be fitted with appropriate accessories if gas is rich in oxygen, explosive, corrosive to ferrous metal, chemical reactive with vacuum pump oil. The pump can be operated singly. It also can be as a backing pump when combined with another high vacuum pump, such as diffusion pump, oil booter vacuum pump and roots vacuum pump. Series rotary piston vacuum pump can be used for a longer time than the sliding vane rotary vacuum pump. It is widely used in vacuum coating, vacuum heat treatment, vacuum sintering, molecule distilling and space simulation testing in astronomy etc.