Rotary piston vacuum pump is suitable for pumping air and other ordinary gases, when a gas ballast valve is used it can also pumpcondensable gases. The pump must be filted with appropriate accessories if gas is rich in oxygen, explosive, corosive to ferrous metalchemical reactive with vacuum pump oil. The HGL, HG pump can be operated singly or as a backing pump combined with other higfvacuum pump, such as difusion pump and oil booster pump. lt is widely used in the industry of vacwum coating, vacuum heattreatment, vacuum impregnation, vacuum smelting, vacuum drying, molecular distilation and alitude simulation testing.