Piston pumps are used for most large scale vacuum Rotary Piston Vacuum Pump china applications. These pumps possess a sliding sleeve through which the gas enters, then drawn into a cylindrical chamber and exhausted by a rocking piston plunger. These pumps are extremely hardy and also have pumping speeds that range from 15 cfm to 2,000 cfm and the pumps can reach a pressure of just one 1 x 10-4 Torr. Rotary piston pumps can be ready 
for corrosive and oxygen services.