vacuum unit

Common names for vacuum units
① Main pump: In a vacuum system, a vacuum pump used to obtain the required vacuum degree to meet specific process requirements, such as the oil diffusion pump in a vacuum coating machine.
② Pre stage pump: a vacuum pump used to maintain a pre stage pressure lower than its critical pre stage pressure. The rotary vane or slide valve pump configured before the Roots pump is the front stage pump.
③ Coarse vacuum pump: a vacuum pump that starts pumping air from atmospheric pressure and transfers the system pressure to another vacuum pump to start working. The slide valve pump in a vacuum coating machine is a crude oil pump.