The Roots pump mainly consists of a pair of synchronous high-speed rotating "8" shaped rotors and two semi circular pump cavities. This pump cannot exhaust independently and must be used in series with the front stage pumps (such as slide valve pumps, rotary vane pumps, water ring pumps, oil ring pumps, etc.). Connecting a Roots vacuum pump in series in front of the inlet of the front stage pump can improve the vacuum degree of the front stage pump and greatly increase the pumping rate within an effective range. The limit pressure of the Roots vacuum pump is determined by the front stage pump, and the data in the table is the minimum limit pressure for the standard configuration (equipped with a dual stage oil seal mechanical vacuum pump). Roots pumps are widely used in vacuum casting, vacuum melting, vacuum degassing, vacuum coating industry, Vacuum distillation and vacuum drying in chemical and pharmaceutical industries. The pump is not sensitive to small amounts of dust.