Roots blower is a kind of compressed machine formed by two same rotors, the rotor axis is parallel to each other, there is small gap between the impellers of the rotor, the impeller and casing, impeller and wallboard, thus avoiding contacting with each other. The formed air intake cavity and exhaust cavity  are isolated from each other,  they reversely rotate with the help of two rotors to send the air inside the air intake to the exhaust cavity, thus reaching the air blasting effect. Due to the very small clearance between impellers, the impeller and casing, the impeller and panels, it is not necessary to fill the lubricant to the cylinder, and the auxiliary equipment for the oil and gas separator auxiliary is not needed either. Because there is no mechanical friction between the rotors, the advantages are higher mechanical efficiency, less overall heating and longer service life etc. Roots blower is more sophisticated equipment, during routine maintenance, pay attention to the cleaning and replacement of the inlet filter and the clean and smooth indoor air, and the lubrication shall be guaranteed. Roots blower is a positive displacement blower, it air quantity increases/decreases along with the increase and decrease of the rotating speed. The air pressure is associated with electric current, namely the flow rate is less affected by the back pressure. The refeed valve is just using this feature of Roots blower to realize the constant flow control to the air from loop-seal . During operating, pay attention to that the exhaust pressure of the fan is below the sign value, so as not to damage the internal pressure parts.