RTO series inner watercooling Roots vacuum pumps and RTO/W series aircooling Roots vacuum pumps with overloading protection are the newest products. There are many features and advantages in RTO and RTO/W series, such as the combining cooling structure, the overloading protection, the controlling of gaps between rotor and rotor, rotors and pump chambers, the advantage in maintaining, the high pumping efficiency, the smoothly and quietly running, the low temperature rising, etc. RTO and RTO/W series Roots vacuum pump are used widely in various areas of vacuum engineering. They extend the operating range of fore vacuum pumps, such as rotary vane pumps, rotary piston pumps and water-ring pumps, down to lower pressures. It is of large pumping speed in the range of 1-100 Pa's intake pressure and suitable for the vacuum systems that need to gain large pumping speed in the lower intake pressure, such as for vacuum drying and impregnation in electric transformer, electric capacitor and electric mutual inductance, for vacuum degassing in vacuum heat treatment and vacuum smelting, for vacuum predischarging in vacuum coating equipment, for gas exhausting in low pressure wind tunnel and the fluorescent lamp line. By suitable selection of the forepumps, it is also suitable for the processes in vacuum distillation, vacuum concentration and vacuum drying in chemical industry, pharmacy, food and beverage, light industry and textile industry.