During decarburization procedures the vacuum system must operate long time in a tough pressure range. An efficient gas-cooling is necessary as the extracted hot gases would or else overheat the filter and vacuum system.
With the development of technology and the improvement of product quality in aerospace, electric power, iron and steel digesting, pharmaceutical and chemical industries, these industries have to obtain a specific vacuum environment. At the same time, the vacuum system utilized by these industries can be continuously raising, and the vacuum level is continuously increasing. Moreover, the state’s environmental safety, energy conservation and three wastes discharge to the above-stated industries, etc. 
Certain requirements are more stringent. At present, the existing dry vacuum pumps out there, such as for example screw vacuum pumps and claw vacuum pumps, are Gas-Cooling Roots Pump unable to meet up with the requirements of oil-totally free large pumping speed clean vacuum environment proposed by these industries because of the restrictions of pumping rate characteristics and structural system.
Because of the shortcomings of the prevailing technology, the specialized problem to be solved by the utility model is to provide an all-gas-cooled vacuum system to satisfy the use in a clean vacuum environment with huge oil-free pumping speed.