During decarburization procedures the vacuum system needs to operate very long time in a rough pressure range. A competent gas-cooling is essential as the extracted hot gases would otherwise overheat the filter and vacuum system.
With the development of technology and the improvement of item quality in aerospace, energy, iron and steel digesting, pharmaceutical and chemical industries, these industries need to obtain a particular vacuum environment. Simultaneously, the vacuum system used by these industries can be continuously raising, and the vacuum degree is continuously increasing. Moreover, the state’s environmental Gas-Cooling Roots Pump protection, energy saving and three wastes discharge to the above-mentioned industries, etc. The requirements are more stringent. At present, the prevailing dry vacuum pumps on the market, such as for example screw vacuum pumps and claw vacuum pumps, cannot meet up with the requirements of oil-free large 
pumping velocity clean vacuum environment proposed by these industries due to the restrictions of pumping speed characteristics and structural system.
Because of the shortcomings of the prevailing technology, the technical problem to be solved by the utility model is to provide an all-gas-cooled vacuum system to satisfy the utilization in a clean vacuum environment with large oil-free pumping speed.