From the perspective of the production of Roots pumps abroad, several large foreign companies, such as Leybold, Balzers, Alcatell, Edwards and ULVAC, their sales of Roots pumps accounted for less than 5% of the global sales of Roots pumps. The total of these 5 are only 20%, the output of Roots pump is not large, but the price of the working principle of the Roots pump Roots pump is much higher than that of the domestic pump. Almost all large and small high-vacuum and medium-vacuum systems at home and abroad are equipped with Roots pumps in order to shorten the pumping time and improve production efficiency. Therefore, the domestic Roots pump must try to enter the international market on the basis of occupying the domestic market. It is necessary to further reduce the vibration and noise of the domestic Roots pump, completely solve the problem of shaft seal oil leakage, improve the appearance quality of the pump, and improve the smoothness and cleanliness of the pump. In addition, it is necessary to consider that the power frequency of some countries and regions is 60Hz, and it is necessary to ensure the reliability of the long-term operation of the Roots pump under the condition of increasing the speed.
Domestic air-cooled direct-flow atmospheric Roots pumps are progressing rapidly and are technically mature. Since the pump is equipped with a gas cooler below the exhaust port, and a part of the cooled gas is returned to the pump chamber through the pipe to cool the rotor, so that the heat of compression is balanced, the pump can be directly exhausted to the atmosphere. In order to meet the requirements of different ultimate vacuum, the pumps can be used in series. Generally, an air-cooled straight-flow atmospheric Roots pump is added in front, and the ultimate vacuum achieved is one order of magnitude higher than that of the foreline pump. This type of pump is actually a dry pump because there is no working medium in the pump chamber. This air-cooled direct-flow atmospheric Roots pump and unit has been tested in the long-term operation of petroleum, chemical, plastics, pesticides, turbine rotor dynamic balance, aerospace space simulation and other devices, so it should be widely promoted and applied in China.