2XZ-1 type pump is equipped with gas-ballast valve. Its function is to fill the exhaust space with certain amount of air , when the valve is open , so to reduce the proportion of the partial pressure of vapor in the total discharge pressure .

As the partial pressure of vapor is lower than that of the saturated vapor pressure corresponding to the working temperature of the pump, vapor can be discharged from the pump with the filled air in order to avoid condensation of vapor in the pump oil and to prevent oil from emulsifying by the condensed vapor so as to prolong the useful lift of oil . However the ultimate vacuum of the pump shall drop , and the temperature of the pump shall rise when the gas-ballast valve is open .

2XZ-1 type pump has the outstanding achievements of small size, less weigh , quiet operation and easy to start . Besides devices to prevent from sucking back of oil and leakage of oil from axle sealing to contaminate environment are also provided.