Matters needing attention of gas ballast valve

When the mechanical pump starts to work, open the air ballast valve, and an air flow will enter the compression chamber of the pump through the air ballast hole. The air flow is controlled by the adjusting screw of the gas ballast valve. During the compression process, the air flow will be mixed with the pumped steam to form a mixture of steam and air. At normal pump temperature, when the mixture is compressed to the exhaust pressure, the partial pressure of steam will not exceed the saturated vapor pressure, so the steam will not condense and will be discharged out of the pump with the air.

In the process of pumping, although the gas ballast valve is opened, the purpose of removing steam is achieved, but air will leak into the suction end of the pump, which will affect the pumping speed and the limit vacuum of the pump and reduce the limit vacuum of the pump. Therefore, when using a vacuum pump with a gas ballast valve, first open the gas ballast valve to remove condensable gas, and then close the gas ballast valve after pumping. To reach the original limit vacuum degree of the pump, it takes some time to pump out the air.

The mechanical pump equipped with the second gas ballast device can not only extract condensable gas, but also purify the pump oil. If the pump oil is polluted by a small amount of condensate, as long as the air inlet of the pump is blocked, and then the gas ballast valve is opened, after a certain period of pumping, the original performance of the pump oil can be restored.