How to reduce the oil return rate of vacuum unit?

During the operation of the vacuum unit, the oil vapor will migrate to the pumped container and the vacuum side of the previous stage (i.e. oil return phenomenon), resulting in high pressure and affecting the operation efficiency of the unit. So how to reduce the oil return rate?

In order to prevent the oil vapor from migrating to the pumped system, a water-cooled oil baffle cap is installed above the nozzle of the vacuum unit. The role of the oil baffle cap is to cut off the steam flow line, so that the edge line of the flow line falls on the water-cooled wall of the pump housing, ensuring that the upward migrating steam can be completely condensed. Practice has proved that the oil return rate of the pumped system can be reduced by about 95% when the pump works with an oil retaining cap.

This kind of oil baffle cap is only effective within the working pressure range of the pump. When the inlet pressure is high, the steam flow from the nozzle is destroyed by the air flow, and the steam begins to flow back to the pumped system. Therefore, during the operation of the vacuum unit, the pressure of the pumped system must not exceed the working pressure range of the pump.

During normal operation, since the oil baffle at the inlet of the pump and the condenser at the outlet work, the migration of pump oil is not obvious, so the oil return rate of the pump is usually independent of the continuous working time of the pump. Generally, this kind of oil baffle cap can reduce the pumping speed of the pump by 5% – 10%. In addition, a water-cooled disc condenser (consisting of some perforated and non perforated disc-shaped copper plates) can be installed behind the jet stage nozzle of the pump, which can also reduce the oil return rate of the vacuum unit.