The saturated vapor pressure of vacuum pump oil is one of the key indexes of saturated vapor pressure. In a closed vessel at constant temperature, the pressure of vapor pressure reaches the dynamic equilibrium of saturated vapor liquid. The saturated steam pressure oil shall be as low as possible, and the operating temperature of the pump shall still have enough low saturated steam pressure, which shall be lower than the limit pressure of the vacuum pump. A temperature of 60 ° C is at least 6.5 x kPa pure (saturation vapor pressure will drop by an order of magnitude due to an increase of 20 ° C). But how do we change oil for vacuum pump in daily life. Let’s share the methods and skills of vacuum pump oil replacement.
Replacement method of vacuum pump oil：
(1) Gravity method: put the container under the drain port, loosen the drain screw, and then let the old oil in the vacuum pump flow into the container automatically. After draining the old oil, pour a small amount of clean vacuum pump oil (100-500ml) from the oil suction port, wash the vacuum pump cavity, start the vacuum pump for about 1 minute, and then close the vacuum pump to drain the injected new oil. If the released oil still fails to work properly, continue to inject new miscellaneous oil and flush until it is clean. Then, screw on the drain screw. Loosen the screw on the oil filling hole, add vacuum pump oil to the vacuum pump to make the oil level reach the oil level, and then screw on the oil filling screw.
(2) Pressure method place the container under the oil drain port, and then unscrew the oil drain screw. Close the suction port and turn on the vacuum pump at the same time. Open the air ballast valve and cover the exhaust port of the vacuum pump to generate enough internal pressure to quickly discharge the dirty oil. Then, flush the interior of the vacuum pump chamber according to method (1) and replace with new oil.
Pay attention to the precautions for changing the vacuum pump oil:
(1) Pay attention to cleaning and prevent dust from entering the vacuum pump.
(2) The time to start the vacuum pump should not be too long, so as to avoid too dry and fatigue of the exhaust valve blades,
（3） Do not use neutral oil, gasoline, alcohol and other non removable Shanghai vacuum pump.
(4) Change the oil after the oil temperature rises in order to drain the internal oil from the vacuum pump.