Rotary vane vacuum pump oil return solution
When the rotary vane vacuum pump is stopped, if there is an oil hole connected with the pump cavity or the exhaust valve, shaft seal, pump cover plane, intake pipe, gas ballast valve and other sealing are not tight, due to the existence of liquid level difference and gravity, and the pressure difference between the oil tank and the pump cavity when the pump cavity is in vacuum, the oil will return to the pump cavity, and when the oil volume is large enough, the oil will return to the air inlet pipe, As a result, the resistance of the next start-up is large, the force on the rotor and rotor is large, the force on the exhaust valve is large, the starting difficulty is affected, the service life of the parts is affected, and the reliability of the pump is reduced. Therefore, we should try to prevent oil return after stopping the pump. The principle is to cut off the oil circuit when the rotary vane vacuum pump is stopped, eliminate the negative pressure in the pump chamber, reduce the liquid level difference and reduce the amount of oil returned.
Common solutions are:
1. Separate the oil near the exhaust valve from the rest, and the oil level is only slightly higher than the partition wall.
2. Move the oil tank and exhaust valve to the side to reduce the oil level and oil quantity.
3. The plane of the valve seat should be flat, and the valve plate should be elastic.
4. The static sealing parts of shaft seal shall be reliable and timely replaced.
5. Add a pipe into the oil hole to make the oil level only slightly higher than the oil inlet.
6. A check valve mechanism is set to automatically close the oil inlet hole when the pump is stopped.
7. The oil pump and auxiliary mechanism are set to cut off the oil circuit when the pump is stopped.
8. The pump port is equipped with a charging valve.
9. Fill the inlet container.
With the structure of check valve, dynamic seal and static seal, even if the pump is not inflated due to sudden power failure, the pump chamber can be kept in vacuum for a long time without significant oil return. But its reliability is affected by the quality of manufacture, assembly, oil seal, exhaust valve and other static seals. If an inlet container is installed, even if the oil return is limited to the container, it is more reliable.
The check valve has the function of controlling the oil quantity. For example, the oil hole is opened only about a quarter of the time per revolution. If there is too much oil, the noise will be bigger. Because of the gas in the oil, the limit full pressure may also decrease. It is difficult to process the small oil hole, and the check valve can overcome this difficulty. In addition, in case the check valve parts are damaged, the rotary vane vacuum pump can still be used after the check valve stem is removed. However, it is necessary to inflate the pump immediately after stopping the pump to prevent oil return. Therefore, timely maintenance should be carried out. For important purposes, vent valve or cut-off valve can be installed.
Users can choose corresponding solutions according to different situations.