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 valve and other seals are not tight, due to the existence of the liquid level difference and gravity, as well as the pressure difference between the oil tank and the pump cavity when the pump cavity is in a vacuum state, the oil will return to the pump cavity. When the oil volume is large enough, the oil will return to the air inlet pipe, causing resistance during the next start-up It is difficult to start because of the large force on the rotor and rotor, the large force on the exhaust valve, which affects the service life of the parts and reduces the reliability of the pump. Therefore, measures should be taken to prevent oil return from stopping the pump. The principle is to cut off the oil circuit when the pump is stopped, eliminate the negative pressure in the pump cavity, reduce the liquid level difference and reduce the amount of oil returned.
Solution to prevent oil return when rotary vane vacuum pump stops
Common solutions for oil return of rotary vane vacuum pump:
1. Separate the oil near the exhaust valve from other oil, 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 volume.
3. The plane of valve seat shall be flat, and the valve plate shall be elastic.
4. The static sealing part of shaft seal shall be reliable and replaced timely.
5. Add a pipe into the oil hole so that the oil level is only slightly higher than the oil inlet.
6. Set check valve mechanism to automatically close the oil inlet when the pump is stopped.
7. Set oil pump and auxiliary mechanism, and cut off the oil circuit when the pump stops.
8. The pump port is equipped with a charging valve.
9. Install the inlet container.
With the structure of check valve, dynamic seal and static seal, the pump cavity can be kept in a vacuum state for a long time even in case of sudden power failure without filling the pump. But its reliability is affected by the quality of manufacture, assembly, oil seal, exhaust valve and other static seals. If an inlet container is added, even if oil return occurs, it is only limited to the container, which is more reliable.
Check valve has the function of controlling the oil flow. For example, only about a quarter of the time each revolution opens the oil hole. If the oil volume is too much and the noise is larger, the ultimate full pressure may also decrease due to the gas content in the oil. It is difficult to machine the small oil hole, and the check valve can overcome this difficulty. In addition, in case of damage to the parts of the check valve, the pump can still be used after removing the check valve rod. However, after the pump is stopped, it is necessary to inflate the pump immediately to prevent oil return. Therefore, timely maintenance is required. For important purposes, a vent valve or a stop band vent valve can be added.
Users can choose corresponding solutions according to different situations. Through the above methods, we still can’t solve the oil return problem of rotary vane vacuum pump. Please contact us at any time, and we will solve your problem in the first time.contact@evpvacuum.com
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