Excessive axial force in vacuum units can have a very adverse impact on usage, so understanding and solving this problem in advance can effectively alleviate axial force and extend service life.
1. The reason for axial force generation: The vacuum pump unit experiences uneven liquid pressure on both sides of the impeller, which is not completely symmetrical, due to unequal pressure at the suction and discharge ports, resulting in axial force. If the liquid pressure on both sides of the impeller is not taken into account the cross-sectional area of the shaft or the influence of impeller rotation on pressure distribution, the force acting on the impeller is the difference between the force acting on the wheel disc and the force acting on the wheel cover. The calculation formula is the product of the difference between the outlet pressure and inlet pressure and the area of the impeller cover. Because the outlet pressure is always greater than the inlet pressure, when the vacuum pump unit rotates, there must be a force acting on the rotor along the axis and pointing towards the inlet.
2. Problems caused by axial force: Unbalanced axial force can increase the working load on the bearings of the thrust vacuum pump unit, which is detrimental to the bearings. At the same time, axial force causes the pump rotor to move towards the suction port, causing vibration of the vacuum pump unit and possibly causing friction between the impeller and the ring, resulting in damage to the pump body.
Vacuum units generally adopt a symmetrical installation of balance plates and impellers. Single stage pumps usually have balance holes on the impeller, and of course, there are also ways to balance axial forces by installing balance blades on the impeller disc.
When using Roots vacuum units, there may be heating phenomenon. Why does this problem occur when many people are using them? They are generally used in an environment with a room temperature not lower than 5 ℃ and a relative temperature not higher than 90% during operation. The gas enters the high vacuum chamber through the intake nozzle, initially under high pressure. Both high and low vacuum chambers are filled with atmosphere, and both exhaust valves are opened for exhaust.
As the pumping progresses, the air pressure decreases (i.e. the vacuum degree increases), and the pressure in the high vacuum chamber is not enough to push open the exhaust valve. Gas enters the low vacuum chamber through the middle partition, and the pressure is not enough to push open the exhaust valve. However, a certain amount of oil enters the low vacuum chamber to help push open the exhaust valve, and the gas is also discharged accordingly. Because the gas discharged is mixed with oil particles, which are filtered by the oil blocking screen to separate the oil, only when the gas is discharged from the pump can it work better.
The oil in the oil seal chamber of the Roots vacuum unit is supplied by oil pool A through the hole on the front end plate. The oil in the low vacuum chamber is supplied by oil pool A through the hole on the rear end plate. The above is an analysis and solution to the heating problem of the vacuum unit.
