Causes of vacuum pump failure in paper mill

The manufacturer of water ring vacuum pump analyzes the causes of the failure of vacuum pump in the paper factory, which are mainly reflected in the following aspects:

1. Pump body vibration

When the vibration of the water ring vacuum pump body is too large, the vibration of the air inlet and exhaust pipelines connected with it is also large. If the vibration of the foundation and base is not large, the vibration caused by the loose foundation fixation can be eliminated, and the main reason is the pump body itself.

(1) Valve plate fracture: when the valve plate fracture, the pump body vibration is strong, the noise is very large, generally for the axial vibration.

(2) Scaling of rotor blades: after scaling of blades, the quality of rotor is unbalanced, resulting in vibration during rotation. Such factors generally have little influence.

(3) Rubber pad of coupling is damaged: rubber cushion is easy to be worn or even thrown out by grinding powder, which leads to direct friction between two pairs of wheel pairs of coupling and increases rotor vibration. Use good quality cushion in work and check its wear condition frequently.

2. Bearing heating

(1) Valve plate fracture: when a valve plate breaks, the pressure on both sides of the impeller will be unbalanced, and the rotor will generate axial force, which will aggravate the load of the ball bearing, and long-term operation will cause the bearing temperature to rise. When the two valve plates are broken, the position of the fracture is not the same, the pressure on both sides of the impeller also has a small amount of imbalance, the axial force will be reduced compared with the fracture of one valve plate, and the bearing temperature will be reduced, but it is still high. When this happens, the valve plate must be replaced in time.

(2) Too large bearing preload: the preload should not be adjusted too much, otherwise the bearing clearance will be reduced or there will be no clearance, which will easily cause bearing heating.

(3) Vibration effect: generally, when the pump body and bearing vibrate greatly, the bearing will generate heat. If the vibration is eliminated, the bearing temperature can return to normal.

3. High pump body temperature

(1) Insufficient working water volume: the reduction of water supply will increase the relative residence time of water in the pump, and all losses will eventually be converted into heat energy, which will increase the working water level, increase the steam content in the exhaust port of the pump, and increase the drainage temperature, resulting in the high temperature of the pump body. After increasing the amount of water, the temperature can be reduced.

(2) Deterioration of vacuum degree of the unit: after the deterioration of vacuum degree, the motor power increases, the working temperature of the unit increases, and the temperature of the gas mixture entering the vacuum pump increases, causing the temperature of the pump body to rise. When the water supply is increased slightly, the temperature of the pump body will be decreased and the vacuum degree of the system will return to the normal level.

4. Impeller cavitation

(1) When the vacuum pump is working, if the pressure in the local area of the pump drops below the saturated steam pressure of the corresponding temperature of the liquid, the liquid will vaporize and generate bubbles. As the liquid flows, these bubbles are carried to the high pressure zone. Under high pressure, the bubbles burst suddenly, and the steam condenses again. At this time, the surrounding water flows to the hole at a high speed, forming a local high-frequency water hammer, whose frequency can be as high as tens of thousands of Hertz, local pressure can be as high as thousands of MPA, resulting in damage to the metal surface, and vibration and noise.

(2) During the operation of vacuum pump, due to the wrong operation, the valve is suddenly closed or opened, resulting in the sudden change of liquid flow speed, which causes the direction and size of pipeline pressure to change repeatedly and sharply, resulting in water hammer phenomenon, causing the metal surface to damage the vacuum pump impeller cavitation, once the impeller is damaged, the distributor on both sides will be worn, resulting in the pump body vibration and heating For example, it will threaten the safe and stable operation of the pump; damage the balance of the impeller and worsen the working conditions of the motor bearing of the vacuum pump, which will increase the temperature of the motor bearing of the vacuum pump, increase the vibration and noise, and even reduce the firmness and stability of the pump foundation and enlarge the accident; in addition, the cavitation of the impeller of the vacuum pump will form a large area of honeycomb and pockmarks, which will make it true The head of air pump is reduced and its performance is deteriorated.

The manufacturer of water ring vacuum pump informs the measures to prevent impeller cavitation:

(1) Increase the flow area at the suction of the pump, reduce the flow speed, and increase the pressure at the suction.

(2) Keep the reasonable water level of the water storage of the steam water separator (300 mm below the full water level line), avoid the blockage of the heat exchanger, and ensure the proper height of the vacuum pump liquid level.

(3) Shorten the length of suction pipe of vacuum pump as much as possible, reduce unnecessary pipe fittings, and make the center line of pump as close to the liquid level of steam water separator as possible. In order to improve the suction performance of the pump, the negative installation height should be adopted as far as possible.

(4) Adopt anti cavitation material. When the service conditions of the pump are limited and it is impossible to completely avoid cavitation, the impeller shall be made of materials with good anti cavitation performance (such as 2Cr13, copper base alloy, etc.), or sprayed on the surface of the pump casing and impeller flow channel to extend the service life of the impeller.

(5) In case of cavitation, the pump shall be stopped and the impeller shall be repaired timely, and anti-corrosion materials shall be applied.

In addition to the above-mentioned water ring vacuum pump manufacturer’s analysis of the causes of vacuum pump failure in the paper factory, there are other causes. Each cause of failure is followed by solutions. If your vacuum pump is not due to the reasons mentioned above, you can find a regular vacuum pump maintenance manufacturer.