Vacuum pump failure

When the vacuum pump fails or completely fails, it will seriously affect the overall performance and operation of the vehicle. Vacuum pump in the process of use of some common failures and treatment methods, hoping to help users to deal with these failures in time, to ensure the service life of vacuum pump.

Problems, solutions and preventive measures in the operation of vacuum pump

1. There is a leak in the vacuum system

The return valve of vacuum pump is closed gradually in a short time (within a few hours), and the vacuum degree gradually drops until it falls to a certain range. At this time, check that the temperature of the vacuum pump is normal. After the standby pump is started, when two pumps are running at the same time, the vacuum degree is only increased by 1%, which can not meet the production needs. After shutdown, the inspection found that the vacuum degree dropped quickly as soon as the vacuum pump stopped running, and one liquid-phase pipe of the vacuum system leaked liquid. It was a leak in the vacuum system.

After the materials of the vacuum system are treated, the corroded pipes are replaced, and then the vacuum pump is turned on, and the vacuum system returns to normal. The temperature of vacuum pump is normal, and the vacuum degree is only increased by 1% when two pumps are started, which can eliminate the failure of vacuum pump. At this time, it is likely that there is a leak in the vacuum system. As the leakage point is not easy to be detected under vacuum condition, the vacuum pump must be stopped and the system shall be inflated and pressurized for leakage test. Fortunately, the leakage point is in the liquid phase. If it is in the gas phase, the system must be pressurized for leakage test.

As the vacuum system is a corrosive material, after a certain point of the vacuum system is corroded, the leakage point will become larger and larger. The atmosphere enters the vacuum system from the leakage point and destroys the vacuum. The load of the vacuum pump becomes higher and higher, that is, the opening of the return valve of the vacuum pump becomes smaller and smaller until it is completely closed, resulting in a lower and lower vacuum degree, which eventually affects production.

Preventive measures: strengthen leakage test when parking, find out the leakage point in time, and carry out treatment.

2. Insufficient circulating capacity of liquid ring water and water shortage of vacuum pump

The vacuum degree drops in a short time, the pump shell temperature rises (generally, it is not allowed to be higher than 40 ℃, and the optimal operating temperature is below 25 ℃), the make-up water of vacuum pump is normal, and the overflow of gas-liquid separator is normal. At that time, the liquid ring circulating system of vacuum pump was descaled. Therefore, it can be concluded that the vacuum degree of vacuum pump cavity was reduced due to water shortage. Therefore, add primary water directly from a discharge valve in the liquid ring circulating system of vacuum pump.

The drain valve is located under the vacuum pump and is mainly used to drain the water in the vacuum pump when the pump is stopped in winter. After the primary water enters the pump cavity directly, the vacuum degree soon returns to normal. Subsequently, the overflow water volume of the vacuum pump gas-liquid separator is also increased, and the overflow water contains some solid impurities. After the solid impurities in the overflow water are discharged, remove the primary water directly added from the drain valve in the liquid ring circulating system of the vacuum pump, and the vacuum pump operates normally.

If the vacuum degree of vacuum pump drops and the pump shell temperature is high, and the scaling problem of liquid circulating water system is eliminated, it is likely that there is blockage in the liquid circulating water system. The circulation of liquid ring water of vacuum pump is realized by the pressure difference between the gas-liquid separator and the inlet of vacuum pump water. The pressure difference is small, which is not enough to flush out the sundries in the system. Even if it can be flushed out, the sundries also enter the gas-liquid separator, and the drainage of the separator is in the middle and upper part, so the sundries cannot be discharged from the system, which eventually causes the blockage of sundries in the liquid ring circulation system. The discharged impurities are analyzed. It is a polymer formed by the reaction of organic gas and water in the vacuum system.

Preventive measures: solve from the source, reduce the temperature of the distillation system, intercept and recover the organic gas; increase the flow of vacuum washing water, absorb the organic gas to the maximum extent, and prevent the organic gas from entering the vacuum pump.

3. High operating temperature of vacuum pump

In a short time (a few days), the opening of the return valve of the vacuum pump gradually decreases until it is completely closed, and the vacuum begins to decrease; the pump shell temperature of the vacuum pump is higher, while the temperature of the cooling water of the heat exchanger of the coolant circulating water is not high. Start another vacuum pump and let the two pumps run together. The vacuum degree is almost unchanged. Considering that the vacuum degree of vacuum pump is reduced in a few days, and there is no effect when two pumps are started, it is considered that the possibility of scaling in the liquid ring water circulation system is greater, so the scale remover is used to scale the liquid ring water circulation system. As soon as the scale remover is poured in, a large number of bubbles will appear, which indicates that the scale of liquid circulating water system is serious. After the descaling, the vacuum pump returns to normal operation.

The return valve of the vacuum pump is used to adjust the vacuum degree. When the vacuum degree of the vacuum pump is less than the set value, the return valve will automatically close; otherwise, when the vacuum degree of the vacuum pump is greater than the set value, the return valve will automatically open. When the return valve of the vacuum pump is gradually closed for several days, it means that the liquid circulating water system of the vacuum pump has been scaling. After the return valve of the vacuum pump is fully closed, the vacuum degree gradually drops, the temperature of the vacuum pump rises, and there is no change in the vacuum degree after opening two vacuum pumps, which means that the vacuum pump is seriously scaling and has been unable to operate normally. At this time, only the liquid circulating water system can be descaled.

Preventive measures: the make-up water of liquid ring water circulation system of vacuum pump is primary water, which has high hardness and is easy to scale. The scaling problem can be prevented by changing the make-up water from primary water to desalted water or softened water.

4. Excessive circulation of liquid ring water in vacuum pump

When the water overflow of the gas-liquid separator at the outlet of the vacuum pump is not timely or the water supplement quantity is too large, the circulation quantity of the liquid ring water of the vacuum pump is too large, the crescent shaped space formed between the impeller hub and the inner surface of the water ring in the pump cavity becomes smaller, and the volume of the vacuum pump suction becomes smaller, which gradually causes the vacuum degree of the distillation system to be insufficient. If the water circulation of the vacuum pump continues to increase, it will cause the pump cavity to be filled with water, increase the operating load of the vacuum pump, and damage the impeller.

Preventive measures: strictly control the liquid level of the gas-liquid separator of the vacuum pump to ensure the circulating amount of liquid ring water of the vacuum pump; if the liquid level of the gas-liquid separator rises, discharge or stop the pump in time.

5. High resistance at the gas outlet of vacuum pump

In the vacuum pump system of vacuum distillation unit, in order to ensure that the exhaust gas can meet the discharge standard, the exhaust gas of vacuum pump should be washed generally. When the gas discharge port of vacuum pump is blocked or blocked, the gas outlet resistance of vacuum pump increases, resulting in incomplete discharge of vacuum pump gas, part of the gas circulates in the pump, thus affecting the gas suction of vacuum pump, resulting in insufficient vacuum degree of distillation system.

Preventive measures: prevent liquid accumulation at the gas discharge port of vacuum pump; frequently check the tail gas washing system to prevent the packing from falling off and blocking the gas phase pipeline.

vacuum pump maintenance:

1. Keep the vacuum pump clean and prevent impurities from sucking into the pump cavity. It is recommended to configure the filter, but the distance between the upper interface and the lower interface of the filter is about 3 / 5 of the height of the whole filter. When there is too much water solution, it can be discharged through the drain plug, and then screwed down in time. The filter can buffer, cool and filter.

2. Maintain the oil level. Vacuum pump oil of different types or brands shall not be mixed. In case of pollution, please replace it in time.

3. Improper storage, water or other volatile substances into the pump cavity, can open the gas valve purification. If the limit vacuum is affected, oil change can be considered. When changing the pump oil, first turn on the pump and run it empty for about 30 minutes to make the oil thin and drain the dirty oil. At the same time, add a small amount of clean vacuum pump oil from the air inlet slow case to wash the pump cavity.

4. In case of noise increase or sudden seizure of vacuum pump, the power supply shall be cut off immediately for inspection.

The structure of vacuum pump is simple, but it plays an important role in distillation process. Once the vacuum degree is insufficient, it will affect the operation of the whole distillation unit. Therefore, to ensure the vacuum degree of vacuum pump is the guarantee of the normal operation of vacuum distillation unit.

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