Addtime： 2020-07-18 Browse times： 3569
1. Working steam and its dryness
The low steam pressure and pressure fluctuation have great influence on the capacity of vacuum pump, so the steam pressure should not be lower than the required working pressure. However, the structural design of the vacuum pump used has been finalized. If the steam pressure is increased too much, the pumping capacity and vacuum degree will not be increased. In addition, to ensure that the steam pressure supplied by the boiler is stable, it is better to use a boiler to provide working steam for the steam jet pump, so that the steam pressure will not fluctuate and the performance of the vacuum pump will be stable.
The dryness of steam also has a great impact on the performance of vacuum pump, in which water content will cause vacuum fluctuation, and if water content is too much, it will even be unable to pump vacuum. The usual method is to install a steam separator in front of the drum to obtain the working steam with higher dryness, and to effectively insulate the steam pipeline. In order to obtain the best working benefit, the working steam for jet vacuum pump should be superheated steam of 5 ℃ ~ 10 ℃. Especially for the fifth stage pump, the quality of steam is very high. If there is a small amount of water, it may cause ice jam in the nozzle, which will cause the vacuum degree of the fifth stage ejector to drop or not work.
2. Circulating cooling water
If the cooling water supply is insufficient, the condenser will heat up, the sound of air flow will increase, the vacuum degree will drop rapidly, and even the steam will return to the suction pipe. For the intercooled condenser, the water supply pressure should be 0 and 2MPa, and the water supply should be slightly larger than the actual consumption, so that the fluctuation of water consumption will be more stable. In addition, in order to avoid the vacuum fluctuation caused by unstable water supply, the central vacuum pump thinks that it is better to use a separate circulating water system to supply water to the condenser of the vacuum pump.
If the cooling water temperature is too high, the capacity of vacuum pump will decrease, and sometimes even can't pump vacuum, which is generally less than 32 ℃. In addition, the higher the cooling water temperature, the more steam consumption.
The influence of cooling water quality on the capacity of vacuum pump is also a factor that can not be ignored. If the water quality is poor and the hardness is high, the condenser will be fouling or even blocked, which will seriously affect the heat exchange performance and make the steam difficult to condense, thus affecting the vacuum degree. Therefore, the circulating cooling water should be pure softened water.
3. Sealing requirements of vacuum pump system
When the vacuum pump is in the limit state, there is little or sometimes no water discharged from the first stage. Therefore, the first stage pump has a large amount of water discharged, it can be considered that the system has leakage. The common causes of air leakage are: the gasket is not installed, installed wrongly or damaged, the bolts are not tightened, the flange surface is damaged, there are sand holes in the weld, and the joints (pressure gauge, vacuum gauge, etc.) are not installed properly.
The most common leak detection method is that the whole system is filled with pressurized air and smeared with soapy water. If there is a leak, there will be bubbles at the leak point, and sometimes even the sound of leakage can be heard. The final requirement for checking whether there is air leakage is to test the tightness of vacuum system (including pump body and atmospheric leg) with 0 and 2MPa compressed air, and the pressure drop in 24h shall not exceed 4 or 8%.
4. Nozzle
The nozzle is an important part that affects the performance of vacuum pump. The existing problems are: the nozzle is installed incorrectly, installed Skewly, blocked, damaged, corroded and leaked. No matter what preventive measures are taken, the nozzle blockage is inevitable. On the one hand, when the steam pipe is installed, the residual iron chips and welding slag in the pipe will block the nozzle; on the other hand, when the vacuum pump system is stopped, the steam pipe is easy to rust, and the rust spots fall down and block the nozzle when using. Generally speaking, the nozzle diameter of stage 1 and stage 2 is large, which is not easy to be blocked. The nozzle of stage 3, stage 4 and stage 5 are most likely to be blocked. Whether the nozzle is blocked can be confirmed by touching the temperature of pump head and condenser.
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