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Eight measures to improve the performance of vacuum pump

Today, the vacuum pump manufacturer has found eight measures to improve the performance of vacuum pump for you. Come to understand with us.


1. Function of air pump inlet regulating valve


Vacuum pump is generally used for vacuumizing, but not all occasions require that the lower the vacuum degree, the better. In some occasions, it is required to control within a certain required vacuum degree range, or the pressure in the pump cavity is too low, and serious cavitation will occur in the pump cavity. When the vibration and noise of the pump are too large and affect the use, an additional one can be added in the suction area of the pump When the above conditions occur, the vacuum regulating valves can be properly opened to mitigate the impact of vibration and noise, or reduce the vacuum degree to meet the required vacuum degree requirements. This is a method for more reasonable application of vacuum pump.


2. The function of air ejector


There is a vaporization pressure for any liquid at any temperature. The limit vacuum degree of water ring vacuum pump is related to the saturated vapor pressure of the circulating liquid of vacuum pump. The medium with high saturated vapor pressure has a lower limit vacuum degree of vacuum pump, on the contrary, the higher the limit vacuum degree. We can see that the vacuum state is formed in the cavity during the suction process of vacuum pump 1-5. According to Dalton's law, when the liquid ring is stirred by the impeller, we think that the cavity 1-5 is filled with the sum of the saturated vapor pressure of liquid circulation and the pressure of suction gas. When the suction gas volume is zero, the suction pressure of vacuum pump is the lowest and the vacuum degree is the highest. At this time, the pressure of cavity 1-5 is the highest The force is the saturated vapor pressure of the liquid ring. Therefore, the minimum absolute pressure at the inlet of the vacuum pump must be the saturated vapor pressure of the liquid ring medium at this temperature.


3. The effect of replenishing working fluid system on the performance of vacuum pump


The replenishment of working fluid must be continuous. But how to make up the working fluid and how to determine the flow and pressure of the working fluid can improve the performance of the vacuum pump.


4. Increasing vacuum degree and pumping group by reducing working fluid temperature


It is known that the vaporization pressure of the liquid has a great relationship with the temperature of the liquid. High temperature and vaporization pressure lead to low vacuum degree of the pump, so reducing the temperature of the working liquid is conducive to improving the vacuum degree of the pump. For the working liquid with high temperature, we need to reduce the temperature of the working liquid through heat exchange to improve the vacuum degree of the vacuum pump. Taking water as an example, the saturated vapor pressure of water at 20 ℃ is 0.0233bar, and that of water at 50 ℃ is 0.1234bar.

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5. Using different working fluid to improve the performance of vacuum pump


Under the same temperature, the vaporization pressure of water and oil is quite different. We use water and oil as the liquid ring of the water ring pump, and the diameter of the pump is 50 and 80mm respectively. It can be seen that the point water above 300MMHG pressure as the liquid ring of the vacuum pump and oil as the liquid ring of the vacuum pump basically have the same pumping capacity, but at the pressure point below 300MMHG, we can see that the suction capacity of the oil ring is larger than that of the water ring, and the lower the pressure is, the more obvious it is 。 And the limit vacuum pressure of water ring is 20mmhg, while the limit vacuum pressure of oil ring is 4MMHG.


6. Improving the performance of vacuum pump by filling liquid from different positions


In the vacuum pump cavity, it is the low-pressure cavity area in the pump body, and it is the high-pressure cavity area. If the liquid filling port is located in the low-pressure area, the external liquid supply can realize the liquid filling through the self-priming mode of the pump itself, with low requirements for the liquid filling pressure. If the liquid is replenished in the high-pressure chamber, then the liquid replenishment pressure must be greater than the pressure in the pump chamber to replenish the liquid in the pump chamber. Otherwise, if the working liquid is not replenished in time, the gas will return from the compression chamber to the suction chamber and affect the performance of the vacuum pump. After many times of verification, it is found that the use of pump self-priming to make up the liquid can reduce the performance of the pump, because the pump makes up the liquid at the suction cavity or makes up the liquid from the end face of the impeller, and the working liquid has been working for a period of time (starting from the completion of the working liquid compressed gas), that is to say, there is a certain loss of energy, plus at this time, the make-up liquid will produce impact damage to the liquid ring Loss also reduces the effective work done by the working fluid on the gas and consumes part of the energy. If the make-up liquid is placed in the position of the air chamber, the make-up liquid obtains sufficient energy, and participates in the next round of suction and exhaust process under the condition of almost no energy loss, so the make-up liquid at the position of the high-pressure chamber is good for improving the performance of the vacuum pump.


But it is not that the higher the filling pressure is, the better it is. After verification, it is reasonable that the pressure is generally 1-1.5bar. Otherwise, the pressure is too high and the added liquid is too much, which makes the liquid occupy the space of suction gas. The air extraction and exhaust pressure of the vacuum pump will be reduced. At the same time, the liquid delivered by the pump will be increased, so the shaft power will be increased, the pump efficiency will be reduced, and there will be vibration and The noise is generated and a large amount of water is periodically discharged from the exhaust port of the pump.


7. Reasonable supplement of working fluid and improvement of vacuum pump performance


When is the supply quantity of working fluid most reasonable? Let the vacuum pump in an optimal operation state. The supply quantity can be determined by calculation.


Some people often think that only the power loss part can be converted into heat, otherwise for the dry gas pump, it is to convert all the shaft power into heat.


Through calculation, the vacuum can be replenished clearly. This kind of reasonable replenishment can give full play to the role of liquid ring, discharge the heat generated by the compressed gas of vacuum pump out of the pump cavity in time, ensure that the temperature of liquid ring of vacuum pump will not rise greatly, effectively seal the gap between the impeller and pump body of liquid ring pump, improve the volumetric efficiency of vacuum pump, and replenish with gas in time Discharge the working fluid outside the pump cavity, lubricate the shaft seal and improve the reliability, stability and efficiency of the vacuum pump.


8. Special gas-liquid separation device to improve the utilization rate of dissolved gas


The outstanding advantage of liquid ring pump is that it can transport toxic, harmful, flammable and explosive gases, which will not cause harm to the environment and man-made. The other outstanding advantage is that the compression process of liquid ring pump can be considered as isothermal compression, so that the compression of dry flammable and explosive gases will not cause danger of combustion and explosion. However, if the pumped gas is dissolved in the liquid ring, then the pumping of liquid ring pump The gas volume will change, the more easily the gas dissolved in the liquid ring, the larger the gas volume change, the less the amount of gas pumped. Therefore, in order to recover the gas in the solution dry liquid ring as much as possible, the structure of the gas-liquid separator can be set. It can be seen that the gas discharged from the vacuum pump first enters the primary air-water separator, and the discharged gas is discharged from this separator. The working liquid full of dissolved gas is delivered to the next low-pressure air-water separator. Due to the decrease of pressure, the gas dissolved in the liquid is released, and the released gas is delivered to the inlet of the pump for circulation. Due to the circulating use of working fluid, the liquid pressure separated from the next stage separator becomes very low, so it is necessary to use a pump to pressurize and then replenish the vacuum pump.


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