The best water ring vacuum pump is the most commonly used form of vacuum pump in the paper industry. Most of the paper machine projects completed at present are still using water ring vacuum pump as the standard configuration of vacuum system.
water ring vacuum pump advantages:
1. The structure is simple, the manufacturing accuracy is not high, and it is easy to process.
2. Compact structure, high rotation speed of vacuum pump, generally can be directly connected with motor, without deceleration device. Therefore, with a small structure size, a large exhaust volume can be obtained, and the floor area is also small.
3. The compressed gas is basically isothermal, i.e. the temperature change of the compressed gas process is very small.
4. Because there is no metal friction surface in the pump cavity, there is no need to lubricate the pump, and the wear is very small. The seal between rotating parts and fixed parts can be directly completed by water seal.
5. The suction is even, the work is stable and reliable, the operation is simple, and the maintenance is convenient.
water ring vacuum pump disadvantages:
1. Low efficiency, generally around 30%, better up to 50%.
2. The vacuum is low, which is not only limited by the structure, but also by the saturated vapor pressure of the working fluid. Using water as working fluid, the limit pressure can only reach 2000 ~ 4000Pa.
water ring vacuum pump energy saving:
1. The higher the temperature is, the larger the gas volume is. When the vacuum pump reaches the same vacuum degree, its suction flow will also rise, which will lead to the increase of load and energy consumption. Therefore, it is very important to control the temperature of circulating white water in summer, which requires the cooling system to maintain a good cooling effect. Generally speaking, circulating white water should not exceed 35 ℃. If the temperature is too high in summer, the cooling water flow can be increased properly, but at the same time, it should be noted that the excessive cooling water flow will also cause the increase of energy consumption, so the cooling water flow should be reduced properly in winter.
2. If the capacity of vacuum pump obviously exceeds the demand of vacuum system, there will be excess vacuum and waste of effective pumping rate. The frequency of frequency converter is adjusted by PID control, so as to adjust the effective pumping rate of mechanical pump, which can achieve the purpose of energy saving and consumption reduction.
3. When the motor speed is fixed and the water level is within a certain range, the water ring formed by the high water level is large, and the water ring formed by the low water level is small, that is to say, when the water ring is too large, the power consumption will increase, so the efficiency of the water ring vacuum pump will decrease, and the power consumption will increase. Regular monitoring of the surface vacuum value of the water ring pump and human intervention of the water ring water supply can ensure the maximum efficiency of the vacuum pump (also can be made into PID regulation).
4. Internal wear: after 3-5 years of operation, due to the wear of the rotor and distribution board, the gap between the rotor and the pump housing increases, and the vacuum will leak, resulting in the decrease of the suction capacity. The rotor and distribution board shall be repaired or replaced to prevent the increase of energy consumption caused by the decrease of the vacuum suction capacity.
water ring vacuum pump operation problems:
1. In the paper industry, the working medium of the water ring vacuum pump is mainly clean water or white water. The hardness of water in North China is usually high, while the metal ions in white water are complex, so the internal parts of vacuum pump will form scale after a long-term physical and chemical process. The scaling problem of vacuum pump can be solved by washing in series. After the vacuum system is completely cleaned and replaced with clean water, add 5% dilute hydrochloric acid and appropriate system cleaning agent, keep the temperature at 45-50 ℃, circulate for 2 hours, and then add clean water for washing in series. The cleaning cycle is generally 3 months. At the same time, the scale inhibitor can be used for a long time to keep the impeller clean and the whole vacuum circulation system clean.
2. Vibration problems often occur in water ring vacuum pump, such as broken valve plate, scaling of rotor blade, damage of coupling rubber gasket, large change of water ring, etc. During the shutdown, the above problems need to be checked one by one to ensure that the abnormal problems are found in advance and solved in advance.
3. The impeller of the water ring vacuum pump may be reduced to below the saturated steam pressure of the corresponding temperature of the liquid due to the pressure in the local area of the pump, then the liquid will vaporize, generate bubbles, and finally cause high-frequency water hammer; or because of the operation error, suddenly close or open the valve, resulting in the sudden change of the liquid flow speed, resulting in repeated and sharp changes in the direction and size of the pipeline pressure Water hammer will be produced and the metal surface will be damaged.
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) Maintain the reasonable water level (300m m below the full water level line) of the water storage in the steam water separator, avoid the blockage of the heat exchanger, and ensure the proper height of the vacuum pump liquid level.
(3) Shorten the suction pipe length of the vacuum pump as much as possible, reduce unnecessary pipe fittings, and make the center line of the vacuum pump as close to the liquid level of the steam water separator as possible. In order to improve the suction performance of vacuum pump, the negative installation height should be adopted as far as possible.
(4) Adopt anti cavitation material. When the service conditions of vacuum 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 pump casing and impeller channel to extend the service life of impeller.
(5) In case of cavitation, the vacuum pump must be stopped to repair and weld the impeller in time and coated with anti-corrosion materials.