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1, the principle of water ring vacuum pump cavitation cavitation is caused by the liquid gasification, liquid molecules escape the name of the liquid, into the gas molecules, called "gasification." The level of vaporization of a liquid is independent of the size and the heat of the pressure. The gas dissolved in the liquid will also be released when the pressure and heat change, forming an air pocket. When the external pressure of the hydraulic province rises and falls below the saturated vapor pressure of the liquid at the heat, bubbles or cavities are formed in the entire sea area; and when the pressure rises, the central air bubble is suddenly crushed by the four pressures, and the fluid flow is elastic. Extremely high progress was squeezed toward the bubble core, causing hydraulic assaults to the facility. The production of such microbubbles, cracking, and the formation of physical and chemical effects on the nominal overcurrent are called cavitation. When the bubbles generated during cavitation are fixed to the low pressure, their volume decreases to disillusion. This view of bubbles disappearing in the liquid because of the pressure rise is called cavitation collapse.
When the vacuum pump is in operation, if the whole flow of the whole area of ​​the whole flow (usually some place behind the impeller blade inlet) of the vacuum pump, the relative pressure of the pumped liquid rises to the liquid vaporization pressure of the later heat, the liquid will Gasification ends there, producing a large volume of vapor-forming bubbles. When a liquid containing a large number of bubbles passes forward through the low-pressure zone in the impeller, the low-pressure liquid around the bubbles causes the bubbles to expand rapidly to cause cracking. At the same time as the collapse of bubble condensation, the liquid particle fills the cavity with a high degree of progress. In this case, a very strong water hammer is created, and the high-impact efficiency results in striking the nonmetal name. Atmospheric pressure, how many times per second the efficiency of the charge reached, will be a major breakdown of the wall thickness.
The inner part of the vacuum pump in which helium bubbles and bubbles burst so that the overflow element is destroyed is the inside of the cavitation in the vacuum pump. After the vacuum pump generates cavitation, it will produce noise and vibration and cause the performance of the pump to rise unless it destroys the overflow element. When the vacuum pump is heavy, it will stop the liquid in the pump and make it impossible to deform.
The cavitation erosion of the water ring pump is at the site of bubble generation and cracking. The phenomenon of pitting corrosion appears in the name of non-metal. Major honeycomb deterioration will occur. After that, the air pump impeller has a large residual stress in the cavitation, and it also causes stress release and cracking. Because the bubble cavitation in the pump in the low pressure area suddenly produced a sudden rupture, and along with the strong water hammer generated noise and vibration, can hear the sound of pods like pod beans. Then the above-mentioned bubbles burst in the name of non-metals. The name of the non-metal will be subjected to successive strong water hammers. The non-metallic grains will loosen and flake off into a honeycomb or perforation. In addition to mechanical action, cavitation damage also accompanies many simple actions such as electrolysis and chemical attack. The theoretical damage motivation indicates that the part where the evaporating component of the pump flow-through component is destroyed is the center where the bubble disappears. Vacuum pumps require liquids as working media. Each liquid has a corresponding saturated vapor pressure at a certain heat. When the relative pressure of the inhaled sea is closer to the saturated vapor pressure of the liquid, the liquid is more likely to evaporate. At that time, a large amount of air bubbles would be generated in the name of the working fluid sucked into the sea, because the liquid steam generated by the liquid in the working chamber would make room for the entire working chamber of the dragon's tiger, and the external suction power of the pump would increase. When the pressure of the inhaled sea reaches the saturated vapor pressure of the working fluid, it can be considered that the working chamber is fully filled with working fluid vapor. At this time, the external suction power of the pump is approaching zero, and the evaporative appearance of the pump is also the most significant.
Then the working fluid is water, and the higher the water temperature, the more the pumping performance of the pump rises. The water temperature of the water ring pump must be greater than the water temperature, and the performance curve of the water ring pump is measured at a water temperature of 15°C. Therefore, the pumping rate of the water ring pump in response to the water ring pump is continuously modified.
2, the water ring vacuum pump evaporating scene clearing steps and prevention of water ring vacuum pump in the cavitation state, a short time operation, will cause the pump noise, vibration, and even cause damage to the pump, and therefore should be heavy volume to prevent the water ring vacuum pump in the steam Work in an etched state, following steps:
(1) Increasing the heat of water Because the increase in the temperature of the icing water in the vacuum pump will result in a significant increase in the pumping capacity, the seal water temperature of the vacuum pump must be lower than the saturation heat corresponding to the exhaust pressure, or it will make the vacuum better. Will cause vacuum pump impeller cavitation corrosion. As a result, the heat of water is increased to prevent cavitation.
(2) The correctness of universal selection makes the vacuum pump operate in the insurance sea area during the selection stage. When choosing vacuum pump suction pressure and water heat, the amount should be avoided to avoid the evacuation pressure scale easily generated by the vacuum pump, that is, to prevent the vacuum pump from being in the critical vacuum level. Or within the critical discharge pressure of the sea area, heavy volume increase cavitation.
(3) Device evaporating shield tube device Vacuum pump with evaporative shield tube, the bubbles generated in the cavitation burst in the middle of the compression, the introduction of high pressure non-condensable gas from the inside can be promptly added to emerge due to bubble burst The space can greatly increase the damage of cavitation to the pump and increase the noise and vibration caused by cavitation.
Some pumps have a cavitation shield interface, such as working under extreme pressure, opening the evaporating shield tube connector (or coupling with a soda-blender) can clear the cavitation sound in the maximum guarantee suction pneumatic machine conditions, and the pump continues cover.
(4) Atmospheric ejector Atmospheric ejector function is to use atmospheric pressure absolute vacuum pump pressure difference, generate atmospheric jet, in the ejector to lose the suction pressure lower than the vacuum pump, so as to eliminate the vacuum pump limit pressure, prevent vacuum pump cavitation It plays a role in shielding the vacuum pump. Since the atmospheric ejector is provided to prevent vacuum pump cavitation and protect the vacuum pump, a vacuum pump of an atmospheric ejector is normally provided, and the vacuum constituted by the suction is better than that of the vacuum ejector.
(5) The adoption of a lower saturated vapor liquid as a working fluid changes the working fluid from the original water to the transformer oil, and its ultimate vacuum loses a higher promotion due to the lower saturated vapor pressure of the oil. In the process of extracting larger gases and in some extraordinary applications, the working fluid of the vacuum pump can also use other liquids (such as organic solvents such as propanol, ethanol, xylene, aniline, and amfepram hydrochloride, which have low viscosity). Its ultimate vacuum is determined by the saturated vapor pressure of the working fluid.
The oil ring vacuum pump can be operated at 20~90°C. Therefore, when the steam and other gases are removed, the oil temperature is high, the steam is not easily condensed, and the pump oil is not easily emulsified, thereby popularizing the service life of the pump oil. When using organic solvents as working fluids, attention should be paid to whether the motor is explosion-proof or does not erode the vacuum pump and its seals.
(6) The pump's impeller, disc, etc. adopt the anti-cavitation erosion power. There are many ingredients that can resist the power of anti-erosion. Usually, high hardness and high elasticity data have stronger anti-erosion power. Overseas recommendation of low-carbon chromium-nickel alloy steel, such as 13Cr4N as a hydraulic machine operating in the cavitation state, there is a good anti-corrosion performance. Impeller coating steps are rarely used, non-non-metallic coatings applied epoxy resin, nylon powder, polyurethane and so on. The motives for preventing cavitation damage in the name of the runner alloy or the sprayed alloy have also been decisively motivated, such as the stainless steel wire surfacing method, the stainless steel plate welding repair method, and the alloy powder spray welding.
Compared with the number of non-metal and alloy (including stainless steel) steps, the non-non-metallic coating is economical, but it should be widely grasped to prevent coating shedding. The adoption of alloy powder spray welding has good motives but high profits, and some centers may not be able to continue.
3. In the end, cavitation produced by vacuum pumps is a common failure of vacuum pumps. Any vacuum pump will produce cavitation. In the daily life of brick and tile enterprises, do a good job in the fundamental protection of the facilities, have a vague sense of vacuum pump cavitation, and the right to choose the steps to prevent cavitation, will certainly be able to achieve the goal of aggravating the vacuum pump cavitation.
Water ring pump cavitation erosion principle and how to prevent
The water ring type vacuum pump is referred to as the water ring pump, and the vacuum pump is a rotary type variable capacity vacuum pump. It must be used with a foreline pump. It can be used in a wide pressure range with a large pumping speed. The pumped gas contains dust and water. Steam insensitivity is widely used in metallurgy, chemical, food, electronic coating and other industries.