Addtime： 2020-07-17 Browse times： 3055
1、 Corrosion of water ring vacuum pump
When the water ring vacuum pump is used in chemical industry, it often encounters the problem of corrosion. As for the corrosive gas or liquid, the best treatment method is to choose the material of corrosion resistance to make pump. But domestic products are usually made of cast iron and carbon steel. In this case, when encountering corrosive gas or liquid, the following two methods can be adopted:
1. Vacuum tank method is adopted
Vacuum tank is also called parting tank, buffer tank, etc. It is mainly used to suck corrosive liquid. In order to prevent the liquid from flowing into the pump, a vacuum tank can be set on the vacuum pipe before the inlet, so that the liquid will flow into the tank when it flows through the pipeline, and will not enter the pump.
2. The method of coating anti-corrosion layer is adopted
The corroded parts of shaft and impeller are wrapped with epoxy resin and glass fiber, and then coated with epoxy resin and glass fiber. This coating three layers, let it naturally dry for 2-3 days, and then drying in the furnace through the steam pipe. Starting from 40 ℃, the temperature rises by 20 ℃ every 2 hours, and then it is dried to 120 ℃. The anti-corrosion data made in this way is called glass fiber reinforced plastic, and then the mechanical processing of the shaft and impeller wrapped with glass fiber reinforced plastic is stopped according to the drawing requirements.
After adopting such anti-corrosion treatment, great effect has been achieved. For example, in some factories, the impeller with corrosive liquid is corroded and can not be used in only 20 days. After using FRP data, it can be used for at least one year. However, it is not suitable to resist the corrosion of nitric acid and concentrated acid (the concentration is more than 70%), which needs to be improved.
2、 Analysis of water ring vacuum pump scale
Scaling in water ring vacuum pump is very common, especially in coal preparation plant and chemical plant.
In industry, the water containing calcium salt and magnesium salt is called hard water. The seawater, well water and spring water in nature dissolve many impurities due to contact with soil and rock. Most of these impurities are calcium and magnesium carbonate, sulfate and chloride, so they are generally hard water, while rainwater is soft water.
Calcium and magnesium salts in water are easy to synthesize into insoluble carbonate precipitates, which are attached to pump parts and form scale. The scale is easy to block the pore and gap, and the joint surface of the parts is glued tightly, which affects the working performance of the pump, so that the pump can not work normally.
The following methods can be adopted for the places where scale threat is serious:
1. Adding proper amount of hydrated lime or sodium carbonate (soda) in hard water can make bicarbonate in water form insoluble carbonate precipitation, and then through filtration, the soft water is obtained. The above reaction in hot water is faster than that in cold water, which is why the water temperature is high and the scale phenomenon is serious.
2. The water used in the water ring vacuum pump is used for blocking circulation. The amount of calcium and magnesium salt in the circulating water is fixed, so that the scale will not increase after reaching a certain amount, which can prevent the deepening of scale harm.
3、 Safety measures for cleaning air in water ring vacuum pump
There is air in the water ring vacuum pump. If the compressed gas is not safe after mixing with air, then the air must be swept from the pump before use. For example, hydrogen is a flammable and explosive gas. In the air, if the hydrogen content is between 4-75%, it will be extinguished, and it can be ignited with only two parts of 100000 joules of energy. Therefore, before delivering hydrogen, it is necessary to connect the water ring vacuum pump to the nitrogen tank with a certain pressure, so that the nitrogen can overflow the water ring vacuum pump and exhaust the air. The cleaning effect can be determined by quenching method.
4、 Problems in pumping gas containing particles by water ring vacuum pump
If the gas to be pumped contains solid particles, one part of the particles will be discharged from the pump with the gas, and the other part of the particles will rub at the gap in the pump from time to time, resulting in the increase of the leakage and the decrease of vacuum and gas volume. Therefore, water ring vacuum pump is not suitable for pumping gas containing a large number of solid particles, especially solid particles with larger particle size and higher hardness.
If it is impossible to prevent it, purification treatment can be carried out when the gas enters the pump (such as setting filter screen, leaving the tank, etc.). If the purification is difficult, then after the end of pumping, the particles in the pump should be washed clean with water.
5、 Installation of circulating water for water ring vacuum pump
If the pumped gas has a certain solubility in the water, in order to prevent the loss of this gas, do not let it drain with water; or the compressed gas is toxic, in order to prevent harm and pollution; or in order to reduce scale, the water in the pump should not cross with the outside, and use the blocking circulation method.
6、 Problems of liquid pumping by water ring vacuum pump
If the water ring vacuum pump contains a certain amount of water in the gas it sucks, or when it pumps water or other liquids completely, the performance of the pump is quite different from that when pumping gas. Their main differences are as follows:
1,
2. The shaft power increased significantly,
3. The pump is unstable in a certain range.
7、 Cavitation of water ring vacuum pump
At a certain temperature and pressure, liquid and vapor can be converted to each other. For example, water at 100 ℃ boils to steam at 1 atm. Similarly, water vapor at 100 ℃ can condense into water at or above 1 atm.
This phenomenon of water vapor transformation depends on the water temperature and the external pressure of the liquid. For example, when the surface pressure is 6.5 mmHg, water at 5 ℃ will also boil. Similarly, any liquid has this phenomenon similar to water.
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