Water ring vacuum pump is prone to problems in application
Water ring vacuum pump in the chemical industry, often encountered corrosion problems. For corrosive gas or liquid, the best solution is to choose corrosive materials to make pumps. But domestic products are generally made of cast iron and carbon steel. In this case, the following two methods can be used to transport corrosive gases or liquids:
1. Use the vacuum tank method
Vacuum tank also called separation 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 up on the vacuum tube path before the inlet, so that the liquid can flow into the tank when passing through the pipe, not to enter the pump.
2. Adopt the method of coating anti-corrosion layer
Coat the corroded parts of the shaft and impeller with epoxy resin and glass fiber. Apply three layers in this way, letting it dry naturally for 2-3 days, and then dry it in the oven through the steam pipe. Beginning from 40 ℃, temperature rise every 2 hours 20 ℃, bake until after 120 ℃, so anticorrosive material is glass fiber reinforced plastic, and then according to the drawing requirements of glass fiber reinforced plastic wrap shaft and impeller machining.
After such antiseptic treatment, great results have been achieved. For example, in some factories, the impeller transporting corrosive liquid is corroded and cannot be used in 20 days. It can be used for at least one year after the adoption of fiberglass materials. However, borui steel is not suitable to resist the corrosion of nitric acid and concentrated acid (concentration above 70%), which needs to be improved.
二、The scale asked:
Water ring vacuum pump in the phenomenon of scaling is quite common, especially coal preparation plants and chemical plants more prominent.
In industry, water containing calcium and magnesium salts is called hard water. In nature, sea water, well water, spring water and so on, because of the contact with soil and rocks, dissolved a lot of impurities, these impurities are mostly calcium and magnesium carbonate, sulfate and chloride, so they are generally hard water, while rain water is soft water.
Calcium and magnesium salts in water are easy to be decomposed into insoluble carbonate deposits, which attach to pump parts and form scale. The scale can easily block the hole and clearance, and the joint surface of the parts is glued firmly, which affects the working performance of the pump and even prevents the pump from working normally.
Where scale is a serious threat, the following measures can be adopted:
1. Adding appropriate amount of lime or sodium carbonate (soda) into hard water can make the hydrocarbonate in water form an insoluble carbonate precipitation, and then after filtration, the soft water is obtained. These reactions occur more rapidly in hot water and more slowly in cold water, which is why water temperature is so hot and scale is so severe.
2. The water used in the water ring vacuum pump is used for closed circulation, and the amount of calcium and magnesium salt in the circulating water is certain, so that the amount of scale formed will not increase after a certain amount, which can avoid the deepening of scale hazards.
三、Safety measures for removing air from water ring vacuum pump:
Air is present in the water ring vacuum pump. If compressed gas is not safe to mix with air, air must be removed from the pump before use. Hydrogen, for example, is a flammable and explosive gas. In the air, hydrogen content between 4 and 75% will cause combustion, and it can be ignited with only two parts per 100,000 joules of energy.
Therefore, before transporting hydrogen, it is necessary to connect the water ring vacuum pump to the nitrogen gas cabinet with a certain pressure so that the nitrogen can be filled in the water ring vacuum pump and the air can be discharged. The elimination effect can be determined by combustion method.
四、Problems of pumping out particulate gases:
If the gas pumped contains solid particles, some of them will be discharged out of the pump along with the gas, and some of them will rub continuously in the gap in the pump, causing the gap to increase, resulting in increased leakage and decreased vacuum and gas volume. Therefore, it is not suitable for water ring vacuum pump to pump gas containing a large number of solid particles, especially the large size and high hardness of solid particles.
If unavoidable, the gas can be cleaned before entering the pump (such as setting up the filter screen, separation tank, etc.). If purification is difficult, the particles in the pump should be rinsed with water after pumping.
五、Water circulation device of water ring vacuum pump:
If the gas that is pumped has a certain solubility in water, in order to avoid the loss of this gas, do not let it go with the water; Or compressed gases are toxic to avoid harm and pollution; Or in order to reduce the scale of water, the water should not exchange with the outside world, but adopt the closed circulation method.
六、The problem of pumping liquid:
If the water ring vacuum pump contains a certain amount of water in the gas it is sucking, or completely pumps water or other liquids, the performance of the pump is quite different from that of the gas it is pumping. The main difference between them is:
1. Decreased air volume,
2. The shaft power is significantly increased.
3.The pump is not stable in a certain range.
At a certain temperature and pressure, liquid and steam can be converted to each other. For example, 100 ℃ under one atmospheric pressure boiling water into steam. Also, 100 ℃ under the condition of water vapor in the atmospheric pressure is equal to or higher than 1 can also condenses into water.
This phenomenon of water and steam transition depends on the water temperature and the pressure on the surface of the liquid. For example when the liquid level is 6.5 mm hg air pressure, 5 ℃ water is boiling phenomena will happen.Similarly, any liquid has the same phenomenon as water.