Matters needing attention in selecting liquid ring vacuum pump

The liquid ring vacuum pump is a multi-blade rotor eccentrically mounted in the pump housing. When it rotates, the liquid (usually water) is thrown into the pump shell and a liquid ring concentric with the pump shell is formed. The liquid ring and the rotor blade form a rotary variable volume vacuum pump with periodic variation. Water ring vacuum pump is the most common type of liquid ring vacuum pump. This kind of water ring vacuum pump is mainly used in the process of rough vacuum and large pumping capacity. It has been widely used in chemical, petroleum and light industries. The advantages of this pump are: simple structure, easy manufacture, reliable operation, convenient use and durability. It can extract very large gases, including corrosive gases, dusty gases and gas-water mixtures.

What should be paid attention to in liquid ring vacuum pump?

1. Understand the composition of the extracted gas. The gas contains no condensable vapor, particulate dust and corrosiveness. When choosing a vacuum pump, it is necessary to know the gas composition and select the appropriate pump for the pumped gas. If the gas contains vapor, particles, and corrosive gases, it should be considered to install auxiliary equipment such as condenser, dust collector in the intake pipeline of the pump.

2. Choose the working point of the liquid ring vacuum pump correctly. Each pump has a certain working pressure range, such as: the working pressure range of LEM series water ring vacuum pump is 760 mmHg ~ 25 mmHg (absolute pressure). Within this wide pressure range, the pumping speed of the pump varies with the pressure (detailed changes refer to the performance curve of the pump), and its stable working pressure range is 760 ~ 60 mmHg. Therefore, the working point of the pump should be selected within this range, rather than allowing it to work for a long time under 25-30 mmHg.

3. How does the oil vapor discharged from the liquid ring vacuum pump affect the environment? If the environment is not allowed to be polluted, oil-free vacuum pumps can be selected, or oil vapor can be discharged outdoors. Whether the vibration generated during working has an impact on the process and environment. If the process is not allowed, vibration-free pumps should be selected or anti-vibration measures should be taken. Vacuum pump price, operation and maintenance costs.

4. Combine the liquid ring vacuum pump correctly. Because of selective pumping, sometimes a pump can not meet the requirements of pumping, and several pumps need to be combined to complement each other in order to meet the requirements of pumping. For example, the titanium sublimation pump has a high pumping speed for hydrogen, but can not pump helium, while the tripolar sputtering ion pump (or the bipolar asymmetric cathode sputtering ion pump) has a certain pumping speed for argon, the combination of the two will make the vacuum device get a better vacuum degree. In addition, some vacuum pumps can not work at atmospheric pressure, need pre-vacuum; some vacuum pumps outlet pressure is lower than atmospheric pressure, need the front pump, so they need to be combined to use.

5. Its working pressure should meet the requirement of the vacuum equipment's limit vacuum and working pressure. For example, a vacuum drying process requires a working vacuum of 10 mmHg, and the limit vacuum of the selected vacuum pump should be at least 2 mmHg, preferably up to 1 mmHg. Usually the limit vacuum of the pump is half to one order of magnitude higher than the working vacuum of the vacuum equipment.

6. Requirements of vacuum equipment for oil pollution. If the equipment is strictly oil-free, all kinds of oil-free pumps should be selected, such as water ring pump, molecular sieve adsorption pump, sputtering ion pump, cryopump, etc. If the requirements are not strict, you can choose to have oil pumps, plus some anti-oil pollution measures, such as adding cold traps, baffles, oil traps, etc., can also meet the requirements of clean vacuum.

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