Roots vacuum pump is a kind of rotary volumetric, roots vacuum pump must have the front pump to use in a wide range of pressure with a large pumping speed, to be removed gas containing dust and water vapor is not sensitive, widely used in gold, chemical, food, electronic coating and other industries.
The ultimate pressure of roots vacuum pump should meet the working pressure of the process. Usually the limit pressure of the selected pump is about an order of magnitude below the process requirements.
Each type of pump has a certain working pressure range, so the working point of the pump should be selected within this range, and the working pressure should not be allowed to work longer hours.
When choosing an oil-sealed pump, you should first know whether your vacuum system has requirements for oil contamination. If the equipment strict requirements without oil, should first all kinds of no oil pump, such as: water ring pump, cryogenic pump. If the requirements are not strict, can choose a pump, plus some anti-oil pollution measures, such as cold trap, oil trap, baffle, can also meet the requirements of clean vacuum.
To understand the composition of the extracted gas and whether the gas contains condensable steam, particles and corrosive gas, it should be considered to install auxiliary equipment on the inlet pipe of the pump, such as condenser, dust collector and so on.
The type of roots vacuum pump is mainly determined by the air volume, vacuum degree or exhaust pressure required for work.
When roots vacuum pump works, the following two aspects need to be paid attention to:
1, as far as possible in the high efficiency zone, that is, in the critical vacuum or critical exhaust pressure area.
2. Avoid running near super vacuum degree and super exhaust pressure. Running in this area, not only the efficiency is very low, but also the work is very unstable, easy to produce vibration and noise. For roots vacuum pump with higher vacuum degree, cavitation phenomenon often occurs when the wind runs in this area. The obvious signs of this phenomenon are noise and vibration inside the pump. Cavitation will lead to the pump body, impeller and other parts of the damage, so that the pump can not work.
According to the above principle, when the vacuum degree or gas pressure required by the pump is not high, the priority can be selected in the single stage pump. If the vacuum or exhaust pressure is higher, the single-stage pump is often unable to meet, or, the pump in the case of a higher vacuum is still larger volume, that is, the performance curve in the higher vacuum is relatively flat, can choose two-stage pump. If the direct air pump requirements above -710nnhg, can choose water cup – large air pump or water ring – roots vacuum unit as the vacuum pumping device.
If only for roots vacuum pump, then choose a single action pump is better. If the single-acting pump structure is simple, easy to manufacture and maintenance, and in the case of vacuum cavitation is good. If only for the larger air volume of the compressor, the choice of dual role pump is more appropriate. Because the double action pump gas capacity, small volume, light weight, radial can be free balance, shaft is not easy to produce fatigue fracture, the service life of the pump is long.
After selecting the type of roots vacuum pump according to the air volume required by the system, the type of roots vacuum pump should be selected according to the air volume required by the system.