Oil free screw vacuum pump is a dry running, non-contact, equal pitch screw vacuum pump. The two screws are precisely dynamically balanced and supported by bearings. The equipment is located in the pump casing. There is a certain clearance between the screws. The pump operates smoothly without conflict, and there is no medium in the operating room. Therefore, the oil-free screw vacuum pump can extract gas containing more condensable gas and dust. It is an environment-friendly and energy-saving vacuum pump. It is more suitable than oil sealed mechanical vacuum pump, liquid ring vacuum pump, reciprocating vacuum pump and other models of vacuum pump.
1、 Selection of dry screw vacuum pump
1. The dry screw vacuum pump shall be able to discharge all the gas generated in the process of vacuum pump equipment under its working pressure.
2. Each pump has a certain working pressure range. Therefore, the working point of the pump should be selected within this range, rather than allowing it to work under the allowable working pressure for a long time.
3. The limit pressure of dry screw vacuum pump should meet the working pressure of the process. Generally speaking, the limit pressure of the pump is about an order of magnitude lower than the process requirements.
4. Select vacuum unit:
(1) Know the composition of the extracted gas, whether the gas contains condensable steam, whether there is particulate dust, whether it is corrosive, etc. When selecting dry screw vacuum pump, it is necessary to understand the gas composition and select the corresponding pump for pumping gas. If the gas contains steam, particles and corrosive gases, it should be considered to install auxiliary equipment on the inlet pipe of the pump, such as condenser, dust collector, etc.
(2) Whether the vibration produced during the operation of dry screw vacuum pump has an impact on the process and environment. If the process does not allow, the vibration free pump should be selected or anti vibration measures should be taken.
5. When choosing an oil seal pump, you should first know whether your vacuum system has requirements for oil contamination. If the equipment is strictly required to be oil-free, various oil-free pumps should be selected, such as water ring pumps, cryogenic pumps, etc. If the requirements are not strict, the oil pump can be selected, and some oil can also meet the requirements of clean vacuum by adding anti pollution measures such as cold trap, oil baffle and baffle.
6. When one pump cannot meet the requirements of air extraction and vacuum pumping, it needs to be supplemented by multiple pumps to meet the process requirements.
7. When selecting an oil sealed vacuum pump, the impact of the oil vapor (oil smoke) discharged by the vacuum pump on the environment should be considered. If it is not allowed to pollute the environment, an oil-free vacuum pump should be selected, or the oil steam should be discharged outdoors.
8. The small vacuum pump cannot work under atmospheric pressure and needs pre vacuum; Some dry screw vacuum pumps have outlet pressure lower than atmospheric pressure and need a front stage pump, so they need to be used in combination. The combined vacuum pump is called vacuum unit, which can obtain better vacuum degree and exhaust volume. We should choose the combined vacuum pump correctly, because different vacuum pumps have different requirements for the extracted gas. For example, generally speaking, roots vacuum unit is not suitable for systems containing more condensable gases.