There are many manufacturers of dry vacuum pumps on the market. Before choosing the manufacturer, we should know what the function of this pump is. Dry vacuum pump is a kind of mechanical vacuum pump, which can start pumping under atmospheric pressure and discharge the pumped gas directly into the atmosphere. There is no oil or other working medium in the pump room, and the limit pressure of the pump is the same or close to that of the oil seal vacuum pump. There are mainly dry screw vacuum pump, oil-free reciprocating vacuum pump, claw vacuum pump and oil-free scroll vacuum pump, which are widely used.
The dry vacuum pump appeared very early, but there is no clear definition. As for the replacement of oil seal mechanical pump, the general term is: it can work within the pressure range from atmospheric pressure to 10-2Pa; in the pumping channel (such as pump cavity) of the pump, it is not allowed to use any oil and liquid, and the exhaust port is connected with the atmosphere, and can continuously exhaust gas to the atmosphere, which is called dry vacuum pump (also known as oil-free vacuum pump).
Dry vacuum pump classification
Now there are many kinds of dry pumps available on the market. There are only two basic principles, namely:
① Positive displacement oil-free vacuum pump, such as multi-stage Roots pump, claw pump, piston pump, screw pump and scroll pump. The limiting pressure of the dry pump is generally 0.1-10 PA, and the pumping speed is 0.01-0.04 m3 ö s.
② Momentum transfer type oil-free vacuum pump, such as turbine type oil-free pump. The exhaust side is connected with the atmosphere and has a high compression ratio under the condition of continuous flow. It is a crude pump, which can be pumped from atmospheric pressure to 1022pa. In the structure, the compound structure of radial flow and circumferential flow pump is adopted, and multi-stage series air extraction is adopted. The limited pressure of the turbine pump is about 10-2Pa and the pumping speed is 0.02-0.15m3 ö s. Traction type dry pump also belongs to momentum transfer type dry pump.
Compared with oil sealed mechanical pumps, these dry-type pumps reach the same limit pressure, and their residual gas composition is totally different. The analysis results show that the residual gas of oil sealed pumps, CnHm gas (hydrocarbon gas) is the main composition, and the residual gas of dry-type pumps is the composition of air. This proves that there is no oil pollution in the dry pump.
Some dry-type pumps are still using lubricating oil in structural design, such as the transmission gear and bearing of the pump, and synthetic oil, such as PFPE oil and its grease, is also used. Some measures are taken to make the oil vapor not exist in the pump cavity. Strictly speaking, it is not an oil-free pump, but after analysis, the composition of this synthetic oil at the pump inlet is very small and has no impact.
Dry vacuum pump application
1. For distillation, drying, defoaming and packaging in chemical industry, pharmaceutical industry and food industry, organic solvent pollution shall be prevented, which is suitable for dry vacuum pump.
2. In addition to semiconductor technology, some processes that produce particles do not want the particles to be mixed into the pump oil, but they want the particles to be discharged from the pump. A dry vacuum pump can meet the requirements.
3. Dry vacuum pump can be used as the front pump of ordinary oil-free clean vacuum system to prevent oil pollution.
4. Semiconductor etching process. Corrosive gases and abrasive particles are commonly used or produced in these processes.
5. The application of polysilicon in low pressure CVD.
With the development of science and technology, the technology of vacuum pump manufacturing enterprises is also constantly improving, which is less affected by reactants and has good stability. Choose a good manufacturer to buy, the quality is more guaranteed.