The quality of the vacuum pump system depends on its machine layout and the quality of the oil. It must be maintained when the vacuum pump is used. If distillation of volatile organic solvents, organic solvents will be oil absorption effect increased vapor pressure, thereby reducing the efficiency of the pumping time, if it is acid gas, this will erode the oil pump, if it is water vapor will make oil into emulsion and pumping out the vacuum pump.
Therefore, we must pay attention to several points when using vacuum pump system：
1. between the distillation system and the vacuum pump, it must be equipped with suction assembly.
2. before distillation, the steam from the organic solvent outside the system must be pumped completely.
3. If the pump can be used for pumping, can the use of water pumps, such as distillates containing volatile materials, whether the first pump to reduce pressure pumping, and then switch to oil pumps.
4. The decompression system must be kept sparse without air leakage, all the rubber plugs should be suitable for the large and small warfare channels, and the rubber tubes should be vacuum rubber tubes. Ground glass is coated with vacuum grease.
|Size||Speed(m3/h)||Vacuum pump||Pumpquantity||Pressure(MPA)||Vacuum tank(m3)|
According to the limitation of application, can the vacuum pump be divided into three categories?
(1) the pressure of normal pump does not reach 1.333~100kPa (10~760mmHg) as a “fine” vacuum.
(2) the pressure of the oil pump can reach 0.133~133.3Pa (0.001~1mmHg) as a “secondary high” vacuum.
(3) the pressure of the dispersed pump can reach 0.133Pa with high and (10-3mmHg) high vacuum.
If you want lower pressure, you need to use the oil pump. The oil pump can pump 133.3Pa (1mmHg) high.
There are two kinds of vacuum pumps which are often used in organic chemistry laboratory, one is water pump, the other is vacuum pump. If the pressure is not very low, the other is water pump. If the layout of the pump is high and the water pressure is high, the pumping efficiency can reach 1067 ~ 3333 Pa (8 ~ 25 mmHg).
The lowest pressure that the pump can draw is actually equivalent to the steam pressure at high temperature. For example, when the water temperature is 25, 20, and 10, the vapor pressure is 3192, 2394, and 1197 Pa (8-25 mmHg). When pumping air with a water pump, a quiet bottle should be installed in front of the pump to prevent high water pressure drop and reverse suction of water flow; before pumping is stopped, the pump should be deflated first and then closed.