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Vacuum and Gas Kinetics
Published in Eiichi Kondoh, Micro- and Nanofabrication for Beginners, 2021
Rotary pump A rotary pump or rotary vane pump is probably the most common vacuum pump. It functions from the atmospheric pressure down to about 100 Pa in the case of single-stage usage. Figure 2.14 is an example of a rotary vane pump. Two vanes attached to a rotor at the center are pressed to the inner wall of a cylinder. As the axis of the rotor is offset from the cylinder axis, the volume of the space bounded by the vanes, the rotor, and the cylinder changes as the rotor rotates. Gas enters when this space has a larger volume, gets compressed with rotation, and is finally exhausted to the outlet port thorough a gas ballast valve. The internal space, such as the cylinder, is filled with oil. The oil serves to seal the outlet valve from leaks and also lubricates the moving parts. The capacity of rotary pumps for laboratory experiments (as well as for semiconductor manufacturing) have a pumping speed of 50–2000 ℓ/min. Rotary pumps are economically affordable, irrefrangible, easy-to-use or -to-maintain, and function from the atmospheric pressure so that no roughening/backing pumps are necessary. For these reasons, rotary pumps are widely used. One serious drawback is oil emission. As the gas directly gets in contact with oil, the oil vapor is easily incorporated to the vacuum which limits the achieving pressure and leads to contamination. The oil must be exchanged regularly as the oil degrades, but usually not so often.
Coarse Vacuum Pumps
Published in Marsbed H. Hablanian, High-Vacuum Technology, 2017
Vane pumps are rather simple in the basic concept and have been used for pumping liquids at least as early as 500 years ago. However, for high-vacuum application, which began about 90 years ago, a remarkable degree of effectiveness has been achieved. A single-stage oil-sealed rotary vane pump can produce inlet pressures near 0.010 torr for air while discharging to atmosphere. This represents a compression ratio of 105. Modern two-stage pumps, Figure 5.6 can produce at the inlet a partial pressure of air below 1 × 10−5 torr while discharging to the atmosphere, thus achieving a pressure ratio of almost 108.
Mechanical Displacement Pumps
Published in Igor Bello, Vacuum and Ultravacuum, 2017
The pumping of reactive gaseous substances may cause deterioration of oils, in consequence of which the pumps can develop mechanical problems. Special oils may provide good thermal stability; however, they may provide inadequate corrosion protection. For pumping of alkaline and acid vapor, rotary-vane pump oil B can be used. Rotary-vane pump oil B with low saturation pressure (<10−5Pa), mass density of 870 kg/m3 at 20 °C, flash point of 264 °C, and kinematic viscosity of 94 mm2/s at 40 °C is characteristic with much greater chemical stability at pumping gaseous substances such as alkaline and acid vapors, making it superior to the standard mineral oils. (Note, the unit mm2/s of kinematic viscosity is equivalent to the unit of centistokes, abbreviated as cSt. Consistent with ISO 3104, it is measured with calibrated capillary viscometers.)
Integration of two-stage nanofiltration with arsenic and calcium intermediate chemical precipitation for gold mining effluent treatment
Published in Environmental Technology, 2019
Laura H. Andrade, Wadson L. Pires, Luiza B. Grossi, Alice O. Aguiar, Míriam C. S. Amaral
The NF unit had a maximum operating pressure of 15 bar, which was provided by a rotary vane pump equipped with a speed controller and maximum flow of 530 L h–1. A needle-type valve was used to adjust the feed flow rate and the trans-membrane pressure. Feed temperature was controlled using cold bath.