Oil-free vacuum

Light gases with higher thermal velocity are pumped less than heavier ones. This is why turbo pumps produce an (almost) oil-free vacuum. The lubrication of turbo pumps is made with a special vacuum grease. Pumps with magnetically levitated rotor are available, but they are more expensive. 

DC 705,4 10 ° mbar). The specified provisions with a liquid-nitrogen-cooled baffle or cold trap would enable an absolutely oil-free vacuum to be produced. 

Modern leak detectors are being more frequently equipped with oil-free vacuum systems, the so-called dry leak detectors (UL 200 dry, UL 500 dry). Here the problem of gas being dissolved in oil does not occur but similar purging techniques will nonetheless be employed. 

Vacuum System Oil Diffusion High Vacuum Pum= Oil-Free Vacuum System... 

There are some special cases for which it is unnecessary to add a lubricant. Magnetic bearings and bearings that are suspended by a pressurized gas have no metal-to-metal contact so that wear and heat buildup are avoided. Several companies sell oil-free vacuum pumps that eliminate the trouble and expense of changing the oil, disposal costs, and contamination of process chambers, which is especially important in the manufacture of semiconductors and liquid crystal crystal displays.40 Plastic gears of nylon or polytetrafluoroethylene are self-lubricating and need no added lubricant. They reduce the noise associated with ma-... 

The SiOx films we fabricated was done by physical vapor deposition of SiO with controlled oxygen admission in an oil-free vacuum apparatus at 1 x 10 mbar base pressure. The experimental set-up is shown schematically in Figure 19.4. Thermal evaporation of SiO from two Ta boats was directed to rotating 10 cm Si(lOO) wafer substrates heated by rear illumination with tungsten halide lamps. To achieve uniform film thickness over the large area of the Si wafer, the angle between the evaporators and substrate center was fixed at 53°, while the distance between the substrate plane and evaporator plane was kept at 20 cm. Routinely, films of 100 run... 

Figure 18.8 shows the flow chart of the hollow fiber membrane system for oxygen production with the vacuum operating mode. The membrane module is placed under a vertically positioned tubular furnace with the sealing points kept out of the bottom inlet of the furnace tube. An oil-free vacuum pump is connected to the lumen of the fibers to yield a negative pressure and to collect the oxygen product. 

Curve 5 in Figure 7.7 demonstrates the use of IRRAS to monitor the purity of metallic surfaces before chemical modification. The samples were polished with diamond paste, washed in CCI4 and hot water, etched in HNO3 in order to remove the damaged layer, swilled in bidistilled water, and then annealed for 1 h in an oil-free vacuum at f = 200°C. The spectra show only the bands of the natural oxides and no bands from impurities. 

Oil-free vacuum pumps are now available which will eliminate the risks of oil back-migration and associated hazards. 

Figure 19 (a)-(c) Oil free vacuum pump sets, (a) Schema of a dry vacuum pump... 

Vacuum System and Separation of Signals from Background Gases A reliable, oil-free vacuum system is an essential part of a KEMS system. The loca-... 

Oil-free vacuum pump (vacuum technology) See Dry pump. 

The chemist is going to need a source of vacuum. When distilling high boiling stuff like valuable ecstasy free base oil, a vacuum is... 

For the pumping of large quantities of gas in this pressure region, vapor ejector pumps are by far the most suitable. With mercury vapor ejector pumps, completely oil-free vacua can be produced. As a precaution, the insertion of a cold trap chilled with liquid nitrogen is recommended so that the harmful mercury vapor does not enter the vessel. With the medium vacuum sorption traps described under a), it is possible with two-stage rotary vane pumps to produce almost oil-free vacua down to below 10" mbar. 

Absolutely oil-free vacua may be produced in the medium vacuum region with adsorption pumps. Since the pumping action of these pumps for the light noble gases is only small, vessels initially filled with air can only be evacuated by them to about 10 2 mbar. Pressures of lO mbar or lower can then be produced with adsorption pumps only if neither neon nor helium is present in the gas mixture to be pumped. In such cases it can be useful to expel the air in the vessel by first flooding with nitrogen and then pumping it away. 

Developments in vacuum Pumping systems based on mechanical pumps with an oil free swept volume N cuum, 38, 968, 757-760... 

Mechanical high-vacuum pumps with an oil-free swept volume J. c. Sci. Technol. A5 (4) 1987, 2608-2611... 

NEPCCO SoilPurge soil vapor extraction systems are noncontacting, oil-free, explosion-proof vacuum systems designed to remove volatile organic compounds (VOCs) from soil in situ. According to the vendor, benzene, toluene, ethylbenzene, and xylenes (BTEX), chlorinated solvents and other hydrocarbons can be treated with SoilPurge systems. The technology can also remove radon from soil. 

In most cases, the nonsterile containers must be cleaned in line (e.g., inverted, blown with clean, dry, oil-free, compressed air from a probe in the bottom of the container, then sucked out, with vacuum sited at the neck). The resulting dislodged particles are then sucked away from the container while the air probe is being withdrawn. 

Oil-free Ion pump provides clean, ultrahigh vacuum pumping. 

P = 10-100 W. Mass flow controllers for gases and a standard pressure of 6 Pa were adjusted. For production of an oil-free high vacuum a turbomolecular pump was applied. Using aggressive gases or vapours a cryo trap was interposed between reactor and pump. 

If liquids other than water are used they should have a low evaporation rate under vacuum and a high boiling point (>170°C) aromatic or aliphatic compounds are suitable. The use of oil presents a particular problem in that it is difficult to ensure that the outside of the bottle is completely oil free. 

A reliable medium vacuum (about 12mm Hg) can be provided by oil-free Teflon lined diaphragm pumps (e.g. KNF, Vacuubrand, Divac). These pumps are extremely useful and can often be used instead of either water... 

Various oil-free electric diaphragm pumps can be used to provide vacuum levels down to about lOmmHg. Some models are Teflon lined (e.g. KNF, Vacuubrand, Divac) and designed to withstand solvent vapours, and these... 

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