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VWR International is an American company involved in the distribution of research laboratory products, with over 1,200,000 items to more than 250,000 customers in North America and Europe. The U.S. division is headquartered in Radnor, Pennsylvania .
A turbomolecular pump is a type of vacuum pump, superficially similar to a turbopump, used to obtain and maintain high vacuum. [ 1 ] [ 2 ] These pumps work on the principle that gas molecules can be given momentum in a desired direction by repeated collision with a moving solid surface.
The inert-gas line is vented through an oil bubbler, while solvent vapors and gaseous reaction products are prevented from contaminating the vacuum pump by a liquid-nitrogen or dry-ice/acetone cold trap. Special stopcocks or Teflon taps allow vacuum or inert gas to be selected without the need for placing the sample on a separate line. [3]
Single-stage vacuum pumps typically produce vacuum to 35 torr (mm Hg) or 47 millibars (4.7 kPa), and two-stage pumps can produce vacuum to 25 torr, assuming air is being pumped and the ring-liquid is water at 15 °C (59 °F) or less. Dry air and 15 °C sealant-water temperature is the standard performance basis, which most manufacturers use for ...
In the field of oil regeneration and re-refining, vacuum pumps create a low vacuum for oil dehydration and a high vacuum for oil purification. [44] A vacuum may be used to power, or provide assistance to mechanical devices. In hybrid and diesel engine motor vehicles, a pump fitted on the engine (usually on the camshaft) is used to produce a vacuum.
A vacuum ejector, or simply ejector, or aspirator, is a type of vacuum pump, which produces vacuum by means of the Venturi effect.. In an ejector, a working fluid (liquid or gaseous) flows through a jet nozzle into a tube that first narrows and then expands in cross-sectional area.
An oil diffusion pump is used to achieve higher vacuum (lower pressure) than is possible by use of positive displacement pumps alone. Although its use has been mainly associated within the high-vacuum range, down to 1 × 10 −9 mbar (1 × 10 −7 Pa), diffusion pumps today can produce pressures approaching 1 × 10 −10 mbar (1 × 10 −8 Pa) when properly used with modern fluids and accessories.
No refrigeration unit is needed for the storage vessel because the liquid oxygen remains cold due to the efficiency of the vacuum container and the loss of latent heat as oxygen vaporizes. Nevertheless, if no oxygen is used the temperature of the storage vessel gradually rises until after about a week the oxygen pressure causes excess oxygen to ...