(He) Helium
A colorless, odorless, nonreactive inert gas which is
compressed to high pressures. It acts as a simple asphyxiant by
displacing air.
- Helium is used as an inert gas shield in arc
welding, as a lifting gas for lighter-than-air aircraft,
as a gaseous cooling medium in nuclear reactors, to
provide a protective atmosphere for growing germanium and
silicon crystals for transistors, to provide a protective
atmosphere in the production of such reactive metals as
titanium and zirconium, to fill cold-weather fluorescent
lamps, to trace leaks in refrigeration and other closed
systems, and to fill neutron and gas thermometers. It is
used in cryogenic research such as for superconductivity.
In mixtures with oxygen, it has medical applications.
Radioactive mixtures of helium with krypton are available
to users licensed by the Nuclear Regulatory Commission.
Liquid helium is also gaining wide use for cooling
superconductive magnets used in magnetic resonance
imaging.
- The primary source of helium is from natural
gas wells. it is obtained by a liquefaction and stripping
operation. A new process for recovering helium utilizes
the diffusion of helium through quartz. Helium is also
obtained in small quantities from the air by
liquefaction, rectification, and selective adsorption on
charcoal at low temperatures.
- Gaseous helium is commonly stored in high
pressure cylinders, hydril tubes, or tube trailers.
Liquid helium is commonly stored at the consumer site in
cryogenic liquid cylinders and specially designed
insulated tanks. To minimize helium transfer losses, the
shipping container for liquid helium is normally used for
storage.
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