Helium

Chemical Symbol:        He
DOT Proper Shipping Name:    Helium, Compressed / Helium, Refrigerated

 

 

PHYSICAL CONSTANTS    
     
  U.S. Units SI Units
Chemical formula: He He
Density of gas: 4.00 4.00
At 70oF (21.1oC) and at 1 atm:          0.0103 id/ft3 0.165 kg/m3
Specific gravity of the gas: 0.138 0.138
Boiling Point at 1 atm: -452.1oF (-268.9oC)     -450.3oF (-267.9oC)
  33.0 psia 27kPa, abs
Latent heat of vaporization
at boiling point and at 1 atm:
8.72 BTU/lb 20.28 kJ/kg


  

DESCRIPTION

After hydrogen, helium is the lightest element and has the smallest molecular cross-section of any gas. Helium Is one of the rare gases in our earth’s atmosphere in which it is present in a concentration of 5 ppm. It is completely inert to chemical reaction and radiation. Its thermal conductivity surpasses that of any other inert gas and is three times greater than neon, its nearest inert competitor.

Helium’s boiling point of -452.1°F (268,9°C) gives its refrigeration capabilities beyond those of any other substances. Helium provides a high rate of permeability and ease of detection with only slight solubility in the bloodstream. It is non flammable and slightly soluble in water. It is usually shipped at high pressures at or above 2,400 psig at 70°F in cylinders and in bulk units. It is also shipped as a cryogenic liquid.

 

USES

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. It is also used 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. Its thermal conductivity makes it an important gas for lasers and fibre optic production. It is used extensively in chromatography due to its inertness and high conductivity. It is used in cryogenic research such as for superconductivity. Liquid helium is used for cooling superconductive magnets, used in magnetic resonance imaging, and in magnetic separation.

 

PHYSIOLOGICAL EFFECTS

Helium is non-toxic and inert. It can act as a simple asphixlant by diluting the concentration of oxygen in air below levels necessary to support life. Inhalation in excessive concentrations can result in dizziness, nausea, vomiting, loss of consciousness, and death.

Gaseous helium must be handled using ail the precautions necessary for safety with any non-flammable, non-toxic compressed gas. Extensive tissue damage similar to burns can result from exposure to liquid helium or cold helium vapours.

 

SAFE STORAGE, HANDLING AND USE

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, portable customer stations, and specially designed insulated tanks. To minimise helium transfer losses, the shipping container for liquid helium is normally used for storage. Users of liquid helium must also take special precautions in addition to those necessary for the safe handling of such inert liquefied gases as nitrogen and argon. The extremely low temperature of liquid helium makes these special precautions imperative; it can solidify all other gases and cause air to condense on any uninsulated or inadequately insulated pipe through which it passes. Liquid helium must not be allowed to come in contact with air and must not be equipped with pressure relief devices that prevent back-leakage of air into liquid helium equipment. Plugging by solidified air constitutes a serious safety hazard. If air enters and plugs the vent of a helium container, a serious hazard is created. Liquid and gaseous systems should be designed and installed only under the direction of personnel thoroughly familiar with liquid and gaseous helium equipment and in full compliance with ail state, provincial, and local requirements.

 

SAFE STORAGE, HANDLING AND USE

Small Portable Containers (dewars) - Liquid helium is shipped and stored in small insulated portable containers, which hold quantities ranging from 1 gal to 132 gal (3.8L to 500L) or more.

 

Portable Tanks

Liquid helium is shipped domestically and internationally in intermodal or ISO-type containers under DOT exemption. These specially designed vessels can be transported without venting by highway or sea for periods exceeding 30 days.

 

METHODS OF MANUFACTURE

Helium is extracted from natural gas cryogenically, then purified via cryogenics or pressure swing adsorption processes, or both, and is generally liquefied for the reason of distribution economics.

Currently all major quantities of helium worldwide are recovered as a by-product of natural gas processing.