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Name: helium gas
Purity: 99.9~99.999%
Property: colourless, odourless, non-flammable, non-reactive, inert gas
Application: Helium has been initially and widely used in Electronic industry, chemical industry,colleague laboratory and dirigible-balloons.
Helium is used for many purposes that require some of its unique properties, such as its low boiling point, low density, low solubility, high thermal conductivity, or inertness. Of the 2008 world helium total production of about 32 million kg (193 million standard cubic meters) helium per year, the largest use (about 22% of the total in 2008) is in cryogenic applications, most of which involves cooling the superconducting magnets in medical MRI scanners. Other major uses (totalling to about 78% of use in 1996) were pressurizing and purging systems, maintenance of controlled atmospheres, and welding. Other uses by category were relatively minor fractions.
Controlled atmospheres
Helium is used as a protective gas in growing siliconand germaniumcrystals, in titaniumand zirconiumproduction, and ingas chromatography, because it is inert. Because of its inertness, thermally and calorically perfect nature, high speed of sound, and high value of the heat capacity ratio, it is also useful in supersonic wind tunnels and impulse facilities.
Gas tungsten arc welding
Main article: gas tungsten arc welding.
Helium is used as a shielding gas in arc weldingprocesses on materials that at welding temperatures are contaminated and weakened by air or nitrogen. A number of inert shelding gases are used in gas tungsten arc welding, but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity, like aluminium or copper.
Minor uses
Industrial leak detection
One industrial application for helium is leak detection. Because helium diffusesthrough solids three times faster than air, it is used as a tracer gas to detect leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers. The tested object is placed in a chamber, which is then evacuated and filled with helium. The helium that escapes through the leaks is detected by a sensitive device (helium mass spectrometer), even at the leak rates as small as 10−9 mbar·L/s (10−10 Pa·m3/s). The measurement procedure is normally automatic and is called helium integral test. A simpler procedure is to fill the tested object with helium and to manually search for leaks with a hand-held device.
Helium leaks through cracks should not be confused with gas permeation through a bulk material. While helium has documented permeation constants (thus a calculable permeation rate) through glasses, ceramics, and synthetic materials, inert gases such as helium will not permeate most bulk metals.
Flight
Because it is lighter than air, airshipsand balloons are inflated with helium for lift. While hydrogen gas is approximately 7% more buoyant, helium has the advantage of being non-flammable (in addition to being fire retardant). While balloons are perhaps the most well-known use of helium, they are a minor part of all helium use. Another minor use is in rocketry, where helium is used as an ullage medium to displace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to make rocket fuel. It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles. For example, the Saturn Vbooster used in the Apollo program needed about 370,000 m3(13 million cubic feet) of helium to launch.
Minor commercial and recreational uses
For its low solubility in nervous tissue, helium mixtures such as trimix, heliox and heliair are used for deep divingto reduce the effects of narcosis. At depths below 150 metres (490 ft) small amounts of hydrogenare added to a helium-oxygen mixture to counter the effects of high pressure nervous syndrome. At these depths the low density of helium is found to considerably reduce the effort of breathing.
Helium-neon lasers, a type of low-powered gas laser producing a red beam, had various practical applications which included barcode readers and laser pointers, before they were almost universally replaced by cheaper diode lasers.
For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.
Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number. The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.
Scientific uses
The use of helium reduces the distorting effects of temperature variations in the space between lenses in sometelescopes, due to its extremely low index of refraction. This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.
Helium is a commonly used carrier gas for gas chromatography.
The age of rocks and minerals that contain uraniumand thoriumcan be estimated by measuring the level of helium with a process known as helium dating.
Helium at low temperatures is used in cryogenics, and in certain crygenics applications. As examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as insuperconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain the temperature at 1.9 kelvin.
Typical technical data
Name | Specification | Impurity content (ppm) | Carry out Standard |
Helium(H2) | 99.99% | O2 +Ar≤3,N2 ≤60,CO≤5,CO2 ≤5,CH4 ≤10,H2 O≤30 | GB/T 7445-1995 |
99.999% | O2 +Ar≤1,N2 ≤5,CO≤1,CO2 ≤1,CH4 ≤1,H2 O≤3 | GB/T 7445-1995 | |
99.9999% | O2 +Ar≤0.2,N2 ≤0.4,CO≤0.1,CO2 ≤0.1,CH4 ≤0.2,H2 O≤1 | GB/T 7445-1995 |