Helium is used in a large range of applications due to its extreme unique properties of the noble gas. The chart below shows the main application areas in which helium is consumpted. Each application area is associated with one or more properties of helium.
The application areas of helium are now explained in more details.
Helium is used as a super coolant for cryogenic applications such as Magnet Resonance Imaging (MRI), Nuclear Magnetic Resonance (NMR) spectroscopy, particle accelerators, Large Hadron Collider, Superconducting Quantum Interference Device (SQUID), Electron Spin Resonance spectroscopy (ESR), Superconducting Magnetic Energy Storage (SMES), magnetohydrodynamic superconducting generators, power transmission, magnetic levitation transport, superconducting sensors, mass spectrometers, superconducting magnets, strong-field magnetic separator, toroidal field superconducting magnets for fusion reactors and other cryogenic research. Helium cools low-temperature superconducting materials and low-temperature superconducting magnets to a temperature close to absolute zero, so that the electrical resistance of superconductors drops abruptly to zero. The very low electrical resistance of superconductors enables to create more powerful magnetic fields. In the case of MRI equipment in hospitals the more powerful magnetic field yields greater detail in the radiological image scans. Helium is used as super coolant, because helium has the lowest melting and boiling points of any element and helium does not solidify at atmospheric pressure and 0 K and helium is chemically inert. Furthermore helium is superfluid below 2.2 Kelvin. Untill now the unique property superfluidity is not exploited in any industrial application. Helium as super coolant cannot be substituted in cryogenic applications, if temperatures below 17 Kelvin are required.
Helium is the second lightest element after hydrogen and the density of helium is lighter than air. Therefore helium is used as lift gas for balloons, meteorological balloons, airships and blimps since WWI. Despite helium is less buoyant than hydrogen, helium is the preferred lift gas, because it is not flammable. The use of helium as lifting gas was the first application of helium since its discovery on Earth. As lift gas helium can be substituted by hydrogen or a mixture of hydrogen and nitrogen.
Helium is applied as a shielding gas in arc welding and plasma arc welding due to its highest ionization potential of any atom. The protective atmosphere of helium around the welding site prevents that the metal oxidizes in the molten state. The high ionization potential of helium enables the plasma arc welding of exotic metals such as titanium, zirconium, magnesium and aluminum alloys used in construction, shipbuilding and aerospace. As shielding gas helium can be substituted by argon or hydrogen, however for plasma arc welding of certain materials like titanium helium cannot substituted, because helium is the only gas with high enough thermal activity to be safe.
Inner atmosphere operations
Helium is applied in pressure purging operations where liquid hydrogen or another gas is replaced by helium as liquid hydrogen or another gas is used, because helium is the only gas with a lower boiling point than hydrogen and helium is inert. Nitrogen is not used as purging gas for liquid hydrogen systems, because in these conditions nitrogen would solidify. Helium as purging gas is used in the aerospace industry for space agencies like Arianespace and NASA. For example, in Delta IV rockets helium was used to maintain pressure in liquid oxygen fuel tanks. As liquid oxygen is burned as rocket fuel, helium is injected into the fuel tanks to keep them from collapsing. Helium as purging gas can be substituted by nitrogen, except for liquid hydrogen systems.
Helium is used for leak detection, because helium has the smallest molecular size and it is likewise a monatomic molecule. Therefore helium passes easily through the smallest leaks. During leak detection an object is filled with helium and in case of a leak a helium mass spectrometer will detect where the leak is located. Helium provides for detecting leaks in rockets, fuel tanks, heat exchanges, gas lines, various electronic devices, television tubes and other manufactured components. Helium for leak detection was first applied during the Manhattan Project to find leak in the uranium enrichment plants. Helium for leak detection can be substituted by hydrogen or nitrogen or a mixture of hydrogen and nitrogen.
Helium is applied as carrier gas and purging gas for gas chromatography, because helium is chemically inert and high purity. Chromatography is a collective term used for laboratory techniques to separate mixtures. Chromatographs are widely used for qualitative and quantitative analysis in processes and laboratories. As carrier gas helium can be substituted by hydrogen or nitrogen.
Helium is used as preferred protective gas due its chemically inertness and helium is used as cooling gas due its very high specific heat and thermal conductivity in semiconductor manufacturing. For example, helium is used as the sleeve in rods that create LCD screens. Another example, during the processing of semiconductor chips helium is used as protective gas for flushing vessels. Furthermore helium is used as protective gas and cooling gas, when growing silicon and germanium crystals. Helium can be substituted by argon or hydrogen or nitrogen depending on its application.
Fiber optics manufacturing
Helium is used as coolant during the fiber optical cable manufacturing due its very high specific heat and thermal conductivity. The liquid helium’s low temperature and inertness makes it ideal to cool rapidly silica strands in a cooling tube as glass fibers are drawn from a glass billet or preform. Helium as cooling medium can be substituted by hydrogen or nitrogen.
Heat transfer medium in nuclear reactors
Helium is used as heat transfer medium in the new generation nuclear reactors. Helium has several advantages as heat transfer medium. Helium has a very high specific heat and a high thermal conductivity, so that it is one of the most efficient heat transfer gas. In addition helium does not cause corrosion and it is radiologically inert (no radioactive isotopes). Helium does not change aggregate state and it does not influence neutron multiplication factor. Nuclear plants with helium as heat transfer medium have higher efficiency and higher operating temperatures. Helium as heat transfer medium can be substituted by nitrogen.
Helium is used as deep sea diving gas at water depths below 30 m due to its extremely low solubility in water and blood. Helium/oxygen breathing mixtures such as heliair, trimix and heliox are used instead of nitrogen /oxygen breathing mixtures to avoid nitrogen narcosis or the build-up of nitrogen in blood. In addition helium does not cause corrosion to the equipment and it is not toxic. Hydrogen is investigated as a substitute for helium as deep sea diving gas.
Metal coating spraying
Helium is used as powder carrier gas for thermal spraying and cold spraying due its extremely high speed of sound and its chemically inertness. Thermal spraying and cold spraying, also commonly known as metal spraying is a surface coating processes where a wide range of metals and ceramics can be sprayed at great velocities onto the surface of another material to create metal coatings. In addition the very high sonic velocity of helium makes your voice sound high pitched or squeaky after inhaling helium. Helium as powder carrier gas can be substituted by nitrogen.
Lasers and Lighting
Helium is used as working gas in lasers and lighting. The resonator gas helium is applied in gas lasers such as helium-neon laser and CO2 laser and metal-vapor lasers like helium-cadmium metal-vapor laser. Helium is used in lasers for excitation. Different lasers with the working gas helium are applied for different applications like scientific research, interferometry, holography, spectroscopy, barcode scanning, alignment, laser eye surgery, optical demonstrations, printing and typesetting applications, welding and cutting. Most helium-neon lasers are now substituted by cheaper diode lasers. Furthermore helium is used as working gas in gas-discharge lamps. Helium emits colors from white to orange. Helium gas-discharge lamps are used by artists for special purpose lighting. As working resonator gas helium in some laser types helium cannot be substituted.
Helium is used in some hard drives. Hard drives are filled with helium in order to achieve large amount of disks and high data storage capacity. Helium has one-seventh the density of air and therefore reduces mechanical power dissipated in air drag and air shear. In addition it allows the spinning disks to be closer to each other. The spinning disks are also more energy efficient, because less motor power and less cooling are required due to the gas helium.
Helium is applied in solar telescopes. The helium reduces the distorting effects of heat between lenses in some telescopes due to exceptionally low index of refraction and a high thermal conductivity. Helium can be substituted by using vacuum telescopes.
Thermoacoustic heat pump
Helium is applied in thermoacoustic heat pump due to the fact helium is a light weight inert gas with small atomic size. With usage of helium gas the gap between the stack plates will be minimized to a large extent. Because with the less atomic size vanderwaals forces are weaker with respect to other noble gases. Therefore kinematic viscosity is very low. So, the molecules are free to vibrate even in a small gaps resulting high utilization of gas molecules for to participate in heat transfer.