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As defined here, industrial gases encompass a large number of products that are gaseous at room temperature and pressure, and while they may actually be stored as a liquid or solid, they are commonly used in gaseous form. From a more scientific perspective, a gas is a state of matter without a prescribed shape or volume. Gases have unique properties and characteristics depending upon such variables as the temperature, pressure, and volume to which they are subjected. Gases have low densities, assume the volume of their containment (or dissipate to the atmosphere), mix well with other gases, and are more compressible than solids and liquids.
Industrial gases are comprised of elements, molecular compounds, or mixtures. The most common industrial gases are oxygen, hydrogen, nitrogen, carbon dioxide, and noble gases such as argon, neon, xenon, and krypton. Some industrial gases such as nitrogen, oxygen, argon, LNG, and liquefied petroleum gas are liquefied at high pressure for ease of storage and transport. At even lower temperatures these liquids can turn to a solid. Dry ice, a solid form of carbon dioxide, is a common example of a normally gaseous material (at ambient conditions) that has useful properties as a solid. Much of the carbon dioxide will sublimate; meaning it will move directly to the gaseous phase from the solid phase without becoming a liquid. Finally, some industrial gases, such as hydrogen, are highly volatile and need special handling and storage to ensure safe usage.
How to Safely Set Up a Propane/ Oxygen Torch
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Industrial gas suppliers typically provide the gas as well as the storage and processing equipment necessary to facilitate transportation and proper usage. Industrial gas equipment may include storage tanks and distribution systems, vaporizers and pressure vessels (dewars, cylinders, and tanks), and cryogenic trailers. Each of these items typically includes a means of controlling pressure and flow.
Gas Storage and Delivery
Because gases must be contained and readily available at point of use, the means of delivery is critically important to ensure system compatibility and safe transportation. A variety of storage containers include: bulk containers, cryogenic cylinders (Dewars), gas cylinders, and glass bottles (ampules). Additionally, there are more application-specific containers, including permeation tubes and safe delivery systems. Although not covered here, (see Gas Generation Equipment), gases may be produced in an on-site generation system.
Bulk and Microbulk Delivery
Bulk gases can be supplies by several methods: stationary cylinders, horizontally-mounted tube trailers, or pipelines. The stationary cylinder must be refilled periodically from a gas line or cryogenic tank trailer. Cryogenic tank trailers can deliver liquid gas in bulk form. Pipeline delivery is only available in areas near a gas production plant.
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A gas cylinder or tank is a pressure vessel used to store gases at high pressure.
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Cryogenic Cylinder / Dewar (Liquid)
An insulated container used especially to store liquefied gases; having a double wall with a vacuum between the walls and silvered surfaces facing the vacuum.
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Glass Bottle or Ampule
Glass bottles or sealed ampules are used for small quantities of gases for R&D, analytical standards, or specialty applications.
These systems produce a gas where it will be used. For example, there are complete systems to concentrate oxygen and nitrogen from air that are built within industrial facilities, thereby eliminating transportation costs.
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Permeation tubes are small, inert capsules containing a pure chemical molecule. At constant temperature, the device emits the molecule through the permeable tube wall at a constant rate.
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Safe Delivery System
SDS (safe delivery system) is a groundbreaking technology designed to reduce the hazards and environmental risks associated with transporting, storing, and delivering highly toxic gases.
In all cases, safe and proper handling of the stored gases is essential!
Compressed Gas Cylinder Training Video.
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LPG Gas Cylinder Training
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Physical Properties of Gases
As mentioned earlier, gases are compressible and, as such, knowledge of the pressure generated by a gas as it relates to temperature and volume are critical to any application from both a performance and safety perspective.
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From a performance perspective, knowledge of the boiling point and freezing point may be relevant, but the auto-ignition temperature, the minimum temperature required to ignite a gas or vapor in air without a spark or flame present, is of paramount importance.
The flammable (or explosive) range is the range of a gas or vapor concentration that will burn or explode if an ignition source is introduced. Limiting concentrations are commonly called the lower explosive or flammable limit (LEL/LFL) and the upper explosive or flammable limit (UEL/UFL).
Other properties that are relevant to particular applications include:
- Specific Volume (ft3/lb., m3/kg)
- Density of liquid at atmospheric pressure (lb./ft.3, kg/m3)
- Absolute Viscosity (lb.m/ft. s, centipoises)
- Specific Heat - cp - (Btu/lboF or cal/goC, J/kgK)
- Specific Heat Ratio - cp/cv
- Gas constant - R - (ft. lb./lboR, J/kgoC)
- Thermal Conductivity (Btu/hr. ft. oF, W/moC)
- Boiling Point - saturation pressure 14.7 psia and 760 mm Hg - (oF, oC)
- Latent Heat of Evaporation at boiling point (Btu/lb., J/kg)
- Freezing or Melting Point at 1 atm (oF, oC)
- Critical Temperature (oF, oC)
- Critical Pressure (psia, MN/m2)
- Critical Volume (ft.3/lb., m3/kg)
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One important way to look at compressed gases, because of how they are used, is their capacity as oxidizing agents, flammable gases, and inert gases.
- Oxidizers are not flammable by them self, but will contribute to combustion as an oxidant. Some common oxidizers include:
- Nitric Oxide
- Nitrogen Dioxide
Flammable gases, together with air or oxygen in the right concentration, burn or explode if ignited. If the mixture is too lean or too rich, the mixture will not ignite. Some flammable gases include:
Inert gases do not take part in combustion processes and they do not react with other materials. An inert gas supplied to a room or limited space will reduce the amount of oxygen and limit a combustion process of a fire. Examples include:
- Carbon Dioxide
Application and Use of Gases
Industrial gases are used in a myriad of applications that are dependent upon the many unique properties of specific gases. For example, industrial gases are commonly used in manufacturing, especially in cutting and welding applications. Acetylene gas is a highly flammable gas used in such applications as the production of organic compounds such as neoprene and rubber. It may also be pressurized to produce benzene. Oxygen acetylene torches mix oxygen and acetylene gas in controlled amounts to produce an extremely hot flame. Oxy acetylene welding is used to cut steel or weld iron, and can produce a flame as hot as 6300° Fahrenheit. Other cutting devices include carbon dioxide lasers. CO2 laser cutting uses a laser beam focused with a lens to cut materials and is typically used for precision applications such as laser surgery. Rare industrial gases such as argon are also commonly used in laser applications.
Major applications include:
- Calibration Gas / Gas Standard - a defined gas concentration used to establish the response curve of an analyzer.
- Chemical Process / Petrochemical - pure gases, gas mixtures, or gas standards for reactions, water treatment, sterilization, instrumentation calibration, heating, and processing in the chemical, petrochemical and pulp and paper industries.
- Electronic and Semiconductor - specialized for microelectronic manufacturing or semiconductor processing applications such as thin film deposition (CVD, PVD), etching, RTP, packaging, or soldering.
- Environmental Monitoring - reference for compliance with regulatory mandates.
- Food & Beverage / Packaging - food and beverages require gases for storage, ripening, carbonation, to minimize oxidation, sustain freshness, and more.
- Laboratory / Analytical - used to ensure a uniform and/or inert environment for research, quality control, analytical work and other laboratory needs.
- Laser Gas - lasers require special gases to create a laser beam.
- Pharmaceutical / Medical Gas - used for patient care, surgical procedures, and therapy.
Welding / Thermal Process Gas - high temperature processes require gases with a high energy content and low flash point.
Major Industrial Gases
While there are literally thousands of available industrial gases, certain industrial gases are major elements of the world economy. Major gases include:
Hydrogen (H) - a colorless, highly flammable, gaseous element. It is used in the production of synthetic ammonia and methanol, in petroleum refining, in the hydrogenation of organic materials, as a reducing atmosphere, in oxyhydrogen torches, and in rocket fuels. Ordinary hydrogen gas is made of diatomic molecules (H2) that react with oxygen to form water (H2O) and hydrogen peroxide (H2O2), usually as a result of combustion.
- Hydrogen Bromide - an irritating, colorless gas used in the manufacture of barbiturates and synthetic hormones.
- Hydrogen Chloride (HCl) - a highly corrosive and toxic, colorless gas. White fumes form on contact with humidity. HCl often refers to hydrochloric acid, which is actually a mixture of hydrogen chloride in water.
- Hydrogen Fluoride (HF) - a colorless, fuming, corrosive liquid or a highly soluble, corrosive gas used in the manufacture of hydrofluoric acid; as a reagent, catalyst, and fluorinating agent; and in the refining of uranium and the preparation of many fluorine compounds.
- Hydrogen Sulfide (H2Se) - a colorless, flammable, poisonous gas with a characteristic rotten-egg odor. It is used as an antiseptic, bleach, or reagent.
Nitrogen - a nonmetallic element that constitutes nearly four-fifths of the air by volume. It occurs as a colorless, odorless, almost inert, diatomic gas (N2), in various minerals. Nitrogen is found in all proteins and used in a wide variety of important manufactures, including ammonia, nitric acid, TNT, and fertilizers. Atomic number 7; atomic weight 14.0067; melting point -209.86°C; boiling point -195.8°C; valence 3, 5.
- Ammonia (NH3) - toxic and corrosive to some materials; with a pungent odor. Ammonia is used in the production of fertilizers, explosives, polymers, and household cleaners
- Nitric Oxide (NO) - a toxic air pollutant produced by automobiles and power plants.
- Nitrous Oxide -include dinitrogen oxide (N2O, nitrous oxide), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5).
- Nitrogen Dioxide (NO2) - a poisonous brown gas often found in smog and automobile exhaust fumes. It is synthesized for use as a nitrating agent, a catalyst, and an oxidizing agent.
- Nitrogen Trifluoride (NF3) - a colorless gas that has a melting point of -206.6°C and a boiling point of -128.8°C; used as an oxidizer for high-energy fuels.
Air - a colorless, odorless, tasteless, gaseous mixture; mainly nitrogen (approximately 78 percent) and oxygen (approximately 21 percent), with lesser amounts of argon, carbon dioxide, hydrogen, neon, helium, and other gases.
- Oxygen (O2) - an atmospheric gas. The abundance of free oxygen is due to photosynthesis by plants.
- Carbon Dioxide (CO2) - a common chemical compound formed as a byproduct of respiration, fire, and combustion.
- Carbon Monoxide (CO) - a flammable, toxic, colorless, and odorless. It is also a major byproduct of combustion.
- Ethylene Oxide (CH2)2O - a colorless gas, soluble in organic solvents and miscible in water; boiling point 11°C; used in organic synthesis for sterilizing, and fumigating. Also known as 1,2-epoxyethane epoxide; oxirane
- Sulfur Dioxide - sulfur dioxide (SO2) is a colorless, extremely irritating gas or liquid used in many industrial processes, especially the manufacture of sulfuric acid.
The Noble Gases:
- Argon -one of the inert or noble gases. Argon gas is colorless, odorless, nontoxic, and nonflammable. Argon is typically shipped as a compressed gas.
- Helium - a colorless, odorless, inert, gaseous element occurring in natural gas and with radioactive ores. It is used as a component of artificial atmospheres and laser media, as a refrigerant, as a lifting gas for balloons, and as a superfluid in cryogenic research. Atomic number 2; atomic weight 4.0026; boiling point -268.9°C; density at 0°C 0.1785 gram per liter.
- Krypton - a whitish, largely inert, gaseous element used chiefly in gas discharge lamps and fluorescent lamps. Atomic number 36; atomic weight 83.80; melting point -156.6°C; boiling point -152.30°C; density 3.73 grams per liter (0°C).
- Neon - a whitish, largely inert, gaseous element used chiefly in gas discharge lamps and fluorescent lamps. Atomic number 36; atomic weight 83.80; melting point -156.6°C; boiling point -152.30°C; density 3.73 grams per liter (0°C).
- Xenon - a colorless, odorless, highly unreactive, gaseous element found in minute quantities in the atmosphere, extracted commercially from liquefied air and used in stroboscopic, bactericidal, and laser-pumping lamps. Atomic number 54; atomic weight 131.29; melting point -111.9°C; boiling point -107.1°C; density (gas) 5.887 grams per liter; specific gravity (liquid) 3.52 (-109°C).
The Hydrocarbon Gases:
- Acetylene - a colorless, highly flammable or explosive gas; C2H2 is used for metal welding and cutting and as an illuminant. Also called ethyne.
- Butane - two isomers of a gaseous hydrocarbon; C4H10 is produced synthetically from petroleum and is used as a household fuel, refrigerant, and aerosol propellant, and in the manufacture of synthetic rubber.
- Butadiene - a colorless, highly flammable hydrocarbon, C4H6 is obtained from petroleum and used in the manufacture of synthetic rubber.
- Butene - any of three isomeric hydrocarbons C4H8; all used in making synthetic rubbers; also known as butylene.
- Ethane - a colorless, odorless, gaseous alkane; C2H6 occurs as a constituent of natural gas and is used as a fuel and a refrigerant.
- Ethylene - A colorless flammable gas; C2H4 is derived from natural gas and petroleum, and is used as a source of many organic compounds: in welding and cutting metals, to coloring citrus fruits, and as an anesthetic. Also called ethene.
- Methane - an odorless, colorless, flammable gas; CH4, the major constituent of natural gas, is used as a fuel, and is an important source of hydrogen and a wide variety of organic compounds.
- Propane - A colorless gas, C3H8 is found in natural gas and petroleum, and is widely used as a fuel.
- Propylene - a flammable gas, CH3CH:CH2 is derived from petroleum hydrocarbon cracking and used in organic synthesis. Also called propene.
- Chlorine (Cl2) - a diatomic gas that is yellow-green in color. It is a halogen that combines easily with nearly all other elements. Chlorine irritates the respiratory system and mucous membranes. It is fatal in amounts of 1,000 ppm or more. Prolonged exposures at lower, non-fatal levels weaken the lungs.
- Boron Trichloride - A flammable gas, CH3CH:CH2 is derived from petroleum hydrocarbon cracking and used in organic synthesis. Also called propene.
- Chlorine Trifluoride (ClF3) - a colorless, poisonous, corrosive, and very reactive gas that condenses to a pale, greenish-yellow liquid -- the form in which it is most often sold (pressurized at room temperature). The compound is primarily of interest as a component in rocket fuels, in industrial cleaning and etching operations in the semiconductor industry, in nuclear reactor fuel processing, and other industrial operations
- Dichlorosilane (H2SiCl2) - or DCS as it is commonly known, is usually mixed with ammonia (NH3) in LPCVD chambers to grow silicon nitride in semiconductor processing.
- Ethyl Chloride (C2H5Cl) - a gas at ordinary temperatures and a colorless, volatile, flammable liquid when compressed; used as a solvent, as a refrigerant, and in the manufacture of tetraethyl lead.
- Silicon Tetrachloride (C2H5Cl) - a gas at ordinary temperatures and a colorless, volatile, flammable liquid when compressed; used as a solvent, as a refrigerant, and in the manufacture of tetraethyl lead.
- Trichlorosilane - a chemical compound containing silicon, hydrogen, and chlorine. At high temperatures it decomposes to produce silicon, and therefore purified trichlorosilane is the principal source of ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a silicone polymer while giving off hydrochloric acid. Because of its reactivity and wide availability it is frequently used in the synthesis of silicon-containing organic compounds.
- Fluorine (F) - a poisonous, pale, yellow-green gas that is the most chemically reactive of all the elements. It is highly dangerous in its pure form and can cause severe burns if it comes into contact with the skin.
- Boron Trifluoride (BF3) - a pungent, colorless toxic gas that forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.
- Sulfur Hexafluoride (SF6) - one of the most popular insulating gases (next to air). It is non-flammable, non-toxic, moderately inexpensive, and a good insulator because of its electronegativity. SF6 has a breakdown strength of about three times that of air. At normal temperatures it is non-corrosive and fairly inert; however, at temperatures above 500°C SF6 decomposes. The decomposition products (i.e., fluorine) react with most substances, especially any water vapor.
- Tungsten Hexafluoride - an inorganic compound with the formula WF6. This corrosive, colorless compound is the densest known gas at a pressure of 1 atm and room temperature (25 °C). The gas is most commonly used in the production of semiconductor circuits and circuit boards through the process of chemical vapor deposition.
Other notable gases:
- Arsine (AsH3) - a flammable and toxic gas. Synonyms include arseniuretted hydrogen, arsenous hydride, arsenic trihydride, and hydrogen arsenide.
- Diborane (B2H6) - a colorless gas with a repulsive, sweet odor. It mixes easily with air and will ignite spontaneously in humid air at room temperatures. Diborane is a respiratory irritant. Symptoms can occur immediately or be delayed for up to 24 hours after exposure.
- Germane (GeH4) - a flammable, toxic, colorless gas that reacts with oxidizers and halogens.
- Mercaptans and Sulfur Compounds
- Tungsten (VI) fluoride (WF6) - also known as tungsten hexafluoride. This corrosive, colorless compound is the densest known gas at a pressure of 1 atm and room temperature (25 °C). The gas is most commonly used in the production of semiconductor circuits and circuit boards through the process of chemical vapor deposition.
- Phosphine (PH3) -a colorless, spontaneously flammable, poisonous gas that has a fishy odor. It is used as a doping agent for solid-state components.
- Phosgene (COCl2) - a colorless, volatile liquid or gas known as a poison gas but used widely in making glass, dyes, resins, and plastics.
- Silane (SiH4) - a colorless gas that is both flammable and pyrophoric (i.e., capable of igniting spontaneously upon contact with air). It has a repulsive odor. Silane is used as a silicon source for the epitaxial deposition of single-crystal and polycrystalline silicon, for the low temperature chemical vapor deposition of silicon dioxide, and for the chemical vapor deposition of silicon nitride films. It also is used for growth of amorphous silicon films.
- Calibration Gas / Gas Standard
- Carbon Dioxide
- Carbon Monoxide
- Chemical Process / Petrochemical
- Electronic and Semiconductor
- Gas Cylinder
- Gas Mixture
- Hydrogen Chloride
- Hydrogen Fluoride
- Hydrogen Sulfide
- Mercaptans and Sulfur Compounds
- Nitric Oxide
- Nitrogen Dioxide
- Hydrogen, Hydrides and Hydrogen Compounds:Other
- Nitrogen and Nitrogen Compounds:Other