Liquid Oxygen

 

Chemical Symbol:  O2
Synonyms: LOX (liquid only)
Proper Shipping Name:                                    Oxygen, Compressed
Oxygen, Refrigerated Liquid
Classification: 2.2 (Non-flammable Gas)
Label: NON-FLAMMABLE, OXIDIZER
TC Shipping Name: Oxygen, Compressed
Oxygen, Refrigerated Liquid

 

PHYSICAL CONSTANTS    
     
  U.S. Units    SI Units
Chemical formula: O2 O2
Molecular weight: 31.9988 31.9988
Density of gas at
70oF (21.1oC) and at 1 atm:      
0.08279 lb/ft3     1.326 kg/m3
Freezing point at 1 atm: -361.1oF -361.8oC
Triple point: -361.8oC -218.8oC
Latent heat of vaporization at boiling point:   91.7 BTU/lb 213 kJ/kg
Latent heat of fusion at -361.7oF (-218.4oC):   5.98 BTU/lb 13.9 kJ/kg

 

 

DESCRIPTION

 

Oxygen - the colourless, odourless and tasteless elemental gas that supports life and combustion, constitutes about a fifth of the atmosphere (20.95% by volume and 23.2% by weight). At temperatures below -300oF (184oC), it is a transparent, pale blue liquid that is slightly heavier than water. All elements except the inert gas combine directly with oxygen to form oxides. Oxygen is non-flammable but it readily supports combustions. All materials that are flammable in air, burn much more vigorously in oxygen. Some combustibles, such as oil and grease, burn with nearly explosive violence in oxygen if ignited.

 

Oxygen is shipped as a non-liquefied gas at pressures of 2,000 psig (13,790 kPa) or above, and also as a cryogenic liquid at pressures and temperature below 200 psig (1,380 kPa) and -232oF (-147oC)

 

USES

 

The major uses of oxygen stem from its life sustaining and combustion supporting properties. It is used extensively in medicine for therapeutic purposes, for resuscitation in asphyxia, and with other gases in anaesthesia. It is also used in high-altitude flying, deep sea diving, and both as an inhalant and power source in the United States space program. Industrial applications include its very wide utilisation with acetylene, propane, hydrogen, and other fuel gases for such purposes as metal cutting, welding, hardening, and scarfing. In the steel industry, oxygen helps to increase the capacity and efficiency of production in steel and iron furnaces. One of its major uses is in the production of synthesis gas (a hydrogen-carbon monoxide mixture) from coal, natural gas or liquid fuels; synthesis gas is in turn used to make gasoline, methanol, and ammonia. Oxygen is similarly used in manufacturing some acetylene in partial oxidation of the hydrocarbons in methane-rich feedstocks such as natural gas. It is also used in the production of nitric acid, ethylene, and other compounds.

 

PHYSIOLOGICAL EFFECTS

 

The inhalation of the gaseous oxygen is used appropriately in many medical emergencies, as well as for long-term therapy. Such use, except for emergencies, should be with the advice of a physician.

 

Inhalation of high concentration of oxygen for a few hours has not been found to produce harmful effects except for some special classes of patients. Premature infants may suffer permanent visual impairment or blindness from inhalation of oxygen at high concentration, and their oxygen therapy must be carefully controlled. Patients with chronic obstruction pulmonary disease retain carbon dioxide abnormally. If oxygen is administered to them, raising the oxygen concentration in the blood depresses their breathing and raises their retained carbon dioxide to a dangerous level.

 

The two systems in adults most likely to be damaged by high concentration of oxygen are the respiratory and the central nerve system (CNS). When pure oxygen is inhaled at two or more atmospheres, CNS toxicity supervenes. Symptoms include nausea, vomiting, dizziness or vertigo, muscle twitching, vision changes, and loss of consciousness and generalized seizures.

 

MATERIALS OF CONSTRUCTION

 

Gaseous oxygen is noncorrosive and may consequently be contained in systems constructed of any common metal and designed to safely withstand the pressure involved. At the temperature of liquid oxygen, ordinary carbons steels and most alloy steels lose their ductility and are therefore considered unsatisfactory for liquid oxygen service. These compatibilities must be considered in their selection for service with either gaseous or liquid oxygen.

 

Care must be taken to remove all oil, grease, and other combustible material for piping system and containers before putting them into oxygen service. Cleaning methods used by manufacturers of oxygen equipment are described.

 

SAFE STORAGE, HANDLING AND USE

 

General precautions for safe handling of gaseous oxygen are contained in CGA G-4, Oxygen. When liquid oxygen in held in any closed container or space, there must be an appropriate pressure relief device because of the very large pressure increases that can occur as a liquid oxygen is vaporized by heat flowing onto the container. Liquid oxygen must also be handled with all the precautions required for safety with any cryogenic fluid. In addition liquid oxygen exhibits strong oxidizing properties. Contact between the skin and liquid oxygen, or uninsulated piping or vessels containing it, can cause severe burnlike injuries.

 

All easily combustible materials, especially hydrocarbon oils and greases, must be kept from contact with high oxygen concentrations. Sources of ignition should be eliminated to the extent possible. Sudden opening of valves, and particles carried by oxygen flowing at high velocity are to be avoided since these actions can result in ignition. Valves therefore should be opened slowly. When this cannot be done, precautions must be taken to prevent severe damage or injury to personnel should an ignition occur.

 

HANDLING LEAKS AND EMERGENCIES

 

Turn off ignition sources in the general area, if possible. The source of the leakage should be shut off, if possible, and the area adequately ventilated. If liquid oxygen is spilled over asphalt or other surfaces contaminated with combustibles, such as oil-soaked concrete or gravel, do not walk on or roll equipment over the area for at least ½ hour after the frost has disappeared. A violent reaction may occur simply by impact or shock. Contact the supplier for assistance.

 

FIRST AID

 

In case of frostbite from contact with liquid oxygen, place the frostbitten part in warm water, 100oF to 105oF (37.7oC to 40.6oC). If warm water is not available or is impractical to use, wrap the affected part gently in blankets.

 

CONTAINERS

 

The shipment of liquid or pressurized gaseous oxygen is under the jurisdiction of DOT or TC and must be done in containers meeting specifications of the applicable regulations. Gaseous oxygen is authorized for shipment in approves cylinders, tank cars, and tube trailers: Oxygen is shipped as a cryogenic liquid in insulated cylinders, tank trucks, anf tank cars. Oxygen service requires certain restriction for container design and materials, and applicable regulations should be consulted.

 

CYLINDERS

 

Cylinders meeting TC/DOT specifications 3A, 3AA, OR 3AL are the types usually used to ship gaseous oxygen, but oxygen is authorized for shipment in any cylinders designated for nonliquefied compressed gases. The include cylinders that comply with DOT specifications 3A, 3AA, 3AX, 3AAX, 3AL, 3B, 3E, 3T, 4B, 4BA, 4BW, and 39. Liquid oxygen is authorized for shipment in cylinders which meet TC/DOT specification 4L.

 

Most cylinders authorized for gaseous oxygen service must be requalified by hydrostatic retest every 5 or, under more restricted service requirements, 10 years. No periodic retest is required for cylinders of specifications 3C, 3E, 4C, and 7. Cylinders of specification 4L authorized for liquid oxygen service are also exempt from periodic retest requirements. See 49 CFR 173.34. Tube trailers and Cargo Tanks on Trucks or Trailers

 

Gaseous oxygen at pressures up to 2,640 psig (18,200 kPa) is shipped in tube trailers with capacities that may exceed 40,000 ft3 (1,133 m3). These trailers commonly serve as the storage supply for the user with empty trailers being replaced periodically by the supplier.

 

Most liquid oxygen is shipped in bulk at pressures below 25.3 psig (174 kPa) in special insulated cargo tanks on trucks, and truck trailers with capacity up to or in excess of 400,000 ft3 (11,327m3).

 

 

SMALL PORTABLE LIQUID CONTAINERS

 

Liquid oxygen is packaged in small portable containers that hold quantities ranging from 1 gal to more than 25 gal (3.8 L to 95 L). These containers, generally termed dewars, are encased in steel shells and are vacuum insulated; they maintain the liquid at atmospheric pressure and are consequently not subject to DOT/TC regulations.

 

 

METHODS OF MANUFACTURE

 

Commercial oxygen is produced at air separation plants by liquefaction of atmospheric air and separation of the oxygen by fractionation. Very small quantities are produced by the electrolysis of water.

 

Oxygen ranging in purity between 90% and 97% is produced by pressure swing absorption (PSA) techniques. PSA oxygen is used chiefly in making steel, but there are also many small units in homes producing therapeutic oxygen. Recent innovations in membrane technology are also being used for production of oxygen form the air.