in the Chemical laboratory
...a
Edited by N O R M A N V. STEERE, School of Public Health, University of Minnesota, Minneapolis, Minn., 55455
IX.
feature
Cryogenic Safety Eric W. S p e n c e r , Sofefy Representdive MIT. Lincoln Laboratory* Lexington, Massachusetts 02 7 73
Cryogenics may be defined as low temperature technology, or the science of ultra-low temperatures. The prefix "m'; is from the Greek word meaning "frost,," hence cryogenics is a name aplied to the terhnalogy of very low temperatures. To distinguish between cryogenics and refrigeration, a commonly used measure is to consider any temperature lower than - 1 0 0 T as cryogenic. There is sonw rontroversy in the field about this distinction, and there are same who insist that only those areas within a few degrees of absolute zero (-459.6g°F) may he considered as cryogenic. The broader definibion will he used for our purposes. Low temperatures in the cryogenic area are primarily achieved by the liquifaction of gases. There are more than twentyfive gases which are currently in use in the rrpogenic area, i.e., gases which have a boiling point -lOODF. However, there are seven gases which account for the greateat volume of use and applications in industry and research. These are
helium, hydrogen, nitrogen, fluorine, argon, oxygen, and methane (natural gas). The cost of these Liquified gases ranges from approxim&ely one-half cent per pound for liquid oxygen to over 82200 per pound for xenon, one of the rarest gases. Cryogenics is being applied to a wide variety of industrial and research areas, a few of which are: transport of gas in liquid form, food processing and refrigeration, rocket propulsion fuels, spacecraft life support systems, space simulation, electronics, data processing, metalworking, medicine and surgery. Cryogenic fluida (liquified gases) are characterized by extreme low temperatures, ranging from a boiling point of -109.3"F for carbon dioxide to -453.8"F for helium. Another common prapetry is the large ratio of expansion in volume from liquid to gas from nppraximately 553 to 1 for carbon dioxide, to 1438 to 1 far neon. Table 1 contains a more complete summary of the properties of cryogenic fluids.
Eric W. Spencer, groduote of Hofrtra University, 1953, BBA in Management; Asri~tant to the Sofety Engineer ot MIT. A member of the Boston Chapter of the American Society of Sofety Engineers. Mr. Spencer's principle assignment is Sofety Representative ot the Lincoln Laborotory. He osrvmed his present position in 1961 after 4 yeor. ar Supervisor of Safety and Training ot the Brooklyn Plant of the American Con Cornpony.
P r o ~ e r t i e sof Crvoaenic Fluids
Gas Helium-3 Helium-4 Hydrogen Deuter~un~ Tritium Neon iYit,rogen Carbon Monoxide Fluorine Argon Oxygen Methane Krypton Tetrafluoromethane Ozone Senm Ethrlene Boron Trrfluoride Xitro~isOxide Ethane Hydrrngen Chloride Aretvlene
--
"C
Bailing Point"-"F
K
Val. expansion to (;as
.? 9
767 to 1
Flammable
Tori?
No
Nnr
Yes Yes Yes No No Yes No No No Yes KO No Yes XI, Yes
N 0.
Yo 1-e~
KO
