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Section 8
Safety Bulletin
Oxygen Enriched
An oxygen enriched atmosphere occurs whenever the normal oxygen
content of the air is allowed to rise above 23. While oxygen is
Atmospheres
nonflammable, ignition of combustible materials can occur more readily in
an oxygen-rich atmosphere than in air; and combustion proceeds at a faster
rate, although no more total heat is released.
It is important to locate an oxygen system in a well-ventilated location
since oxygen-rich atmospheres may collect temporarily in confined areas
during the functioning of a safety relief device or leakage from the system.
Oxygen system components, including but not limited to, containers,
valves, valve seats, lubricants, fittings, gaskets and interconnecting
equipment including hoses, shall have adequate compatibility with oxygen
under the conditions of temperature and pressure to which the
components may be exposed in the containment and use of oxygen. Easily
ignitable materials shall be avoided unless they are parts of equipment or
systems that are approved, listed, or proved suitable by test or by past
experience.
Compatibility involves both combustibility and ease of ignition. Materials
that burn in air may bum violently in pure oxygen at normal pressure, and
explosively in pressurized oxygen. In addition, many materials that do not
bum in air may do so in pure oxygen, particularly when under pressure.
Metals for containers and piping must be carefully selected, depending on
service conditions. The various steels are acceptable for many applications,
but some service conditions may call for other materials (usually copper or
its alloys) because of their greater resistance to ignition and lower rate of
combustion.
Similarly, materials that can be ignited in air have lower ignition energies
in oxygen. Many such materials may be ignited by friction at a valve seat
or stem packing, or by adiabatic compression produced when oxygen at
high pressure is rapidly introduced into a system initially at low pressure.
Thermo Scientific
230 liter LN2 Supply Tank
8-3
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