NETZSCH LFA 447 Nanoflash Operating Instructions Manual page 8

TM
LFA 447
Safety regulations for handling liquid nitrogen LN
FIRE AND EXPLOSION HAZARDS
MATERIAL HAZARDS
01/09 J:\LFA447\CHAPTER1.DOC
General Information
It is imperative that you observe the safety regulations for
handling nitrogen.
Neither gaseous nor liquid nitrogen are flammable and do not in
themselves constitute a fire or explosion risk.
gaseous and liquid nitrogen are normally stored under pressure
and the storage vessels, whether gas containers or liquid tanks,
should not be located in areas where there is a high risk of fire or
where they may normally be exposed to excessive heat. Vessels
containing compressed gaseous nitrogen may rupture violently if
overheated as a result of exposure to fire.
Oil-lubricated compressors operated continuously on nitrogen
supply for a prolonged period should not be switched to air supply
without thorough cleaning.
unoxidized pyrophoric deposits which may have formed in the
machine will explode violently on contact with compressed air.
At equal pressures, the boiling point of liquid nitrogen is lower
than that of liquid air. Air will condense on the external surfaces
of vessels or pipework containing liquid nitrogen at an equilibrium
pressure less than 1.5 bars absolute if the vessels are either not
lagged, or are lagged with a porous cellular-type insulator. The
liquid air produced can result in oxygen enrichment of the
atmosphere local to the equipment.
therefore be taken with regard to the insulation of the vessel
before any maintenance or repair work is started, particularly
where the use of open flames or other potential sources of
ignition is intended.
Certain steels, such as carbon steel, and some other materials are
unsuitable for use at sub-zero temperatures because they lose
impact strength and become extremely brittle.
cannot be used safely at temperatures below -30°C (-20°F) and is
obviously unsuitable for use with liquid nitrogen.
normally suitable for use at low temperatures are the austenitic
stainless steels, aluminum and copper and its alloys. In an area
where liquid nitrogen spillage can occur, care should be taken to
ensure that the liquid does not come into contact with vulnerable
steel structures and vehicle tires.
Care should be taken to ensure that liquid nitrogen and cold
nitrogen vapor are not trapped in a closed system without any
form of automatic pressure relief. Otherwise, pressures well in
excess of the equipment working pressure will be generated as the
system warms up, thus creating a possible rupture hazard.
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However, both
Otherwise there is a danger that
Special precautions must
Carbon steel
Materials
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