xii Rev. 2
Foreword
General Precautions
General Precautions
Cryogen Safety
The two most common cryogenic liquids used in superconducting magnet
systems are nitrogen and helium. Both of these cryogens are extremely
cold at atmospheric pressure (321°F and 452°F, respectively). The
following paragraphs outline safe handling precautions for these liquids.
Personnel handling cryogenic liquids should be thoroughly instructed and
trained as to the nature of the liquids. Training is essential to minimize
accidental spilling. Due to the low temperature of these materials, a
cryogen spilled on many objects or surfaces may damage the surface or
cause the object to shatter, often in an explosive manner.
Inert gases released into a confined or inadequately ventilated space can
displace sufficient oxygen to make the local atmosphere incapable of
sustaining life. Liquefied gases are potentially extreme suffocation
hazards since a small amount of liquid will vaporize and yield a very large
volume of oxygen-displacing gas. Always ensure the location where the
cryogen is used is well ventilated. Breathing air with insufficient oxygen
content may cause unconsciousness without warning. If a space is suspect,
purge the space completely with air and test before entry. If this is not
possible, wear a forced-air respirator and enter only with a co-worker
standing by wearing a forced-air respirator.
Cryogenic liquids, due to their extremely low temperatures, will also burn
the skin in a similar manner as would hot liquids. Never permit cryogenic
liquids to come into contact with the skin or allow liquid nitrogen to soak
clothing. Serious burns may result from careless handling. Never touch
uninsulated pipes or vessels containing cryogenic liquids. Flesh will stick
to extremely cold materials. Even nonmetallic materials are dangerous to
touch at low temperatures. The vapors expelled during the venting process
are sufficiently cold to burn flesh or freeze optic tissues. Insulated gloves
should be used to prevent frost-bite when operating valves on cryogenic
tanks. Be cautious with valves on cryogenic systems; the temperature
extremes they are typically subjected to cause seals to fail frequently.
In the event a person is burned by a cryogen or material cooled to
cryogenic temperatures, the following first aid treatment should be given
pending the arrival and treatment of a physician or other medical care
worker:
1. If any cryogenic liquid contacts the skin or eyes, immediately flush
the affected area gently with tepid water (102°F 105°F, 38.9°C
40.5°C) and then apply cold compresses.
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