Specifications

18
SAFETY BULLETIN
67
General
Cryogenic containers, stationary or portable, are from
t
ime to time subjected to assorted environmental con-
ditions of an unforeseen nature. This safety bulletin is
intended to call attention to the fact that whenever a
cryogenic container is involved in any incident whereby
the container or its safety devices are damaged, good
safety practices must be followed. The same holds
true whenever the integrity or function of a container
is suspected of abnormal operation.
Good safety practices dictate that the contents of a
damaged or suspect container be carefully emptied
as soon as possible. Under no circumstances should a
damaged container be left with product in it for an ex-
tended period of time. Further, a damaged or suspect
container should not be refilled unless the unit has
been repaired and recertified.
Incidents which require that such practices be followed
include: Highway accidents, immersion of a container
in water, exposure to extreme heat or fire, and
exposure to most adverse weather conditions (earth-
quakes, tornados, etc.). As a rule of thumb, whenever
a container is suspected of abnormal operation, or has
sustained actual damage, good safety practices must
be followed.
In the event of known or suspected container vacuum
problems (even if an extraordinary circumstance such
as those noted above has not occurred), do not con-
tinue to use the unit. Continued use of a cryogenic
container that has a vacuum problem can lead to pos-
sible embrittlement and cracking. Further, the carbon
steel jacket could possible rupture if the unit is exposed
to inordinate stress conditions caused by an internal
liquid leak.
Prior to reusing a damaged container, the unit must
be tested, evaluated, and repaired as necessary. It is
highly recommended that any damaged container be
returned to Chart Inc. for repair and recertification.
The remainder of this safety bulletin addresses those
adverse environments that may be encountered when
a cryogenic container has been severely damaged.
These are oxygen deficient atmospheres, oxygen en-
riched atmospheres, and exposure to inert gases.
Oxygen Deficient Atmospheres
The normal oxygen content of the air is approximately
2
1%. Depletion of oxygen content in air, either by com-
bustion or by displacement by inert gas, is a potential
hazard and users should exercise suitable precautions.
One aspect of this possible hazard is the response of
humans when exposed to an atmosphere containing
only 8 to 12% oxygen. In this environment, uncon-
sciousness can be immediate with virtually no warning.
When the oxygen content of air is reduced to about
15 or 16%, the flame of ordinary combustible materi-
als, including those commonly used as fuel for heat
or light, may be extinguished. Somewhat below this
concentration, an individual breathing the air is men-
tally incapable of diagnosing the situation because
the onset of symptoms such as sleepiness, fatigue,
lassitude, loss of coordination, errors in judgment and
confusion can be masked by a state of “euphoria”,
leaving the victim with a false sense of security and
well-being.
Human exposure to atmospheres containing 12%
or less oxygen leads to rapid unconsciousness.
Unconsciousness can occur rapidly, rendering the
user essentially helpless. This can occur if the condition
is reached by an immediate change of environment,
or through the gradual depletion of oxygen. Most indi-
viduals working in or around oxygen deficient
atmospheres rely on the “buddy system” for protection
– obviously, the “buddy” is equally susceptible to as-
phyxiation if he or she enters the area to assist an
unconscious partner unless equipped with a portable
air supply. Best protection is obtained by equipping
all individuals with a portable supply of respirable air.
Life lines are acceptable only if the area is essentially
free of obstructions and individuals can assist one an-
other without constraint.
If an oxygen deficient atmosphere is suspected or
known to exist:
1. Use the “buddy system”. Use more than one
“buddy” if necessary to move a fellow worker in
an emergency.
2. Both the worker and the “buddy system” should
be equipped with self-contained or air-line
breathing equipment.