of nitrous oxide and acetylene may concentrate at the
evaporate and the beaker to warm up to room
bottom of tanks, and it can detonate.
temperature.
REFRIGERANTS.--Compounds present in the
5. When the liquid has completely evaporated,
form of refrigerants (Freon) may indicate leaks present
remove the watch-glass and smell the beaker
in the generating plant during manufacturing of the
c o n t e n t s a t f r e q u e n t i n t e r va l s u n t i l t h e
LOX. In such cases, manufacturing equipment must be
accumulated frost on the outside of the beaker
repaired to eliminate the sources of contamination.
has completely melted.
Such compounds may also be a residue of equipment
Odors will be most noticeable when the beaker has
cleaning operations.
warmed to nearly room temperature. If odors are
SOLVENTS.--Solvents present in LOX may be a
present, purge the LOX container or system in
cleaning residue, or may have been introduced into the
accordance with existing directives. You, as the AS,
oxygen system at the intake air stream of the
will be responsible for LOX washing your cart.
generating plant.
S A M P L E A NA LY S I S . -- A f t e r a n a i r c r a f t
Detection of Contamination
accident/incident, a LOX sample must be sent to a test
site for analysis. Include details of the incident,
Liquid oxygen contamination is detected by means
including the history of the supply source of the LOX,
of an odor test, and by conducting sampling analysis.
which should be traceable back to your LOX cart.
Odor testing is a simple, but reliable, test conducted by
you, the AS, and sampling analysis is a more precise
test done in a laboratory.
ODOR TESTING.--An odor test should be
Purging is the cleansing of impurities from oxygen
performed on LOX trailers under each of the following
systems and containers. There are two ways to purge
conditions:
oxygen containers, LOX washing and hot nitrogen
After filling the storage tank
purging.
LOX WASHING.--The LOX wash method is
After maintenance actions affecting the liquid
used on large containers, such as storage tanks and
system
LOX trailers. In LOX washing, you lower the
When the tank has been left empty without
contamination to acceptable levels by replacing the
positive pressure
c o n t a m i n a t e d L OX w i t h L OX k n ow n t o b e
uncontaminated. But before LOX washing, the
Whenever contamination is suspected
containers must be prepared, and the preparation is
different for a warm container than for a cold one.
Aircraft LOX systems also require an odor test as
soon as possible after an aircraft accident/incident, or
Wa r m C o n t a i n e r s . -- To p r e p a r e a w a r m
following a report of in-flight odors by the pilots or
container for LOX washing, first pressurize the
aircrew.
container to 30 to 40 psig with unheated, dry nitrogen
gas (conforming to Federal Specification BB-N-411).
An odor test is performed as follows:
T h e n , ve n t t h e c o n t a i n e r. A f t e r r e p e a t i n g t h i s
1. Cover the bottom of a 400-milliliter beaker (or a
procedure three times, you can perform the LOX wash.
simi1ar container) with clean, dry, filter paper or
Cold Containers.--To prepare a cold container
other absorbent paper.
for LOX washing, first dump residual LOX from the
2. Pour approximately 200 milliliters of the
container by using the build-up coil for expulsion. DO
suspect LOX into the beaker.
NOT open the vent during the dump procedure. When
the container is empty of residual LOX, you can
3. Partially cover the top of the beaker with a
proceed to the LOX wash.
w a t c h - g l a s s c o v e r. ( T h i s w i l l p r e v e n t
atmospheric constituents from being absorbed
The LOX Washing Procedure.--Partially fill the
by the exposed liquid as it evaporates.)
c o n t a i n e r w i t h L OX t h a t i s k n ow n t o b e
uncontaminated and that meets the concentration
4. Place the beaker in an area free from air currents
limits for storage containers. (See MIL-O-27210.)
and extraneous odors, and allow the LOX to
10-19
