An odor test will be performed on LOX trailers
Q8-8. Information and instructions for maintenance
after the first filling of the day, or each 6 days when the
of the TMU-70/M are found in what publica-
trailer is not in service. Aircraft LOX systems require
tion?
an odor test to be performed as soon as possible after an
Q8-9. What type of LOX must be used to service
aircraft accident/incident or a report of in-flight odors
aircraft LOX systems?
by pilots or aircrew. The sample taken after an
accident/incident must be sent to a test site for analysis
CONTAMINATION CONTROL
with details of the incident, including history of the
supply source of the LOX.
LEARNING OBJECTIVE: Describe con-
tamination control procedures for oxygen
Odor Test
equipment to include detection, purging, and
purging equipment.
The odor test is performed by pouring a
The importance of using uncontaminated LOX in
200-milliliter (6.8 oz) sample into a clean 400-milliliter
aircraft systems cannot be overstressed. Because of
(13.8 oz) beaker or similar container after covering the
this, the Navy has established the Aviators Breathing
bottom of the beaker with clean, dry filter paper or other
Oxygen (ABO) Surveillance Program Laboratory and
absorbent paper. A watch glass cover or some other
Field Guide (A6-332SAO-GYD-000). For additional
means of partially covering the top of the beaker will be
information on contamination control, oxygen sam-
provided as the 200 milliliters evaporates to dryness.
pling, and oxygen system purging, refer to that manual.
This will prevent atmospheric elements from being
absorbed by the exposed liquid. The liquid is permitted
LOX produced by generating plants contains
to evaporate to dryness and warm up to approximately
contaminants, which are not completely removed by
room temperature in an area free from air currents or
the generating process. Atmospheric air, from which
extraneous odors. When the liquid has completely
LOX is generated, is the primary source of
evaporated, the watch glass is removed and the beaker
contamination. Additional sources of contamination
contents smelled at frequent intervals until the
are the compressors and other equipment of the
accumulated frost on the outside of the beaker has
generating plants. Airborne contaminants and those
completely melted. Odors will be most prevalent when
added by the generating plants are partially removed by
the beaker has warmed to nearly room temperature. If
a system of filters, absorbers, driers, and heat
odors are present, the LOX container or system will be
exchangers before the air is finally liquefied. When the
purged in accordance with existing directives.
LOX separates from the liquefied air it carries with it
those contaminants that are not completely removed.
Sampling
The variety and concentration of contaminants that
Sampling and analysis of LOX is required any time
separate with the LOX depend on how effective their
contamination is suspected. Contamination of oxygen
removal has been during the generating process.
used in aircraft can cause many problems, from
Generating plants are designed to remove contamina-
fire hazards to death of the crewmember using the
tion to the lowest limits possible, both for safety of
oxygen system. The most dangerous contaminate is
operation and for quality of product. The contamination
hydrocarbons. The presence of hydrocarbons in LOX
limits of LOX produced by any generating plant for the
constitutes a potential fire and explosive hazard as
Navy and Marine Corps as breathing oxygen are
well as causing psychological and physiological
specified as procurement limits. Procurement limits
dangers to aircrews. Psychologically, the effects
and the ultimate use limits of contamination are based
may be uneasiness, apprehension, or possible panic
on the types and significance of contaminants, and the
resulting from detection of odors. Physiologically,
sources of increasing contamination in liquid oxygen
the effects may be nausea, illness, intoxication, or
during storage, handling, and transfer.
possibly asphyxia. Acetylene is the most hazardous
DETECTION
hydrocarbon contaminate because it is highly insoluble
in LOX, changing into a solid at extremely low
LOX contamination is detected by means of an
concentrations. Once in its solid form, it can readily be
odor test, sampling, and analysis. Only the odor test
set off into ignition, and since it is chemically unstable,
will be discussed in this chapter because all other tests
it can decompose under certain conditions and become
and analysis must be performed in a laboratory.
its own source of ignition. The presence of acetylene in
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