GASEOUS OXYGEN SERVICING
LOX has caused several major LOX generating plant
TRAILERS
explosions.
Inert solids are small contaminants that do not react
LEARNING OBJECTIVE: Identify compo-
with oxygen to create a fire or explosion, such as rust,
nents and operating procedures for gaseous
dust, and fibers. They may cause mechanical
oxygen servicing trailers.
malfunctions or failures by plugging filters, lines, or
There are several different models of gaseous
valves. Other contaminants commonly found in oxygen
oxygen servicing trailers currently in use by naval
are water vapor, carbon dioxide, nitrous oxide, and
activities. This section will discuss the type No-2 and
halogenated compounds (Freons).
the A/U26U-1A oxygen servicing unit.
PURGING
TYPE NO-2 GASEOUS OXYGEN SERVICING
TRAILER
Purging and other maintenance of LOX trailers is
performed by the Aviation Support Equipment
The type No-2 servicing trailer is shown in figure
Technician (AS) rating. Purging is the cleansing of
8-5. Equipment provided on the trailer includes six
impurities from oxygen systems and containers. There
manifold control valves with pressure gauges, an upper
are two ways to purge oxygen containers: LOX wash
and lower manifold, two pressure regulators, a recharge
and gas purging.
valve, four shutoff valves, a drier assembly, six
The LOX wash method is used on large containers,
cylinders and connecting flexible hoses, and a servicing
such as storage tanks and LOX trailers, to lower the
hose fitted with a line servicing valve fitted with a
contamination to acceptable levels by replacing
high-pressure charging adapter. The function of each of
the contaminated LOX with LOX known to be un-
these components is described in the following text.
contaminated.
Components
Gas purging is used on aircraft LOX converters if
the system pressure is allowed to deplete or if odor is
Complete familiarity with the following trailer
detected. Gas purging of aircraft LOX systems must be
components is a basic prerequisite for safe operation.
done if any maintenance is performed on the system
MANIFOLD CONTROL VALVES.--The six
that opens it to the atmosphere.
manifold control valves serve to shut off the flow of
oxygen from the cylinders to the system being charged.
These valves are lever-type valves. The manifold
Q8-10.
What manual should you refer to for
control valves should not be used as a shutoff for
information on contamination control for
long-time storage. Always use the hand-wheel type
oxygen?
valves located on the cylinders.
Q8-11.
What is the primary source of contamination
for LOX?
UPPER MANIFOLD.--The upper manifold
provides connections/mounting for the six manifold
Q8-12.
State the three ways LOX contamination is
control valves with pressure gauges (each connected to
detected.
a supply cylinder), a recharge valve, and two
Q8-13.
An odor test will be performed on a LOX cart
upper/inlet shutoff valves that connect to the inlet side
if it has not been in service for what amount of
of the regulators.
time?
PRESSURE REGULATORS.--The pressure
Q8-14.
When is LOX sampling performed?
regulator controls the charging pressure when the
trailer is being used to service aircraft oxygen systems.
Q8-15.
Of all the hydrocarbons associated with LOX,
Only one pressure regulator is used during operation.
why is acetylene the most dangerous?
The spare is provided to ensure uninterrupted operation
Q8-16.
List four contaminants commonly found in
should one fail.
oxygen.
RECHARGE VALVE.--The recharge valve is
Q8-17.
What rate is responsible for purging of LOX
provided as a means of recharging the trailer cylinders
trailers?
directly through the upper manifold without the
8-10
