the converter and pass hot nitrogen 250°F (122°C)
through the converter at 50 psi for at least 2 hours.
The gas exiting the converter should exceed 100°F
(38°C), or be in accordance with purging equip-
Next, service the converter and install it in the
aircraft. Use an oxygen mask to smell for odors.
If odors persist, drain and purge the converter
again. Aircraft systems are purged in the same
manner as a LOX converter. If an adapter is not
supplied with the purging unit, use a supply
fitting from a LOX converter.
Different types of purging equipment is used
to purge oxygen containers and systems. Only one
type unit, the Aircraft Liquid Oxygen System Gas
Purging Set, manufactured by Avel Corporation,
will be discussed here.
This unit is designed to use water pumped
gaseous nitrogen or gaseous oxygen to perform
the purging process.
NOTE: Gaseous oxygen is to be used only if
gaseous nitrogen is not available. All oxygen
safety precautions must be strictly adhered to.
The unit consists of a hand truck and housing
assembly, which contain the necessary controls
and valves (fig. 5-11). Located within the housing
assembly is an electrical enclosure containing a
heater block assembly, switches, indicator lamps,
and circuit breaker. When not in use, the supply
and delivery lines, fittings and filler valve,
electrical adapter (for conversion to 400 Hz
power), and the electrical power connecting cord
are stowed within the housing assembly. The
housing assembly may be removed from the hand
truck for use as a bench-mounted installation in
the oxygen/converter repair shop.
Principles of Operation
As illustrated in figure 5-12, gas flows from
the gas cylinders to the hand shutoff valves
(HDV-1 and HDV-2), and then to the high-
-pressure relief valve (RV-1). This valve relieves
Figure 5-12.Purging unit functional diagram.