Description

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- ment instructions. 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. Description 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. 5-15