AIRCRAFT Lines and Fittings

Lines and Fittings:

(1)       Replace any oxygen line that is chafed, rusted, corroded, dented, cracked, or kinked.

(2)       Clean oxygen system fittings showing signs of rusting or corrosion in the threaded area. To accomplish this, use a cleaner recommended by manufacturers of oxygen equipment. Replace lines and fittings that cannot be cleaned.

(a)    The high-pressure lines which are located between the oxygen bottle (outside the oxygen service filler) and the regulator are normally fabricated from stainless steel or thick=wall, seamless copper alloy tubing. The fittings on high-pressure lines are normally silver brazed.

NOTE: Use silver alloys free of cad­mium when silver brazing. The use of silver brazing alloys, which contain cadmium, will emit a poisonous gas when heated to a molten state. This gas is extremely hazardous to health if inhaled.

(b) The low-pressure lines extend from the pressure regulator to each passenger and crew oxygen outlet. These lines are fabricated from seamless aluminium alloy, copper, or flexible hose. Normally, flare- or flange type connections are used.

CAUTION: Do not allow oil, grease, flammable solvent, or other combusti­bles such as But or dust to come in contact with threads or any parts that will be exposed to pressurized oxygen.

(c)    It is advisable to purge the oxy­gen system any time work has been accomplished on any of the lines and fittings. Use dry nitrogen or dry air for purging the system. All open lines should be capped immediately after purging.

(d)    When oxygen is being lost from a system through leakage, a sequence of steps may be necessary to locate the opening. Leak age may often be detected by listening for the distinct hissing sound of escaping gas. If this check proves negative, it will be necessary to soap-test all lines and connections with a cas­tile soap and water solution or specially com­pounded leak-test material. Make the solution thick enough to adhere to the contours of the fittings. At the completion of the leakage test, remove all traces of the soap and water.

Regulators, Valves, and Gauges: Line maintenance of oxygen regulators, valves, and gauges does not include major repair. These components are precision made and their re­pair usually requires the attention of a repair station or the manufacturer. Care must be taken when reinstalling these components to ascertain if the threaded area is free of nicks, burrs, and contaminants that would prevent the connections from sealing properly.

CAUTION: Do not use petroleum lu­bricants on these components.

Masks and Hoses:

(1)       Troubleshooting. If a mask assem­bly is defective (leaks, does not allow breath­ing, or contains a defective microphone), it is advisable to return the mask assembly to the manufacturer or a repair station.

(2)       Maintenance Practice and Cleaning.

(a)    Clean and disinfect the mask as­semblies after use, as appropriate.

NOTE: Use care to avoid damaging the microphone assembly while cleaning and sterilizing.

(b)    Wash the mask with a mild soap solution and rinse it with clear water.

(c)    To sterilize, swab the mask thor­oughly with a gauze or sponge soaked in a water merthiolate solution. This solution should contain 1/5-teaspoon of merthiolate per 1 quart of water. Wipe the mask with a clean cloth and air dry.

(d)    Replace the hose if it shows evi­dence of deterioration.

(e)    Hoses may be cleaned in the same manner as the mask.

(f)     Observe that each mask breathing tube end is free of nicks, and that the tube end will slip into the cabin oxygen receptacle with ease and not leak.