(7)
Repeat step (2) and recheck precharge on accumulator. Recharge if necessary.
(8)
Ensure swivel hexagon nut is tight and replace cap on charging valve.
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OXYGEN SERVICING
1. General
A. Passenger (ALL EXCEPT ATI Interior) and crew oxygen system servicing is accomplished by the cylinder replacement method in par. 2 or if desired, on airplanes with an external servicing provision, by the external servicing method in par. 3.
B. On ATI Interior, passenger oxygen system servicing is accomplished by replacing the chemical oxygen generator in each service unit (Ref 35-22-11, R/I).
C. Portable oxygen servicing is accomplished by replacing the cylinders with fully serviced cylinders (Refer to 35-31-0, D&O for location).
D. Oxygen Requirements
(1) Gaseous oxygen for aviation purposes shall contain not less than 99.5% oxygen by volume and be free from all contaminants of known toxicity to the maximum practicable extent. Moisture content shall not exceed 0.005 milligram of water vapor per liter of gas at temperature of 700F and pressure of 760 millimeters of Hg. Oxygen per Specification MIL-O-27210, Type I, meets these requirements and is preferred. Deviation per S.A.E. (AS 1065) for moisture content is allowed.
E. Precautionary Measures
(1)
Ensure that hands, clothing, tools, servicing area, and servicing equipment are clean and free of petroleum products, other oils and greases, hydraulic fluid, or dirt before servicing the oxygen system.
(2)
Keep oxygen away from all sources of ignition (hot exhausts, sparks, flame, smoking, etc.).
(3)
Do not allow oxygen to mix with other gases, fumes, or flammable materials.
(4)
Use only aviation grade breathing oxygen. Welding and hospital oxygen are not acceptable for use in the airplane system due to lack of purity and moisture controls.
(5)
Open all oxygen valves slowly to prevent sudden pressure rise. This will minimize the possibility of fire due to resultant temperature rise. Ensure that valves are also open fully.
WARNING: VALVES MUST BE OPENED SLOWLY OR EXCESSIVE TEMPERATURES MAY RESULT.
(a) Opening Oxygen Cylinder Valves 1) Provide electrical power (Ref 24-22-0 MP). 2) Ensure that OXYGEN IND & VALVE or OXYGEN SYSTEM IND (as applicable)
circuit breaker on P18 panel is closed.
3) Slowly open oxygen cylinder shutoff valve to full open. Do not exceed 25 pound-inches (finger-tight). Then close valve one-fourth turn. Lockwire valve in this position when restoring system to normal.
CAUTION: IF GIVEN TORQUE IS EXCEEDED, VALVE MAY BE DAMAGED.
NOTE: Use the 0.020-inch diameter copper lockwire.
4) Immediately check that applicable pressure indicator on aft overhead panel agrees with average of applicable oxygen cylinder gages士 100 psi.
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2. Service Oxygen System (Cylinder Replacement Method)
A. Prior to performing maintenance, review oxygen system safety precautions and general maintenance instructions outlined in 35-00, Maintenance Practices.
B. Ensure that airplane is properly grounded (Ref 20-40-11).
C. Gain access to oxygen cylinder (s).
D. Close all oxygen cylinder valves finger-tight. This is equivalent to a maximum torque of 25 pound-inches.
CAUTION: IF GIVEN TORQUE IS EXCEEDED, VALVE MAY BE DAMAGED
E. Ensure that hands, clothing, tools, oxygen cylinders, and associated connections are clean and free of petroleum products, other oils and greases, hydraulic fluid, or dirt.
F. On ALL EXCEPT ATI Interior, loosen fittings at cylinder carefully to bleed system pressure and then disconnect.
WARNING: RESIDUAL PRESSURE MAY EXIST IN LINES AND ESCAPE WITH SOME FORCE.
CAUTION: DISCONNECT HIGH PRESSURE OXYGEN LINE AT VALVE COUPLING, NOT AT FLARELESS TUBE CONNECTION. DO NOT DISASSEMBLE THERMAL COMPENSATOR.
G. On ATI Interior:
(1)
Gradually loosen high pressure cylinder coupling nut from oxygen cylinder port to relieve pressure.
WARNING: RESIDUAL PRESSURE MAY EXIST IN LINES AND ESCAPE WITH SOME FORCE.
(2)
Disconnect high pressure cylinder coupling nut.
H. Disconnect overboard discharge line.
I. Release clamps and remove cylinder assembly. Cap connections on cylinder. If replacement cylinder is not immediately installed, cap airplane connections.
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