(3) Precautionary Measures
(a)
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.
(b)
Keep oxygen away from all sources of ignition (hot exhausts, sparks, flame, smoking, etc.).
(c)
Do not allow oxygen to mix with other gases, fumes, or flammable materials.
(d)
Use only aviation grade breathing oxygen. Welding oxygen and hospital oxygen may be pure enough for breathing but could contain excess water which could freeze and plug the lines, regulators, and valves of the airplane oxygen system.
(e)
When beginning the oxygen servicing operation, open valves slowly to prevent sudden pressure rise. This will minimize the possibility of fire due to resultant temperature rise. Use pressure reducing valve on oxygen servicing equipment to control supply pressure.
B. Equipment and Materials
(1)
Oxygen Requirements
(a) 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 70°F and pressure of 760 millimeters of Hg. Oxygen per Specification MIL-0-27210, Type I, meets these requirements and is preferred. Deviation per S.A.E. (AS 1065) for moisture content is allowed.
(2)
Oxygen Ground Servicing Equipment Requirements
WARNING: TO MINIMIZE POSSIBILITY OF FIRE, ENSURE THAT OXYGEN SERVICING EQUIPMENT IS PROPERLY MAINTAINED IN A CLEAN CONDITION PER AIRPLANE STANDARDS. REFER TO CHAPTER 35.
(a) The following components must be included to cover the minimum requirements for a satisfactory oxygen ground servicing system. 1) High pressure oxygen storage cylinders with shutoff valves to supply oxygen,
per specification in par. (1), at a pressure and volume sufficient to fill the airplane oxygen cylinders to capacity.
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2) Manifold and other high pressure connecting tubing fabricated from brass or corrosion resistant steel.
3) Check valves having brass body and metal seats.
4) Filter with sintered bronze filter element.
5) Pressure reducing valve with following features: Heavy duty type with brass body; manual pressure adjustment from 0 to 3000 psi; pressure gages to show the supply cylinder pressure at the inlet port and the reduced pressure at the outlet port; outlet port relief valve set at 2400 psi; and outlet port vented to ambient pressure when valve is closed.
6) Supply shutoff valve -slow opening, heavy duty type with metal-to-metal valve seats and clockwise shutoff.
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7) High pressure flexible teflon lined supply hose for oxygen service, approximately 25 feet long (MS22028 hose assembly procured under Military Specification MIL-H-26633).
NOTE: Refer to QPL-26633-8 for list of approved vendors.
8) Supply hose adapter made of brass or corrosion resistant steel to attach to airplane filler port. The airplane filler port end fitting is a cone-type connection with a 0.375-24 UNF-3A thread per AND10089-3.
9) Protective cover (metal cap and polyethylene bag) to prevent contamination of supply hose adapter. 10) Stowage provisions for supply hose and protective provisions for stowing adapter end of hose. 11) Static ground cable permanently attached to equipment.
(b) Deleted
C. Prepare for Oxygen Servicing
(1)
Review paragraphs A and B before beginning the servicing operation.
(2)
Ground airplane and oxygen servicing equipment (Ref Chapter 20, Static Grounding).
WARNING: AIRPLANE MUST BE ELECTROSTATICALLY GROUNDED AND BONDED TO OXYGEN SERVICING EQUIPMENT TO PREVENT THE POSSIBILITY OF SPARKS.
(3)
Before servicing equipment supply hose is carried to airplane, remove protective cover from supply hose adapter, examine for cleanliness and with ground servicing equipment pressure reducing valve set at a nominal outlet pressure of 100 to 150 psi, slowly open servicing equipment supply shutoff valve to purge supply hose and adapter of any possible contaminants. Close supply shutoff valve and replace protective cover on supply hose adapter.
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