B767 ATA 35 Student Book

TRAINING MANUALFOR TRAINING PURPOSES ONLY

B767-3S2F ATA 35-00 Page - 1 4/10/13 EFF - ALL

CH 35

OXYGEN



TABLE OF CONTENTS

OXYGEN SYSTEMS .........................................................................................4

CREW OXYGEN SYSTEM ................................................................................6

CREW OXYGEN PRESSURE REGULATION................................................... 8

THIRD CREW OXYGEN BOTTLE / DISCHARGE PORT................................ 10

CREW OXYGEN PRESSURE INDICATION................................................... 12

CREW OXYGEN BOTTLE SERVICING.......................................................... 14

CREW OXYGEN MASK...................................................................................16



STUDENT NOTES:



OXYGEN SYSTEMS

General

The crew system supplies each crew member with oxygen. The crew masksreceive oxygen from a pressurized cylinder. Each mask has controls foradjustment by each crew member.

The crew system includes: 3 cylinders, each with a pressure regulator, a pressure transducer, a shutoff valve, and pressure indication. The crew masks have diluter-demand regulators, and supply and discharge lines. The cylinderstores high pressure oxygen for the crew. A pressure regulator reducesoxygen pressure to the crew masks. A diluter-demand regulator in eachmask further reduces the pressure as it flows from the mask. Pressureindication within the system shows an average of cylinder pressure. Cylinders with low pressure can be serviced from the forward electrical compartment or replaced depending on station policy.



OXYGEN SYSTEMS



CREW OXYGEN SYSTEM

Oxygen Cylinder

Two light weight composite cylinders are installed horizontally on the right side of the main equipment center and one is installed vertically in the right side of forward cargo compartment just aft of main equipment center. The cylinder has a volume of 115 cubic feet and is normally pressurized to 1850 psi at 70°F. The cylinder neck has a shutoff valve, a pressure gage, a pressure regulatorconnection, and a pressure relief valve. The shutoff valve controls flowin and out of the cylinder, while the pressure gage gives a directreading of cylinder pressure. The pressure relief valve opens whencylinder pressure reaches 2850 plus or minus 150 psi and discharges the oxygen overboard.

Overboard Discharge

If the crew cylinder becomes overpressurized, the thermal relief valve,on the cylinder neck, opens. The high pressure oxygen routes through anoverboard discharge line to the overboard discharge port. When pressurein the overboard discharge line reaches 500 psi a green disk in theoverboard discharge port pops out and lets the oxygen escape. The diskis held in its position by a snap-ring. The overboard discharge port isadjacent to the nose wheel well on the lower right side of the fuselage. The third bottle has a discharge port forward of lower lobe forward door.

Pressure Regulator

The pressure regulator attaches to the oxygen cylinder neck. The inletport receives high pressure oxygen from the cylinder. The valve stem isspring-loaded open, but closes when downstream pressure reaches 70 psi. The valve stem opens and closes to maintain 70 psi of oxygen to theoutlet port. The outlet port supplies oxygen to the crew masks. Theregulator has a relief valve which begins to open at 120 psi, and opensfully at 160 psi in case the valve stem malfunctions.

A pressure transducer is attached to each pressure regulator. Each transducer sends an electrical signal to a voltage averaging unit. It combines the signals and sends an electrical signal to the EICAS computers to show cylinder pressure.



CREW OXYGEN SYSTEM



CREW OXYGEN PRESSURE REGULATION

Crew Oxygen Cylinder

The crew oxygen cylinder is located outboard of the nose wheel well along the right side of the fuselage in the forward equipment center. It has 76 cubic feet volume.

The normal cylinder charge is 1850 psi @ 70oF. Full cylinder charge is set at 2000 psi to compensate for gas temperature increase associated with the charging process from 100 psi to 1850 psi. The cylinder must be removed/replaced or removed/recharged/reinstalled if the oxygen pressure is unacceptably low. A frangible disk is a fitting on the cylinder neck provides for thermal relief at 2500 to 2775 psi.

Also located in the neck is a shut-off valve to shut off oxygen flow at the cylinder, a direct reading pressure indicator, and connections for the regulator and the thermal relief overboard discharge vent line.

Crew Oxygen Pressure Reducing Regulator

The regulator inlet port attaches to the cylinder neck. It receives high pressure oxygen from the cylinder (1850 psi). The outlet port connects to the flight compartment supply line. The output pressure of the regulator is a nominal 70 psi. The regulator also incorporates a relief valve to relieve excessive supply line pressure set to begin opening at 120 psi and be full open at 160 psi.

Crew Oxygen Pressure Transducer

A pressure transducer is attached to each pressure regulator. Each transducer sends an electrical signal to a voltage averaging unit. It combines the signals and sends an electrical signal to the EICAS computers to show cylinder pressure.



CREW OXYGEN PRESSURE REGULATION



THIRD CREW OXYGEN BOTTLE / DISCHARGE PORT

Additional Oxygen Cylinder

In the forward lower lobe cargo compartment there is a supplemental crew oxygen bottle. It is the same as the other two bottles.

Crew Overboard Discharge Indicator Disks

The overboard discharge fittings, containing the indicator disk, is located outboard of the nose gear wheel well on the right side and forward of FWD Cargo door for third bottle. The fitting extends through the fuselage skin and is attached to the oxygen cylinder thermal discharge line. The fitting has an o-ring seal, green indicator disk and a snap ring.

The crew oxygen cylinder will thermally discharge at a pressure of from 2500 to 2775 psi, and in doing so will blow out the green indicator disk. During a walk around inspection the disk is checked. If the disk is missing the cylinder should be checked for thermal discharge indications.



THIRD CREW OXYGEN BOTTLE / DISCHARGE PORT



CREW OXYGEN PRESSURE INDICATION

Indication

The cylinder pressure shows only at the gauge on the cylinder. This gauge is a direct reading type.

Pressure in the high pressure manifold shows on the STATUS page and at the service panel. A pressure transducer monitors manifold pressure and gives the pressure information for the STATUS page and the service panel. As long as the shutoff valve on the cylinder is OPEN, cylinder pressure and manifold pressure should be the same.



CREW OXYGEN PRESSURE INDICATION



CREW OXYGEN BOTTLE SERVICING

Servicing

Before you do an oxygen servicing procedure, read the precautions and general maintenance instructions (AMM 12). Keep oxygen away from all sources of ignition.

Open all the oxygen valves slowly. This will decrease the risk of a fire.

WARNING: DURING THE SERVICING PROCEDURES OF THE CREW OXYGEN SYSTEM, MAKE SURE THAT THE AIRCRAFT AND OXYGEN CART IS CORRECTLY GROUNDED.

Close the shutoff valve for each crew oxygen cylinder slowly.

Note: The shutoff valve can be tightened by hand which is equivalent to 25 pound-inches.

Note: The shutoff valve on the composite cylinder is fully closed approximately at 4 to 5 revolutions.

WARNING: LOOSEN THE CONNECTION SLOWLY. THE REMAINING OXYGEN CAN RELEASE WITH A LARGE FORCE, AND CAUSE THE TEMPERATURE TO INCREASE. HEAT AND OXYGEN CAN CAUSE A FIRE. INJURIES TO PERSONNEL, AND DAMAGE TO EQUIPMENT CAN OCCUR.

Slowly loosen the coupling nut that attaches the pressure regulator and transducer assembly to the valve of the oxygen cylinder. Let all the pressure go out of the connection. Then disconnect the pressure regulator assembly from the cylinder valve. Disconnect the overboard discharge line from the union at the valve of the oxygen cylinder. Hold the union with a wrench. Then disconnect the overboard discharge line from the union. Remove the union from the valve assembly of the cylinder. Remove the packing from the union. Keep the union. The union is used to install the oxygen cylinder.

Note: The oxygen cylinder weighs between 35 and 43 pounds.

Install oxygen clean caps or plugs on the open ports of the cylinder valve.



CREW OXYGEN BOTTLE SERVICING



CREW OXYGEN MASK

Stowage

Each crew member station is equipped with an oxygen mask/regulator stored in a box which is secured to the airplane. When the mask/regulator is stowed and the box doors closed, oxygen flow to the mask is prevented by a valve inside the box. With the doors closed the "reset/test lever" on the left door holds this valve closed. A flow indicator is on the opposite side of the box from the valve. It can be seen with the doors open or closed.

Pneumatic Harness

The pneumatic harness that holds the mask to the face is deflated when stowed. When the mask/regulator is removed from the box with the harness inflation control "red ears" depressed (only one moves), the box doors open thus opening the shutoff valve in the box, the harness inflates and can be placed over the head and face. Releasing the inflation control deflates the harness and holds the mask on the face. The harness fits all head sizes.

"In-Place" Check-Out

The mask/regulator can be tested without removal from the storage box. Push the "Reset/Test Lever" in the direction of the arrow until the painted white band appears. The flow indicator (blinker) should turn yellow momentarily, then black again, showing the regulator is leak tight.

Hold the "Reset/Test Lever" depressed and push the "Press To Test" knob on the regulator through the opening between the doors. The blinker should again turn yellow momentarily, then black, which checks the regulator demand mechanism. Microphone electrical integrity can be checked by listening to relevant airflow noise through the communication set. Release both controls. The "reset/test lever" should return to the position covering the white band and close the valve. Pressure downstream of the valve is vented to atmosphere.

Complete Mask/Regulator Test

Take the mask/regulator out of the box, hold the mask and keep the harness inflation control depressed. Make sure that the blinker turns yellow, goes black again in a few seconds, showing that the pneumatic harness is leak tight. Raise the mask/regulator unit and place it over your head. Breathe; regulator

positioned to dilution, then to "100%" position; in each case, check for flow on the blinker. With the regulator set to "100%", rotate the "emergency" control knob. After some breathing, cancel the emergency mode and store the mask/regulator.

Regulator Controls

RESET/TEST SLIDE LEVER (spring loaded)

PUSH - • Mask stowed- turns oxygen on momentarily to test regulator • Mask not stowed and stowage box doors closed- turns oxygen off

FLOW INDICATOR • Shows a yellow cross when oxygen is flowing

RELEASE LEVERS (red) • SQUEEZE AND PULL releases mask from storage box • Oxygen turns on when storage box is open • Flow indicator shows a yellow cross momentarily as harness inflates

NORMAL/100% SELECTOR

• NORMAL - Air/Oxygen mixture on demandRatio is dependent on cabin altitude

• 100% - Pushing selector supplies pure oxygen on demand



CREW OXYGEN MASK

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B767 ATA 35 Student Book