backward. If a towing vehicle is not available,
3. Remove the plug from the nitrogen module
lock the swivel caster in the DOWN position and
recharge connection (figure 10-15, left side
apply the hand brake.
view) and attach the recharge hose to the
connection.
2. Close the oxygen cylinder valve.
NOTE: The number in parentheses following a
3. B l e e d p r e s s u r e f r o m t h e l i n e b e f o r e
component name refers to figure 10-13.
disconnecting the hose.
4. Ensure that the oxygen servicing unit's nitrogen
4. Disconnect the oxygen hose from the cylinder
cylinder valves (3), nitrogen module supply
valve.
valve (7), and boost pump drive vent valve (16)
5. Install the cylinder safety cap.
are closed/OFF.
6. Unlatch the oxygen cylinder clamp assembly.
5. Open the nitrogen recharge source servicing
(See figures 10-12 and 10-14.)
valve.
7. Remove the empty cylinder.
6. Open the servicing unit's nitrogen cylinder
valves (3).
INSTALLING THE FULL CYLINDER.--
Follow these procedures to install a full cylinder on the
7. Close the nitrogen recharge source servicing
servicing unit:
valve when the servicing unit's nitrogen module
supply pressure gauge (6) indicates 3,500 psi.
1. If possible, fasten the servicing unit to a towing
vehicle before loading the cylinder so that the
8. After ensuring that the cylinders (1) are fully
trailer does not become unbalanced and tilt
charged, close the cylinder valves (3).
backward. If a towing vehicle is not available,
9. Vent the recharge unit servicing hose by opening
lock the swivel caster in the DOWN position and
the nitrogen supply pressure valve (7) and boost
apply the hand brake.
pump drive vent (16) on the oxygen servicing
2. Ensure a safety cap is installed on the oxygen
unit.
cylinder to be loaded.
10. Close all valves on the oxygen servicing unit
3. Load the fully charged cylinder on the trailer
when its nitrogen supply pressure gauge (6) and
rack.
boost pump drive pressure gauge (12) indicate
4. P o s i t i o n t h e cy l i n d e r f o r p r o p e r w e i g h t
zero.
distribution.
11. Disconnect the external nitrogen recharge hose.
5. Close the clamp assembly around the cylinder
12. Install the plug on the nitrogen module recharge
and latch it in the fully closed position.
connection.
6. Manually check the cylinder for movement and,
Replacing The Oxygen Cylinder
if necessary, tighten the clamp assembly by
The oxygen cylinder on the A/U26U-1 servicing
positioning the hook bolt adjustment nut.
unit can not be recharged without removing it from the
7. Remove the safety cap.
trailer; therefore, you must replace an empty cylinder
NOTE: Before connecting the hose to the
with a full one.
cylinder, crack (open) the cylinder valve slightly to
NOTE: Never completely expend the oxygen
blow any foreign matter from the outlet of the valve.
supply from a cylinder. The cylinder should have a
Then close the valve.
minimum of 25 psi when removed from the servicing
8. Connect the oxygen hose to the cylinder valve.
unit.
Be careful to ensure the hose is not twisted when
REMOVING THE EMPTY CYLINDER.--
tightened.
When cylinder pressure is low, the cylinder is removed
9. Connect the cylinder grounding clamp and strap
as described in the steps below: (Refer to figures 10-12
between the hose fitting and cylinder valve.
and 10-14.)
After replacing the empty cylinder, the cylinder
1. If possible, fasten the servicing unit to a towing
valve should remain closed until the unit is to be used to
vehicle before unloading the cylinder so that the
service an aircraft system.
trailer does not become unbalanced and tilt
10-36