Table 9-1.--Portable High-Pressure Nitrogen Cylinder Troubleshooting Chart
Trouble
Probable Cause
Remedy
Recharge cylinder
With shutoff valve open, cylinder
Cylinder completely discharged
pressure gauge reads zero
Replace safety disc
Cylinder safety disc blown
Replace shutoff valve
Shutoff valve defective
With shutoff valve open and
Gas leaking
Locate and repair leak
pressure regulator set to zero,
cylinder loses pressure
Regulator control has no effect on
Delivery pressure gauge defective
Replace delivery pressure gauge
delivery pressure gauge reading
Regulator defective
Replace regulator
Unit does not charge an external
Hose valve in BLEED position
Rotate hose valve to FLOW
system during charging operation
position
Replace hose valve
Hose valve defective
Servicing hose defective
Replace servicing hose
Replace recharge valve
Cylinder does not pressurize
Recharge valve defective
during recharging operation
Replace safety disc
Safety disc blown
Shutoff valve regulator and hose valve Close shutoff valve, regulator, and
hose valve
are open
Cylinder is loose in its mounting
Cylinder clamp loose
Tighten cylinder clamp
water-pumped nitrogen with compressed air or
discussed in detail in the following paragraphs. The
oil-pumped nitrogen.
A/M26U-4, shown in figure 9-4, is typical of other
nitrogen servicing trailers you might encounter, and
Do not charge this system with oxygen or
most of what you will learn about it applies to the other
interchange components with oxygen
trailers.
components. To do so may cause an explosion.
The A/M26U-4 has a welded frame assembly
Never charge systems at higher than prescribed
mounted on a two-wheel axle and a retractable swivel
pressures.
caster front wheel. The compressed gas cylinders are
Always close the regulator after use to prevent
mounted to the frame in two groups of three.
accidental over-pressurization during
A drawbar coupler ring on the front of the frame
subsequent charging operations.
assembly allows the equipment to be towed by a
Because of the high pressure used in this system,
vehicle that is equipped with a pintle assembly.
do not, under any circumstances, interchange
A hand-operated, mechanical brake is used to
components of this system with parts from other
systems.
secure the cart while it is stationary. The brake system
uses a cable linkage connected to a cam, which is
Release all pressure from the nitrogen cylinder
located on the wheel backplate.
before disconnecting any tubing.
Components
NITROGEN SERVICING TRAILERS
Figure 9-5 is a view of the control panel of the
Nitrogen servicing trailers provide a mobile source
trailer, and figure 9-6 is a system nitrogen flow
of high- and low-pressure nitrogen for servicing
diagram. The numbers inserted in parentheses in the
aircraft high-pressure systems and for inflating tires.
text are to help you locate the various components in
The nitrogen servicing trailer most widely used in the
the figures.
fleet is the A/M26U-4 nitrogen servicing unit. It is
9-6
