c. Pressure Control System.
(1) To maintain a constant supply of air, the compressor operates in a "loading and unloading cycle" controlled
by the pressure control system. Components of the pressure control system include the intake valve
unloader, unloader pilot, slow-down assembly, and the check and bleed valve.
(2) When air pressure drops to 90 psi in the air receiver, the pressure control system will "load" in the following
manner: The unloader pilot valve shuts off air to the intake valve unloaders to close the intake valves. The
check and bleed valve releases air from the slowdown assembly and temporarily restricts the flow of air
from the suction valve unloaders. The slowdown plunger backs off from the governor lever to increase
engine speed.
(3) When air pressure reaches 100 psi in the air receiver, the pressure control system will "unload" in the
following manner: The unloader pilot valve admits air to the intake valve unloaders to open the intake
valves. The slowdown plunger pushes out against the governor lever to reduce engine speed to idle.
d. Air Receiver and Hose Reels.
(1) The air receiver is equipped with a safety valve for protection against a build-up of excess pressure and two
drain cocks to drain off condensation within the receiver. Compressed air in the receiver may be released
from the two service valves connected to the rear of the air receiver or from the service valves in the hose
reels.
(2) There are two hose reels, one on each end of the air receiver, to provide handy and safe storage for air
hoses.
e. Auxiliary Equipment and Tools.
(1) The pneumatic tools furnished with this unit are clamped in special tool boxes. After use, all pneumatic
tools should be returned to their special designated places.
(2) A set of on-equipment maintenance tools have been packed in a separate tool bag. A list of these on-
equipment tools will be found in appendix III. Included in this set are the most necessary tools to perform
most of the common maintenance services on the engine-compressor.
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