Air Brake Manual
Air Brake Manual
Air Brake Manual
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Placing the compressor in the unloading stage is<br />
done by directing air pressure to the inlet valves of<br />
the compressor, holding them open, allowing the air<br />
to be pumped back and forth between the two<br />
cylinders, instead of compressing the air. When the<br />
pressure in the system drops, the inlet valves close,<br />
returning the compressor to the “loading” stage.<br />
The governor must place the compressor in the<br />
“loading” stage at no lower than 80 psi. During the<br />
“unloading” stage, the compressor is able to cool.<br />
It is very important the air that enters the system be<br />
kept as clean as possible. The air must first pass<br />
through a filter to remove any dust particles. The air<br />
filter must be cleaned regularly. A dirty filter will<br />
restrict the flow of air into the compressor, reducing<br />
its efficiency. Some vehicles have the inlet port of<br />
the compressor connected to the intake manifold<br />
and receive air that has been filtered by the engine<br />
air cleaner.<br />
A piston type compressor operates on the same<br />
principle as the intake and compression strokes of<br />
an engine.<br />
· Intake stroke: The downward stroke of the piston<br />
creates a vacuum within the cylinder which causes<br />
the inlet valve to open. This causes atmospheric air<br />
to flow past the inlet valve into the cylinder.<br />
Compressor (Unloading stage)<br />
Inlet<br />
valve<br />
Compressor (Intake stroke)<br />
Inlet<br />
valve<br />
Unload<br />
plunger<br />
Unload<br />
plunger<br />
Piston<br />
Piston<br />
Discharge valve<br />
From governor<br />
Intake air filter<br />
Discharge<br />
valve<br />
Intake air filter<br />
Usually compressors are lubricated from the engine<br />
lubrication system, although some compressors are<br />
self-lubricating and require regular checks of the<br />
lubricant level.<br />
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