Air Brake Manual
Air Brake Manual
Air Brake Manual
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Note: The trailer brake hand valve is not to be used for<br />
parking, as air may bleed off if the engine is stopped<br />
or the hand valve moves to the released position.<br />
Two-way Check Valves<br />
The purpose of a two-way check valve (26) is to<br />
direct air flow into a common line from either of two<br />
sources. This valve will permit air to flow from the<br />
source that is supplying the higher application<br />
pressures. The shuttle will shift so that the higher<br />
pressure will be directed to the trailer through the<br />
control (service) line. This valve is located between<br />
the foot-operated valve and the hand-operated<br />
valve.<br />
<strong>Air</strong> from<br />
hand valve<br />
<strong>Air</strong> from foot<br />
valve<br />
Shuttle<br />
To trailer<br />
Foot Valve Application<br />
30 26<br />
31<br />
The driver has applied the brakes by using the foot<br />
valve (31). Application air is directed to the brake<br />
chambers of the tractor and to the trailer brakes<br />
through a two-way check valve (26). The shuttle has<br />
shifted to the low pressure side, closing off any air<br />
flow toward the hand valve side. The hand valve (30)<br />
is in the closed position and equal pressure is being<br />
applied to the brake chambers of the tractor and the<br />
brake chambers of the trailer.<br />
40
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