BC Transit – Air Brake Course

Trailer Break-Away
In this case the trailer has completely parted company from the tractor:
1) The Emergency Relay Valve will “sense” the loss of air in the supply line due to the trailer’s
separation from the tractor. It will immediately “dynamite” the trailer brakes, meaning that all
air in the trailer reservoir will be dumped onto the trailer brakes. The one-way check valve
prevents any loss of air through the severed supply line.
2)The Trailer Supply valve will remain open, allowing a loss of air from the tractor until the
reservoir pressure reaches 45 to 20 psi, or the operator closes the valve manually.
3) The operator makes a foot valve application (green) to bring the tractor to a stop. That
application air travelled to the tractor brakes, but “dead-ended”at the tractor protection valve
preventing an air loss there.
Left click to start animation
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