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| Illustration 1 | g00526002 |
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Location of pressure protection valve for the brake air system | |
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| Illustration 2 | g00277838 |
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Pressure protection valve (1) Supply passage (2) Valve (3) Delivery passage | |
The pressure protection valve for the brake air system is located next to the brake relay valve for the Automatic Retarder Control (ARC). The brake relay valves are located on top of the frame behind the fuel tank.
The pressure protection valve for the brake air system prevents a complete loss of air pressure in the event of a failure of the relay valve for the ARC.
Air flow from the primary air tank flows through the pressure protection valve. Air will not flow through the pressure protection valve until the air pressure at the supply passage reaches the valve opening pressure. When the air pressure reaches the valve opening pressure, valve (2) moves in order to allow air to flow through the pressure protection valve to delivery passage (3). The pressure protection valve closes when the air pressure reaches the valve closing pressure.