HEATER GROUP 3P3598 - Caterpillar

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Quick Release and Holding Valve on Tractor
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Quick Release and Holding Valve on ScraperThe Engine Has Been Removed For Photographic Purposes.The quick release and holding valves reduce the time that is required to apply the parking and secondary brakes. This is done by hastening the exhaust of air pressure from the secondary brake chambers.
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Quick release and holding valve in the release positionThe parking and secondary brakes are applied in this position. (1) Outlet port to brake chamber (2) Sealing washer (3) Exhaust port to atmosphere (4) Outlet port to brake chamber (5) Shuttle assembly (6) Inlet port (7) Rubber sealing bandWhen the parking and secondary brake control valve is pushed in order to release the brakes, air enters the quick release and holding valve through inlet port (6). Shuttle assembly (5) moves against sealing washer (2) to close exhaust port (3). Air pressure enters a drilled passage inside shuttle (5), which expands rubber sealing band (7). As sealing band (7) expands, sealing band (7) unseats from the opening in the air passage. This allows air to flow to the parking and secondary brake chambers in order to release the brakes. When the valve assumes the holding position, the pressures at inlet port (6) and outlet ports (1) and (4) are equal. Sealing band (7) closes the air passage through shuttle (5) by contracting. This blocks the air from returning from the secondary brake chambers.A pressure reduction at inlet port (6) will actuate the quick release and holding valves. This could be caused by either an application of the parking and secondary brake control valve or a failure. Shuttle (5) unseats from exhaust port (3), which allows the air in the parking and secondary brake chambers to exit in order to apply the brakes.