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C1Difficulty 2/5

What is the function of an air-brake reservoir’s safety or overpressure relief valve?

Correct answer

To prevent overpressure in the system.

It protects against excessive pressure by releasing air above its specified opening pressure. It is distinct from a quick-release valve, which exhausts brake-chamber air when braking ends, and from the reservoir drain valve used to remove condensation. These have different functions. Follow system specifications and maintenance; do not adjust or disable the valve to raise pressure.

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  • To prevent overpressure in the system.

  • To automatically bleed air from the hydraulic fluid.

  • To allow air to pass into the semi-trailer circuit.

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