What main function is assigned to the relief valve within an air brake circuit?

Question

DentroTest · Accepted Answer

The relief valve (usually associated with the pressure regulator) performs a safety function: it relieves pressure when it exceeds the working limit of the circuit, expelling the excess to the atmosphere to avoid breakages or failures caused by overpressure. Letting air through to the semi-trailer is not its job, because the supply and control of the trailer brakes are handled by the coupling heads and the trailer control valves. Expelling air pockets from the hydraulic fluid lines is not its job either, because that belongs to a hydraulic system and not to an air brake, which works with compressed air.

What main function is assigned to the relief valve within an air brake circuit?

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