What is the function of a relief valve in a hydraulic system?

• A. To limit system pressure to a safe maximum and protect components from overpressure
• B. To increase system pressure
• C. To cool the hydraulic oil
• D. To store hydraulic fluid

Answer: (A)

The main idea here is that a relief valve protects the hydraulic system from overpressure. It stays closed as long as the system pressure is below its set point. When pressure climbs to that limit, it opens to allow fluid to flow back to the reservoir or to a lower-pressure part of the circuit, preventing further rise. This keeps pressures within the design limits so pumps, hoses, seals, and actuators aren’t damaged by spikes or blockages. It also helps smooth out pressure surges that can occur during rapid changes in load or startup.

It doesn’t serve to raise pressure, cool the oil, or store fluid. Those functions are handled by other components: increasing pressure is done by the pump or pressure-boosting devices; cooling is done by oil coolers; storage is handled by the reservoir.