What is the primary purpose of a relief valve in a hydraulic system?

• A. To increase system pressure above safe levels
• B. To measure pressure values for monitoring
• C. To lubricate hydraulic fluid
• D. To limit system pressure and protect components from overpressure

Answer: (D)

A relief valve is a safety device that keeps hydraulic pressure from getting too high. It sits in the system and stays closed during normal operation. If the pump tries to push more fluid than the system can handle and the pressure rises to a preset limit, the valve opens and allows fluid to flow back to the reservoir. This release keeps the pressure at a safe, designed level, protecting components like seals, hoses, cylinders, and the pump from damage. The relief valve can be set to a specific pressure, giving a built-in margin so a transient surge won’t cause harm.

That’s why it’s not about increasing pressure or measuring it, and it’s not for lubricating fluid. Lubrication and pressure measurement come from other parts of the system (oil, lubricants, and gauges).