What is the function of a hydraulic relief valve?

• A. To filter contaminants
• B. To increase system pressure
• C. To limit system pressure by venting excess fluid back to the reservoir or tank
• D. To pump hydraulic fluid

Answer: (C)

A hydraulic relief valve is a safety device that keeps system pressure from getting too high. It is spring-loaded and normally closed, so as the pump raises pressure, the valve stays shut until the set point is reached. When that point is exceeded, the valve opens and sends excess fluid back to the reservoir, limiting further pressure rise. This protects components like hoses, seals, and actuators from overpressure and helps the system respond safely under high-load conditions. It isn’t used to filter contaminants, increase pressure, or pump fluid—that’s the job of a filter, a pressure-boosting device, or a pump, respectively.