FAA AMT (Aviation Maintenance Technician) Airframe Practice Exam

Hydraulic system thermal relief valves are set to open at a pressure

1. Equal to the system relief valve

2. Lower than the system operating pressure

3. Higher than the system relief valve

4. Slightly above atmospheric pressure

The correct answer is: Higher than the system relief valve

Thermal relief valves in a hydraulic system are designed to prevent damage to the system from excessive pressure buildup caused by extreme temperatures. The pressure at which these valves open is critical, as it must be high enough to release excess pressure, but not so high that the system's operating pressure is compromised. Option A is incorrect because setting the thermal relief valve to equal the system relief valve could result in the valve opening too early and causing system failure. Option B is also incorrect because setting the thermal relief valve too low could lead to unwanted valve opening and potentially damage the system. Option D is incorrect because setting the thermal relief valve only slightly above atmospheric pressure would not provide sufficient relief for the system in case of extreme temperatures. Therefore, option C, setting the thermal relief valve higher than the system relief valve, is the most appropriate choice to prevent damage to the system and ensure proper functioning.