In a fuel system, the purpose of a cut-off valve is to act at what specific operational condition?

A cut-off valve in a fuel system is designed to function at specific operational conditions to ensure the safe handling and management of fuel flow. The correct answer highlights the role of this valve in maintaining operation at 80% of the system's working pressure.

Operating at this percentage of pressure is critical because it provides a safety margin, reducing the risk of overpressure situations that could damage the system or lead to fuel leaks. By engaging the cut-off valve at this specified level, the system can effectively prevent the potential hazards associated with exceeding optimal pressure limits, which is crucial in maintaining the integrity and reliability of the entire fuel delivery mechanism.

When the pressure approaches this threshold, the cut-off valve helps regulate the flow and ensures that the system operates smoothly without risking safety or efficiency issues that may arise from high-pressure situations. This proactive approach to managing fuel flow and pressure illustrates the importance of cut-off valves in maintaining operational safety and efficacy within fuel systems.