What happens when the safety valve lifts at not higher than the MAWP?

When the safety valve lifts at or below the Maximum Allowable Working Pressure (MAWP), it ensures that the boiler remains within safe operational limits. This is crucial because the primary function of a safety valve is to provide protection against overpressure conditions that could lead to dangerous situations, including boiler explosions. The lifting of the valve signals that the internal pressure has reached a critical level, allowing steam to escape and thereby reducing the pressure inside the boiler back to a safe state.

Operating within the MAWP is essential for maintaining structural integrity and functionality of the boiler, as exceeding this threshold could compromise safety. By ensuring that the safety valve functions correctly at or below the MAWP, the system effectively prevents potential hazards related to overpressure, reinforcing safe operation.

The other options, while relevant to boiler operation, do not directly relate to the primary function of the safety valve in context to the MAWP. Increasing efficiency, preventing overheating, or reducing fuel consumption connect to different operational aspects or goals but do not address the immediate safety and pressure regulation role rendered by the safety valve at the specified pressure limit.