What safety device is primarily used to prevent overpressure in a boiler?

A pressure relief valve is designed to automatically open when the pressure within the boiler exceeds a predetermined limit, allowing steam or water to escape and thus preventing further increases in pressure. This is crucial for maintaining the safe operation of a boiler, as exceeding pressure limits can lead to catastrophic failures, including explosions. The pressure relief valve acts as a safeguard, effectively protecting both the equipment and personnel by ensuring that pressure does not reach dangerous levels.

In contrast, a flow meter measures the rate of fluid flow, a temperature gauge provides information on the temperature within the system, and a water level indicator shows the water level in the boiler. While these devices contribute to overall monitoring and operational efficiency, they do not directly prevent overpressure conditions in the same manner as a pressure relief valve. Therefore, the pressure relief valve is the essential safety device specifically designed for this purpose.