Which safety device is commonly used to prevent overpressure in a boiler?

The pressure relief valve is an essential safety device in a boiler system designed to prevent overpressure. When the pressure within the boiler exceeds a predetermined limit, the pressure relief valve opens to release steam or water, thereby reducing the pressure back to safe levels. This mechanism is crucial for maintaining the integrity of the boiler and preventing dangerous situations such as explosions or system failures caused by excessive pressure.

Other devices listed, such as pressure gauges, temperature sensors, and flow meters, serve different purposes. A pressure gauge measures the current pressure within the system but does not actively regulate or relieve pressure. A temperature sensor monitors the temperature of the boiler and helps determine operational conditions, while a flow meter measures the rate of fluid movement but does not directly address pressure management. The primary role of a pressure relief valve is to safeguard the system by actively responding to pressure increases, making it the correct choice in this context.