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

The pressure relief valve is a critical safety device in a boiler system designed to prevent overpressure, which can lead to catastrophic failures. Its primary function is to automatically release excess pressure within the boiler when it exceeds preset limits. This is essential in maintaining safe operational conditions and ensuring that pressure does not build up to dangerous levels that could compromise the integrity of the boiler or lead to explosions.

When the pressure inside the boiler rises beyond a specified threshold, the pressure relief valve opens, allowing steam or water to escape, which effectively reduces the internal pressure brought back to a safe range. This mechanism is vital for protecting the entire system from potential damage and is a standard safety requirement in boiler operations.

Other devices listed do not fulfill this particular function. For instance, steam traps serve to remove condensate and air, water gauges provide a visual indication of the water level, and blow-off valves are used primarily for flushing out sediment and impurities from the boiler but do not specifically manage pressure levels. Therefore, the role of the pressure relief valve in preventing overpressure makes it the correct choice in this context.