Fusible plugs used as protective devices in HRT boilers producing low-pressure steam should melt at what temperatures?

• A. Above the boiling point of water
• B. At the same temperature as the steam
• C. Below room temperature
• D. At 250 degrees Fahrenheit

Answer: (B)

Fusible plugs are safety devices used in high-rupture temperature (HRT) boilers to prevent overheating and potential damage or failure of the boiler. They are designed to melt and release steam when the temperature exceeds a certain limit, thus providing a safety mechanism.

The correct answer indicates that fusible plugs should melt at the same temperature as the steam. This is essential because it ensures that if the boiler temperature becomes excessively high, which could lead to dangerous pressure increases, the fusible plug will melt and allow steam to escape. This action helps to reduce the pressure and prevents potential explosions or catastrophic failures.

Choosing the right melting temperature for fusible plugs is crucial for the safe operation of the boiler. It must be calibrated to react before any critical damage occurs, keeping the system safe and functional. In contrast, selecting a melting temperature above the boiling point of water or a specific temperature like 250 degrees Fahrenheit would not provide adequate protection, as it could allow the boiler to reach unsafe conditions before the plug activates.