Minnesota Boiler License Practice Exam

What material should safety valves made for discharging super-heated steam over 450 degrees F be constructed from?

1. Brass

2. Cast iron

3. Malleable iron

4. Steel alloy

The correct answer is: Steel alloy

The proper construction of safety valves designed for discharging super-heated steam at temperatures exceeding 450 degrees Fahrenheit is critical for ensuring safety and performance. Steel alloy is the preferred material for these valves due to its high strength, durability, and resistance to the extreme conditions present when handling super-heated steam. Steel alloys can withstand higher pressures and temperatures compared to other materials, making them more suitable for demanding applications like this. They also exhibit excellent fatigue resistance and corrosion properties, which are essential in preventing valve failure and ensuring the longevity of the equipment. In contrast, brass, cast iron, and malleable iron are generally not recommended for high-temperature steam applications. Brass may not withstand the high temperatures and can lead to deterioration over time. Cast iron is strong but can become brittle at elevated temperatures. Malleable iron, while more robust than standard cast iron, still does not provide the same level of heat resistance and structural integrity that a steel alloy offers. Thus, steel alloy is the right choice for safety valves in high-temperature environments.