What material must the boiler blow-off fittings be when the pressure exceeds 100 psi?

When the pressure in a boiler exceeds 100 psi, it is crucial to use materials that can withstand the high pressures and temperatures associated with boiler operation. Steel is the correct choice for boiler blow-off fittings in this case because it has excellent strength and durability, making it suitable for high-pressure environments.

Steel fittings are designed to handle the mechanical stresses and thermal expansion that occur in pressurized systems. They also provide better resistance to potential corrosion and thermal fatigue compared to other materials. This is particularly important in boiler systems, where the blow-off function is critical for removing sediment and preventing boiler damage, ensuring safe and efficient operation.

Other materials, such as plastic, brass, and copper, do not possess the same level of strength and pressure resistance as steel at elevated pressures. Using them in high-pressure scenarios could lead to failures, leaks, or system malfunctions, posing risks to safety and operation.