According to ASME B31.1, what material should boiler blow-off fittings be made from when boiler pressure exceeds 100 psig?

When boiler pressure exceeds 100 psig, the materials used for boiler blow-off fittings must meet specific standards for strength and durability to handle high-pressure conditions. ASME B31.1, which is the American Society of Mechanical Engineers' code for the Power Piping system, specifies that steel is the appropriate material for these applications due to its high tensile strength, resistance to pressure, and ability to withstand elevated temperatures that can be present in boiler systems.

Steel exhibits excellent structural integrity under high-stress conditions, making it the preferred choice for fittings that will experience significant pressure and thermal variations during operation. Using steel for boiler blow-off fittings ensures safety and reliability, minimizing the risk of failures that could lead to hazardous situations.

In contrast, materials like plastic and copper would not provide the necessary strength and pressure resistance required for fitting applications in high-pressure environments. Alloys may be used in some contexts, but for specific boiler fittings at pressures above 100 psig, steel is the standard that is strictly adhered to according to ASME B31.1 requirements.