What cast iron item is not allowed on a high pressure boiler?

In high-pressure boiler applications, the materials used must be able to withstand elevated temperatures and pressures without failure. Cast iron, while suitable for certain applications, is generally not utilized for components that experience high-stress conditions, such as nozzles or flanges in high-pressure systems.

Nozzles and flanges are critical points in a boiler where the integrity of the connection is essential to maintain pressure and prevent leaks. Cast iron has relatively low tensile strength and can be brittle, especially in high-stress situations, making it an unsuitable choice for these components in high-pressure boilers. Instead, materials such as forged steel or other alloys that can better handle the mechanical demands are typically specified for nozzles and flanges.

On the other hand, components like bolts, pipes, and fittings can sometimes be made from cast iron in lower pressure applications or where the mechanical stresses are more manageable. In high-pressure boiler systems, however, the use of cast iron for nozzles or flanges is explicitly prohibited to ensure safety and reliability.