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

In high-pressure boiler systems, specific materials and components are critically important due to the extreme conditions they must withstand. Cast iron is known for its strength and durability, but it has limitations when exposed to high pressures.

Flanges and fittings made of cast iron can often be used in lower-pressure applications; however, when it comes to high-pressure boilers, the risk of failure under stress is significantly increased. Cast iron can become brittle, especially under high temperatures and pressures, leading to catastrophic failures.

Nozzles, which are crucial for directing the flow of steam or water in a boiler, must be constructed from materials that can handle high-pressure conditions without risk of fracture or deformation. The combination of nozzles and flanges made from cast iron would not meet the safety and performance requirements necessary for high-pressure boilers, hence their prohibition.

This highlights the necessity of using alternative materials, such as forged steel, which can endure the demanding environments present in high-pressure boiler systems. Thus, the choice of nozzles and flanges made from cast iron being disallowed reflects the critical safety standards essential in high-pressure applications.