Which type of safety relief valve body is prohibited for high-temperature water boilers?

The type of safety relief valve body that is prohibited for high-temperature water boilers is made from cast iron. This is primarily due to the fact that cast iron has limitations in terms of temperature and pressure tolerance. At high temperatures, cast iron can become brittle or may not withstand the stresses placed on it, which could lead to catastrophic failure.

In contrast, brass and steel are materials often used for safety relief valves because of their better performance characteristics under high temperature and pressure conditions. Brass has good tensile strength and resistance to corrosion, making it suitable for various applications, including in high-temperature settings. Steel also provides robustness and can endure higher temperatures and pressures than cast iron.

Plastic is not typically used in high-temperature applications either but is generally discussed in different contexts, such as in low-temperature or low-pressure systems due to its risk of degradation under heat. Thus, it is essential for safety and performance that the materials used in safety relief valves for high-temperature water boilers are chosen carefully, making cast iron a prohibited choice.