Class _____ malleable iron fittings are used with steam lines containing steam at 300 psi.

• A. 100
• B. 200
• C. 300
• D. 400

Answer: (C)

Malleable iron fittings are categorized into different classes based on the pressure they can withstand. Class 300 malleable iron fittings are designed specifically to handle higher pressure applications such as steam lines, making them suitable for use with steam operating at 300 psi.

The material properties of Class 300 fittings ensure they can withstand the stresses associated with hot, high-pressure steam while maintaining structural integrity. This makes them appropriate for industries where steam is utilized, like power generation and HVAC systems. Higher classes, such as Class 400, are typically used for even more stringent conditions, but for a steam line operating specifically at 300 psi, Class 300 fittings are the designated standard.

Understanding the appropriate class of fittings to use is crucial for ensuring the safety and efficiency of piping systems, particularly in high-pressure applications. Hence, choosing Class 300 for this particular scenario aligns with industry standards and practices.