Rhode Island Master Pipefitter Practice Exam

In the context of piping materials approved for use in steam systems, plastic is generally not permissible because it cannot withstand the high temperatures and pressures associated with steam. Steam systems require materials that can handle these conditions without deforming or failing. Steel and malleable iron are often used due to their strength and durability, making them suitable for high-pressure applications like steam. Copper is also commonly used in steam systems because it is highly resistant to corrosion and has excellent thermal conductivity. Malleable iron, while sturdy, is not typically used for steam applications primarily due to its limitations in extreme conditions compared to other materials that possess better temperature tolerance and strength under pressure. Therefore, plastic is explicitly prohibited, making it the material that cannot be used in steam systems, as it does not meet the stringent requirements needed for such applications.