Which type of valves are typically used in high-pressure, high-temperature systems?

The use of alloy steel valves in high-pressure, high-temperature systems is primarily due to their superior strength and durability under extreme conditions. Alloy steel is engineered to withstand stress and deformation, making it suitable for environments where both pressure and temperature can reach significant levels.

High-pressure systems demand materials that can handle the forces exerted on them without failing. Additionally, high temperatures can lead to material degradation, so alloy steels, which often have improved resistance to heat, are ideal for these applications. They also provide good corrosion resistance, which is critical in systems where various fluids are transported.

In contrast, the other materials listed—brass, PVC, and copper—do not possess the same level of mechanical strength or heat resistance necessary for high-pressure and high-temperature applications. Brass, while strong, can corrode under certain conditions, and PVC is not suited for such extreme environments due to its limited temperature range. Copper, although it has good thermal conductivity, may not be reliable in high-stress situations, especially at elevated temperatures and pressures. Hence, alloy steel valves are the most appropriate choice for ensuring safety and performance in critical systems.