If valves are to be used for steam, their seals must be resistant to high temperature. Graphite filled PTFE (up to +260°C), or stainless steel reinforced PTFE (up to +260°C), are the most common materials for ball valve seats. PEEK also has good resistance to high temperatures and is used for ball valve seats intended for operating temperatures up to +250°C. For extreme temperatures, pure graphite (up to +500°C) or metal (up to +500°C) is used for ball valve seats.
The optimum choice for steam applications are steam globe valves (shut-off, shut-off/control, or shut-off/non-return) and gate valves with high operating parameters (up to +425°C) and a relatively low price.