Sub-high temperature means that the working temperature of the valve is in the range of 325 to 425°C. If the medium is water and steam, WCB, WCC, A105, WC6 and WC9 are mainly used. If the medium is a sulfur-containing oil, it is mainly used for anti-sulfide corrosion of C5, CF8, CF3, CF8M, and CF3M. They are mostly used in refinery atmospheric and vacuum units and delayed cokers. At this time, CF8, CF8M, CF3, and CF3M valves are not used for corrosion of acid-resistant solutions, but for sulfur-containing oils and oil and gas pipelines. In this case, the maximum operating temperature limit for CF8, CF8M, CF3, and CF3M is 450 °C.