The power plant valve usually should be high pressure and high temperature with medium water, steam, air. So material WCB, WC6, WC9 are widedly usded as main body material. The valve are designed with pressure seal bonnet for class 600 900, 1500, 2500 depends on size and working condition. The valve are usually with butt weld ends connection to avoid any leakage.Hard face sealing surface are often adopted.
Following are some pic of Power plant gate valves SGV offer.
Body inner side machining:
Main parts casting of gate valve:
Valve pressure test for Flange connection big size high pressure gate valve: