Plug valve, opening and closing parts (cone plug or ball) Rotating plug valve around its own centerline is a valve that uses a plug body with a through hole as an opening and closing part to realize the opening and closing action through the rotation of the plug body and valve stem. In recent years, as one of the earliest valves used by people in history, not only has it not been replaced by ball valves and other types of valves, but the market is showing a trend of becoming more and more popular.