Trunnion Type Ball Valve is a 90 degree operated type with a fixed ball connected with stem. For floating ball valve, ball is fixed on stem, but for trunnion ball valve, there is a shaft at the bottom of valve body to fix ball together with stem. Then this makes ball more stable with high pressure. So trunnion ball valve is more suitable for big size and high pressure pipelines with lower cost than floating ball valve.
Compare to trunnion ball valve, floating ball will move during high pressure of medium. When operating, the ball will oppress seat directly when fluid come. Then make the torque increase on stem. However for trunnion type ball valve, when fluid comes, the stem and shaft will protect ball on both side, it will not add torque on stem and seat.
