The upper seal can be replaced when the valve is in line and under pressure. Stem is separate from ball. Fugitive Emission Packing Seal - Flow Control trunnion mounted ball valves include an independent multi seal system as a sensible economical solution to provide zero leakage against dangerous emissions. Each ball valve has block and bleed capabilities with independent upstream and downstream seals which permit draining and venting of fluid from within the body cavity. Automatic body pressure release to down stream.
Bonnet construction allows ease of mounting extensions, gears and actuators.
Antistatic features ensure electrical continuity between stem, ball and body. The spring loaded seats can move slightly along the longitudinal axis of the valve. Upstream pressure is exerted over area A1 which is counteracted over area A2. The remaining differential force over area D pushes the seat tightly on the ball. Even when line pressure, PL, is low, the mechanical action of the springs pushes the seats onto the ball thereby achieving perfect tight sealing.