The ball on a trunnion ball valve does not move with medium pressure. Trunnion ball valves have floating seats. This valve uses pressure actuated seats with locked-in non-metallic face seals. To assure tight sealing at low pressures, special springs force the seats against the ball. At higher pressures, the upstream seat is forced against the ball by the pressure working across the differential between the area of the seat insert and the seat O-Ring; the higher the pressure, the tighter the seal.
Sealant Injection Device
Trunnion mounted ball valves are provided with devices, which are on both the stem and the seat of the valves DN 150 (NPS6) and larger and in the body cavity for valves less than DN 125. When the stem o-ring or the body seating ring is damaged, the medium leakage between the body and stem can be prevented by injecting sealant through the device.
Double Block and Bleed
The pressure actuated seats and bleed fittings allow double block and bleed operation. When used for block and bleed, this feature permits the valve to take the place of two valves. It also allows the operator to check up and downstream sealing by bleeding off the body pressure.
The ball of the trunnion ball valve is in close contact with the trunnion, adjusting cushion, and trunnion end cap, thus providing a passage for static electricity to escape the confines of the valve.
Fire Safe Design
In case of fire, non-fireproof material for packing and seat will be burnt-out and considerable medium leakage may possibly cause the fire to spread. FBV uses metal to metal or graphite seals as an auxiliary safeguard to prevent medium leakage in cases of fire as shown in figures. The fire safe design confirms to the requirements of API607, API 6FA, BS 6755 and JB/T 6899.