Double Piston Trunnion Ball Valve
A trunnion mounted valve with two seats such that when the closed valve is pressurised from one side, the downstream seal is designed to seal if the upstream seat should fail.
Key Specifications / Features
Double Piston Trunnion Ball ValveA trunnion mounted ball valve with two seats such that when the closed valve is pressurised from one side, the downstream seal is designed to seal if the upstream seat should fail. This feature may be provided on both sides or on one side only.
Double piston effect seats are pressure energized in both direction. They will not release valve body cavity overpressure, a pressure relief design shall be added then.An external body relief valve is installed to protect the body cavity from excess pressure which can be vented to atmosphere or recycled back to the upstream side of the valve or to flare.
However, double piston effect seats offer valve sealing redundancy.
If upstream seat fails, downstream seat can still insure valve tightness. Interesting in specific applications (high integrity required) or for some pipe testing issues during construction.
With the ‘DPE’ seat option, if a leakage occurs in the upstream seat, the pressure entering the body cavity pushes the downstream seat against the ball and valve seals. Line pressure forces a seal against the floating seat.