Trunnion Mounted Ball Valve
(A) Standard : Single Piston Effect Seats (Self Relieving Seats)
Medium pressure, both upstream and downstream, creates a resultant thrust to the seat rings against the ball to assure tight sealing; medium pressure acting in the body cavity creates a resultant thrust to push the seat rings away from the ball. The single piston design permits the automatic release ofany over pressure in the body cavity when the valve is in the fully open or fully closed position.
(B). Option 1 : Double Piston Effect Seats
Medium pressure, both upstream and downstream as well as in the body cavity, creates a resultant thrust that pushes the seat rings against the ball. Valves with double piston effect seat rings require a cavity pressure relief device to reduce the build-up of over pressure in the body cavity.
(C). Option 2 : Combination Seats
Combination seats design is available on request. That is a standard seat design used for upstream side and a double piston effect seats design used for downstream. The advantage is it can reach double piston effect seats design function without cavity pressure relief device to saves the cost, meanwhile only need a little care to install valve per flow direction arrow.
Large Diameter Special Features
Primary seat sealing is provided by a soft sealing ring of different rubber types. Alternatively, a PTFE hard sealing ring (or PTFE modifications) can be used for primary sealing. Secondary sealing is provided by metal-to-metal contact of the seat to the ball. Emergency sealant, which can be injected between the seat and ball, can be used as tertiary sealing. Seats with soft sealing rings are automatically supplied as DPE design (Fig.7). DPE design means, that if the upstream seat is damaged, function of a ball valve is still secured by a downstream seat.
Self Relieving Seat
pressure works on seat area “A” which is wider than area “B”; therefore the differential area creates a piston effect which forces the seat against the ball surface producing a tight effective seal.
The self relieving features when the pressure in the body cavity exceeds the inlet or the outlet pressure. In this case area “C” is wider than area “D” and when the piston effect created becomes greater than the constant spring load, the self relieving effect is obtained.
Doulbe Piston Effect Seat
pressure works on seat area “A” which is wider than area “B”; therefore the differential area creates a piston effect which forces the seat against the ball surface, producing a tight effective sealing.
pressure inside the body on seat area “D” which is wider than area “C”‘ therefore the differential area creates a piston effect which forces the seat against the ball, producing a tight effective seal.
(A).External Leakage Prevention
All the possible external leakage point between stem and gland flange, gland flange and body, body and adapter are sealed with primary O-ring then secondary graphite gasket. When fire burned out the primary O-ring seal, the secondary graphite gasket seal still can prevent the process medium from external leakage.
(B).Internal Leakage Prevention
When fire burned out the primary O-ring seal between the floating seat ring and adapter, also the seat insert between seat ring and ball, the secondary
graphite seal between seat ring and adapter, and seat ring & ball metal to metal contact preloaded by spring will minimize the internal process medium
Emergency Sealant Injection System
Each valve of size 6″ and larger (or smaller size on request), is equipped with sealant injection located at stem and seats area. The injection is integrated with check valve to provide backup sealing, also a check valve is equipped at front of seat sealant injection to avoid blowing out in case wrong operation. When the soft sealing materials (seat inserts and O-ring) are damaged and leakage happened by fire or other accident, the sealant can be injected through the injection fittings.
Valve with extended stem shall be supplied as per the client requirement.Distance from valve center line to operator flange to be mentioned by the client.