WCB CASTED BALL VALVE, Design : ASME B16.34 API 6D

Seat sealing

Soft seats are standard. Seat inserts of synthetic material such as Nylon. 
PTFE, RTFE, or Peek are contained within a one-piece metal seat ring with no or very low line pressure. 
Sealing between the seats and ball is achieved by seat spring with higher line pressure. 
The line pressure, in conjunction with the spring load, forces the upstream seat ring against the ball,which results in tighter sealing.

Seat sealing

Soft seats are standard. Seat inserts of synthetic material such as Nylon. 
PTFE, RTFE, or Peek are contained within a one-piece metal seat ring with no or very low line pressure. 
Sealing between the seats and ball is achieved by seat spring with higher line pressure. 
The line pressure, in conjunction with the spring load, forces the upstream seat ring against the ball,which results in tighter sealing.

Self Relieve Seat

This feature is designed to prevent excessive pressure build up within the valve by automatically,relieving pressure when body cavity pressure exceeds the spring load on the seats. 
Double Piston Seat is also available as and option.