Cavity relief for Trunnion Ball Valve
Cavity relief for Trunnion Ball Valve
(OP)
My custome has required a Trunnion mounted ball with cavity relief by seat leakage to inside of valve.
Normaly the Trunnion type are self relief sealing but in this case i dont' understood what's mean about cavity relief by seat TO INSIDE OF VALVE !!
Normaly the Trunnion type are self relief sealing but in this case i dont' understood what's mean about cavity relief by seat TO INSIDE OF VALVE !!





RE: Cavity relief for Trunnion Ball Valve
Set point is a big issue. It only takes a couple of psi of over pressure to lift the seat from the back. If you set the PSV at a couple of psi then it will lift every time you shut the valve.
Tough problem. You can solve it with a dP control valve that samples upstream and downstream and sends the lower pressure to the static side of a dP PSV which is set to lift when the cavitiy is 2-3 psid higher than the low pressure side of the Trunion. It sounds complicated, but it is pretty easy.
David
RE: Cavity relief for Trunnion Ball Valve