Double piston effect ball valve
Double piston effect ball valve
(OP)
Ref: http://www.eng-tips.com/viewthread.cfm?qid=205580
Although the seating configuration appears to be the same in the Velan catalogue. How is that the single piston effect is able to seal from either direction and also be able to be self relieving, whereas the DPE is non-self relieving?
A client spec calls for the following,
Seat for all ball valve shall be of double piston effect seat design.
Safety relief valve for body cavity relief shall not be permitted.
Supplementary cavity relief when required for DPE type seats. What will be the alternative to not having a safety relieve valve for the cavity relief?
Although the seating configuration appears to be the same in the Velan catalogue. How is that the single piston effect is able to seal from either direction and also be able to be self relieving, whereas the DPE is non-self relieving?
A client spec calls for the following,
Seat for all ball valve shall be of double piston effect seat design.
Safety relief valve for body cavity relief shall not be permitted.
Supplementary cavity relief when required for DPE type seats. What will be the alternative to not having a safety relieve valve for the cavity relief?





RE: Double piston effect ball valve
-There is a valve in service with a fluid that does generate vapor pressure
-The operating pressure is 150 bar
When the valve is closed, the downstream pressure drops to 10 bar. Many DPE valves will relieve cavity pressure at 15 to 25 bar above the low-side line pressure, so in this case would release cavity pressure down to 35 bar, or possibly as low as 25.
"Safety relief" and "cavity relief" are not necessarily the same thing.
Are you an engineering company who is doing the layout on a plant or are you a valve manufacturer?
RE: Double piston effect ball valve
I am from an engineering company doing the buying specifications for the valve.
RE: Double piston effect ball valve
Where they said "Safety relief valve for body cavity relief shall not be permitted" they probably meant no pop-off type relief valve venting to atmosphere. I suspect they would require a valve venting back into the process piping somewhere. Possibly even a controlled valve and not a setpoint relief valve.
RE: Double piston effect ball valve