Some checkvalves, mostly with weightload and arm, or/and spring closing will have a possibillity to adjust and set the opening force (and hence opposite the closing force) at a certain value. Could this be the explanation?
Not in forty years but I would like to learn. Please explain where you came cross the reference. Hopefully not some consultant who wrote a specification based on half a dozen different manufacturers brochures that have been combined. Hence no one can comply.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
Thanks gerhardl, that sounds logic to me.
stanier, it's a request on a Hitachi data sheet. Talking to Hitachi, they even do not know what it is....
We just stated N/A.
My only other thought, would they possibly be talking about a cracking pressure verification test? All spring loaded check valves have an allowable variance + or - 20% for example. A cracking pressure verification test will tell you exactly where within that allowable range the check valve is cracking.
Thanks for the idea, I was thinking about the same, but check valves of different designs in operation show cracking pressures of approximately 105 to 110% of the operating or closing pressure. (Rule of thumb)
This is a known rule of thumb to piping engineers which normally is not of any concern.
