The valves in following services will be considered critical (in the opinion of our Contractor):

We have large deaerators in our generating station that have a rupture disc on them (approx 10"). Ocassionally one will blow up a pipe through the roof.

10hp down hole centrifugal pump.Set at about 70 feet.Pressure measured and found at center of BEP.Rated flow 90g/min.

For Heater charge , we have two pumps ( Pneumatic and electric diaphragm pumps both are motor driven) .

A calculation involving a centrifugal pumping from vacuum vessel.Fluid: Water @ 180 DegF.Fluid Density: 0.970

I don't think there is an ASME spec for the packing. The pervasive practice in the industry is to call out the spec number from the packing manufacturer used,

For the minimum amount of time that the pump is operating, it would probably be a better to design to omit the relief valve entirely and use a constant recirculation line with an appropriately sized o

Cv is proportional to the open area and a disch coeff.the problem with ball valves is that they are classified as high recovery valves. Check Appendix A, Crane Technical Paper 410.