Inlet loss and combination factor for BD?

[mrtangent]

On inlet loss calculations do you include the Bursting disc in the pressure drop before the valve...or

do you down rate the valve capacity and exclude it..

 

[don1980]

Yes, the rupture disk is a factor in calculating the inlet pressure loss. A blown disk causes a flow resistance (K value), and it's treated just like the resistance from a pipe fitting. The K value for a blown disk is called Kr and it's determined by the manufacturer according to a certified test procedure mandated by ASME. You can easily find this value in the vendor's catalog, vendor website, or in the National Board redbook.

So, add this Kr to the other resistances (fittings, valves, inlet loss, etc) in the inlet piping system and calculate the resulting pressure drop.

 

[Chance17]

To answer your question --- you do both
1.) Include the disk in inlet line PDrop evluation
2.) Derate the disk-PSV combination