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[seetheforest]

Hi,

I have a question that has been bothering me for a while. In UG-127(a)(2)(a)(3), ASME states that rupture disks must not exceed a coefficient of discharge, K_D, of 0.62.

However, I must say that I am mystified by the difference between the coefficient of discharge, K_D, and the flow resistance coefficient, K_R.

Moving to section UG-131(e), there is a definition of the coefficient of discharge and an equation (Wt = 51.5 A*P) to which the coefficient of discharge can be applied (Appendix 11). However, in UG-131(k)-® ASME starts defining the flow through a burst rupture disk in terms of K_R--flow resistance.

My question boils down to... what's the difference between K_R and K_D? Can I use K_R in the Wt = 51.5 A*P equation?

Or, more generally, if I calculate my own theoretical flow through a valve or an orifice, should I multiply that value by the appropriate K_D or K_R that I can get from the valve manufacturer? And why does UG-127 set a limit for the rupture disk K_D if rupture disks are always characterized by K_R?

I'm somewhat confused.

Edited by seetheforest, 13 March 2012 - 03:34 PM.

[Shivshankar]

Hi Seeforest,

Please go through article (blog ) by ankur on, read it carefully, I hope you will understand the difference between Kr and Kd and when to use it.

http://www.cheresour...ngineers-part-2

Regards
Shivshankar