thomasfpe
Specifier/Regulator
- Oct 10, 2016
- 3
Hello,
I joined this board today after using it intermittently when I had a challenging project or problem. Now that I've been designing for a while, I have a question that relates to a 2011 post where I noticed that a member posted that the Hazen-Williams formula, if derived, has a 1.85:1 safety factor, or 85%.
From all the research I have done on this topic, I cannot find any substantiation of this claim. Further, it appears that, based on flow tests I have witnessed, that this is not the case. Instead, I've found that the exp(1.85) in the equation simply brings it up to reality for the calculation, and without it the equation doesn't hold. My understanding is that the equation is empirically derived, meaning that given a large set of flows, correlated with the proper C-factor, that the equation simply fits the flows, and that is why we have a 10%+ safety factor required by many AHJs.
Please forgive me if I am wrong, but I have a bet with a local AHJ on this and both of us have been through some extensive hydraulic calcs in the past... I have an MS in FPE, and about 15 years practical experience before that, and have never seen this safety factor in any literature on fire sprinkler flows.
Thank you
RT
I joined this board today after using it intermittently when I had a challenging project or problem. Now that I've been designing for a while, I have a question that relates to a 2011 post where I noticed that a member posted that the Hazen-Williams formula, if derived, has a 1.85:1 safety factor, or 85%.
From all the research I have done on this topic, I cannot find any substantiation of this claim. Further, it appears that, based on flow tests I have witnessed, that this is not the case. Instead, I've found that the exp(1.85) in the equation simply brings it up to reality for the calculation, and without it the equation doesn't hold. My understanding is that the equation is empirically derived, meaning that given a large set of flows, correlated with the proper C-factor, that the equation simply fits the flows, and that is why we have a 10%+ safety factor required by many AHJs.
Please forgive me if I am wrong, but I have a bet with a local AHJ on this and both of us have been through some extensive hydraulic calcs in the past... I have an MS in FPE, and about 15 years practical experience before that, and have never seen this safety factor in any literature on fire sprinkler flows.
Thank you
RT