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# Chemical plant design & operations FAQ

## Hydraulic Analysis -fluid mech

 What is the difference between Fanning and Moody friction factors? by chemebabak faq124-1746 Posted: 6 Oct 11 Many folks calculate 4 times greater head loss (or 4 times less) than the actual friction loss.  This comes from confusion between Moody and Fanning Friction factors.  Some friction factor graphs are for Moody Friction factor, which is 4 times Fanning friction factor.  That is, f = 64/Re is Moody and f = 16/Re is Fanning.Be careful with your hydraulic calcs.  It is easy to mix the two and calculate 400% greater (or 25% less) head loss.  The calculation for head loss in feet is:using Moody Friction factor -h(friction) = f(M) * (L/D) * v^2 / (2 * g)using Fanning Friction factor -h(friction) = 4*f(F) * (L/D) * v^2 / (2 * g)where,h(friction) = head loss by friction in feetf(M) = Moody Friction factorf(F) = Fanning Friction factorL = length in feetD = pipe inside diameter in feetv = velocity in ft/sg = 32.174 ft/s^2, acceleration due to gravityThe Colebrook-White equation is an iterative method that calculates Fanning friction factor.f(F)^2 = 1 / ( -4 * Log(eps / (3.7 * D) + 1.256 / (Re * √f(F) ) where,eps = pipe roughness in feetRe = Reynold's number Back to Chemical plant design & operations FAQ Index Back to Chemical plant design & operations Forum

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