Sunday, June 6, 2010
Firewater, service, portable and drinking water network is common network present in most Oil & gas, Refinery and Industry plant. Water balancing in this network is important and critical in maintaining a constant supply to all users. Correct frictional loss estimation within network is the key activity in providing a well balance of water supply. Hazen-William formula is one the method widely accepted and used in industry in estimating frictional loss.
Hazen-William frictional loss is a function of fluid velocity, hydraulic radius and a constant subject to fluid condition and type of pipe. Equation as follow :
C Change with Pipe Material
Hazen-William friction loss coefficient (C) subject to condition and type of pipe. It possibly range from 60 to 150. The following summary listed the Hazen-William friction loss coefficient (C) for different type of material
(source : Handbook of Chemical Engineering Calculation)
Another set of Hazen-William friction loss coefficient also listed in NFPA 15-2007.
(source : NFPA 15-2007)
From above figures, the C factor is almost decrease with surface roughness.
C Decrease With Service Life
One shall take note that Hazen-William friction loss coefficient will decrease with service life. From King & Crocker "Piping Handbook", C = 120 when the pipe is new and decrease to C=90 after 20 years. From "Handbook of Chemical Engineering Calculation", C factor for a new Cast-iron pipe (30 inches) is 130, decrease to 120 after 5 years, decrease to 115 after 10 years, decrease to 100 after 20 years, decrease to 90 after 30 years, decrease to 80 after 40 years and decrease to 75 after 50 years.
An excel spreadsheet prepared by Ankur is under reviewed. Find out in "Quick Estimation of Frictional Loss in Water Network - Spreadsheet Available".