Design Requirements for Sewage Pumping Stations - The City of ...

City of Wentzville, MissouriEngineering Design Criteriad. Total Dynamic Head1) Static Head (H S )E h = Maximum force main elevationE 1 = Wet well low water elevation (Pump Off)H S (feet) = E h - E 12) Loss (L f ) due to friction in force mainLength = Total equivalent length of force main (feet)L f (feet) = Length x Friction Factor3) Loss (L s ) from friction in the station pipingLength = Equivalent length of station piping (feet)L s (feet) = Length x Friction Factor4) To Calculate the Friction Factors, use the Hazen andWilliams formula with the following c-Factors:For the design pump operating point:Unlined iron or steel pipe: C=100All other pipe (including Plastic and lined DIP) C=120To insure pump motor does not overload after initialinstallation:Plastic Pipe and lined DIP C=150All other pipe C=140The operating point on submersible pump stations willbe evaluated at low water cutoff.Friction head loss per 100’ pipe:= 0.2083 x (100/C) 1.85 x Q 1.85 / d 4.86555) TDH (feet) = H s + L f + L sPlot a worst case TDH curve, using the lower C valuesabove, and a best case TDH curve, using the higher Cvalues above, on a manufacturer’s pump performancecurve sheet.The Constant Speed Rating (CSR) or the pump’soperating point is the point where the worst case TDHand the pump manufacturer’s pump performance curveintersect.Find where the best case TDH and the pumpmanufacturer’s pump performance curves intersect andcheck the pump is not in an overload condition.4 - 3 Approved 6/10/09