Aluminium, drawn/pressed: new: 0.0013 - 0.0015 mm: Aluminium, drawn/pressed: used: to 0.03 mm: Asbestos-cement: new, smooth: 0.03 - 0.1 mm: Brass, drawn/pressed Fiberglass pipe has a smoother internal surface than steel pipe, with a Hazen - Williams roughness coefficient of 160 when new, or 150 used. Steel pipe, on the other hand, has a Hazen Williams - roughness coefficient of 120 when new, or 65 used. The far greater loss in smoothness for the steel pipe is due to scale build-up on the steel pipe.

*friction factor depends on the roughness of the pipe. The Colebrook equation has a term for this roughness. In order to avoid the iteration of the Darcy friction factor from the Cole-brook equation, new equations are deduced. In this study three equations to replace the Colebrook equation are validated. These three are the Blasius,*Regression equations which relate roughness coefficients to surface cover and Reynolds number were derived from the laboratory data. Gilley and Kottwitz (1994) determined Darcy-Weisbach roughness coefficients for selected standing vegetation. Laboratory measurements were used to derive regression equations which relate roughness coefficients to ... Aluminium, drawn/pressed: new: 0.0013 - 0.0015 mm: Aluminium, drawn/pressed: used: to 0.03 mm: Asbestos-cement: new, smooth: 0.03 - 0.1 mm: Brass, drawn/pressed Determining Friction Factor for DI Pipes by Direct Surface Roughness Measurement ... to the values obtained using the implicit Colebrook-White equation while the computational efficiency is ...