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Engineering ToolBox > Steel Pipe Schedule 40 - Friction loss and Velocity Diagram

Friction loss and velocity diagrams - in imperial (psi/100 ft, ft/s) and SI (Pa/100m, m/s) units

The diagram below indicates friction loss for water flow through ASME/ANSI B36.10/19 schedule 40 steel pipe.

The pressure drop calculations are made with the D'Arcy-Weisbach Equation.

• Fluid : Water
• Pipe : Steel Pipe - Schedule 40
• Temperature : 20.0 ^oC (68.0 ^oF)
• Density : 998.3 kg/m³ (62.0 lb/ft³)
• Kinematic Viscosity : 1.004E-6 m²/s (0.01 stokes) (1.08E-5 ft²/s)
• Pipe Roughness Coefficient : 4.5E-5

Pressure Drop - Imperial Units

• 1 gal (US)/min =6.30888x10^-5 m³/s = 0.0227 m³/h = 0.06309 dm³(litre)/s = 2.228x10^-3 ft³/s = 0.1337 ft³/min
• 1 ft/s = 0.3048 m/s
• 1 psi (lb/in²) = 6,894.8 Pa (N/m²) = 6.895x10^-3 N/mm² = 6.895x10^-2 bar = 27.71 in H₂O at 62^oF (16.7^oC) = 703.1 mm H₂O at 62^oF (16.7^oC) = 2.0416 in mercury at 62^oF (16.7^oC) = 51.8 mm mercury at 62^oF (16.7^oC) = 703.6 kg/m² = 2.307 Ft. H₂O

Pressure Drop - SI Units

• 1 Pa = 10^-6 N/mm² = 10^-5 bar = 0.1020 kp/m² = 1.02x10^-4 m H₂O = 9.869x10^-6 atm = 1.45x10^-4 psi (lbf/in²)
• 1 liter/s = 10^-3 m³/s = 3.6 m³/h = 0.03532 ft³/s = 2.1189 ft³/min (cfm) = 13.200 Imp.gal (UK)/min = 15.852 gal (US)/min = 792 Imp. gal (UK)/h
• 1 m/s = 3.6 km/h = 196.85 ft/min = 2.237 mph

A table presentation of the diagrams above can be found in "Steel Pipe Schedule 40 - Friction loss and Velocities".