Head Loss

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

hydraulic head lossHead loss, abbreviated as \(h_l\), is a pressure loss due to the resistance of the fluid and obstructions along the way in a pipe.  There are a number of factors that affect head loss such as:

  • flow rate
  • corrosion and scale deposits
  • fittings (bends, elbows, exits, expanders and reducers, tees)
  • inside diameter of the pipe
  • roughness of the pipe wall
  • viscosity of the liquid
  • length of the pipe
  • straightness of the pipe
  • valves


Major Head Loss

Major head loss, abbreviated as \(h_{l-major}\), is the pressure drop caused by friction loss.  It does not matter if the pipe is horizontal, vertical or on an incline.

Major Head Loss formula

\(\large{ h_{l-major} = f \; \frac{l}{d} \; \frac{v^2}{2\;g}  }\)   


\(\large{ h_{l-major} }\) = major head loss

\(\large{ f }\) = friction factor

\(\large{ g }\) = gravitational constant (32.2 ft/sec)

\(\large{ l }\) = lenght of pipe

\(\large{ d }\) = pipe inside diameter

\(\large{ v }\) = velocity of flow


Minor Head Loss

Minor head loss, abbreviated as \(h_{l-minor}\), is the pressure drop caused by fittings and valves.

Minor Head Loss formula

\(\large{ h_{l-minor} = K \; \frac{v^2}{2 \; g}  }\)   


\(\large{ h_{l-minor} }\) = minor head loss

\(\large{ g }\) = gravitational constant (32.2 ft/sec)

\(\large{ K }\) = loss coefficient

\(\large{ v }\) = velocity of flow


Tags: Equations for Hydraulic Equations for Head