# Head Loss

Head 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

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

### Where:

Units |
English |
Metric |

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

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

\(\large{ g }\) = gravitational constant | \(\large{\frac{lbf-ft^2}{lbm^2}}\) | \(\large{\frac{N - m^2}{kg^2}}\) |

\(\large{ l }\) = lenght of pipe | \(\large{ ft }\) | \(\large{ m }\) |

\(\large{ d }\) = pipe inside diameter | \(\large{ in }\) | \(\large{ mm }\) |

\(\large{ v }\) = velocity of flow | \(\large{ \frac{ft}{sec} }\) | \(\large{ \frac{m}{s} }\) |

## Minor Head Loss

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

### Minor Head Loss formula

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

### Where:

Units |
English |
Metric |

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

\(\large{ g }\) = gravitational constant | \(\large{\frac{lbf-ft^2}{lbm^2}}\) | \(\large{\frac{N - m^2}{kg^2}}\) |

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

\(\large{ v }\) = velocity of flow | \(\large{ \frac{ft}{sec} }\) | \(\large{ \frac{m}{s} }\) |