# Loss Coefficient

Loss coefficient, abbrevated as K, is a dimensionless number that measures the minor loss to the change in velocity due to friction thru pipes, fittings, and valves. Most piping consists of more than a just straight lines, these losses are termed a minor loss. Any bend or tee, expansion or contraction, valve opening or partially closing can cause minor or even major losses.

### Loss Coefficient Formula

\(\large{ K = h_l \; \frac { 2 \; g } { v^2 } }\)

Where:

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

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

\(\large{ h_l }\) = head loss

\(\large{ g }\) = gravitational acceleration

## Loss Coefficient Table

Component | Loss Coefficient \(K\) |
---|---|

Elbows | |

90 Short Elbow, flanged | 0.3 |

90 Short Elbow, threaded | 1.5 |

90 Long Elbow, flanged | 0.2 |

90 Long Elbow, threaded | 0.7 |

45 Long Elbow, flanged | 0.2 |

45 Short Elbow, threaded | 0.4 |

180 Return | |

180 Return, flanged | 0.2 |

180 Return, threaded | 1.5 |

Tees | |

Line flow, flanged | 0.2 |

Line flow, threaded | 0.9 |

Branch flow, flanged | 1.0 |

Branch flow, threaded | 2.0 |

Union, threaded | 0.08 |

Valves | |

Diaphragm, fully open | 2.3 |

Diaphragm, 1/4 closed | 21 |

Diaphragm, 1/2 closed | 4.3 |

Globe, fully open | 10 |

Angle, fully open | 2 |

Gate, fully open | 0.15 |

Gate, 1/4 closed | 0.26 |

Gate, 1/2 closed | 2.1 |

Gate, 3/4 closed | 17 |

Swing Check, forward flow | 2 |

Swing Check, backward flow | \(\infty\) |

Ball, fully open | 0.05 |

Ball, 1/3 closed | 5.5 |

Ball, 2/3 closed | 210 |

Water meter | 7 |

Tags: Equations for Coefficient Equations for Friction Equations for Hydraulic Equations for Head