Minor head loss (or elements pressure drop) are expressed in fluid heights (meters) in pascals or bars.

formula minor head losses

  • Minor head loss (or elements pressure drop) of aeraulic and hydraulic networks are pressure losses caused by the passage of fluid through obstacles and accessories such as valves, fittings, expansion, exit tank, extractor hood etc ... .

  • the Minor head loss are expressed in Pascals, in meters fluid columns (m), or in equivalent meters of straight pipe.. the Minor head loss are also named elements pressure drop. These are the pressure losses due to elements encountered in the fluid path.

  • Minor head loss coefficients are given for the usuals elements of fluid's networks. In general, these data are provided by the manufacturers of hydraulic accessories. Some formulas used to calculate these coefficients, as Weisbach formula for elbows or Lorenz for divergent cones.


Curves of losses of one hundred basic accessories are available and configurable il Mecaflux standard software. (Example closing angle of hydraulic valve, the number of guide vanes in an elbow aeraulic ...)

The minor head loss coefficient is automatically based on parameters you enter..The minor head loss coefficient selected in the graph and the computed pressure drop caused by aeraulic or hydraulic accessories that you have chosen, is given to you in the results sheet.

The chart interface selection and parametrage elments pressure loss (minor head loss) in MECAFLUX:

here a gate valve

hydraulic head loss valve

a grid composed of profile bars

load loss in a grid

a perforated plate filter

a perforated plate filter head losses

calculation procedure with mecaflux:

pressure drop minor head losses interface software

  1. select an aeraulicor hydraulic accessories, choosing a "category" and "element" (nomogram of a hundred different accessories)
  2. fill in the fields with blue text under "parameters"
  3. cliquez sur calculer
If a text box has not been entered correctly a message will tell you.The results are given in meters fluid column and pascals. (use the unit converter if needed) . They are loaded into the inventory to study all losses in a network:

the inventory memo allows adding the pressure losses in the network

ou can add elements to the list of minor pressure losses elements.To do this a nomogram element editor is available.

the losses in the heat exchangers is treated in regular elements:

pertes de charge dans un echangeur

Here are some examples of items already included in mecaflux (not complete list ... mecaflux integrates the charts of one hundred basic accessories Ventilation and hydraulic configurable)

losses in an elbow

pressure drop of a tank outlet

minor head losses in a  diaphragm

pressure drop in a widening

major loss of load air input

loss in a filter

loss coefficient pressure drop  in a hood

losses in a duct fitting

narrowing duct

flow junction


separation ducts



Pressure drop coefficient valve

Pressure loss coefficient valve

pressure loss coefficient cone

head loss in a bend

Exemples of charts for minor head loss coefficients of some usual éléments in a fluid network

Table Example pressure drop for various standard accessories

Table Exampleminor head loss coefficients

example coefficient minorhead loss, in equivalent length of straight duct