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Lechapt and Calmon

This module allows to calculate the pressure losses in a circular pipe from the Lechapt and Calmon abacuses.

It allows the calculation of the value of one of the following quantities:

  • Flow rate (m3/s)
  • Pipe diameter (m)
  • Total head loss (m)
  • Pipe length (m)
  • Singular pressure loss coefficient

The total head loss is the sum of the linear head losses \(J_L\) obtained from the Lechapt and Calmon abacuses and singular \(J_S\) depending on the above coefficient.

Lechapt and Calmon abacuses

Lechapt and Calmon formula is based on adjustements of Cyril Frank Colebrook formula:

\[J_L=\frac{l_T}{1000}L.Q^M.D^{-N}\]

With:

  • \(J_L\): headloss in mm/m or m/km;
  • \(l_T\): pipe length in m;
  • \(Q\): flow in L/s;
  • \(D\): pipe diameter in m;
  • \(L\), \(M\) and \(N\) coefficients depending on roughness {ϵ}.

The error made with respect to the Colebrook formula is less than 3% for speeds between 0.4 and 2 m/s.

The correlation table of the coefficients is as follows:

Material ϵ (mm) \(L\) \(M\) \(N\)
Uncoated cast iron or steel - Coarse concrete (corrosive water) 2 1.863 2 5.33
Uncoated cast iron or steel - Coarse concrete (low corrosive water) 1 1.601 1.975 5.25
Cast iron or steel with cement coating 0.5 1.40 1.96 5.19
Cast iron or steel bitumen coating - centrifuged concrete 0.25 1.16 1.93 5.11
Rolled steel - smooth concrete 0.1 1.10 1.89 5.01
Cast iron or steel centrifugal coating 0.05 1.049 1.86 4.93
PVC - polyethylene 0.025 1.01 1.84 4.88
Hydraulically smooth pipe - 0.05 ≤ D ≤ 0.2 0.00 0.916 1.78 4.78
Hydraulically smooth pipe - 0.25 ≤ D ≤ 1 0.00 0.971 1.81 4.81

Table: Materials and coefficients used in the Lechapt and Calmon formula