Coefficient of discharge for sharp-edged orifice plates with corner, flange or D and D/2 tappings and no drain or vent hole (Reader-Harris/Gallagher equation):
:and if D < 71.2mm in which case this further term is added to C:
:In the equation for C,
::and only the three following pairs of values for L and L' are valid:
:::corner tappings: 
:::flange tappings: 
:::D and D/2 tappings: