text: 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: