C = 0.5961 + 0.0261 β 2 − 0.216 β 8 + 0.000521 ( 10 6 β R e D ) 0.7 + ( 0.0188 + 0.0063 A ) β 3.5 ( 10 6 R e D ) 0.3 + ( 0.043 + 0.080 e − 10 L 1 − 0.123 e − 7 L 1 ) ( 1 − 0.11 A ) β 4 1 − β 4 − 0.031 ( M 2 ′ − 0.8 M 2 ′ 1.1 ) β 1.3 {\displaystyle C=0.5961+0.0261\beta ^{2}-0.216\beta ^{8}+0.000521{\bigg (}{\frac {10^{6}\beta }{Re_{D}}}{\bigg )}^{0.7}+(0.0188+0.0063A)\beta ^{3.5}{\bigg (}{\frac {10^{6}}{Re_{D}}}{\bigg )}^{0.3}+(0.043+0.080e^{-10{L_{1}}}-0.123e^{-7{L_{1}}})(1-0.11A){\frac {\beta ^{4}}{1-\beta ^{4}}}-0.031(M'_{2}-0.8{M'_{2}}^{1.1})\beta ^{1.3}} and if D < 71.2mm in which case this further term is added to C: + 0.011 ( 0.75 − β ) ( 2.8 − D 0.0254 ) {\displaystyle +0.011(0.75-\beta ){\bigg (}2.8-{\frac {D}{0.0254}}{\bigg )}} [15][16] In the equation for C, A = ( 19000 β R e D ) 0.8 {\displaystyle A={\bigg (}{\frac {19000\beta }{Re_{D}}}{\bigg )}^{0.8}} M 2 ′ = 2 L 2 ′ 1 − β {\displaystyle M'_{2}={\frac {2L'_{2}}{1-\beta }}} and only the three following pairs of values for L1 and L'2 are valid: corner tappings: L 1 = L 2 ′ = 0 {\displaystyle L_{1}=L'_{2}=0} flange tappings: L 1 = L 2 ′ = 0.0254 D {\displaystyle L_{1}=L'_{2}={\frac {0.0254}{D}}} [16] D and D/2 tappings: L 1 = 1 {\displaystyle L_{1}=1} L 2 ′ = 0.47 {\displaystyle L'_{2}=0.47}