Effect of errors in pressure tap locations on the discharge coefficient of a flange-tapped orifice plate

Abstract

The effects of errors in the location of the flange taps on the discharge coefficient of orifice plates have been invesgated experimentally. A specially designed fixture by which it was possible to change upstream and downstream tap locations independently was used to study the effects of errors in each location separately. The effect of plate displacement was investigated by making appropriate changes in both upstream and downstream tap locations. Three orifice plates of β = 0.4, 0.6 and 0.75 were tested. The study covered the effects for 51 mm (2 in) and 102 mm (4 in) meter runs. Full-scale tests were conducted for the 51 mm case while model tests with a scale ratio of 1 : 2 were conducted to simulate the 102 mm (4 in) case. Calibrations were done against a dynamic weigh tank system while differential pressures were measured by a number of D-P cells interfaced with a laboratory computer. The results indicate that the effects of tap location errors exceeding those allowed by the standards are negligible in some instances.