COMPARISON OF ORIFICE AND SLOTTED PLATE FLOWMETERS

The performance of a standard beta = 0.50 orifice flowmeter is compare d to the same flowmeter with a slotted orifice plate replacing the sta ndard orifice plate. The slotted orifice plate has the same total open area as the standard plate and consists of three concentric rings, ea ch of which contains several radial slots. The flow upstream of both o rifice plates is preconditioned using a concentric pipe device to prod uce a wide range of axial velocity profiles without swirl. The dischar ge coefficient of the standard plate varies from the base value by -1% to +6%, while that of the slotted orifice plate varies by only +/-0.2 5%. When swirl is generated upstream of the orifice plates, the discha rge coefficients vary by 5% and 2% for the standard and slotted orific e plates, respectively. These data indicate that the slotted orifice f lowmeter is superior to the standard orifice flowmeter in maintaining its calibration over a wide range of inlet flow conditions. The slotte d orifice plate can be a 'drop in' replacement for a standard orifice plate.