Rotary Oil Meters of the Positive-Displacement and Current Types

Abstract

Abstract While much research has been done and a corresponding amount of written material presented on discharge coefficients and operating limitations of the orifice and venturi type of meter for oil measurement, little has been presented on the corresponding performance of quantity meters of the displacement and current or impeller classification. The several types of quantity meters which have found application in the petroleum industry are discussed by the author. The first of these is the displacement meter of the piston type, which has an accuracy essentially independent of the density and viscosity of the liquid measured. A second type in the displacement class is the disk meter, which is critically discussed with respect to accuracy, operating range and rate of flow, and effects of viscosity of the liquid on the accuracy. The third displacement meter discussed is the rotary-vane type which offers a high volumetric efficiency and great accuracy, and is comparable to the piston type with respect to density and viscosity of fluid. In each case, the characteristic accuracy curve of each type of meter is analyzed and the general field of application, together with operating limitations of each meter, are outlined. The current-type meter receives a more lengthy discussion covering both details of construction and operating characteristics for a type which has been adapted for measuring crude oils. Account is given of test results of oils of viscosity from 60 to 500 seconds Saybolt Universal and the effects of viscosity upon accuracy are analyzed and limitations stated. In general, this type of meter offers the advantage of direct reading of quantity and, in its present state of development, with a degree of accuracy equivalent to, and in some cases better than, measurement with the orifice meter, which is brought out by a comparison of possible accuracy with the square-edge orifice in the region of Reynolds’ number lower than 100,000 and the performance of the oil current meter in the same region. Within the range of 60 to 350 S.S.U. viscosity and over an operating range of 15 per cent to maximum, the current meter shows acceptable accuracy in measurement of oil.