PURPOSE AND SCOPE This Data Item is one of a group on the flow properties of non-Newtonian fluids. The first@ ESDU 82036@ provides an introductory guide to the classification and characteristics of non-Newtonian fluids. The second@ ESDU 91025@ outlines the various methods available for estimating frictional pressure losses for fully-developed isothermal flow of non-Newtonian fluids in straight pipes of uniform circular cross-section. This Item is concerned with obtaining the relevant viscometric data required for pressure drop prediction using ESDU 91025. The methods are applicable to fluids that can be considered pseudohomogeneous (non-settling) under conditions of steady shear. The overall pressure loss@ ??pT@ in a length of pipework is in general given by ??pT = ??p+??pF+??ps@ where ??p is the frictional pressure loss from flow through the straight sections of the pipework@ ??pFis the pressure loss from flow through various types of fittings (for example@ valves@ bends@ contractions@ expansions@ etc) and ??pFis the pressure loss or gain resulting from elevation changes and is negative for a reduction in static head and positive for an increase in static head. The relative magnitudes of the three pressure loss terms in Equation (2.1) is dependent on the pipeline length. For short pipelines@ ??p and ??pF may be insignificant compared with ??ps whereas@ for very long pipelines@ ??p is usually the main contributor. Table 2.1 summarises various methods used for estimating ??p@ together with the rheological data they require. This Item is relevant only to those that utilise viscometric data. These data usually comprise a flow curve for the fluid in the form of a plot of shear stress versus shear rate or alternatively a viscosity curve in the form of a plot of viscosity (the ratio of shear stress to shear rate) versus shear rate. A primary purpose of this Data Item is to guide the user in the selection of the most appropriate viscometer for determining the flow curve for the sample under test and the pipeline application in question. The layout is as follows. ? Section 3 summarises the classification and behaviour of homogeneous and pseudohomogeneous non-Newtonian fluids. ? Section 4 describes the various flow curve models used in pipeline design. ? Section 5 states criteria used in viscometric testing to obtain rheological data for pipeline design. ? Section 6 describes five types of viscometric geometries used for flow curve determination of non-Newtonian fluids; they are tube@ coaxial cylinder@ rotating disc@ cone-and-plate and parallel plate. With these geometries@ several sources of error can arise when making flow curve measurements. To obtain the corrected flow curve@ a step-by-step procedure is given for each geometry. ? Section 7 discusses the various material and equipment considerations which must be taken into account when carrying out viscometer selection. ? Section 8 deals with the flow curve data generation and interpretation.