This standard describes the various classes of cold-water turbine meters in sizes 3/4 in. (20 mm) through 20 in. (500 mm) for water supply customer service,
mainline metering, and custody transfer of water among purveyors, and the materials and workmanship employed in their fabrication. The turbine meters described in this standard are divided into class I and class II meters. Both classes of meters register by recording the revolutions of a turbine set in motion by the force of flowing water striking its blades. Class I meters are the vertical-shaft models. Class II meters are the in-line,horizontal-axis, high-velocity-type turbines characterized by lower head loss and a wider normal operating flow range than class I models.