This standard describes the various classes of cold-water trubine meters in sizes 3/4 in.(20mm)through 20 in.(500mm)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 classⅡ 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. Class Ⅰ meters are the vertical-shaft and low-velocity, horizontal-shaft models.
Class Ⅱ. Class Ⅱ meters are the in-line, horizontal-axis, high-velocity-type trubines characterized by lower head loss and a wider normal operating flow range than class Ⅰ models.