دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: on a kelly bushing, an arrangement of rollers, roller pins, and roller bearings that mate with the kelly as it moves up or down inside the kelly bushing. The roller assembly transfers the turning motion of the kelly bushing to the kelly, and, at the same time, allows the kelly to move up and down freely. See rolle!;roller bearing, roller pin.