دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a kelly bushing that has a square-shaped base that fits into a corresponding square-shaped recess in the master bushing. When the base is engaged in the recess, and the master bushing is rotated, the kelly bushing, the kelly, and the attached drill stem also rotate. See also kelly bushing, master bushing.