دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n pI: slips for drill pipe that fit into the tapered insert bowl of a four-pin master bushing and whose taper length is 12� inches (324 millimetres) long. Compare long rotary slips. See also master bushing, slips.

n: a master bushing that has four holes symmetrically positioned on its outside perimeter and into which fit four corresponding steel dowels. or pins. on the kelly bushing. When the pins are engaged into the holes and the master bushing turns. the kelly bushing also turns. See kelly bushing, master bushing.