Keith Rappold Drilling Editor The increase in drilling of deep extended reach and horizontal wells has stimulated a number of design improvements in overhead rotary system technology. Overhead rotary systems, or top drives, are being developed with larger, more powerful motors capable of producing output torque up to 60,000 ft-lb. The load ratings of top drive systems have increased to improve rig floor safety and to allow running of larger casing strings. Overhead rotary drilling systems are referred to as derrick drillers, top drives, or overhead power swivels, depending on the manufacturer. All of the systems perform simi...

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