National Oilwell Power Swivels are the result of the company's long history of building rugged efficient drilling machinery products.  The following six basic models offer numerous configurations to meet rig designs and anticipated drilling conditions. All current design models have the following basic design features. Features of specific models are found on page 27. Power Swivels 24 750 tons 750 tons 1000 tons 500 tons Casing load capacity PS2-750 PS2-650/750 PS2-1000 PS-500A PS2-500A Model 2 speed gear box, two motor drive 2 speed gear box, single motor drive 2 speed gear box, two motor drive 1 or 2 speed gear box, single motor drive 650 tons 650 tons 650 tons 500 tons Drilling load capacity 500 tons PS-350/500 1 speed gear box, single motor drive 350 tons PATENTED DUAL LOAD-PATH. Below: Casing and tripping loads are carried separately from drilling loads.  They do not pass through the swivel stem, swivel bearing, or API rotary shouldered connections.  The Dual Load Path isolates the main swivel bearing and stem from the high stresses, impact loading, and fatigue that are associated with tripping and casing handling activity. PATENTED PNEUMATIC COUNTERBALANCE SYSTEM An integral pneumatic system counterbalances the weight of the Power Swivel.  It is accurate to ± 500 lbs.  The system allows a "soft" landing of threaded connections.  When breaking out, it "jumps" pin connections out of the box. PS2-650/750 PS2-1000 POWER SWIVEL MODELS PS2-750 PS2-500A PS-350/500 PS-500A AVAILABLE MODELS DC OR AC MOTORS Load Path From The Elevators Drilling Load Path Elevator Link Stem Housing Sleeve Main Bearing Elevator and Shear Rings Bearings Handling Ring Housing Beam Main Link Load Path To Traveling Beam