Definition
Top Drive — A top drive is a motor-driven device suspended in the derrick that rotates the drill string from its top end and allows drilling and circulation in stand-length increments, replacing the kelly and rotary table for imparting rotation.
Also known as: top drive, top drive system, TDS, power swivel
What a top drive does
A top drive is an electric or hydraulic motor unit that hangs from the traveling block and turns the drill string through a threaded quill connected to the string’s top connection. Because it drills a full stand (about 27–30 m / 90 ft) at a time before adding pipe, it reduces connection frequency compared with a kelly-and-rotary system, and it can rotate and circulate while tripping to work the string past tight spots and ream through doglegs.
The top drive integrates a saver sub to protect its threads, an internal blowout preventer (IBOP) for well control in the string, and a pipe-handling elevator, combining rotation, hoisting-connection and circulation in one unit above the rig floor.
Advantages over the kelly
- Drills in stands, cutting the number of connections and making trips safer.
- Rotates while tripping, helping to ream, back-ream and avoid stuck pipe.
- Integral IBOP and saver sub for well control and thread protection.
Its ability to rotate at any point in the string makes the top drive standard on modern drilling and casing-running rigs.
Why it matters for rentals
Top-drive strings still rely on saver subs, crossovers and IBOPs matched to the quill connection. See our kelly equipment and drilling application, or contact us for compatible subs and valves.