1. n. [Drilling]

A length of ordinary steel link chain used by the drilling crew to cause pipe being screwed together to turn rapidly. This is accomplished by first carefully wrapping the chain around the lower half of the tool joint that is hanging off in the slips, stabbing another joint into that one, and then throwing the chain in such a manner that it wraps itself on the new upper joint. At the proper time, the driller must pull tension on the chain while a member of the floor crew holds some tension on the free end of the chain. This causes the new drillpipe joint to act like a spool, and as the driller pulls the chain on one end using the drawworks, the spool (or new pipe joint) turns and screws into the joint hung off in the slips. If the floor crew members are not extremely careful, loose clothing or worse, fingers, may become trapped in the unspooling chain and be severely damaged or cut off. Most rig contractors have discontinued the use of spinning chains because of high accident rates. The chains are still available on the rigs, but are not routinely used, having been replaced with other mechanical spinning devices.

See: drawworks,  kelly spinner,  slips,  tool joint