In areas where three 8-hour tours are worked, the shift of duty on a drilling rig that starts at or about daylight. Compare evening tour and […]

Term used to describe the change in regulated pressure required before a hydraulic pressure regulator automatically adjusts to the change. Also called search band.

The drilling line from the crown block sheave to the anchor, so called because it does not move. Compare fastline.

A device to which the deadline is attached, securely fastened to the mast or derrick substructure. Also called a dead-line anchor.

A mechanical slope indicator that consists of a ball rolling on a calibrated surface within a liquid filled enclosure that gives a visual indication of the […]

The device used to remove unwanted gas from a liquid, especially from drilling fluid.

The mass or weight of a substance per unit volume. Specific gravity, relative density, and API gravity are other units of density. See API gravity, specific […]

A large load-bearing structure, usually of bolted construction. In drilling, the standard derrick has four legs standing at the corners of the substructure and reaching to […]

The crew member who handles the upper end of the drill string as it is being hoisted out of or lowered into the hole. He or […]

A centrifugal device for removing sand from drilling fluid to prevent abrasion of the pumps. It may be operated mechanically or by a fast-moving stream of […]

A centrifugal device for removing very fine particles, or silt, from drilling fluid to keep the amount of solids in the fluid at the lowest possible […]