Rig Glossary: D–G



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

Deadline Tie-Down Anchor

A device, to which the deadline end of the drilling line is attached, securely fastened to the mast or derrick substructure.


The equipment used to separate unwanted gas from the drilling fluid.


A large load-bearing mast-like structure. In drilling, the standard derrick has four legs standing at the corners of the substructure with the crown block attached to the top.

Die Drives

A special tool that is used to drive the tong die out of the tong die retaining slot.


A removable, hard-steel, serrated piece that fits into the jaws of the tongs and firmly grips the body of the drill pipe, drill collars, or casing while the tongs are making up or breaking out the pipe.

Diesel Electric Power

The power supplied to a drilling rig by diesel engines driving electric generators.

Diesel Engine

A high-compression, internal-combustion engine used extensively for powering drilling rigs. In a diesel engine, air is drawn into the cylinders and compressed to very high pressures; ignition occurs as fuel is injected into the compressed and heated air. Combustion takes place within the cylinder above the piston, and expansion of the combustion products imparts power to the piston.

Directional Tools

Tools utilized in achieving directional drills. These include whip stocks, bottom hole assembly (BHA) configurations, three-dimensional measuring devices, mud motors and specialized drill bits.

Diving Board

See Monkey Board.

Dog Collar

A clamp placed tightly around a drill collar that is suspended in the rotary table by drill collar slips.


A small enclosure on the rig floor used as an office and/or as a storehouse for small objects. Also used as an office for the Driller.

Dope Brush

A soft-bristled brush used for applying pipe dope to pipe threads.


The hoisting mechanism on a drilling rig. It is essentially a large winch that spools off or winds up the drilling line which lowers or raises the drill string.

Drawworks Brake

The mechanical brake on the drawworks that can slow or prevent the drawworks drum from rotating. Also called “band brakes.”

Drawworks Drum

The grooved spool-shaped cylinder in the drawworks around which drilling line is wound or spooled.

Drill Collar Dope

An oil based lubricant that is spread over the threads and seal area of the drill collar and allows the two opposite drill collars to be screwed together and unscrewed without damaging the threads.

Drill Collars

A heavy, thick-walled tube, usually steel, used between the drill pipe and the bit in the drill string, used to stiffen the drilling assembly and put weight on the bit so that the bit can drill.

Drill Pipe

The heavy seamless tubing used to rotate the bit and circulate the drilling fluid. Joints of pipe are generally approximately 30 feet (9.5 metres) long. The ends of the drill pipe are called “tool joints”. Drill pipe is classified by size, length, grade, weight and class.

Drill Pipe Screen

A screen that is placed in the drill pipe to help prevent larger solids from passing through to the down-hole equipment being used.

Driller's Console

The control panel with all the controls where the driller operates the different drilling equipment.

Drilling Line

A heavy duty wire rope hoisting line, reeved back and forth through the sheaves of the crown block and traveling block (in effect a block and tackle). One end is secured to the deadline anchor and the other end is secured into the drawworks drum (fast-line). The primary purpose of this pulley system is to hoist or lower the drill string or casing in or out of the well.

Drive Bushing

See Kelly Bushing.

Drive Chain

A chain by means of which a machine is propelled; rotary table or mud pumps.

Drive Shaft

In power transmission, a connection extending between a driving shaft and a driven shaft.



Elevator Door Latch

The opening of the elevators that allows a tubular to be placed in the elevators.

Elevator Ear Retainer Bolts

Removable retaining arms that allow the bale ears to be attached then secured into the bale ears.

Elevator Ears

Openings on the side of the elevators, secured by retaining arms, that hold the bale eyes in position.

Elevator Hinge Pin

The large pin at the back of the elevators that is the main connection and support for the two elevator halves; which allows the elevators to swing open and closed.


Hinged steel heavy duty clamps with manual operating handles that crew members latch onto a tool joint (or a sub). Designed to grip a single size tubular and provide the means to hoist and lower the drill string.

Escape System/T-Bar/Geronimo

A device normally mounted near the monkey board to afford the Derrickhand a means of quick exit to the surface in case of emergency. It is usually affixed to a cable, one end of which is attached to the derrick or mast and the other end to the surface. To exit by the safety slide, the Derrickhand grasps a handle on it and rides it down to the ground. Also called a “Geronimo” or “Escape Buggy”.

Eye Wash Station

A designated station in an easily accessible area in which employees may flush their faces with water in the event of an emergency.




The end of the drilling line that is affixed to the drum or reel of the drawworks, so called because it travels with greater velocity than any other portion of the line.


A pipe part (such as a coupling, elbow, collar, etc.) used to connect various pipe.

Flare Stack

Primarily used as a safety measure to prevent the accumulation of gases that could pose a hazard. Also used to manage small volumes of waste gas that cannot be efficiently captured and returned to the system for processing.

Float Collar

A short length of casing fitted with a check valve. The check valve prevents the cement from coming back into the drill pipe during cementing operations.

Flow Nipple

A pipe at the top of the BOP stack which changes the vertical fluid flow direction to the horizontal flow line.

Fuel Tanks

Fuel storage tanks for the power generating system.




Any material (such as paper, cork, asbestos, stainless steel or other types of metal, or rubber) used to seal two essentially stationary surfaces. Picture is of a ring gasket.


The curved connection between the rotary hose and the swivel.

Guide Trough

Sunken strip down the center of the catwalk that guides the travel path of tubulars as they are being raised to the rig floor.

Courtesy of Ensign Drilling Inc.