Rig Glossary: T–W


Table Lock

A mechanical device that allows you to lock the rotary table if desired.

Tag Line

A rope attached to the bottom of a load suspended by the crane or truck, which, when grasped by a crewmember, allows the crewmember to prevent rotation and to assist in guiding the load and remain from underneath the load.


To measure and record the total length of pipe, casing, or tubing that is to be run in a well.

Tally Tape

A measuring device used to measure the length of drill pipe or casing being put in the well.

Telescoping Mast

A portable mast that can be erected as a unit, usually by a tackle that hoists the wireline or by a hydraulic ram. The upper section of a telescoping mast is generally nested (telescoped) inside the lower section of the structure and raised to full height either by the wireline or by a hydraulic system.

Tension Limiter

Reduces the forces that workers may be exposed to when being raised by a hoist. The device is designed to lengthen by as much as 24 feet (7.3 m) by extension of a metal coil when subjected to a continuous load greater than the coil setting. This action limits the force on the worker who may have been caught up in the structure, and provides the operator time to stop the hoist.

Test Plug

A mechanical plug that is seated in the bowl of the casing to isolate the BOP system for testing purposes.

Ton Mile/Mega Joule

Drilling Ton-Mile is the measurement of cumulative load lifted in tons and the distance lifted or lowered in miles. When the predetermined ton-mile limit is reached, drilling contractors will perform slip and cut drilling line to prevent drilling line fatigue.

Tong Controls

A series of levers to control the pulling force applied to either the Make-up or Breakout.

Tong Die Retainers

Items such as Roll Pins or Cotter Keys that are used to secure the tong dies in the Tong Die Retaining Slot.

Tong Die Retaining Slot

Lipped grooves designed into a tong jaw body to hold tong dies in place and acts as a guide when sliding the die down or up.

Tong Hanging Line

A steel cable that suspends the tongs above the rig floor in a working position.

Tong Jaws

All of the movable segments of the tongs that wrap around the tubular components of the drill string.

Tong Rear Keeper Pin

A pin that secures the snub and breakout/make-up lines to the end of the tong arm.

Tong Tie-Back Chain

A chain to secure the tongs to the A-legs, out of the way of operations when not in use.

Tong Torque Sensor and Lines

A torque sensing device attached to the snub lines to measure the amount of torque applied to a connection.


The large wrenches used for turning when making up or breaking out drill pipe, casing or other pipe; variously called casing tongs, rotary tongs, and so forth according to the specific use. Power tongs or power wrenches are pneumatically or hydraulically operated tools that serve to spin the pipe up and, in some instances, to apply the final makeup torque.

Tool Joint Shoulder

Also referred to as the seal area of a pin or box end of a tubular.

Top Drive

A device similar to a power swivel that is used in place of the rotary table to turn the drill string.

Torque Gauge

The torque gauge measures the turning force that is applied to a shaft or other rotary mechanism to cause it to rotate or tend to do so. Torque is measured in foot-pounds, joules, newton- metres, and so forth.

Tour Sheet

A legal document recorded each shift. It includes employees’ time and records the different drilling information that is required by the oil company, and state and local governments.

Travelling Block

The travelling block is an assembly of sheaves mounted in a framework that allows the block to move up and down by use of the drilling line that is reeved over the crown block sheaves and through the travelling block sheaves.


Any kind of pipe. Oilfield tubular goods include tubing, casing, drill pipe, drill collars and heavy-weight drill pipe. Also called tubular goods.

Tubular Threads

Threaded area in the pin and box end of tubulars.


A winching machine that hoists or pulls when a cable winds around a revolving drum. Also called a “winch”.

Tugger Line

Steel cable winch line positioned by the V-Door used to hoist items to the rig floor from the catwalk or ground level.



U-Joint/Universal Joint

A joint or coupling in a rigid rod that allows the rod to ‘bend’ in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft.

Under Gauge Hole

A hole drilled with an under gauge bit is said to be undergauge.

Upper Kelly Cock

A valve installed above the kelly that can be closed manually to protect the rotary hose from high pressure that may exist in the drill string.




A device used to control the rate of flow in a line to open or shut off a line completely, or to serve as an automatic or semiautomatic safety device. Those used extensively include the check valve, gate valve, globe valve, needle valve, plug valve, and pressure relief valve.

V-Door Opening

An opening at floor level in a side of a derrick or mast. The V-door is opposite the drawworks and is used as an entry to bring in drill pipe, casing, and other tools from the catwalk.

V-Door Ramp

An angled ramp for dragging drill pipe, casing and other materials up to the drilling floor or bringing such equipment down.



Walking System

A custom designed machine that is designed to move a drilling rig substructure. The system is connected to the drilling rig with struts and pins, and is comprised of lift cylinders, rollers, travel cylinders, and walking feet which allow the system to lift and move the drilling rig from well to well. The system can also be used to jack and level the rig.


Metal walkways sections running between buildings at ground level. Some walkways may house steam, water, air and fuel lines enclosed within. An area cleared for moving through by personnel. Also referred to as “suitcases”.

Wash Pipe Packing

Layers of dense flexible material that is stacked around the swivel’s wash-pipe and the swivel’s interior body seal. It helps seal between the static wash-pipe and the turning swivel body to ensure that high-pressure drilling mud flows through the swivel’s stem and into the kelly.

Wear Bushing

Retrievable cylindrical device that protects the internal surfaces of wellhead equipment and the top of the last casing suspended.

Weight Indicator

An instrument near the Driller’s position on a drilling rig that shows both the weight of the drill string that is hanging from the hook (hook load) and the weight that is placed on the bottom of the hole (weight on bit). A device for measuring the weight of the drill string.


A borehole; the hole drilled by the bit. A wellbore may have casing in it or it may be open (uncased); or part of it may be cased, and part of it may be open. Also called a borehole or hole.


A winch device mounted on the rig floor, that is used for lowering special tools (such as survey tools, and so forth) into the well.

Wireline Survey

A general term used to refer to any type of survey tool being run in a well using the wireline winch.

Wire Rope

A cable composed of steel wires twisted around a central core of fiber or steel wire to create a rope of great strength and considerable flexibility.

Courtesy of Ensign Drilling Inc.