A draw-works is the primary hoisting machinery

Winch

A winch is a mechanical device that is used to pull in or let out or otherwise adjust the "tension" of a rope or wire rope . In its simplest form it consists of a spool and attached hand crank. In larger forms, winches stand at the heart of machines as diverse as tow trucks, steam shovels and...

 that is a component of a rotary drilling rig

Drilling rig

A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...

. Its main function is to provide a means of raising and lowering the traveling blocks

Traveling block

A traveling block is the freely moving section of a block and tackle that contains a set of pulleys or sheaves through which the drill line is threaded or and is opposite the crown block ....

. The wire-rope drilling line winds on the drawworks drum and extends to the crown block

Crown block

A crown block is the stationary section of a block and tackle that contains a set of pulleys or sheaves through which the drill line is threaded or and is opposite and above the traveling block....

 and traveling blocks, allowing the drill string to be moved up and down as the drum turns. The segment of drilling line from the draw-works to the crown block is called the "fast line". The drilling line then enters the sheaves of the crown block and is makes several passes between the crown block and traveling block pulleys

Pulley

A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...

 for mechanical advantage

Mechanical advantage

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...

. The line then exits the last sheave on the crown block and is fastened to a derrick

Derrick

A derrick is a lifting device composed of one tower, or guyed mast such as a pole which is hinged freely at the bottom. It is controlled by lines powered by some means such as man-hauling or motors, so that the pole can move in all four directions. A line runs up it and over its top with a hook on...

 leg on the other side of the rig floor

Drill floor

The Drill Floor is the heart of any drilling rig and is also known as the pad. This is the area where the drill string begins its trip into the earth. It is traditionally where joints of pipe are assembled, as well as the BHA , drilling bit, and various other tools. This is the primary work...

. This section of drilling line is called the "dead line".

A modern draw-works consists of five main parts: the drum, the motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

(s), the reduction gear

Gear

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

, the brake, and the auxiliary brake. The motors can be AC

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 or DC

Direct current

Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

-motors, or the draw-works may be connected directly to diesel engines using metal chain-like belts. The number of gears could be one, two or three speed combinations. The main brake, usually operated manually by a long handle, may be friction band brake, a disc brake

Disc brake

The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while it is in motion.A brake disc is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon–carbon or ceramic matrix composites. This is connected to the wheel and/or...

 or a modified clutch

Clutch

A clutch is a mechanical device which provides for the transmission of power from one component to another...

. It serves as a parking brake when no motion is desired. The auxiliary brake is connected to the drum, and absorbs the energy released as heavy loads are lowered. This brake may use eddy current rotors or water-turbine-like apparatus to convert to heat the kinetic energy of a downward-moving load being stopped.

Power catheads (winches) located on each side provide the means of actuating the tongs used to couple and uncouple threaded pipe members. Outboard catheads can be used manually with ropes for various small hoisting jobs around the rig.

The drawworks often has a pulley drive arrangement on the front side to provide turning power to the rotary table

Rotary table (drilling rig)

A rotary table is a mechanical device on a drilling rig that provides clockwise rotational force to the drill string to facilitate the process of drilling a borehole.In the diagram, #20 is the rotary table...

, although on many rigs the rotary table is independently powered.

External links

• Oilfield Glossary by Schlumberger
  Schlumberger
  Schlumberger Limited is the world's largest oilfield services company. Schlumberger employs over 110,000 people of more than 140 nationalities working in approximately 80 countries...
  
  

Manufacturers

• LeTourneau Technologies – Drilling Rig and Draw-Works Manufacturer
• Bentec GmbH – Drilling Rig and Draw-Works Manufacturer
• NOV – Drilling Rig and Draw-Works Manufacturer
• http://www.drillquest.net – Drilling equipment sales and repair