A drawworks is the primary hoisting machinery component of a rotary

drilling rig A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill wat ...

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

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 (wire rope) is threaded oreevedand is opposite (and under) the crown block (the stationary section). The ...

. The wire-rope

drill line In a drilling rig, the drill line is a multi-thread, twisted ''wire'' rope that is threaded oreevedthrough in typically 6 to 12 parts between the traveling block and crown block to facilitate the lowering and lifting of the drill string into and ...

winds on the drawworks drum and over the

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 (wire rope) is threaded oreevedand is opposite and above the traveling block. The combination of the traveling b ...

to the traveling block, allowing the drill string to be moved up and down as the drum turns. The segment of drill line from the drawworks to the crown block is called the "fast line". The drill line then enters the first sheave of the crown block and makes typically 6 to 12 passes between the crown block and traveling block

pulley A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that ...

s for

mechanical advantage Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for t ...

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

derrick A derrick is a lifting device composed at minimum of one guyed mast, as in a gin pole, which may be articulated over a load by adjusting its guys. Most derricks have at least two components, either a guyed mast or self-supporting tower, and a ...

leg on the other side of the rig floor. This section of drill line is called the "dead line." A modern drawworks consists of five main parts: the drum, the power source, the reduction

gear A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called ''cogs''), which mesh with another (compatible) toothed part to transmit (convert) torque and speed. The basic pr ...

, the brake, and the auxiliary brake. The apparatus can be powered by AC or DC, or the drawworks may be connected directly to internal combustion 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 a friction band brake, a

disc brake A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hol ...

or a modified

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

. 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 the kinetic energy of the moving load to heat and dissipate it. 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 A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. Some rotary tables allow the use of index plates f ...

, although on many rigs the rotary table is independently powered. The drawworks is used to hoist or lower several hundred thousand pounds of weight and comes in AC, DC or mechanical power units. Horsepower ratings for drawworks can also have a wide range, often ranging from 1000 HP to over 3000 HP.

References

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External links

drawworks - Oilfield Glossary
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Schlumberger Schlumberger Limited (), doing business as SLB, is an oilfield services company. Schlumberger has four principal executive offices located in Paris, Houston, London, and The Hague. Schlumberger is the world's largest offshore drilling compa ...

Drilling technology