A derrick is a lifting device composed of one tower

Tower

A tower is a tall structure, usually taller than it is wide, often by a significant margin. Towers are distinguished from masts by their lack of guy-wires....

, or guyed mast

Guyed mast

A guyed mast is a tall thin vertical structure that receives support from guy lines.Guyed masts are frequently used for radio masts. The mast can either support aerials mounted at its top, or the entire structure itself can function as an antenna ; this is called a mast radiator...

 such as a pole which is hinged freely at the bottom. It is controlled by lines (usually four of them) 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 the end, like with a crane

Crane (machine)

A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of...

. It is commonly used in dock

Dock (maritime)

A dock is a human-made structure or group of structures involved in the handling of boats or ships, usually on or close to a shore.However, the exact meaning varies among different variants of the English language...

s and onboard ships. Some large derricks are mounted on dedicated vessels

Crane vessel

A crane vessel, crane ship or floating crane is a ship with a crane specialized in lifting heavy loads. The largest crane vessels are used for offshore construction. Conventional monohulls are used, but the largest crane vessels are often catamaran or semi-submersible types as they have increased...

, and are often known as "floating derricks".

The device was named for its resemblance to a type of gallows

Gallows

A gallows is a frame, typically wooden, used for execution by hanging, or by means to torture before execution, as was used when being hanged, drawn and quartered...

 from which a hangman's noose hangs. The derrick type of gallows in turn got its name from Thomas Derrick

Thomas Derrick

Thomas Derrick was a notable English executioner from the Elizabethan era.In English history, executioner was not a commonly chosen career path because of the risk of friends and families of the deceased knowing who the executioner was and where to find him. Executioners were sometimes coerced into...

, an English

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 executioner from the Elizabethan era

Elizabethan era

The Elizabethan era was the epoch in English history of Queen Elizabeth I's reign . Historians often depict it as the golden age in English history...

.

Oil derrick

Another kind of derrick is used over oil well

Oil well

An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...

s and other drilled holes. This is generally called an oil derrick and is a complex set of machines specifically designed for optimum efficiency, safety and low cost. This is used on some offshore oil and gas rigs.

The centerpiece is the archetypical derrick tower, used for lifting and positioning the drilling string

Casing string

Casing string is a long section of connected oilfield pipe that is lowered into a wellbore and cemented. The pipe segments are typically about in length, male threaded on each end and connected with short lengths of double-female threaded pipe called couplings...

 and piping above the well bore

Bore

Bore may refer to:* Bore , the diameter of a cylinder in a piston engine* Bore , the interior chamber of a wind instrument* Bore , a district of Ethiopia that includes the town of Bore* Boré, Mali...

, and containing the machinery for turning the drilling bit around in the hole. As the drill string goes deeper into the underlying soil or rock, new piping has to be added to the top of the drill to keep the connection between drill bit and turning machinery intact, to create a filler to keep the hole from caving in, and to create a conduit

Waterway

A waterway is any navigable body of water. Waterways can include rivers, lakes, seas, oceans, and canals. In order for a waterway to be navigable, it must meet several criteria:...

 for the drilling mud. The drilling mud is used to cool the drilling bit and to blow rock debris clear
from the drill bit and the bottom of the well. The piping joints sections—usually each about 10 meters (30 ft) long—have threaded ends, so they can be screwed together. The piping is hollow to allow for the mud to be pumped down into the drilling hole, where it flushes out at the drilling bit. The mud then proceeds upwards towards the surface on the outside of the piping, carrying the debris with it.

The derrick also controls the weight on the drilling bit, because the drill bit works at an optimum rate only when it is pushed with a precise degree of pressure relative to the rock beneath it. Too much weight can break the drilling bit, and not enough weight will prolong drilling time. At the start of drilling extra heavy piping collars are used to create enough weight to drill. Since the weight of the pipes above the drill bit will increase the pressure on it as it goes deeper, the derrick will apply less pressure as piping sections are added. It will eventually lift the nearly entire drill string-and-piping complex to prevent too much weight as the well goes deeper.

Hallen Derrick

The boom

Boom (sailing)

In sailing, a boom is a spar , along the foot of a fore and aft rigged sail, that greatly improves control of the angle and shape of the sail. The primary action of the boom is to keep the foot of the sail flatter when the sail angle is away from the centerline of the boat. The boom also serves...

 is connected with the lower part of the mast

Mast (sailing)

The mast of a sailing vessel is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship...

 which is shaped like a “Y” or a bipod

Bipod

A bipod is a support device that is similar to a tripod or monopod, but with two legs. It provides significant stability along two axes of motion .-Firearms:...

 and therefore it is a single swinging derrick. On the cross trees, two guys

Guy-wire

A guy-wire or guy-rope, also known as simply a guy, is a tensioned cable designed to add stability to structures . One end of the cable is attached to the structure, and the other is anchored to the ground at a distance from the structure's base...

 are fastened using swivel

Swivel

A swivel is a connection that allows the connected object, such as a gun or chair, to rotate horizontally and/or vertically. A common design for a swivel is a cylindrical rod that can turn freely within a support structure. The rod is usually prevented from slipping out by a nut, washer or...

 outriggers which are stayed vertically and horizontally. In order to maintain a good controlling angle between guys and derrick, the outriggers cannot pass the inboard parallel of the centerline. Looking at the illustration, one can easily see that the right outrigger stays in the centerline and the left outrigger has moved outboard. This derrick will lower or heave cargo as both guys are veered or hauled. Three winches, controlled by joystick, are necessary to operate the Hallen Derrick; two for the guys and one for the purchase. To avoid an over-topping or over-swinging limit-switches are used. However, the limits can be modified if a different working range or a special vertical stowage is required. The safe working load

Safe working load

Safe working load is the load that a lifting device such as a crane, a cherry picker, or a lifting arrangement can safely lift, suspend or lower. Other synonyms include working load limit , which is the maximum working load designed by the manufacturer. The load represents a mass or force that...

 (SWL) of the Hallen is between 10 and 80 tonnes. In a Hallen Universal derrick, which has no Hallen D-Frame, the halyard

Halyard

In sailing, a halyard or halliard is a line that is used to hoist a sail, a flag or a yard. The term halyard comes from the phrase, 'to haul yards'...

 has an extended length since it runs through further blocks on the centerline. The Universal Hallen derrick, replacing the D-frame option, is a kind of traditional topping lift. The Hallen D-Frame is a steel bracket welded on the mast in the centerline. For an observer standing a beam

Beam (structure)

A beam is a horizontal structural element that is capable of withstanding load primarily by resisting bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment.- Overview...

, the frame has a “D”-shape. The D-Frame supersedes the outriggers and provides a good controlling angle on the guys. The Hallen derrick has a good purpose for e.g. containers, logs, steel rail, sawn timber and heavy lifts and doesn't lend itself for small, general cargo. It keeps the deck clear of guy ropes and preventors. Only one winchman is needed and within a few minutes the Hallen is brought into use. It is less expensive than a crane. A disadvantage is the low working range of the Hallen Derrick, it is able to swing 75° from the centerline and can work against a list of up to 15°.

Velle Derrick

The Velle derrick is quite similar to the Hallen but without use of outriggers. On top of the boom is a T-shaped yoke

Yoke

A yoke is a wooden beam, normally used between a pair of oxen or other animals to enable them to pull together on a load when working in pairs, as oxen usually do; some yokes are fitted to individual animals. There are several types of yoke, used in different cultures, and for different types of oxen...

 assembled. Also here, the guys serve for topping and lowering the boom but they are fastened on the yoke with four short, steel-wire hanger-ropes. The ends of the topping and lowering ends of the halyard are secured to half-barrels on one winch. In this way the boom moves in the same speed as the winch veers the topping end of the halyard and hauls the lowering end of the halyard, and vice versa. The slewing ends are also wound on to another half-barrel. For hoisting the cargo, there is a third winch to hoist to cargo on the yoke. Runners decrease swing and rotation of the cargo. A joystick duplex controller steers the Velle derrick.

Stülcken Derrick

The patent Stülcken derrick is used for very heavy cargo. It stems from the German shipyard HC Stülcken & Sohn which has been taken over later by neighboring yard Blohm & Voss. This derrick can handle up to 300 tonnes. The Stülcken can be made ready in few minutes, which is a lot faster than a traditional heavy derrick, doesn't require lots of space and is operated by four winches. Between two v-shaped, unstayed Samson-posts is the Stülcken secured. This makes it possible to let the derrick swing through the posts to reach another hatch. For each post is a hoisting winch, a span winch and a lever that is run by one man only. Bearings, swivels, sheaves and the gooseneck can be unattended for up to four years and create only a friction of about 2%. The span tackles are independent and the halyard is endless. With the revolving suspension heads on the posts it takes ten minutes to swing all the way through. In the double-pendulum block type, half of the cargo tackle can be anchored to the base of the boom. In order to double the hook speed, the halyard passes through the purchases since one end is secured which reduces the SWL to its half. Typical dimensions of a 275 tonne Stülcken are: 25.5 m length, 0.97 m diameter, 1.5 m to 3.4 m diameter of posts, 18 m apart the posts (upper end) and 8.4 m apart the posts (lower end). The hook of a full-loaded 275 tonne Stülcken can move 2.3 m per minute. If only one purchase is secured and the derrick is loaded with 137 tonnes the hook gains velocity to 4.6 m per min. Even more speed can be gained when the winch ratios are reduced to 100 tonnes (triple speed) and 68 tonnes (quadruple speed). Detaching the union table the double-pendulum block type of Stülcken is able to swing through which allows the lower blocks to swing freely to each side of the boom. In this way the derrick reaches a vertical position. A bullrope easily pulls the derrick to the other side until the weight of the cargo tips the derrick over. The span tackles now have the weight on the other side. The union table is fixed again and the derrick can start its work on the other side. There are also Stülcken with single-pendulum blocks. At this type the cargo hook is detached and the lower and upper cargo block are hauled into the center of the Stülcken. To tip the derrick over the gravity is here used again. A derrick helps pump oil in most offshore rigs.