Crane - Construction

A crane is a mechanical lifting device equipped with hoists, wire ropes and sheaves to be used to lift and lower materials and move them horizontally. It uses one or more simple machines to create mechanical advantage and move loads beyond normal capability of a human.

Cranes are commonly employed in transport for the loading and unloading of freight; in construction industry for the movement of materials; and in the manufacturing industry for the assembling of heavy equipment.

There are two major considerations that are taken into account in the design of cranes.

A crane must be able to lift a load of a specified weight and the second is that the crane must remain stable and not topple over when the load is lifted and moved to another location.
Lifting capacity
Cranes illustrate the use of one or more simple machines to create mechanical advantage.

The lever. The principle of the lever allows a heavy load attached to the shorter end of a beam to be lifted by a smaller force applied in an opposite direction to the longer end. The ratio of the load's weight to the applied force is equal to the ratio of the lengths of the longer arm and the shorter arm, and is called the mechanical advantage.
The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block. Cables are wrapped multiple times round the fixed block and round another block attached to the load. When the free end of the cable is pulled by hand or by a winding machine, the pulley system delivers a force to the load that is equal to the applied force multiplied by the number of lengths of cable passing between the two blocks. This number is a mechanical advantage.
The hydraulic cylinder. Used directly to lift the load (as with a HIAB), or indirectly to move the jib or beam that carries another lifting device.
Stability of crane: In order for a crane to be stable the sum of all moments about any point such as the base of the crane must equate to zero.

Types
railroad crane

Crane with flanged wheels, used by railroads. The simplest form is just a crane mounted on a railroad car or on a flatcar. More capable devices are purpose-built.

Mobile crane
Consists of steel truss or telescopic boom mounted on a mobile platform, which may be rail, wheeled (including "truck" carriers) or caterpillar tracks. The boom is hinged at the bottom, and can be raised and lowered by cables or by hydraulic cylinders. A hook is suspended from the top of the boom by wire rope and sheaves.

Telescopic crane
A telescopic crane has a boom that consists of a number of tubes fitted one inside the other. A hydraulic or other powered mechanism extends or retracts tubes to increase or decrease the total length of the boom. These types of booms are often used for short term construction projects, rescue jobs, lifting boats in and out of the water, etc. The relative compactness of telescopic booms make them adaptable for many mobile applications.

Tower crane

A modern form of balance crane. Fixed to the ground, tower cranes often give the best combination of height and lifting capacity and are used in construction of tall buildings. To save space and to provide stability the vertical part of the crane is often braced onto the completed structure which is normally the concrete lift shaft in the center of the building.

Truck-mounted crane
A crane mounted on a truck carrier provides mobility for this type of crane. Generally, these cranes are designed to be able to travel on streets and highways, eliminating the need for special equipment to transport a crane to the jobsite. When working on the jobsite, outriggers are extended horizontally from the chassis then down vertically to level and stabilize the crane while stationary and hoisting.

Rough terrain crane
A crane mounted on an undercarriage with four rubber tires designed for pick-and-carry operations and for off-road and "rough terrain" applications. Outriggers that extend horizontally and vertically are used to level and stabilize the crane for hoisting. These telescopic cranes are single-engine machines where the same engine is used for powering the undercarriage as is used for powering the crane, similar to a crawler crane. However, in rough terrain crane, the engine is usually mounted in the undercarriage rather than in the upper, like the crawler crane.

Crawler crane
A crane mounted on an undercarriage with set of tracks that provide for the stability and mobility of the crane. Crawler cranes have both advantages and disadvantages depending on their intended use. The main advantage of a crawler is that they can move on site and perform lifts with very little set-up, as the crane is stable on its tracks with no outriggers. In addition, a crawler crane is capable of traveling with a load. The main disadvantage of a crawler crane is that they are very heavy, and cannot easily be moved from one job site to the next without significant expense. Typically, a large crawler must be disassembled or moved by barge in order to be transported.

Gantry crane
A gantry crane has a hoist in a trolley which runs horizontally along gantry rails, usually fitted underneath a beam spanning between uprights which themselves have wheels so that the whole crane can move at right angles to the direction of the gantry rails. These cranes come in all sizes, and some move very heavy loads, particularly the extremely large examples used in shipyards or industrial installations . A special version is the container crane (or "Portainer" crane, named after the first manufacturer), designed for loading and unloading ship-borne containers at a port.

A portainer (also known as a container crane, container handling gantry crane, quay crane, ship-to-shore crane or a STS crane) is a large dockside crane in the form of a specialised type of gantry crane used to load and unload container ships, and only seen at container terminals. The term Portainer is a registered trademark of Paceco Corp.

Overhead crane
Also known as a suspended crane, this type of crane works in the same way as a gantry crane but without uprights. The hoist is on a trolley which moves in one direction along one or two beams, which move at right angles to that direction along elevated tracks, often mounted along the side walls of an assembly area in a factory. Some of them can lift very heavy loads.

Floating crane

AKA offshore crane - crane vessel

Floating cranes are used mainly in bridge building and port construction, but they are also used for occasional loading and unloading of especially heavy or awkward loads on and off ships. Some floating cranes are mounted on pontoons, others are specialized crane barges with a lifting capacity exceeding 10,000 tonnes and have been used to transport entire bridge sections. Floating cranes have also been used to salvage sunken ships. Crane vessels are often used in offshore construction. The largest revolving cranes can be found on SSCV Thialf, which has two cranes with a capacity of 7100 metric tons each. A crane vessel is a ship that is specialized in lifting heavy loads. The largest crane vessels are often used for offshore construction. The larger vessels are often semi-submersibles, but also conventional monohulls are used. One of the differences with a sheerleg is that the cranes can rotate.

Vessel (Deck) crane
Located on the ships and used for cargo operations which allows to reduce costs by avoiding usage of the shore cranes. Also vital in small seaports where no shore cranes available. Mostly are electric, hydraulic, electro-hydraulic driven.

Aerial crane
Aerial cranes usually extend from helicopters to lift large loads. Helicopters are able to travel to and lift in areas that are more difficult to reach by a conventional crane. Aerial helicopter cranes are most commonly used to lift units/loads onto shopping centers, multi-story buildings, highrises, etc. They can lift basically anything within their lifting capacity, (i.e. cars, boats, swimming pools, etc.). They also work as disaster relief after natural disasters for clean-up, and during wild-fires they are able to carry huge buckets of water over fires to put them out.

Jib crane
A Jib crane is a type of crane where a horizontal member (jib or boom), supporting a moveable hoist, is fixed to a wall or to a floor-mounted pillar. Jib cranes are used in industrial premises and on military vehicles. The jib may swing through an arc, to give additional lateral movement, or be fixed. Similar cranes, often known simply as hoists, were fitted on the top floor of warehouse buildings to enable goods to be lifted to all floors.

Stacker crane
A crane with a forklift type mechanism used in automated (computer controlled) warehouses (known as an automated storage and retrieval system (AS/RS)).

Overhead Cranes
The most common overhead crane use is in the steel industry. Every step of steel, until it leaves a factory as a finished product, the steel is handled by an overhead crane.

Crane Operator Jobs

A Crane Operator course can set out to produce crane operators trained to operate a specific range of machines. Often requires valid certificates/tickets and on-site experience. There are Offshore Crane Operator Training Simulators

lifting equipment - crane barge - crane valves