Cranes: A short guide to the modern construction & industrial workhorse
- What is a Crane?
- How does a Crane work?
- What features & capabilities do different types of Crane have?
- Types of Crane List
- Types of Crane In Depth
What is a Crane?
The crane has been part of the working landscape since its invention in ancient Greece. Cranes are essential for heavy construction work and lifting tasks of all kinds.
Equipped with cables and pulleys and based upon the application of fundamental mechanical principles, a crane can lift and lower loads well beyond the capabilities of human construction workers.
Crane design has evolved to meet the demands of a variety of industrial needs, and modern cranes often coordinate simple systems to achieve complex lifting tasks – sometimes in environments which would be dangerous for human workers.
How does a Crane work?
To operate efficiently and maintain its vital stability, every type of crane must obey the laws of physics.
The two most important considerations in this respect are that the crane must not move weights which exceed its rated capacity, and that any stressful movements occurring beyond each machine’s designated plane of operation should be eliminated wherever possible.
How does it work? A crane is able to lift objects because the load is offset by counterweights which stabilise the crane, allowing it to lift and move its load.
What are the different types of Crane?
- Tower Cranes
- Mobile Cranes
- Static Cranes
- General Cranes
- Heavy Cranes
- Telescopic Cranes
- Mobile Tower Cranes
- Tower Cranes
- Vehicle Mounted Cranes
- Rough Terrain Cranes
- Crawler Cranes
- All Terrain Cranes
- Rail Cranes
- Telescopic Handler Cranes
- Harbour Cranes
- Floating Cranes
- Level Luffing Cranes
- Giant Cantilever Cranes
- Gantry Cranes
- Aerial Cranes
Types and categories of cranes are given different names in different countries – there is some overlap in the list above, where multiple names are used to describe a single type of crane.
What features & capabilities do different types of Crane have?
The various categories and types of crane have a range of different features. Here are some of the common features in cranes that are often considered when purchasing, using a crane hire company or contract lifting service, which are covered in a Load Chart:
- Lifting Capacity – How much weight can the crane lift?
- Lifting Range – Where do you need to lift to?
- Lift Angle – With a high angle of lift, the lift capacity decreases, so the angle of lift is a key consideration.
- Working Radius – What area does the crane need to work over?
- Mobility – How much space is there for the Crane to operate? Is a mobile tower crane required?
- Weight & Dimensions – Situating the crane itself is a key consideration – the size and mobility of the crane need to fit in with the restrictions of the construction site. With outriggers extended lifting capacity is affected, so a confined space requires a certain type of crane.
- Setup Time – Some projects require minimal disruption, so the fast setup time that comes with Mobile Tower Cranes, for example, is a benefit.
- Night Working – Quieter operations and appropriate lighting can be a requirement for working at night.
Types of Crane In Depth
The tower crane is a form of balance crane which is commonly used on urban construction sites. This machine is anchored to the ground and provides an optimum blend of height and lifting capability which is often deployed to erect multi-storey city buildings. Two horizontal arms jut from a central tower, with one used to suspend the heavy loads to be lifted, and the other fitted with heavy concrete blocks as a counter-weight. A tower crane is controlled by a driver who either sits high above in a small cabin located at the top of the tower, or else uses a remote control system to operate his machine from the ground.
Mobile cranes are commonly mounted on wheeled vehicles, but cranes used for railway work are adapted to travel on rail tracks, and various floating cranes can be attached to barges when used for construction work on bridges and waterways. Many types of crane are mobile, including Mobile Tower Cranes.
Many types of crane serve a temporary purpose, and a mobile crane may be little more than a robust steel boom fitted to a transportable platform. The lifting arm is typically hinged to allow it to be hoisted and lowered as required. This is usually achieved by cable systems or hydraulic mechanisms, and the whole mobile structure can be fitted with outriggers to provide further stability during on-site operations.
Driven by a hydraulic mechanism, a telescopic crane features a set of concentric tubular steel booms which can be easily extended and retracted to alter the operational height of the crane. Usually mobile, these adaptable cranes are compact units which perform effectively where space is at a premium. Telescopic cranes are widely used, including by rescue services, and to perform tasks such as launching and retrieving boats at the waterside.
“Static” refers to the requirement that the crane is installed in a certain place, rather than transported in by itself. This is the stark difference between static cranes and mobile cranes. The term “static cranes” encompasses different types of crane including Tower Cranes.
Giant Cantilever Crane
Also known as the ‘hammerhead’, this German-designed crane features a strong, steel-braced central tower on to which is fitted a mighty double-cantilever beam. The forward section of this arm houses the lifting machinery, while the rear section contains a substantial counterbalancing weight. Lifting and then transferring loads via a rotational movement of the whole cantilevered cross beam is the primary function of this type of crane. However, some later models also incorporate a mechanism to move and re-position the suspended load along the front arm, adding to the versatility of the machine.
Using a hoist installed in a fixed machinery housing, or otherwise able to slide along a rail framework, this crane employs a strong overhead gantry to lift and manoeuvre extremely heavy industrial loads. Gantry cranes and other so-called ‘overhead’ cranes – which also carry suspended loads in similar fashion – are widely used in factories and shipyards and similar commercial locations where their robust qualities make them essential equipment.
This crane features a special mechanism in which the crane hook is designed to stay at a constant level. As a result, up and down movements of the jib arm will only move the hook towards, or away from, the base of the crane. The advantage of this type of movement is that the crane can be set to operate at a fixed level, relative to the ground, where such action is necessary to handle load materials with precision – as can be often be required, for instance, during shipbuilding.
A special type of mobile crane fitted with caterpillar tracks, the crawler crane can be used on soft and boggy ground where wheeled vehicles would be unable to operate. This crane is generally very stable because its broad base and tracking spreads the weight over a wide area. These sturdy machines are useful on construction sites during the initial phase of building projects where their ability to move heavy loads over areas of soft soil is a particular asset.
Aerial Cranes/Flying Cranes
Aerial Cranes offer probably the greatest range of any crane, being part of an aircraft. Aerial cranes are attached to a helicopter with the lifting mechanism commonly used for lifting containers, temporary and pre-fabricated buildings, and timber (in the logging industry). Lifting operations using a an aerial crane are sometimes referred to as “longline”, as the load is attached to the crane by a single long line. These helicopters can operate in a broad range of landscapes, including areas it’s simply not feasible to use any other type of crane, and areas without roads. Will drones replace helicopters as the vehicle for aerial cranes in the future?