Cranes are an essential piece of equipment on any major worksite. They are used to lift and move heavy materials from one place to another. While all cranes are able to perform the basic functions of lifting and lowering, there are a number of different types of cranes available that can perform specific functions.
The Different Types of Cranes
While there are dozens of different cranes with different features, functions and capabilities, the two main categories are fixed cranes (also known as tower cranes) and drivable cranes (also known as mobile cranes). Fixed cranes are generally constructed on-site, whereas drivable cranes are pre-constructed and are ready to go once they arrive on-site.
As their name suggests, drivable cranes (mobile cranes) are self-propelled vehicles that can be transported by a driver in a cab. A mobile crane is a complete unit that can either be driven to a construction site or transported to a site by a truck. Many mobile cranes are available, including Franna cranes, city cranes, mini cranes, all-terrain cranes, rough terrain cranes and truck cranes.
Though mobile cranes are preconstructed, some preparation is usually required before they can be used to lift materials. The preparation differs depending on the exact type of mobile crane.
If a crane requires outriggers or stabilisers to provide greater stability during the lift, these will have to be set up once the crane has reached the lifting location. In some cases, counterweights may also need to be applied. Certain mobile cranes have built-in counterweights while others are detachable and need to be removed if the crane is being driven. If a luffing jib is required, the jib may need to be assembled and attached to the crane using a smaller crane before it is operational.
Finally, in order to prepare for a lift, the load must be securely rigged using straps, spreader bars or lifting beams.
Cranes That Require On-site Assembly
Cranes that require on-site assembly, are generally known as tower cranes. A tower crane is a tall vertical metal structure with a large boom and a 360-degree turning angle. They are the tallest type of crane and also have the largest lifting capacity.
How Are Tower Cranes Assembled?
The assembly of a tower crane is a remarkable feat of engineering. The process for assembling a tower crane is as follows:
The Base – A concrete slab is poured and fixed in place using anchor bolts to provide a solid and stable base for the crane
The Foundation – A mobile crane is used to assemble the lowest sections of the crane. The foundation is assembled with the base of the tower and then the job, counter jib, cab, turntable and motor are loaded into place.
The Tower – Once the tower reaches a certain height, the tower crane begins to construct itself using a climbing unit/frame.
The climbing unit is assembled and lifted to the top of the tower
The new section of the tower is lifted by the crane’s hook and transported by trolley to be attached to the climbing unit
Hydraulic machinery pushes the slewing unit up to open up a gap in the climbing frame/unit so a new tower section can be added
A new tower section is placed in the gap and bolted securely to the tower
This process is repeated until the crane reaches the desired height
Once constructed, the tower crane can begin lifting after securely rigging the load.
How Are Tower Cranes Dissembled?
The process for dissembling a tower crane is essentially the same as the assembly but in reverse. The crane will dissemble itself by removing the multiple tower sections and lowering them back down until it reaches the point where a mobile crane can assist. At this point, the mobile crane can return to remove the components it initially attached (jib and cab, etc) and complete the disassembly of the lowest sections and foundation. The concrete base can either be removed or covered over (parking lot and garden beds etc.).
Whether your project is a construction site or a small project, St George Cranes has a variety of mobile cranes available. If you’re considering hiring a mobile crane contact St George Cranes today for a quote or more information.