Tower Cranes
Tower cranes are perhaps the most widely recognized type of crane for construction, if for no other reason than they are hard to miss. Often quite large, their crane towers stand tall in the middle of construction sites for all the world to see.
Tower cranes are made up of the tower, or mast, and the jib, the arm that extends out from the mast. The jib can move a full 360° around the mast, with a trolley that runs up and down the full length of the jib, allowing the block hook to be lowered to the correct location.
Static cranes are the type most often used to build large structures over a longer timeline. They’re commonly used in urban areas where space is limited and the public is rarely far away. Their stability provides an extra layer of safety for both those who work at the sight and those outside the fencing.
They are powerful and capable of lifting large weights very high if necessary, but they are limited to a single area. While they do extend and rotate, there is still a limit to their range of motion.
There are three primary types of tower cranes, including:
Hammerhead cranes
Luffing tower cranes
Self-erecting tower cranes
Hammerhead Cranes
Hammerhead cranes resemble an upside-down L, with the jib remaining at a set level. The jib can usually rotate but cannot be raised or lowered. This model is frequently found on loading docks where many cranes may be operating simultaneously at various levels. They are also used in situations where space may be limited, like inside a structure or at particularly tight construction sites.
There are two basic designs for tower cranes: the A-frame, and the flat top.
The A-frame:
Uses a metal structure to connect cables from the jib to the counter jib, a short but has a heavily weighted structure behind the jib
This is used for leverage and allows this type of tower crane to lift heavier weights
.
The flat-top:
Has no additional structures above the tower and is used for lifting lighter weights
Luffing Jib Crane
The luffing jib type of tower crane is very similar in structure to the hammerhead but has one major difference. The jib can be raised and lowered on luffing jib construction cranes. This design gives them added flexibility while allowing them to lift heavier weights.
The luffing crane is more expensive than the hammerhead, but can be more efficient with a smaller rotation radius, allowing it to be used in tighter construction sites. It can also be used where multiple cranes are operating at the same time.
Self-Erecting Cranes
Relatively speaking, the self-erecting cranes are the lightweights of the static crane family. They are designed to be easily set up and dismantled.
Self-erecting cranes are ideal for working in tight spaces or for shorter-term construction jobs. Their major shortcoming, however, is that they cannot lift as much weight as the other types of tower cranes.
Level Luffing Cranes
Similar in appearance and function to the tower luffing cranes, the level luffing cranes have one major difference — they do not have trolleys that run along the jib. Instead, the hook block is fixed at the end of the jib, and the jib itself moves up and down to move the load. This design allows the load to stay level while being lifted.
This type of construction crane is most often used for shipbuilding and loading and unloading freight.
What are mobile cranes?
Mobile cranes can be moved around a construction site or even from site to site as needed. They are usually mounted on trucks but can also be found on railcars and boats, and are usually outfitted with outriggers to prevent them from tipping over while the crane is lifting.
Mobile cranes:
Are meant for temporary use in any given area
Most consist of a single lifting arm that can be raised or lowered
Frequently feature a telescoping arm to allow the crane to reach higher places
There are several different kinds of mobile cranes, including: