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Construction Cranes explained
Tower cranes are at the heart of many construction sites around the globe. They are the heart and soul of large construction sites. They are the backbone of any construction site.
- How are tower cranes built?
- In what way does an operator get in the cab?
- How can they get the crane to go higher up in the building?
These are questions often asked and in this article, we aim to answer them.
Despite their widespread use, people don’t know much about how a crane works. We will answer the most fundamental questions and then dive deeper.
What is a Construction Tower Crane?
A crane is a common piece of lifting equipment that can be found on construction sites. Because of its tower-like structure, the crane is known as a tower crane. The tower mast supports the counter jib, jib, and hook that does the lifting.
Why are Tower Cranes used?
Tower cranes are used for lifting heavy materials and have a small footprint.
They can lift heavy loads and move materials across construction sites with ease. Tower cranes can reach large areas and have access to all job sites.
Why choose a tower crane over a mobile crane?
Mobile cranes are traditionally set up at ground leve which could have an impact on surrounding construction activities if it is installed in the middle or center of a project.
Although the crane’s reach (jib and hook locations), is large, the actual space that a tower crane occupies on site is relatively small. Think about how small the tower is relative to its reach.
What are the Different Types Of Construction Tower Cranes
You’ll quickly see that cranes can come in many sizes and shapes when you drive through cities like Dublin, Cork or Galway (many of which are supplied by POB Cranes). These are the different types of tower cranes available:
- Hammerhead Crane (Jib Type)
- Luffing Jib Tower Cranes (Jib Type)
- Derrick Cranes (Jib Type)
- Self Supporting Cranes (Mast Type)
- Travelling Cranes (Mast Type)
- Self Climbing Cranes (Mast Type)
What is a Hammerhead Tower Crane?
The hammerhead tower crane, also known as a hammerhead crane, is an extremely common type of tower crane used in construction projects around the globe. It is easily identifiable by its vertical mast (tower), and horizontal jib that supports the cab. The cable and hook are carried by a trolley that runs horizontally along the mast. This allows for the hook to be placed in any location on the mast.
Luffing Jib Tower Crane
Another common type of tower crane is the luffing tower crane. It is easily identifiable by its diagonal arm that extends from the top mast (tower) at an angle. The hook point, unlike the hammerhead, is located at the end of the Jib. Combining the angled arm and the crane counterweights, the luffing tower crane has typically a greater capacity than the hammerhead crane.
The diagonal arm, unlike the hammerhead crane can move in and outside (from vertical to 30 degrees). Because of this movement, they can fit into tight spaces. This is why you see them often in busy urban areas.
Derrick Cranes
Derrick cranes are similar in nature to the luffing-jib type. Because of their small size, these cranes can be positioned on roofs and other small areas. The outriggers that allow Derrick cranes to sit on any surface make them unique.
These cranes are made up of pieces and can be used to assemble or disassemble cranes. The unique characteristic of Derrick cranes is that they don’t have a cab to operate. They are controlled by remote control, which can be wired or wireless.
Mast Type – Self-supporting Tower Cranes
Self-supporting mast types are a type of tower crane used in smaller structures that do not require tower extensions. A weight or reinforced concrete block is used to anchor self-supporting tower cranes at the base. To anchor the base to the bedrock, it may be necessary to use piles.
The cranes that self-support are fixed in place and have a tower that extends out from the anchor point. They then rotate around the tower. Before the tower is installed, it must be considered how far they can be moved once they are in place.
Mast Type – Travelling Tower Crane
The traveling tower crane is used for large projects that have to be moved frequently. The track-mounted or rail-mounted traveling tower crane can be either track-mounted or rail-mounted. The crane can travel horizontally on a path thanks to the rails or tracks.
The base and track design may determine whether loads can be transported during the traveling period. This crane requires that a path is left clear and flat enough for the crane to move. A path that isn’t completely flat and free of debris could lead to the crane tipping.
Mast Type – Self-Climbing Tower Crane
One of the most interesting pieces of equipment on a construction site is the self-climbing tower crane. The self-supporting tower crane is the first thing that a self-climbing tower crane encounters. The tower is built and then anchored to a concrete base.
The tower is attached to the existing structure as it extends vertically. The crane inserts a piece of the tower into the existing tower to increase the crane’s height when the building has reached a point where it cannot clear the structure.
What are the Different Parts of a Tower Crane?
Tower cranes are complex machines. It’s incredible to see the scale of structures from the past. Tower cranes today allow us to reach new heights.
Tower cranes can be broken down into many different parts that are crucial for the operation of the machine. Although there are many parts to a crane, the most important parts can be broken down into these:
- Base Support
- Tower (Mast).
- Operator’s Cab
- Turntable
- Counterweight
- Jib and Counter Jib
- Trolley and Hook Block
Base Support
The base support of a tower crane is what attaches it to the ground or other structures. This is usually attached using reinforced concrete and piles to support the crane to the ground. This tower component should be designed by an engineer.
Tower (Mast).
A tower, or mast, is the part of a tower crane that rises from the ground. It supports the crane’s cab, mast and hook as they rotate around it. The square latticework of steel used to make towers and masts is similar to an open-web steel joist.
Tower Crane Operators Cab
The operator cab is the place where the crane driver sits to operate the crane. It looks like a small glass box that is located on the underside or side of the mast. The cab is usually attached to a computer that feeds information to operators and allows them to operate the crane using a pair of joysticks.
Turntable
The tower crane turntable is the part of the crane that allows the counter jib or jib to spin on the mast. Two plates are inserted inside one another to form the mast which rotates with bearings. The actual rotating circular component is known as a slewing bearing which is the same technology that is used in windmills.
Counterweight
A crane must have a counterweight to balance its load when lifting heavy objects. The tower crane’s ability to lift heavy objects would be greatly reduced without the counterweight. The counterweight is located at the opposite end of the jib.
Counterweights can be made of a variety of materials, including reinforced concrete, steel, and other heavy materials. The crane’s capacity at its final lifting position determines its weight.
Jib and Counter Jib
The most well-known parts of a tower crane are the jib or counter jib. The counter jib is the steel lattice work that extends horizontally from the mast or tower. The jib’s purpose is to transport the crane’s trolley, cabling hook, and load. The counter jib’s purpose is to balance the weight of jib, and keep counter weights in their place.
Trolley and Hook Block
The crane’s work is a lot easier when the trolley and hook block are in place. The trolley can be moved back and forth along the mast, extending the hook as necessary to place it overtop of any load. The hook block is a pulley system that allows the trolley to move up or down depending on how much cabling has been released from the spool. The crane carries loads by attaching them to the hook block.
How are Construction Tower Cranes Built?
A tower crane is built in pieces, much like a jigsaw puzzle. Each component is delivered one by one on trucks and then assembled using a mobile crane. First, the tower is constructed. Next, the turntable and cab are assembled.
Then, the jib, counter jib, and other components are hoisted up and attached. To complete the erection, the cables and counterweights are also installed.
Erecting a tower crane may take several hours or even days, depending on the size and location. If a tower crane is being erected in an urban area, it will usually require the closing of adjacent streets.
How are Tower Cranes dismantled?
Traditional tower cranes are usually removed by other cranes. The components are removed one at a time, starting with the hook, cables, and counterweight. This is then followed closely by the tower, jib and cab. There are generally two types of cranes that can be used to remove a tower crane.
- Mobile Crane
- Derrick cranes
- Mobile Crane Tower Crane Removal
A mobile crane can be used to remove a tower crane from a property. The crane is taken apart by the mobile crane one piece at a time. The mobile crane attaches to a piece of metal and workers take out the fasteners to allow it to be lifted to the ground.
Although this technique is most commonly used in low- or mid-rise construction, some mobile cranes can reach hundreds of feet and are used on high-rise construction.
Tower Cranes and their future In construction
Tower cranes are workhorses in the construction industry. We have been able to build higher and faster than we ever imagined thanks to them. Because of their ability to lift things and the small space they require, construction companies will continue to depend on them.
Do you need a tower crane at your construction site? Contact us to discuss your Crane requirements.
