The tower cranes are the largest type of cranes in the world. They are the most used type of cranes for transporting or lifting heavy and large loads on the construction site.
The importance of tower cranes in construction work and projects cannot be overlooked. They are increasingly becoming a necessity in construction sites nowadays because of the rise of the construction of large buildings everywhere in the world. Construction of large buildings requires heavy lifting and placing of different materials in places that cannot be reached by regular ladders. The ways each tower cranes are built means every different crane come with different advantages and disadvantages.
Tower cranes are also different from traditional cranes and are seen as improved traditional cranes. This is because they have lots of advantages over the traditional cranes. One of the advantages is that some tower cranes that work in sites where big space is an issue. Furthermore, tower cranes can be used for lifting loads vertically higher than traditional cranes. Besides a lot of tower cranes can be operated with electricity and do not make lots of noise. In addition, the last and biggest advantage of tower cranes over traditional cranes is that tower cranes can be used through the space provided for elevators i.e. Elevator Shafts. That itself shows how versatile tower cranes are.
Advantages of Tower Cranes
- Tower Cranes are incredibly tall. They are the only type of cranes with such height. No other type of crane can match them in terms of height.
- They can lift insanely heavy loads. Their lifting capacity is bigger than that of other cranes
- They have excellent stability and are very durable
Disadvantages of Tower Cranes
As good as tower cranes are, they come with their disadvantages which sometimes limit how much they are used for construction works
- Tower cranes are very expensive to build. They also require and an incredibly large amount of time to be completely compiled if they are moved from one place to another.
- The cost of maintenance is very high. Repairing them is quite costly
- Installing them is labor-intensive. This means that it increases the cost of production of a particular construction project it is used in.
Without wasting much of your time, let’s discuss the different Tower Cranes commonly used on Constructions sites. Their advantages and disadvantages will also be discussed which will give you an idea of the best one for you.
Hammerhead cranes which are also called Giant Cantilever Crane are fixed jib cranes that look a lot like a hammer. They produce a racking motion when in use. The hammerhead crane’s design is said to have originated from Germany. As at that time, the hammerhead was designed to be used on battleships for installing heavy and large parts and pieces such as Gun barrels, Armor Plate, etc. on the ships. It is usually very big after full installation on the construction site. It takes quite a bit of space and is only used when there is enough space to spare on the construction site.
To install Hammerhead tower cranes on a construction site, another crane is required to assemble it. they second crane is usually a mobile crane which can easily be removed from the site after complete installation and brought back to the site when the hammerhead crane needs to be disassembled.
There are different kinds of hammerhead cranes. There is one called the Self-lifting hammerhead crane. These kinds of hammerhead cranes can remove and insert different sections into their towers with their Jib. This can be used to change the height of the tower crane.
Advantages of using hammerhead cranes
Here are two of the advantages of Hammerhead cranes over other tower cranes
- It is a static crane which can only be fixed in a place. But it can be used over several meters. There are even modern hammerhead cranes that come with features that allow them to move. The Tower itself does not move, rather the suspended load does the movement after some part of the crane is repositioned
- It is used for specific purposes
Disadvantages of using hammerhead cranes
The following are the major disadvantages of Hammerhead Crane
- They are very difficult to assemble.
- They are fixed to a spot. The disadvantage in this is that before it can be moved, it has to be disassembled and then reassembled. The implication of this is that it can only be used for mega constructions.
Level Luffing Crane
Level Luffing crane is also a type of Tower Crane. It is very versatile and it is used for several operations. What makes it unique among other tower cranes is that it comes with a special feature that allows it to move in very special ways. The crane hook of the luffing crane always stays at a constant level. However, the jib arm is designed to move vertically upward or down as well as away or towards the base of the crane.
The Level Luffing tower crane’s design does not have a trolley. Instead, the hoist rope is kept in a section at the top of the jib which is also where it comes out when it is about to be used. The crane work in single fall, as well as, two falls on the cable. It is extremely fast for lifting loads compared to other types of cranes. The reason for this is that the weight of the load is quickly transferred from the jib unlike other types of cranes. This gives it a much higher and better lifting capacity compared to other cranes.
The level luffing tower crane is of the most commonly used tower cranes because it effectively solves the most dominant problem a lot of construction projects have that is “space issues”. The Luffing Crane is the only crane that can be used when there are lots of existing structures very close to the construction site. Other cranes have to swing their jib in a radius that would mean it has to go over some of the existing buildings. It only uses a small space and needs a small radius to work effectively.
Advantages of Luffing Tower Cranes
Below are the advantages luffing Tower cranes have over other cranes:
- It requires only small space and radius which means it can be used when the construction site is in cities or close to populated areas
- Its design ensures that loads or materials are loaded onto it with great precision and little room for errors or mistakes
- When used, the safety of the general public is guaranteed because the load, as well as the jib arm all, stays within the confines of the construction site.
Disadvantages of Luffing Tower Crane
The Luffing Tower Crane also comes with some drawbacks which are listed below
- It takes a longer time to complete lifting tasks with the Luffing Crane. The main reason for this is that because of its design, there are some movements that the crane needs to perform before the load is lifted.
- It is fixed to as spot i.e. a static crane which means it has to be disassembled before it can be used on another site.
- They are expensive mainly because of their uniqueness. Hence, they are only used when no other crane can successfully operate on the construction site.
Self-Erecting or Telescopic Tower Cranes
The Self-Erecting Tower crane can be referred to as a hybrid crane that combines features from both a Tower Crane and an Ordinary Mobile Crane. The Self-erecting tower crane has outriggers which are the same feature that is present in mobile cranes. It is, however, a static crane which means it cannot be moved from one area to another without disassembling.
The fact that it is a static crane is not much of a drawback simply because as the name implies, it can assemble itself without the need of a second usually mobile crane. this is the biggest advantage it has over other types of Static Cranes because it saves a lot of time with its self-erecting features. there are some Self-erecting Tower Cranes that have the operator’s cab on the jib although most of them do not. A lot of self-erecting tower cranes are usually remote-controlled. In other words, they can be controlled by an operator from the ground.
The self-erecting tower crane can also be equipped to move on a construction site. if the resources to make it mobile by truck mounting it are available, it makes it even more effective. Some self-erecting tower cranes come with a telescoping tower. The benefit of this feature is that the crane can be used for several operations at different heights without having to reconfigure the tower. The crane has a large boom which has several tubes fitted inside it. The tubes with the help of a hydraulic mechanism can increase or decrease in height.
Advantages of self-erecting tower cranes
Some advantages include:
- It does not have to be reconfigured before being operated at various heights
- Because the height can be adjusted, a self-erecting tower crane mounted on a truck can be used for rescue operations
- The movement of the crane and jib when loaded with goods or materials is excellent and precise
- It is usually used in Seaports because of its hydraulic mechanism which it uses to change heights. It is used for embarking and disembarking cargo in ports.
Disadvantages of self-erecting tower cranes
There is no disadvantage in a defined way like in the other tower cranes we already discussed above. However, there is one that needs to be stated even though it is not much of a disadvantage.
- Self-erecting or telescopic tower cranes are not mobile cranes. They are static cranes.
However, they can be modified to move around on a construction site or as a permanent modification. The design of the self-erecting tower cranes makes them suitable for mobile operations when needed. Hence, by mounting them on a truck, the can be used for rescue operations, can be used for short term construction projects, can even be used to lift boats out of the water, and many more applications.
Portal Tower Crane
Portal Tower Crane is another type of tower crane but is not usually used on temporary construction sites. It is used only when the project being worked on is a long term one such as the construction of a factory or shipyard. it is not commonly used because of a lot of reasons. The most common one is that it takes a lot of time and money to set it up.
The portal tower crane can be set up to travel on rail tracks if it is close to the construction site. it s partly mobile because of this feature
- It is expensive to set up and takes a lot of time to be completed. It is also not commonly used.
Remote Control Crane
The remote control cranes are tower cranes that can only be operated with the use of remotes. The remote is usually used on the ground although some remote control cranes come with cabin controls. In such kind of cranes, it can only be operated from the cab.
Disadvantages of Remote Control Cranes
- The remote signal can easily be interrupted by any other remote that emits the same frequency. What this implies is that it has to be used on sites where that kind of signal cannot be interrupted. Interruption of a crane unintentionally by another remote signal while being operated can be dangerous
- The remote is operated on batteries which means they have to be changed regularly when flat
- It is harder and more difficult to see things when remotely controlling the crane from the ground
- The remote can also become faulty while on-site which can cause a delay in the work being done.
Flat Top Tower Crane
This type of tower crane is very good for working on sites with height restrictions. It is also good for sites where multi-cranes are needed. Construction sites close to airports usually use this type of tower crane
A-Frame Tower Crane
This is another type of tower crane that has its upper section designed like the letter “A”
In the construction industry, cranes are one of the most important equipment you will find because of the benefits and functions it offers. There are a lot of cranes but the most used type is the Tower Cranes.
As with any machinery, accidents can easily occur if the machine is not properly used or operated. This is not different for Tower cranes. A lot of accidents that occur in construction sites can be traced back to Tower Cranes. There are even statistics that confirm and proof that Tower cranes majorly contribute to the occurrence of a lot of serious life-threatening accidents. The good thing about this kind of crane-related accidents, that is bodily injuries and property damage is that they can be managed and avoided if the Tower cranes are properly operated or used.
Tower cranes can simply be referred to as modified traditional cranes. A lot of Tower cranes have identical parts although they usually have different working principles. A lot of Tower Cranes have concrete slabs as a base which gives them the ability to offer large lifting capacity than traditional cranes cannot. They are mostly used in the construction of big and tall buildings because they are usually very tall.
Brief Description of the parts that make up a Tower Crane
Tower cranes have concrete slab base which holds down the mast and prevents it from falling over. The base of the crane is then attached to a mast which is usually very long. This is where the Tower crane gets its name from. Once the mast has been attached to the base, it is then attached to a slewing unit which comprises of gear and a motor. It has a unit, Slewing Unit, which gives the crane the ability to rotate. After the slewing unit is attached, three other parts are attached on top of it that is the working arm or long horizontal jib, a short counter jib and a cab where the operator can operate the crane from.
The working arm of the crane is the part that does all the heavy lifting. It is the one that lifts and the one the load is attached to. The counter jib is also important. It usually caries concrete blocks which serve as the counterweight for the working arm while the load is suspended on it. Tower Cranes usually have an operator’s cab. This is usually the place the operator controls the crane from. Some Tower cranes do not have an operator’s cab. In their case, they can be controlled using remote which the operator does from the ground. There is also a lifting hook which is attached to the working arm. The lifting hook of the crane is operated by electric motors which manipulate the wire ropes attached to the hook.
Types of Tower Cranes
There are only two types of tower cranes. We have the Static Tower crane and the Mobile Tower crane. Both of them come in different types, working mechanisms, configurations, and settings.
The configuration of tower cranes can be classified into two. Tower cranes can either have a fixed tower or a slewing tower.
- For tower cranes with fixed towers, the slewing ring of the fixed tower is located at the top of the crane.
- Tower cranes with Slewing towers have their slewing ring attached to the base of the tower. Towers can further be grouped into mono towers, telescopic towers, outer towers and inner towers.
Mono Towers: Mono towers are towers where the jib is supported by only one tower structure. The tower can either be slewing or fixed. Also, these type of towers have provisions that allow them to be modified or extended.
Telescopic Towers: They are unique and very useful. Their tower structure is made of two sections which are intertwined into one another. The two of them are designed in such a way that the height of the tower crane can easily be altered or modified without any need to partially dismantle and reassemble parts to the tower.
Telescopic Towers are also referred to as self-erecting towers and usually have slewing tower types. This kind of towers is commonly found on mobile cranes and some rail-mounted ones.
Inner towers and Outer towers: Inner towers and Outer towers can easily be identified if the tower in question has its jib on a slewing or fixed tower but is supported by a fixed outer tower at the top. This kind of towers can easily be modified if the provisions are made upon its erection or assemblage.
Just like Tower configurations, the jibs on cranes also have different configurations. The configurations are luffing jibs; it has some custom configurations of its own, horizontal trolley jibs, and the articulated jibs. Each of them has special situations where they can be employed.
- Horizontal Trolley Jibs
Horizontal trolley jibs: A-frame types: The horizontal trolley jibs are jibs that are held in slightly raise or horizontal position by ropes or tie bars which are connected to a frame-shaped in the form of the letter “A” at the top of the crane. The lifting hook of this kind of jib is attached to a trolley from which it is suspended.
Horizontal Trolley jibs: Flat-top types: This is another type of Horizontal trolley jib that is directly connected to the top of the tower crane without the use of ropes or tie bars. Also, it does not have any “A” frame. Because of this, it is not as tall as the A-frame jibs. The lifting hook on the flat top horizontal trolley jib is also attached to a trolley.
- Luffing Jibs: This kind of jib is pivoted near its base or its end. These jibs are supported or held by luffing cables. They do not have trolley motors so the hook and hoist rope is kept in a compartment at the head of the jib. For movement, the angle the jib is inclined is tweaked which in turn alters the radius of the hook.
Fixed luffing jibs: This kind of luffing jib is mounted on pivots at their base like the normal luffing jibs. However, they are held by luffing cables at a fixed angle of inclination which cannot be modified. This is not the case in normal luffing cranes. Also, the radius of the hook cannot be tweaked or changed like in the Luffing jibs and its hook is attached to a trolley and sometimes a saddle which is attached to the jib.
Rear Pivoted Luffing Jibs: has its located at the top of the jib which is just below the center of the tower.
- Articulated jibs: The articulated jibs have their pivot around the middle of the jib. They are usually seen on towers that can also have horizontal trolley jibs mounted on them.
Mobile Units of Tower Cranes
The mobile unit on which tower cranes are mounted has a different configuration. Tower cranes can be truck-mounted, wheel mounted or crawler mounted.
- Truck Mounted: As the name implies, there are some tower cranes that are partially static. However, they can be modified into mobile tower cranes buy mounting them on the chassis of trucks or Lorries.
The type of tower cranes in this category has its outriggers extended. The extended outriggers give balance and support to the tower crane when it is operated.
- Wheel Mounted: these kind of tower cranes are not self-propelling like the truck-mounted ones. These type of cranes are usually moved by towing vehicles. They also have jacks and outriggers or stabilizers which provides balance to the crane.
- Crawler Mounted: Crawler Mounted Tower cranes are of two types. They are classified into these two types based on the type of base the tower crane is mounted on.
Twin track crawler mounted type: This type of crawler mounted tower crane are mounted on a pair of crawler tracks. It is necessary that the cranes mounted on this kind of mount have their outriggers or stabilizers extended and their jacks set to provide balance when lifting or carrying loads.
Straddle-type Crawler mounted type: This is the other type of crawler Mounted tower crane and it is mounted on four well-spaced crawler tracks. Each of the four crawler tracks all has adjustable heights.
The two types of crawler mounted tower cranes are always set firm when operated to prevent accidents. While this is good, it also means that cranes that are crawler mounted do not show the kind of mobility truck mounted tower cranes display.
The importance of making a tower crane mobile cannot be overlooked. This is because it saves time that would have been used in dismantling the crane and assembling at another spot it is needed on a construction site.
This is safety devices which are installed on all tower cranes and automatically operates itself. it main function is to prevent damage to the tower crane if the operator makes an error.
Monthly maintenance and inspection of Tower cranes
- The maintenance and inspection personnel should ensure they properly document their work and findings.
- The maintenance and inspection of tower crane(s) need to be done at least once every month.
- Each maintenance and inspection record must be signed by the technician who carried out the inspection
- The record, if applicable, should include:
- Background details like the date the inspection was carried out, the crane model, the wind speed, the name of the crane’s owner, the workplace address, etc.
- Results of the inspection and the maintenance or repair work that was carried out have to be logged with detailed information about the condition of the parts that were inspected. If the repair work required has not been carried out, it should also be in the record.
Before a tower crane is operated for a shift or at the start of a working day, the operator or the personnel trained for the purpose should ensure he or she carries out the following routine checks on the Tower Crane as appropriate:
- Run the checks stated in the manufacturer’s instruction manual
- Examine the automatic safe load indicator and be sure it is set correctly and fitted with the right jib length and hoist rope
- Also, check the visual indicator and be sure that the fixed load-radius scale is the correct and appropriate one.
- Check that the crane level indicator is working
- Also, inspect the visual and audio alarming devices on the crane
- Examine the working space limiter or anti-collision system of the crane
- Inspect the security of the counterweight and be sure it is inoperable and working conditions
- Inspect the lubrication, fuel level and oil level of the crane
- Look for signs of wear or cracks on the hook, rope, anchorages and the rope’s terminal fittings
- Check for loose bolts, nuts, and pins.
- Inspect the air receivers and be sure that all water is drained from it
- Inspect the jib structure for any signs of damage
- Check the condition of the tires of the tower crane if it is a mobile crane
- Inspect the hydraulic system of the tower crane if applicable
- Check for hydraulic oil and brake fluid leakage
- Ensure that all rail clamps are released before operating
- Examine all the switches in the cab and be sure they are working
- If the tower crane has a track, ensure that it is clear of obstruction
- Check the anemometer and be sure it is working. If it reads a wind speed higher than the one recommended in the manufacturers manual, the tower crane should not be operated
- Check the travel warning device and be sure it is working
- Check all Limiting switches stated in the manufacturer’s manual and be sure they are in good working conditions.