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Marine Guide

Straddle Carriers [ULTIMATE GUIDE]

Last updated on July 22nd, 2021

A straddle carrier or also known as a straddle truck is a lifting apparatus. Straddle carriers helps in lifting the containers for stacking them on the terminals. It ensures easy and smooth movement of containers from one place to another. The working of a straddle carrier is different from that of a conventional truck which carries the load on top of itself but a straddle carrier carries the load by straddling it underneath. It is operated by a driver and there is no external assistance to the process.

Waterway or maritime transportation has a lot of influence over global trade. Almost 90% of the global trade is carried out through waterways using ships, large vessels, and container ships.

Mainly ships and vessels are used for transportation because they are capable of carrying almost all kinds of goods. Ships are loaded with containers of standard dimension to carry these goods. It can carry electronic gadgets as well as food and beverages and more such merchandise.

We know that the transportation part is done by the ships but there must be equipment to load and unload goods from the vessels. Thus, ports and terminals are equipped with various facilities to conduct this work. There is equipment like gangways, gantry cranes, stacker cranes, and several such types of equipment. Apart from this machinery, there is a freight-carrying vehicle called a straddle carrier.

In this article, we are going to take a look at all the necessary characteristics and features related to the straddle carriers.

What is a Straddle Carrier?

The Straddle carrier is a machine used for carrying containers and stacking them. It is important machinery needed at the ports and terminals, without which it becomes really difficult to move the containers from one place to another in minimum time.

It can be used for loading and unloading without the use of cranes or forklifts. As we know, a lot of ships are being loaded and unloaded daily as the shipping industry is very vast and busy. Hence, all the major ports are well equipped with modernized machinery to have a fast and safe process of cargo shipping.

Straddle carriers are one of those pieces of equipment that are widely used for loading-unloading and container movement purposes.

Straddle carriers are usually very large but for smaller work, mini-straddle carriers are also built.  There are other different types of straddle carriers also.

Straddle carriers are often compared to conventional trucks. Let us first know what conventional trucks are. Conventional trucks are vehicles that carry containers and are operated by a driver. The basic difference between them is the way they carry the container.

A conventional truck carries the container on the top but the straddle track carries a container in between its upper and lower surface and it moves the container by straddling it. This way of straddling the container makes it easy to stack the container one over the other.

Straddle carriers are very useful at the ports as they do the work of loading and unloading in a very short period. They carry the containers and move them to the terminal or depot and stack them. As of the large ship traffic at the port, straddle carriers have most of the work to do for quick and easy container movements.

Also read: Container Depot: Functions, Uses & Design

Design of  a Straddle Carrier

Straddle Carrier Carrying a Container

Straddle Carrier Carrying a Container

The straddle carrier consists of four long vertical bar-like structures. These four bars are like the pillars of the carrier. The spreader is placed on the top of the carrier and conducts the work of lifting the containers.

Then there is a lifting assembly that’s present on the top and it performs the telescopic spreader process. This means that the lifting assembly can adjust according to the height and can easily slide from up and down.

At the top, there is a driver’s cabin which is built outside the four vertical frames. The reason for constructing it outside of the main body is to get a proper view of the front part and as well as of the rear side. It is also safe for the driver and less fatal than the cabin being placed inside the main body of the carrier. A stairway is also present along with the height of the carrier to provide a safe way to the driver’s cabin and to the machinery platform that is located on the extreme top of the carrier. The cabin is made up of large glass for all-around visibility.

The vertical frame is made up of steel with diagonal braces. The carrier has tires and brakes mechanism for its movement. A total of eight steered wheels are located and hence a good load distribution is observed. A fuel tank is also present in the carrier and is easily accessible as it is present within the carriage beam.

The carriers were previously used for stacking lumber at mills and yards. As it is open from both sides, it can carry more than its weight. This way it got adopted at ports as well for carrying containers.

Also read: Amazing Magdeburg Water Bridge: Longest Navigable Aqueduct in the World

What are the functions of Straddle Carriers?

We know that straddle carriers are very important machinery at the ports and hence let’s look at the functions of the straddle carriers.

The main functions of the straddle carriers are

1) Moving containers from one place to another

When the ship arrives at the deck, it is ready for the transportation and shipping of goods or for unloading of goods that have covered the distance and brought the goods to a particular location. Ships carry all the goods in ISO standard containers. So, these containers need to be unloaded or loaded as per the requirement of the ships.

This work of loading and unloading containers is done by various on-port equipment. The containers first need to be brought to the site of the ship from the terminal or the depot. This is done by straddle carriers. Thus the straddle carriers help in the movement of containers

2) Stacking of containers

The containers are to be stored in depots, ports, or terminals for some time before they are taken to their original destination. Limited space is available for storing the containers and therefore they are stacked one over the other to counter the problem of lack of area. For stacking the containers they must be taken to a height for placing it over another container. The straddle carrier has a telescopic spreader assembly which will help in taking the container up or down.

3) Loading-Unloading vehicles carrying containers

The other main function of the straddle carrier is the loading-unloading of containers from port vehicles. Various vehicles loaded with containers arrive at the port to be unloaded. Train tracks are also constructed at the container depots. To load or unload the trains or trucks, these straddle carriers are used

These are the main functions performed by the straddle carriers. There are many other port machines like reach stackers, empty container handlers, bulk grabs, forklifts, etc. The straddle carrier is the basic machinery because it is flexible and can perform the work that other machineries are designed particularly for.

The structure of the straddle carrier is a little complex. The machinery platform has a hydraulic module, hoist system, brake resistors, switch cabinet, drive unit, and walkway. The hydraulic module supplies hydraulic energy to the spreader, steering cylinders, and brake system. The Drive unit has a high-performance diesel generator set. Brae resistors have both actuated and regulated brakes. The hoist system is related to lifting capacity and maintenance-free three-phase motors.

This was all about the design and structure of the straddle carrier.

Also read: 8 Types Of Gangways – Ultimate Guide

Advantages of Straddle Carriers

Here are some of the advantages of straddle carriers.

1) The chief advantage is that it can carry containers and move them quickly. The speed at which they travel is around 30 km/hr which is more than enough to move around the port.

2) It is quite flexible and hence can stack the container easily.

3) They also have relatively low wheel loads.

4) Straddle carriers can stack the containers by just lifting and straddling them and do not require any kind of support from cranes or forklifts.

5) They can reach tight locations easily.

Disadvantages of Straddle Carriers

As with all the things, a straddle carrier has also some cons.

1) One major disadvantage that goes along with the straddle carrier is that it can lift only 60 t that makes up for two full containers and 60t is divided into 59 long tons and 66 short tons. Thus, it can carry only two containers at a time, and maybe with further innovations, it can carry a minimum of 3 or 4 containers. This weight is also a safety concern for the carrier as it can damage the parts of the carrier.

2) The cost of the straddle carrier is also quite high. The mini- straddle carriers cost up to 300,000 USD. With growing technologies in the making of carriers, the cost will be decreasing but with the capacity of carrying 2 containers, the cost does not appear to be worth it.

3) If the carrier gets damaged due to some reason it will again be costly for the repairing or replacement of the parts.

4) The carrier needs frequent maintenance and repair facilities to keep it in good working condition. This makes it an expensive proposition.

5) The other disadvantage is that it can stack the containers quickly and economically but to a height of 3 to 4 units only. Spreader cranes can reach more height than a straddle carrier and thus giving more space to utilize.

6) The straddle carrier is also not capable of long-distance travel and its use is limited to ports and terminals in short-distance travel areas.

These were some advantages and disadvantages of the straddle carriers. However, many new technologies and innovations are working on improving the performance of the carriers and making them more and more efficient and affordable.

Also read: Major Ports in China

Conclusion

Now that we have discussed straddle carriers in detail, we hope you understand the meaning of the straddle carrier, its design, functions, advantages, and disadvantages of the straddle carrier. Thus, we can conclude that among all the equipment used at the port, the straddle carrier plays an important role.

Straddle carriers can lift the containers and ensure the smooth and safe movement of containers. It can stack the containers. This machinery is very time efficient and reliable. Even automated straddle carriers are being used in many ports for better performance.    

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