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A Guide to Container Sizes and Stacking in Maritime Shipping

Writer's picture: AdminAdmin

Updated: Jan 6

In the year 2022, over 230 million containers were shipped globally, showcasing the immense scale of cargo transport via containerships. These vessels have transformed intermodal transportation, with standard container sizes of 20-foot and 40-foot units (TEUs) being the most commonly used for efficient shipping.


A massive container ship loaded with colorful shipping containers, navigating through calm blue waters
A massive cargo ship, stacked high with multicolored shipping containers, sails through the vibrant blue waters of a bustling port filled with cranes and docked ships in the background.

The introduction of shipping container dimensions has greatly boosted container ship capacity. This has allowed for the transport of goods on a huge scale. The biggest containerships can now carry over 24,000 TEUs. This shows the amazing growth in global trade containers and shipping efficiency.


Containerships have changed a lot over time. Different classes and sizes have come out to meet the growing need for cargo transport. From the first class in the 1960s with 1,000 TEUs to the Ultra Large Containerships (ULCV) in 2013 with over 18,000 TEUs, the industry has seen huge improvements in ship design and capacity.


Key Takeaways

  • Standardized container sizes, such as 20-foot and 40-foot units, have revolutionized intermodal transportation and increased shipping efficiency.

  • The largest containerships can carry over 24,000 TEUs, showcasing the incredible advancements in global trade containers and shipping capacity.

  • Containerships have evolved over the years, with various classes and sizes emerging to accommodate the growing demand for cargo transportation.

  • Efficient stacking techniques and securing methods ensure the safe and stable transport of containers on containerships.

  • Understanding stacking weight is crucial for maintaining the structural integrity of containerships and preventing accidents during cargo transport. 


ISO Containers Dimensions
Illustration depicting size variations of shipping containers, including dimensions for 10 ft, 20 ft, and 40 ft lengths.

The Evolution of Container Ships

The container shipping industry has seen a remarkable transformation since the introduction of the 'Ideal X' in 1955. This vessel, carrying nearly 60 containers from New Jersey to Texas, marked the beginning of a revolution in cargo operations and maritime logistics.


Over the years, technological advancements have significantly grown container ships. Today, vessels can carry thousands of containers. These developments have greatly increased efficiency and reduced carbon emissions in the shipping industry.


The First Container Vessel: 'Ideal X'

The Ideal X, a converted World War II tanker, was the first container ship. Though it carried a modest load, her voyage initiated a new era in the shipping industry.


Technological Advancements in Container Shipping

Since the Ideal X, container ships have dramatically evolved in size, capacity, and technology. Key milestones include:

  • Diesel propulsion became typical for container ships after 1990, improving fuel efficiency.

  • Container ships now travel at speeds ranging from 16 to 25 knots (30–46 km/h).

  • The largest ships can carry over 24,000 TEU (twenty-foot equivalent units) as of 2023.


These advancements have led to a big drop in shipping time by 84% and costs by 35%. In 2009, almost one-quarter of the world's dry cargo was shipped by container. This equated to an estimated 125 million TEU or 1.19 billion tonnes of cargo.


Vessel Category

Capacity (TEU)

Feeder

Under 3,000

Panamax

4,000 - 5,000

Post-Panamax

5,000 - 12,000

Suezmax

12,000

Post-Suezmax

18,000

Ultra Large (ULCV)

more than 18,000


A semi-loaded container ship in the ocean
A cargo ship sails through the open sea under a partly cloudy sky, carrying rows of large shipping containers on its deck.

Standard Container Sizes and Types

Containers vary in size and type to meet the diverse needs of global trade. Approximately 90% of the world's cargo is transported by ships, with dry containers being the most common, making up 90% of sea freight. Understanding the different container sizes and types is crucial for optimizing shipping efficiency and ensuring the safe transport of goods.



20-foot Containers (1 TEU)

20-foot containers, also known as 1 TEU (Twenty-foot Equivalent Unit), are the smallest standard container size. These freight container sizes are ideal for heavy cargo like minerals, metal, and machinery. With a typical height of 8 feet and 6 inches, 20-foot containers offer a compact solution for shipping dense, heavy goods.


40-foot Containers (2 TEU)

40-foot containers, or 1 FFE (Forty-foot Equivalent Unit), are designed for more cargo such as furniture and steel pipes. These shipping container types offer twice the capacity of 20-foot containers, making them a popular choice for many industries. The standard height of 40-foot containers is same as the 20-foot containers (i.e 8 feet and 6 inches).


High Cube Containers

High Cube containers (also known as Hi-Cube containers), are taller than standard containers, with a height of 9 feet and 6 inches. These container sizes are suitable for lighter, more voluminous cargo, as the increased height allows for more storage space without exceeding weight limits. 40-foot High Cube containers are a popular choice for many shippers.



Specialized Containers

In addition to standard dry containers, there are several specialized container types designed for specific cargo needs:

  • Refrigerated containers (reefers) come in various sizes, including 20-foot, 40-foot, 40HC, and 45HC, and offer different temperature ranges for perishable goods. Their controlled atmosphere containers help slow down ripening and preserve perishable produce during transit.

  • Open Top containers have a removable roof for loading tall or bulky cargo.

  • Flat Racks and Platforms are used for oversized or odd-shaped cargo that doesn't fit in standard containers.

  • Tank containers are designed for the safe transport of liquids and gases.


Efficiency in Container Ship Loading

Container ships are loaded with great care and precision. They use advanced technology and are built with special holds. These holds are divided into bays with cell guides.


This setup makes it easy and fast to load 20 and 40-foot containers. It helps in handling and stacking containers well. This way, the ship can carry more cargo safely.


Container handling is thus improved, making the most of the ship's space. It ensures that all cargo is safe during transport.



Planning is the first step in shipping containers. It involves considering the weight, size, destination, and stability of the ship. Advanced software helps by providing real-time data on weather, sea routes, and vessel capacity.


Once the plan is set, loading begins. Specialized cranes, equipped with anti-sway systems and remote control, lift containers onto the deck. These cranes ensure efficient cargo container stacking.


Cell Guides and Cellular Ships

Cell guides are a key feature of modern container ships, enabling secure and efficient container stacking. These vertical guides create a cellular structure, ensuring containers are properly aligned and secured. The use of cell guides maximizes ship capacity and reduces cargo shifting or damage risks during transit.


A containership's cell guide (inside the cargo hold)
A cell guide (highlighted in yellow, for illustration purposes)

Hatch Covers and Ship Stability

Hatch covers are crucial for maintaining ship stability and safety during loading and transport. These large, hydraulically operated covers seal the ship's holds, protecting cargo from elements and preventing water ingress. Modern ships also have advanced stability systems, monitoring balance during loading to ensure stability and safety.


Close-up view of a containership's hatch cover featuring padeyes and raised sockets
Close-up view of a containership's hatch cover featuring padeyes and raised sockets

Geared vs Gearless Container Ships

In the realm of container ship logistics, vessels are categorized as either geared or gearless. This distinction significantly impacts the flexibility and efficiency of maritime trade operations. Geared ships, also known as lift-on/lift-off (LoLo) vessels, are equipped with their own cranes. This allows them to load and unload containers independently. Such a feature enables geared ships to visit ports lacking the necessary infrastructure, such as quayside cranes, thus expanding their potential reach in the global shipping network.


Conversely, gearless ships rely on the port's equipment for container handling. As port infrastructure improves worldwide, gearless ships are becoming more prevalent. These vessels can carry a higher number of containers, as the absence of onboard cranes frees up valuable deck space. Gearless ships are well-suited for high-volume trade routes between major ports, where efficient container ship stacking and quick turnaround times are critical.


The choice between geared and gearless ships hinges on various factors, including the ports of call, cargo type, and the shipping company's operational strategies. Some key statistics underscore the significance of container shipping in global maritime trade:

  • Around 90% of non-bulk cargo worldwide is transported by container ships.

  • In 2009, almost one-quarter of the world's dry cargo was shipped by container, amounting to an estimated 125 million TEU or 1.19 billion tonnes worth of cargo.

  • The container-carrying capacity of ships has increased by more than 1200% compared to 1968.


The following table compares the characteristics of geared and gearless container ships:

Characteristic

Geared Ships

Gearless Ships

Onboard cranes

Yes

No

Port flexibility

High

Limited

Cargo capacity

Lower

Higher

Ideal routes

Diverse, including smaller ports

High-volume, major ports


An aerial view of a busy port, showcasing container ships with stacked cargo containers in vibrant colors, some geared with cranes for loading, others gearless

Refrigerated Containers for Perishable Goods

Reefer containers play a key role in cold chain logistics. They are used to ship perishable cargo. These containers keep the temperature and humidity just right.


This helps keep sensitive goods fresh during long trips. It's all about keeping the cargo in the best condition possible.


Temperature-Controlled Containers

The cooling system of a reefer container comprises a compressor, evaporator fans, a controller, and air vents. These components collaborate to uphold the desired temperature and humidity levels within the container. Advanced sensors enable real-time monitoring and adjustment of these conditions, ensuring the optimal preservation of cargo.


Reefer containers are available in various types to meet specific needs:

  • Closed reefer: Standard containers with integrated heating and cooling units

  • Modified/Controlled Atmosphere (MA/CA): Enhanced insulation for consistent atmosphere inside the container

  • Automatic Fresh Air Management Containers (AFAM): Sophisticated sensors for air exchange rate adjustment


A bustling shipping port scene showcasing multiple refrigerated containers, also known as reefer containers, stacked on a cargo ship
Cargo containers are being loaded onto a ship while workers handle fresh produce in crates at a busy port, showcasing the integration of shipping and agriculture industries.

Controlled Atmosphere Containers

For extremely sensitive perishable cargo, controlled atmosphere containers provide additional protection. These containers regulate temperature and control oxygen, carbon dioxide, and nitrogen levels. By creating an optimal atmosphere, the ripening process of fruits and vegetables can be slowed, extending their shelf life during transit.


When loading a reefer container, it is crucial to follow best practices:

Do's

Don'ts

Set specific temperature and humidity settings

Overload the container (which restricts air flow)

Pre-cool the cargo

Leave gaps that impede proper air circulation

Insure the cargo

Pre-cool the reefer container (to avoid temperature shock on the transported goods)


Special Dimensional Containers

Shipping oversized cargo, out-of-gauge cargo, or project cargo often requires more than standard containers. Special dimensional containers provide tailored solutions for goods that don't fit the conventional mold. They cater to the unique needs of various industries, ensuring efficient and safe transportation.


Open Top Containers

Open top containers are designed for cargo that exceeds standard container heights. They feature a removable roof or tarpaulin cover, facilitating easy loading and unloading of tall or bulky items. Construction, machinery, and aerospace industries frequently use these containers for their specialized shipping needs.


Aerial view of a busy shipping port with various container stacking techniques in action, showcasing colorful shipping containers stacked in different configurations on a large cargo ship and along the dock

Flat Racks

Flat racks are preferred for transporting heavy machinery, construction materials, and other oversized cargo. They have collapsible sides and end walls, offering a flat platform for securing irregular-shaped goods. This versatility makes flat racks a convenient choice for shipping out-of-gauge cargo across various sectors.

Flat racks come in two standard sizes:


Flat Rack Size

Length

Width

Height

20-foot

20 feet

8 feet

8.5 feet

40-foot

40 feet

8 feet

8.5 feet


Platforms

Platforms, or bolsters, are flatbeds without walls or a roof. They are great for moving project cargo that doesn't fit in other containers. Their open design lets you secure and transport odd-shaped goods easily.


This makes platforms a top choice for industries with complex logistics. The global economy's growth has boosted demand for special containers. These containers provide customized solutions for oversized cargo.


They help businesses transport their goods efficiently and safely. They meet the unique needs of different industries, ensuring goods are moved safely.


Containers, Sizes and Stacking Techniques

Efficient container stacking is vital for maximizing ship capacity and ensuring vessel stability. It requires careful consideration of container weight, size, and destination. This ensures optimal use of available space onboard containerships. Effective stacking techniques significantly improve operational efficiency and reduce transportation costs.



Optimizing Ship Capacity

Strategic container stacking is essential for optimizing ship capacity. ISO guidelines permit stacking up to nine containers on top of one another, depending on the maximum weight the bottom container can withstand. The ship's structural strength also plays a crucial role in determining weight limits.


Super cargo ships, like the Evergreen Ever Ace, can carry over 24,000 twenty-foot shipping containers. Stacks can reach ten to twelve boxes high. For safety, it's recommended to stack eight containers, though higher stacks are possible in some cases.


Container Stacking Challenges

Container stacking poses significant challenges, including ensuring safety and stability. The weight of containers is a critical factor. An empty 40-foot container weighs 3,740 kg, while a 20-foot container weighs 2,250 kg. These weights dictate the cargo capacity of each container.


Proper labeling and documentation of containers are also crucial. Containers have unique size and type codes to avoid confusion. Each container has a Container Safety Convention plate on the left-hand door, indicating the ship's maximum weight.


Innovative Stacking Solutions

Various innovative solutions have been developed to overcome container stacking challenges. Advanced software for load planning optimizes container placement based on weight, size, and destination. Lashing systems secure containers in place, reducing the risk of shifting during transit.


A colossal cargo ship navigating through calm waters, loaded with oversized containers featuring unusual shapes and vibrant colors
A massive container ship navigates through open waters under a clear blue sky, loaded with multicolored cargo containers, showcasing the bustling world of maritime trade.

Conclusion

The container shipping industry has seen a significant transformation, revolutionizing global trade. It has enabled the efficient transport of goods worldwide. Starting with the humble Ideal X, container ships have grown to carry over 21,000 TEUs. Advances in design, stacking techniques, and port infrastructure have been key to optimizing operations and boosting efficiency.


The future of container shipping is tied to sustainable practices, digitalization, and automation. Smart ports with advanced technologies and streamlined processes will improve cargo handling speed and reliability. The growth of ship sizes and the challenges of container stacking, like the risk of losing containers at sea, must be tackled. This is to ensure cargo safety and stability.


Sustainable shipping practices, like cleaner fuels, optimized routes, and eco-friendly port operations, are critical. They will help reduce the industry's environmental impact. By embracing innovative solutions and working together, the container shipping sector can build a more efficient, resilient, and green future. As the world depends on the smooth movement of goods, container shipping will remain essential for the global economy's growth.


FAQ

What percentage of the world's non-bulk cargo is transported by container ships?

Container ships are pivotal in global trade, transporting approximately 90% of the world's non-bulk cargo. They are essential for the smooth functioning of international logistics.


How many twenty-foot equivalent units (TEUs) can the largest containerships carry?

The largest containerships have the capacity to carry over 24,000 twenty-foot equivalent units (TEUs). This includes 1 TEU for a 20-foot container and 2 TEU for a 40-foot container.


What was the name of the first container vessel, and how many containers did it carry?

The Ideal X was the first container vessel. She transported just under 60 containers from New Jersey to Texas in 1955. This marked the start of the container shipping revolution.


What is the most common type of container used in sea freight?

Dry containers dominate sea freight, making up 90% of it. They are available in various sizes, including 20-foot (1 TEU), 40-foot (2 TEU), and 40-foot high cube containers.


How do modern containerships optimize the loading process?

Modern containerships feature bays with cell guides for efficient loading of 20 and 40-foot containers. The hatch covers on the ship's hold enhance stability and safety.


What is the difference between geared and gearless container ships?

Container vessels are categorized as geared or gearless based on crane availability. Geared ships, (also called lift-on/lift-off (LoLo)) vessels, can access ports without cranes. Gearless ships are gaining prominence as port infrastructure improves worldwide.


What infrastructure is crucial for the smooth operation of container terminals?

Efficient container shipping relies on cranes, reach stackers, and van carriers at ports. Hinterland connectivity via road, rail, and waterways, along with customs facilities, are also vital for terminal operations.


What are the advantages of controlled atmosphere containers for perishable goods?

Controlled atmosphere containers enhance refrigerated transport by regulating internal conditions to slow down ripening of perishable cargo. This preserves perishable goods during long-distance journeys, extending their shelf life.


What are the challenges in container stacking, and how are they addressed?

Stacking challenges involve considering container weight, size, and destination. To address these, advanced software for load planning and lashing systems are employed. These innovations optimize stacking and enhance container shipping efficiency.


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