Shipping containers or freight containers can be traced back to 1956. Since then, they have been inseparable parts of global trade, helping transport goods overseas. Many different shapes and sizes of shipping containers are available in the market. Understanding the anatomy of shipping containers is important, which means studying their internal structures to understand how they work. These structures’ sturdiness, functionality, and safety are ensured by their key constituents, such as corner castings and twist locks. 

In this blog, we will discuss the anatomy of a shipping container, with a particular focus on corner castings and twist locks and their practical implications and challenges. 

What is the anatomy of shipping containers?

Studying the anatomy of a shipping container will help you to know what factors you should consider while buying a shipping container for your goods. Shipping containers are durable and well structured, along with a weather-resistant framework. Many components contribute to their structural integrity. Let’s explore those structures in this container anatomy guide: 

• Rear end: The rear end consists of the structure at the end of the door, which includes the rear top rail, bottom rail, and corner posts, creating a door opening. The rear container consists of two doors, which are hinges, door handles, container door stops, a locking bar, and holdback cords. 
• Front end: The front end structure is in front or opposite the door. This part includes the top rail, bottom rail, and front corner posts interlinked to the corner castings. This structure assists the front wall standing still and is called the front panel. 
• Sidewalls: The front and rear frames connect to the top and bottom and join the corner castings, ultimately constituting the structure of containers. Side panels, also called side panels, connect to the side walls. 
• Roof panel: Corrugated steel panels are combined with the top, rear, and front-end rails. Extension plates with corner protection plates are at every corner. Some markings, such as the container number, warning labels, and super heavy stickers, are present. 
• Understructure: Bottom side rails, front and rear sills, forklift pockets, cross members, threshold plate, and center rail are some constituents of the understructure. The floor is mainly made up of plywood that is secured with screws and supported by bottom side rails, cross members, and forklift pockets. 

What are corner castings? 

Corner castings play a very important role in the anatomy of a shipping container. They are located at the corner in the form of metal blocks that help connect the equipment for lifting, stacking, and thrashing shipping containers. The shipping container corner castings are the fundamental infrastructural element that helps to maintain the stability of shipping containers, along with their connectivity with vehicles, custom frames, static structures, and other shipping containers. Bridge clamps and twisted locks maintain this type of connection with other structures. They are also called shipping container blocks and are used in eight sets to ensure secure stacking vertically and horizontally. 

Features of shipping corner castings

• Corner castings in containers are available on ISO 6346 shipping containers with three holes, one on each side. 
• All corner posts are built with 10 mm high-tensile steel and must be repaired using strict methods according to IICL5 repair criteria. 
• Corner castings are essential for both repair and construction. 
• These structures are blendable, and they can inculcate any type of structure.

Standards and specifications of corner casting

Some standards are decided according to the ISO (International Organisation of Standardisation) 1161 standards to ensure container transport security. ISO 1161 describes the standard size, strength specification, and functional needs of corner castings used in shipping containers, which also comply with ISO 668 and ISO 496, except for the ones for air transport. The standard corner casting dimension is 178mm x 162mm x 118mm. Companies always search for ISO 1161 certification, as this includes all the compliance and measurement related to corner castings. 

How do corner castings function in shipping containers? 

Corner casting ensures stability while stacking the different types of shipping containers. When the containers are heaped over each other, the corner casting helps to align one container over the other. Also, corner casting uniformly distributes the weight of containers to prevent accidents or falls. Cranes, spreaders, and forklifts lift the containers by connecting their hooks in corner castings.

What are twist locks, and how do they work? 

Twist locks, the inseparable parts of a shipping container’s anatomy, form the basis of transporting goods from one place to another in the form of mechanical locks. These flexible locking devices consist of a twisted cylindrical pin to secure or release it. The rope helps to secure the containers to the modes of transportation they are carried through and also to other containers. 

These cylindrical devices consist of a metal pin, threads, and rotating mechanisms at the end and are employed to tie loads by various means of transport. The twisted lock function in containers is safe when stacked on ships, trains, or trucks. It is the inseparable connection between the containers and transport. Also, it uniformizes the process of loading and unloading. 

What are the different types of twist locks used in shipping?

The best part of twist locks in shipping is that they can be customized as per requirements; this creates a variety of locks available in the market. Let’s understand the twist locks type and uses in brief: 

• Standard twist locks that are used for regular container transport. 
• Tank twist locks prevent liquid containers from any type of accident. 
• Rail twist locks are used in railways to secure the goods carried. 
• Hydraulic twist locks employ hydraulic pressure to fasten the goods tighter. 
• Manual twist locks are the most commonly used by hand to fasten the goods. 
• Then comes semi-automatic twisted locks that secure twisted locks that automatically open up when the containers are put in the transport yet require some human effort. 
• As the name suggests, fully automated locks can be locked and unlocked automatically, making them suitable for bulky cargo handling. Some board systems can also operate them. 

How does the twist lock mechanism interact with corner castings? 

Twisted locks and corner casting are very important parts of the anatomy of a shipping container. Together, they create a standard connector that is enough to secure your containers. Their main task is to connect the containers properly to the modes of transport, lock the container, and allow lifters such as cranes and forklifts to lift them properly. 

Corner casting, the structural element at the corners, is designed in an easy hat that can receive the twist locks while stocking the container. Corner casting installation in the shipping container ensures safety. They both also help stack the containers vertically by over six or more. During loading, cranes insert their hooks in the corner castings and then twist the lock, ensuring double safety from shifting, sliding, or falling. Corner castings and twist locks are standardized elements for intermodal transportation, and they can be used on ships, rails, and trucks to ensure safe container handling.

Practical applications and examples

Some practical implications will help you understand how important these both as a part of the anatomy of a shipping container: 

1. Security traveling through high seas: When huge containers with bulky goods are traveling through rough seas, corner castings and twist locks ensure their safety by not letting them fall, shift, or slide at any costs as they tied along with corner castings and twist locks locking mechanism ensures proper locking of the containers. During heavy storms, these structures prevent any kind of loss of goods. 
2. Efficient port operations: Containers are frequently loaded and unloaded in busy ports like Shanghai. Because of this structure’s standard use, this process becomes faster and more efficient by decreasing the dwell time and reducing the number of containers that can cause congestion at the ports.
3. Easy intermodal transfer: Corner castings and twist locks make transferring goods from ships to trains to trucks very easy and smooth. For example, when the goods are from the port of Los Angeles, the same twist locks can be utilized to fasten the containers. 
4. Cost efficiency: As discussed, corner castings and twist locks make stacking easier and allow more containers to be stacked on the ship. This means ships can now easily carry more containers at a time, reducing costs. 

What maintenance is required for twist locks and corner castings

The two essential constituents of the anatomy of a shipping container, corner castings and twist locks, have some challenges that can occur while handling them, like manual sprains or injuries, which are essential to understand. Manual handling of twist locks involves risk to labor, which also affects the worker’s efficiency and container terminal operations due to their heavy weight and complex structure. 

Corrosion of corner castings and twisted locks is a significant challenge that can be prevented by regular maintenance and re-panting them at intervals. The alignment of the corner castings and twisted locks is necessary if you want proper stacking and safety. A minor displacement can cause a huge loss. Prevent sharp corners, often referred to as stress raisers, as they can cause tears and cracking. Also, the fillets of the radii 3 to 25 mm are used as a standardized design. Be patient with the twisted locks, as they take time to get locked properly. Also, don’t use heavy locks that the workers can’t manage. Smart containers can be used to automate the locking process. 

Every person in the shipping industry needs to understand the anatomy of shipping containers to understand their mechanism and what to look at first while buying one. The floor, sidewalls, and roof play a very important role, but the shipping containers’ twisted locks and corner castings are safety guards. They ensure a secure journey as they help fasten the container properly with other containers and the transport. You must ensure their quality and strength meet your cargo requirements. 

LOTUS Containers offers containers for sale, purchase, and lease for used and new shipping containers. They also support your projects by developing flexibility in container solutions, logistics, and intermodal transportation.