Exporters and Importers at some point have probably noticed the distinct markings on shipping containers and many have wondered what they mean; the truth is that not too many people who see these markings know the meaning behind them and their relevance.

These important markings on a container’s door play a vital role in ensuring the safety of the equipment itself and all the personnel involved in its handling.

Understanding ISO Identification Markings (ISO 6346)

The ‘International Standards Organization‘ (ISO) based in Geneva works in the development and implementation of commercial and industrial standards with a global scope.

The ISO standards covering the coding, identification, and marking of intermodal (shipping) containers are known as “ISO 6346”.

Each container has a unique identification number composed of the Owner Code (assigned by BIC – Bureau International des Containers et du Transport Intermodal), the registration number, and a check digit. Following we will describe the main markings:

The Container Number

The main marking on the backdoor is the container number which is an alphanumeric sequence consisting of 7 numbers and 4 letters. Each is issued by the ‘ISO’ under the specific code: ISO6346: 1995(E). It includes:

  • A 3 lettered Owner Code
  • A letter referring to the Equipment Category
    • ‘ U’ means freight container
    • ‘J’ refers to a detachable container or equipment (such as a power unit), and
    • ‘Z’ applies to trailers and chassis
  • A 6-digit Serial Number
  • And, lastly, one number denoting the Check Digit

Tare Weight and Max Gross weight

Tare Weight is the weight of the container when empty and Max Gross is composed of its tare weight plus the maximum payload it can hold. The maximum payload weight is not the same as the maximum weight allowed by the shipping line or intermodal carrier.

Cube Capacity

Cube refers to the maximum volume that a container can hold.

Classification Society label

Every container undergoes standard testing to identify its strength and seaworthiness and this testing is conducted by one of the 50+ classification societies available in the industry. One of their goals is to provide inspection and surveys on shipping containers to check that their structures remain safe for use. A label such as the one below is put on the door of the container and will indicate by which “society” the container has been certified.

Additional Certifications

A container must operate under the Approved Continuous Examination Program (ACEP) or a Periodic Examination Scheme (PES) as soon as it is manufactured. Although the preliminary inspection isn’t vital until five years later. Failure to include an ACEP sticker or Next Examination.

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