Container sizes. The sizes of containers depend mainly on their external dimensions, so that, for example, a container can be an ISO standard “Series 1 Freight container, Rating 1AA” with external dimensions of 40 feet (length) x 8 feet (width) x 8 feet 6 inches (height). The dimensions are used in either imperial or metric units. Although much of the world has become metricated, the “box” or container is still referred to by its imperial units, for example, a FEU is a forty-foot equivalent unit (of space occupied).
The “maximum gross weight” (MGW) is also significant as a size of the total mass of the container and its contents. For example, for the AA rating container, the MGW is 30.8 tomes. This “rating” (the maximum permitted combined mass of the container and its contents) will be made up of the “tare mass” and the “payload”.
The “tare mass” or “tare weight” is the mass of the empty container including all fittings and appliances associated with a particular type of container in its normal operating condition, e.g., for a mechanically refrigerated container, with its refrigerating equipment installed and full of fuel, if necessary. The “payload” is the maximum permitted mass of contents.
Carriers may advertise their containers with the minimum interior dimensions, door dimensions, cubic capacity and maximum tare mass. This may assist shippers or other users with planning their shipments. For example, a liner company may include in the description of the containers in its fleets the following details:
General Purpose container: 40 feet x 8 feet x 8 feet 6 inches (12.2m x 2.4m x 2.6m) with minimum interior dimensions of 12.0 15m x 2.337m x 2.362m. Door dimensions of 2.335m x 2.260m, a cubic capacity of 66.3 cubic metres and a maximum tare weight of 3.730 tonnes.
Although there are ISO standards for dimensions, many carriers have moved away from standardised sizes for reasons of their own, some of which may be related to marketing promotion. This is mainly the consequence in the United States where containers can be 35 feet, 45 feet, 48 feet and 52 feet in length.
The height of the containers is set by the ISO as 8 feet or 8 feet 6 inches, but there also“high-cube containers” have become the norm.
Container types. A freight container is defined in the ISO standards as:
“an article of transport equipment:
(a) of a permanent character and accordingly strong enough to be suitable for repeated use;
(b) specially designed to facilitate the carriage of goods, by one or more modes of transport, without intermediate reloading;
(c) fitted with devices permitting its ready handling, particularly its transfer from one mode of transport to another;
(d) so designed as to be easy to fill and empty;
(e) having an internal volume of 1 cubic meter or more.”
An “ISO freight container is one which complies with all relevant ISO container standards in existence at the time of its manufacture.
Container types are grouped and the groups are subdivided according to the mode of transport, categories of cargo to be carried and the physical characteristics of the container. General cargo containers are those which are not specially intended for a particular type of cargo. The group of general cargo containers is subdivided into types in which different loading and emptying methods may be used and also into different types of structure. Specific cargo containers are used for cargoes, which are sensitive to temperature, for liquids and gases, for dry bulk cargoes, and for special cargoes such as motor vehicles and livestock. These are sometimes known as “specials”.
The ISO also allocate type codes to containers. The type code consists of two numbers, the first being the category of container (for example, the first zero in “00” indicates the container is a general purpose container). The type code is marked on the side or endplate of the container beneath the owner code and serial number (see “BIG-Code”) and immediately after the size code. For example, a container may be marked:
OCLU 024263 0
This indicates that the container owner is the Overseas Container Line, the serial number is 024263 with a check digit of 0, the country of ownership is the United Kingdom, the size is 20 feet and the type is “00”, which is a general purpose container with openings at one or both ends.
Some other ISO type codes are given below:
Type / General description of container
01 / General purpose container with openings at one or both ends plus full openings on one or both sides.
02 / General purpose container with openings at one or both ends plus partial openings on one or both sides.
03 / General purpose container with openings at one or both ends plus openings at one or both sides plus opening roof.
10 / Closed vented container with passive vents at upper part of cargo space; the total vent crosssectional area less than 25 sq. cm. per meter of nominal container length.
20 / Thermally insulated container.
30 / Thermal refrigerated container with expendable refrigerant.
31 / Thermal refrigerated container with mechanical refrigeration. (These types are called “reefer containers”.)
40 / Thermal container refrigerated and/or heated with removable, externally located equipment.
50 / Open top container with openings at one or both ends.
60 / Platform container. This is a loadable platform having no superstructure.
61 / Platform container with incomplete superstructure but complete and fixed ends. (Platform based containers are also called “flat racks”.)
70 / Tank container for non-dangerous liquids having a test pressure of 0.45 bar. (Note: 1 bar is 1000 kilograms/sq. cm.) 73 Tank container for, dangerous liquids.
77 / Tank container for dangerous gases.
80 / Dry bulk container with gravity discharge system.
81 / Dry bulk container with pressure discharge system.
85 / Specialist livestock container.
86 / Specialist automobile (car) container.
Some ISO types are used for air transport and some for intermodal transport. These have type numbers 90 to 99.