Dimensions Container Design Classifications Conex History

Conex Container Characteristics and Types - Boise Idaho

This information was obtained from U.S. Army Field Manual 55-80 Appendix E and provides an overview of the various types of containers that may be available in Boise, Idaho. Army units should realize that in addition to the EDSS family of containers the 20-foot ANSI/ISO container is the standard for unit equipment deployment. Units interested in procuring ANSI/ISO containers may only purchase 20-foot versions. Procurements must be coordinated through the JTMO.

E-1. STANDARDS AND SPECIFICATIONS. The key to intermodalism and use of intermodal containers is the establishment and compliance with commercially approved common standards. These serve to ensure interoperability in the movement of containers between modes and countries. They increase efficiency and effectiveness and foster a seamless flow of cargo.

E-2. INTERNATIONAL STANDARDS. The International Organization for Standardization develops and maintains a series of standards for international freight containers and equipment. The standards ensure that size, structural capabilities, and interoperability are maintained internationally. Table E-1, provides a listing of ANSI/ISO documents relating to intermodal containers.

Table E-1. ANSI/ISO Document for Freight Containers

1496-1 Series 1 Freight Containers - Specifications and Testing - Part 1: General Cargo Containers for General Purposes
1496-2 Series 1 Freight Containers - Specifications and Testing - Part 2: Thermal Containers
1496-3 Series 1 Freight Containers - Specifications and Testing - Part 3: Tank Containers for Liquids, Gases, and Pressurized Dry Bulk
1496-4 Series 1 Freight Containers - Specifications and Testing - Part 4: Non-Pressurized Container for Dry Bulk
1496-5 Series 1 Freight Containers - Specifications and Testing - Part 5: Platform and Platform Based Containers
1496-6 Series 1 Freight Containers - Specifications and Testing - Part 6: International Cargo - Security Devices
668 Series 1 Freight Containers - Classification and Dimensions, and Ratings
830 Freight Containers - Terminology
2308 Hooks for Lifting Containers up to 30 Tons Capacity - Basic Requirements
1161 Series 1 Freight Containers - Corner Fittings, Specifications
3874 Series 1 Freight Containers
6346 Series 1 Freight Containers - Coding, Identification, and Marking
9897 Freight Containers - Container Equipment Data Exchange

ANSI/ISO Technical Committee 104 handles all matters related to freight containers. It has three subcommittees which address specific aspects of general purpose containers. These areas are: dimensions and structural requirements, special purpose containers, and identification and communication (marking and coding, automatic equipment identification, (EDI)).

The US participates in ANSI/ISO under the sponsorship of the American National Standards Institute. ANSI has established Technical Advisory Groups to form consensus positions. DOD participates in ANSI/ISO Technical Committee 104 (TC 104) through the ANSI Technical Advisory Group to ANSI/ISO TC 104. Both the Tank Automotive Research Development and Engineering Center and the MTMC, Transportation Engineering Agency, are members of this group. ANSI delegates attend ANSI/ISO meetings and participate in developing international containerization standards and advancing US interests.

Since there are no established international standards for transportation systems as a whole and because transportation networks vary from country to country, departures from ANSI/ISO standardization occur. Examples of variance in networks include clearances, axle loading, track curvature, and speed limits. Therefore, commercial international intermodal practices adapt to the regional infrastructure. This is also true for military operations involving strategic deployment and sustainment that use intermodal containers. Theater infrastructure and the commercial and military force structure required to support intermodal operations are primary considerations in deciding where and when intermodal containers may be employed.

The Carriage of Dangerous Goods subcommittee of the IMO publishes and maintains the IMDG Code. The code specifies requirements for containers used for carrying hazardous materials, including ammunition and other military explosives. The IMDG requirements are more restrictive than the International Convention for Safe Containers’ requirements. A decision by the Research and Special Programs Administration, adopted many parts of the IMDG Code into Federal regulation. Of particular interest to the Army is Subpart 176.172 of the regulation which specifies the structural serviceability requirements for freight containers used for shipping Class I (explosives) aboard a ship.

E-3. STANDARDIZATION AGREEMENTS. Certain provisions of this FM are the subject of NATO standardization agreements. They are: STANAGs 2828 (Military Pallets, Packing and Containers); 2829 (Material Handling Equipment); 2926 (Procedures for the Use and Handling of Freight Containers for Military Supplies); 2998 (Materials Handling Glossary of Terms and Definitions); and 4062 (Slinging and Tie-Down Facilities for Lifting and Tying Down Military Equipment for Movement by Land and Sea). The aim of NATO standardization is to increase interoperability and interchangeability of materiel and to improve the combined operational effectiveness of the military forces of the Alliance.

E-4. UNITED STATES STANDARDS. Domestic regional intermodal systems develop in response to commercial competition. For example, large US domestic trade volumes have resulted in container transport systems geared to that traffic. Non-ANSI/ISO standard domestic containers were developed to take advantage of increases in allowable highway transport size. US domestic commercial standard containers are generally 48 and 53 feet in length, 8 feet wide, and 8 feet or higher.

Federal standards for intermodal containers are enforced by US laws, rules, and regulations. These often adopt or enact international agreements, conventions, laws, or regulations for the US. The Army must maintain DOD-owned intermodal containers to ANSI/ISO standards IAW US laws and regulations to ensure compatibility and interoperability with the commercial intermodal transportation system. In 1980, the US enacted the International Safe Container Act. The act implements the International Convention for Safe Containers that the US ratified in 1978. The USCG promulgates regulations implementing the act in Title 49, CFR, Parts 450-453.

The USCG can delegate approval authority that containers meet the standards to persons and organizations (who are independent of the influence of container owners), manufacturers, operators, and/or container lessors. A container must be affixed with a CSC safety approval plate confirming its structural serviceability to be used in international transport.

Federal regulations describe general requirements for container inspections, but do not include detailed inspection criteria. Voluntary industry groups, such as the Institute of International Container Lessors, have translated the general CSC requirements into specific inspection criteria to ensure safety in commerce.

Other international standards and Federal regulations also address container condition and set forth additional requirements particularly for Class I explosive materials. The IMO, a specialized agency of the UN, promotes safety in shipping and the prevention of maritime pollution from ships. The US, with technical expertise provided by the USCG, participates in IMO on the Department of State’s Shipping Coordinating Committee. The USCG and the RSPA represent the DOT at IMO subcommittee sessions. The DOT Office of Hazardous Materials Safety is part of RSPA.

E-5. MILITARY SPECIFICATIONS FOR CONTAINERS. The following are descriptions of MILSPECs for dry cargo and refrigerated containers:

  • MIL-C-52661. Containers, Cargo. This specification covers nominal 20 foot containers for transportation, distribution, and storage of military supplies.
  • MIL-C-52788. Container, Refrigerated (8- x 8- x 20-foot) Insulated. This specification covers a nominal 20-foot (length) container equipped with a 9,000 BTU per hour electric motor-driven refrigeration unit powered by a self-contained 10-kW diesel engine generator or external power source.

E-6. CONTAINER SIZES AND TRENDS. Container dimensions and capabilities vary dramatically, depending upon the manufacturer and the target customer. The majority of containers conform to ANSI/ISO specifications. Table E-2, shows the characteristics of the ANSI/ISO 20-and 40-foot containers. These standards allow for some variance. External dimensions are required dimensions; however, internal dimensions and the door opening size are minimum dimensions.

Table E-2. ISO Standard Characteristics

DIMENSIONS (inches) 20-foot ISO 40-foot ISO





96 and 102


96 and 114

Max Gross Weight 52900 pounds 67200 pounds
* Maximum height is external height minus 9.5 inches

The inventory of US-owned commercial containers continues to grow dramatically. The Maritime Administration’s Office of Port and Intermodal Development, which monitors US ownership, estimated this inventory to be approximately 1.8 million containers and 2.6 million TEUs in 1989. Table E-3, provides an example of this growth for the period 1990 to 1991.

Table E-3. Trends in US-Owned Commercial Container Fleet

Container Type 1990 QTY 1991 QTY Percent Change
20' ISO Box 833,042 849,765 2
40' ISO Box 618,966 751,721 21.5
20' Side-Opener 446 1,340 200.5
20' Flatrack 18,728 19,607 4.7
40' Flatrack 14,002 21,073 50.5
20' Reefer 18,739 22,510 20.1
40' Reefer 42,225 54,073 28.1
20' Open Top 30,643 35,584 16.1
40' Open Top 17,948 21,363 19
20' Half Height 1,193 971 -18.6
20' Tank 5,914 2,948 -50.2
40' Tank 53 53 0
TOTAL Containers 1,603,889 1,782,999 11.2
TOTAL TEUs 2,289,073 2,626,237 14.7

Having to containerize increasing volumes of goods, customers have sought containers of increased height, length, and width. Containers with the original ANSI/ISO external height of 8 feet are generally being replaced by containers measuring 8 1/2 feet high. Also increasing numbers of containers of 45-, 48-, 53-feet lengths have been brought into domestic service within the United States, Canada, and Mexico.

Because of incompatibility with most ship cells, these longer units (particularly the 45 and 53 footers) have generally been considered a domestic asset. Forty-eight footers, 8 feet wide, are becoming popular on some international routes, with the servicing carriers moving these assets either in specially modified holds or above deck.

Despite this trend of volumetric growth, the majority of the US-owned standard dry cargo container fleet remains 20-and 40-foot units with each type continuing to grow as shown in Table E-3. Currently, the US-owned container fleet is essentially equally divided in number between 20-and 40-foot units. This means that approximately two-thirds of the total standard dry cargo carrying capacity is in 40-foot units. Only the 20-foot ANSI/ISO container will be used for the movement of ammunition (Class V). DOD will no longer procure 40-foot containers. The 20-foot container is the container of choice whenever it meets mission requirements. Commercial industry may use 40-foot containers to move all classes of supply (less Class V) and unit equipment subject to theater reception and onward movement capabilities. The Army force structure must be prepared to handle both 20-and 40-foot ANSI/ISO containers.

While it is necessary for DOD to monitor trends in the quantity of commercial containers, the truly important factor to the defense planning community is the availability of these assets. Worldwide economic conditions dictate the number and location of containers which are available for DOD use. A key factor in determining availability is the quantity of lessor-owned containers not already under lease to a DOD shipper or ocean carrier (and hence available for lease by DOD). This quantity, expressed as a percentage of all lessor-owned containers, is referred to as the "off-hire rate." Its value depends largely on the balance of trade, favorable balance of trade will increase the demand for containers for overseas shipment, decreasing the number of off-hire (available) containers within the US.

Off-hire rates can vary considerably by container type. Specialty containers, such as refrigerated units, flatracks, and open containers, often have a higher use rate (lower off-hire rate) than standard dry ANSI/ISO units. In recent years, a specific market niche has been established for the standard 20-foot dry box (serving geographic regions and customers with less intense shipping requirements and lesser developed infrastructures). The off-hire rate for these commercial assets has also generally decreased in recent years.

E-7. CONTAINER TYPES. A sample of container types are depicted in Figures E-1 through E-7. They include both military and commercial intermodal marine containers, most of which are identical in nature.

E-8. ANSI/ISO END OPENING COMMERCIAL. The commercial 20-foot end-opening container can be used to transport munitions or general cargo. The door end corner posts are modified with angle iron to enhance blocking and bracing. As there is no permanent restraint system, wooden blocking and bracing is used to restrain munitions.

End-opening dry cargo units are the most common intermodal containers in the inventory (see Figure E-1). They are DOD-owned and available for lease or purchase from commercial sources. End-opening containers come in various lengths. DOD uses only 20- and 40-foot lengths. DOD owns several container types which fit into this category. All MILVANs and ANSI/ISO end-opening containers can be readily transported by most military and commercial CHE.


Figure E-1

E-9. MILVAN. The Ammunition Restraint MILVAN is made of steel, with wood flooring and walls and is capable of transporting 39,015 pounds of ammunition. The tare weight of this MILVAN is 5,785 pounds. The total gross weight per MILVAN is 44,800 pounds. It has an internal restraint system of eight slotted steel rails permanently installed on each side wall with 25 adjustable crossbars that can be inserted into the slots.

The General Cargo MILVAN container is made of steel, with hardwood flooring and plywood lined walls and is capable of transporting 40,100 pounds of general cargo. The tare weight of this MILVAN is 4,700 pounds. The total gross weight per MILVAN is 44,800 pounds.

MILVANs are still in use today. In 1989 there was a procurement for 1,160 of the ammunition restraint MILVANs. The older ones are gradually being phased out of the system and replaced by commercial containers. The CADS now uses Army-owned and leased standard 20-foot ANSI/ISO containers.

E-10. REFRIGERATED CONTAINER. REEFERs are owned by DOD and are available through commercial sources (see Figure E-2). They provide the capability to transport, temporarily store, and distribute temperature-sensitive cargo such as food or blood. Military-owned REEFERs include a refrigeration unit with a 10-kW generator. They can be plugged into an external power source or run off of their own generators. Most ships are equipped with a power source into which the containers can be plugged. Commercial REEFERs are available with their own generator installed in the front wall of the container with the refrigeration unit. Some commercial REEFERs are plugged into a separate generator which fits into an adjoining container cell. REEFERs have the outer dimensions of ANSI/ISO containers and meet all ANSI/ISO requirements for intermodal shipments.

refer container

Figure E-2

E-11. SIDE-OPENING CONTAINER. Twenty-foot side-opening containers are DOD-owned and are available through commercial sources (see Figure E-3). They are ANSI/ISO containers with two double doors located on one side. These doors open to allow easy access to the container’s contents. The side-opening container can be lifted and transported by commercial and military conveyances. Military versions have internal tie-down rings which can be used to secure cargo during shipment. The military often uses side-opening containers for transporting munitions.

E-12. OPEN TOP CONTAINER. The open top container is used primarily by commercial industry to transport cargo items that are too large and bulky for standard containers. An open top container can be stuffed from the top, or one end can be opened and it can be stuffed from there. It has ANSI/ISO standard corner fittings at the top and bottom and commercial and military handlers and conveyances can readily lift and transport it. Open top containers require tarpaulins for cover during shipping and storage. Open top containers cannot be used for sensitive items requiring high security and may also have agricultural restrictions.

E-13. HALF-HEIGHT CONTAINER. Half-height containers are DOD-owned and are available through commercial sources. They have the footprint of an ANSI/ISO container with ANSI/ISO standard structural members and corner fittings. They are approximately half the height of a standard end-opening container. They have fixed sides, an open top, and one drop-end opening. Material is accessible by either materials-handling equipment or crane. Tarpaulins accompany the containers for cover during shipping and storage. These containers are useful to ship drummed oils and lubricants. 

E-14. TANK CONTAINER. Commercial tank containers are 8 and 1/2 feet in length and are used to haul liquids, gases, and dry bulk cargo. They can be pressurized or non-pressurized. Prototypes of military PLS compatible ANSI/ISO bulk tank containers are being developed. They can be used for intermodal transport of liquids such as Class III and other liquids and gases. They are a half height design. These containers will be available through DOD and commercial sources.

E-15. EQUIPMENT DEPLOYMENT AND STORAGE SYSTEM. EDSS containers are designed to support unit deployments. This category includes QUADCON, TRICON, and ISU containers. QUADCONs and TRICONs are primarily for ground and sea transport and Internal Airlift/Helicopter Slingable Container Units are intended for air transport.  All are available in multiple configurations including different doors, internal shelves, and dividers. ISUs are not covered by ANSI/ISO specifications and are not to be used for marine transport in ANSI/ISO 20- and 40-foot configurations. If transported via ship, they would be carried as secondary loads. 

a. QUADCON. QUADCONs are not a common-use asset. They are unit-owned military containers. They were first used as part of the Marine Corps Family of Intermediate Size Containers. Other Services plan to procure QUADCONs in the near future. These are available to Army units as CTA 50-900 items. The QUADCON is fast becoming the primary EDSS container for surface movements. The QUADCON has ANSI/ISO corner fittings to allow for coupling of the QUADCONs into arrays of up to four units. An array of four QUADCONs has the same external length and width as a 20-foot ANSI/ISO container and is designed to be lifted as a 20-foot unit and/or moved as a 20-foot unit in ocean shipping. The QUADCON is certified to meet all ANSI/ISO standards and CSC approvals. Each has four-way forklift pockets and lockable double doors on each end that provide full access to the contents. To accommodate smaller items, a small item storage cabinet can be installed or removable inserts may be placed as shelves inside the QUADCON.

b. TRICON. TRICONs are not a common-use asset. They are military containers owned by the Army and the Navy. Like QUADCONs, they are lockable, watertight, and made of steel construction. TRICONs have standard ANSI/ISO corner fittings and 3-way forklift pockets on the side and back. The TRICON has ANSI/ISO corner fittings to allow for coupling into arrays of up to three units. An array of three TRICONs has the same external length and width dimensions as a 20-foot ANSI/ISO container and is designed to be lifted as a 20-foot unit in ocean shipping. Two styles of containers have been procured: bulk and configured. Bulk containers do not have drawers, shelves, or rifle racks. Configured containers consist of cabinets with drawers, shelves, rifle racks, or a combination thereof.

c. ISU-60, -90, and -96. The ISU containers provide weather resistant storage and transport but do not meet ANSI/ISO structural standards. CSC restrictions do not apply to containers specially designed for air transport; however, they are certified for internal or external helicopter transport and for all AMC transport aircraft. If transported aboard a ship, they would be carried as secondary loads. A number of these units have been procured by US Army Airborne and Air Assault units. The ISU-96 is a refrigeration model used primarily to transport medical supplies.

E-16. FLATRACKS. Flatracks are owned by DOD or are available through commercial sources. Flatracks enable containerships to transport bulky items such as lumber, steel products, and piping (regular flatrack) and heavy or outsized cargo such as tanks and armored vehicles (heavy-duty flatrack). The flatrack is a structural steel frame, decked over and fitted with tie-down points. One can be used as an individual intermodal container unit or several can be placed side-by-side in a container cell to create a false deck. Some flatracks have corner posts while others have end walls. The corner posts/end walls on most flatracks fold down to facilitate stacking and storage.

The military flatracks come in three sizes: 20-, 35- and 40-foot. Twenty-foot flatracks are PLS compatible. They are used to carry light items that do not fit into a 20-foot container. The 35-footer is used exclusively on FSS. There are three types of heavy duty flatracks (the Titan, the Denardi, and the Phillips). The Titan is equipped with telescoping corner posts adjustable from 102 to 162 inches for various cargo heights. The Denardi and the Phillips have fixed corner posts 156 inches high. Corner posts of all three types fold to facilitate stacking and storage. These flatracks were designed for over-ocean movement and have height restrictions when used in highway/rail transport roles.

E-17. CONTAINER ROLL OFF PLATFORM. The CROP is a PLS flatrack that fits inside an ANSI/ISO standard 20-foot container. The CROP is similar in function to the standard M1077 PLS flatrack except its dimensions: the CROP is 91.5" wide and 230" long so it fits securely inside the ANSI/ISO container. A benefit of using the CROP is that of external protection of ammunition verses tarps. The CROP does not require additional blocking and bracing or materials and only the PLS truck is required to unload in the CSA. Once the CROP is unloaded in the CSA from its ANSI/ISO container, only the CROP flatrack must move forward to ammunition supply/transfer points.