One of the fastest-growing areas of hazardous materials transportation is that of intermodal containers. During 2003, a total of 9,502,563 intermodal containers were shipped by rail and 1,227,852 were shipped on highways, and the U.S. Department of Transportation (DOT) forecasts that total tons of...
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One of the fastest-growing areas of hazardous materials transportation is that of intermodal containers. During 2003, a total of 9,502,563 intermodal containers were shipped by rail and 1,227,852 were shipped on highways, and the U.S. Department of Transportation (DOT) forecasts that total tons of hazardous materials transported will grow by 2% per year. However, growth of transport by intermodal containers is forecast to be three times faster.
The use of intermodal containers is referred to by the DOT as "intermodalism," which means "the use of more than one form of transportation." Intermodal containers resemble many of the other bulk transportation containers found in highway, rail and water modes of transportation, but are smaller in capacity. They are designed to be transported in rail, water and highway modes without the need to off-load the products; that is, the container is transferred from one mode of transportation to another rather than the product being transferred from one container to another.
When aboard a ship, intermodal containers may be found above or below deck. Once a container ship reaches port, the intermodal containers are unloaded by giant cranes. The containers may also be shipped on inland waterways aboard barges. Containers are moved around on land by specially designed forklift-type vehicles that are much larger than a typical forklift. Containers may be found stacked on top of each other on the dock awaiting further shipment on land. From the dock the containers are moved inland by rail or truck.
Intermodal containers are not usually transferred directly from ship to rail or truck. They are unloaded onto the dock and then transferred to rail or truck by specially designed cranes. An added advantage to intermodal containers is that they are portable and can be taken to the end-use site and off-loaded as a stationary storage tank until the product is used up and then returned for refilling.
Intermodal containers are regulated by the DOT and containers are made to specifications prepared by the International Maritime Organization (IMO), an agency of the United Nations that deals with treaties for maritime safety among other matters. Primarily IMO Specification 1, 2, 5 and 7 tank containers are used to transport hazardous materials.
Intermodal containers come in many sizes and shapes. Box containers may be found in varying lengths from 10 to 48 foot lengths. Typical heights are eight feet, six inches, but some styles may vary from eight feet to nine feet, six inches. The standard width of intermodal containers is eight feet. Containers may have doors at the rear with some also having side doors.
Intermodal containers may be insulated or uninsulated, and may have environmental temperature controls. Bulk tanks are designed with a steel structure around the outside to facilitate stacking and movement. They are usually 20 to 28 feet in length and are used for liquids and bulk materials. Tank containers have a capacity that ranges from 4,000 to 6,000 gallons.
Tank containers are used for transport of liquids or gases, including flammables, toxic and corrosive chemicals, cryogenic liquids, and others. Tanks are constructed of metal with two basic components - the tank itself and an outer framework. Usually, containers are constructed of stainless steel, but they can also be aluminum, mild steel or magnesium alloy. Containers may be lined, refrigerated, heated with electricity or steam, and insulated with metal or plastic jackets. Weight, volume and construction details of a tank container vary considerably due to the properties of the transported substance.
The IMO defines five different types of tank containers where the following two types are significant for chemicals. Within the United States, IM 101 and IM 102 portable tanks are the most commonly used containers for both hazardous and non-hazardous materials. They are equivalent to IMO 1 and 2 tanks. Specification 51 tanks also in the United States are equivalent to IMO 5 tanks and are pressurized between 100 and 500 psi.