Moving Hazardous Materials by Truck
Departments
ON HAZARDOUS MATERIALS
Truck transportation of all kinds of commodities has been in the news recently as a result of the change in the federal law allowing larger trucks on the nation’s highways. Of course, with the increase in size comes increased potential for hazardous materials problems for emergency response personnel.
As with rail transportation (which was discussed in last month’s issue), identifying the product being carried by the truck is the first step. Emergency response personnel have several ways to accomplish this task: placards on the outside of the transporting vehicle, shape and style of vehicle, shipping papers, labels on the shipping containers, and the name of the shipper/manufacturer/transporter.
Placards: In most cases, placards are required on the outside of the four sides of the transporting vehicle only if the truck is carrying more than 1000 pounds of a hazardous material. However, if a truck contains any quantity of explosives A and B, poison A, radioactive III, or a flammable solid that is dangerous when wet, then the truck must be placarded.
Obviously, the fact that a truck has no placard cannot be taken as an indication that there are no hazardous materials present in the cargo. The truck could contain hazardous materials and not be placarded because:
- Federal law does not require placarding for certain hazardous products.
- The placards were not put on the vehicle or were lost during transit.
- The truck contains less than 1000 pounds of the product.
Another problem with the placarding system is the general purpose DANGEROUS placard. This placard is used when there is a mixed load of most of the other categories of hazards (corrosives, oxidizers, flammables, etc). As a result, a truck carrying 1000 pounds of a flammable product, 1000 pounds of corrosive, and 500 pounds of an oxidizer must only have the DANGEROUS placard. In addition, since all quantities of some materials must be placarded, they must be separately plac arded even in mixed loads.
While rail c ars cars must be placarded with an empty symbol when the product has been removed, tank trucks do not have such a requirement. As a result, emergency response officials cannot tell whether the tank truck is full or empty until the driver informs them or the shipping papers are found. This is significant because if there is flame impingement on the closed container, more of a potential problem of detonation exists if there is no product inside the tank.
Vehicle shape: The exterior shape of a truck very often can be used to determine the type of commodity being carried. The basic types of trucks include, cargo vans, nonpressurized liquid carrier, compressed gas carrier, liquified gas carrier, cryogenic carrier, and dry bulk carrier.
Cargo vans can carry almost any kind of hazardous material, including compressed gas in cylinders, flammable liquids in drums, oxidizers in bags, and explosives in boxes. These hazardous materials can be carried along with any other general purpose commodity.
Cargo vans themselves can be carried via other modes of transporation before or after they move via roadway. The vans can be placed directly on a railroad flat car [known as a trailer on a flat car (TOFC)] or just the container can be moved by rail [known as a container on flat car (COFC)] or by boat.
The nonpressurized liquid carriers can carry many different products. The one that everyone is familiar with is the gasoline or fuel oil truck. This vehicle is usually made of aluminum or steel and has an elliptical shape with flat ends. Tanks with capacities of over 17,000 gallons have been built, but the more common carry up to 8000 gallons per tank.
Another type of nonpressurized tank truck is the corrosive carrier. The tanks for this type of truck are usually smaller than for flammable liquids because the acids are heavier than the flammables.
The corrosive trucks are usually steel with either a stainless steel, rubber, plastic or glass liner, depending on the type of corrosive being carried. Because of the need for a special internal, smooth lining, structural support for the tank is usually done in the form of external bands.
The compressed gas truck carries a gas as a gas but uses pressure to squeeze more gas into the same volume of space. These types of trucks generally contain several cylinders mounted horizontally on the truck.
The liquefied gas truck carries a compressed gas which becomes a liquid under pressure. These trucks usually have one or at most two cylinders for carrying the Droduct. They can be identified by the arge steel tanks with rounded ends, indicative of a pressure vessel. An example of this is the truck carrying propane.
The cryogenic truck carries gas which has been converted to a liquid by super cooling. In this way, the product is not under a great deal of pressure, but great quantities can be placed into the tank just by keeping the product cold.
Temperatures for cryogenic liquids range from —300° for liquid oxygen to —320° for liquid nitrogen. However, once the product has been liquefied and placed into the truck, there is nothing on the truck to keep it cold. The only thing which keeps the temperature from rising is the fact that the truck is really a large thermos bottle. So, the potential problem faced by emergency response personnel is from the coldness of the product as well as the product’s own characteristics.
Cryogenic trucks have a distinctive shape because they use a large box enclosed area at the rear of the truck for the unloading station.
The dry bulk carrier generally carries an oxidizer as its major hazardous material, usually fertilizer. The shape of the bulk tank provides the clue to this cargo.
All of the gas and liquid carriers have various safety devices that include relief valves, roll-over protection, breakaway valves, fusible links, air or vacuum-operated emergency control valves and remote operation valves.
Shipping papers: The truck’s shipping papers are carried in the cab of the truck. When the driver leaves the truck the papers are supposed to be kept on the seat or in a pocket on the driver’s door.
Shipping papers are known as bills of lading. They will contain the name of the company shipping the product, the company it is going to and the transporter. In addition, the papers will sometimes name the specific commodity being carried. This is the greatest problem that emergency response personnel face, because many times the bills of lading will use general terms and not name the chemical.
If the incident commander cannot determine the name of the product, it will be difficult to obtain information about the hazards of the product. Then it will be necessary to contact the manufacturer, shipper, receiver or transporter.
