Tank cars single-unit

Industrial gases are shipped over the road by either truck or railcar. For very small quantities, cylinders of pressurized gas are transported by truck. Figure 5 is a photograph of a truck used for hauling industrial gas cylinders. For larger quantities, three types of tank car are typically used, single unit tank cars, multiunit tank cars, and Spec. 107A cars. 

Bulk rail shipment of compressed gases is authorized under DOT and TC regulations in containers of three major kinds—single-unit tank cars, multi-unit tank cars, and fixed tanks on tank cars such as specification 107A tank cars. Adaptations of existing tank car specifications and proposed specifications for new types of cars must be approved by the Tank Car Committee of the Association of American Railroads (AAR). 

A single-unit tank car consists of a single, large, pressure tank that is permanently mounted to the car underframe. The tanks can be com-partmented or noncompartmented. Both insulated and noninsulated tank cars are used in compressed gas service. Cryogenic liquids and refrigerated liquids must be shipped in insulated tank cars. 

Single-unit tank cars built to TC/DOT specifications after November 30, 1970, must not exceed 34 500-gal (131 m ) capacity and 263 000 lb (119 000 kg) gross weight on rail. Since the early 1960s, most tank cars for liquefied gases that are shipped in large quantities such as propane and ammonia have nominal water capacities in the range from 30 000 gal (114 m ) to 33 500 gal (127 m ). 

Single-unit tank cars are protected from excessive internal pressure by a spring-loaded pressure relief valve located on the manway cover plate. Excess flow-check valves are installed on the liquid eduction and vapor lines of many tank cars in compressed gas service. These excess flow valves are intended to contain the tank contents in transit, in a wreck environment if the valve is sheared off, or during other incidents when uncontrolled release of product may occur. 

Single-unit tank cars for transporting anhydrous ammonia may be of the Class 105, 112, 114, or 120 type and must have head shields. An exception is Class 105 type tank cars with a... 

With single-unit tank cars and multi-unit tank cars, full responsibility for safe unloading rests with the consignee. Proper equipment and well-trained personnel are a must at unloading locations. 

Liquefied compressed gases are usually transferred from single-unit tank cars by means of a liquid pump or pressure differential from a vapor compressor. All equipment must be designed for the particular gas being transferred. Methods for obtaining the pressure differential required and the gases to which the method may be applied are as follows ... 

In transferring ammonia from containers, including single-unit tank cars, TMU containers, and cargo tank trucks, never use compressed air as it will contaminate the ammonia. 

When single-unit tank cars are unloaded and all the liquid has been transferred, the greater part (but not all) of the methyl chloride vapors may be recovered by creating a slight pressure differential. Observe caution in this operation because a slight residual pressure must always remain on the tank car so that no air is drawn into it to form explosive mixtures when the pipes are disconnected. 

Fire and explosion hazards. Avoid all sources of ignition when unloading single-unit tank cars and TMU containers holding methyl chloride. 

Inhibited 1,3-butadiene is authorized for shipment in cylinders, single-unit tank cars, TMU tank cars, and motor vehicle cargo tanks and portable tanks. 

Single-unit tank cars and TMU tank cars... 

Consumers of chlorine in bulk quantities who receive shipment in single-unit tank cars often... 

Ethylene oxide is authorized for shipment in single-unit tank cars complying with DOT 105J specification and special requirements in 49 CFR 173.323 and CAN/CGSB-43.147-94, Construction and Maintenance of Tank Car Tanks... 

Isobutane and the monoolefins are authorized for shipment in single-unit tank cars and truck cargo tanks, and are usually shipped in bulk units because they are generally used in large quantities. They are also authorized for shipment in cylinders, portable tanks, and TMU tanks. 

Bulk shipment of liquefied petroleum gas is authorized in TC/DOT 105, 112, 114, and 120 single-unit tank cars. Outage calculations and exceptions to outage calculations during the winter months are calculated according to 49 CFR 173.314. Pressure relief device settings are calculated according to 49 CFR 179.15 [9, 10]. 

For TC/DOT 112T340W and 112J340W single unit tank cars, the maximum filling densities are monomethylamine, 61 percent dimethylamine, 61 percent and trimethylamine, 58 percent. See 49 CFR 173.314 [5]. 

In single-unit tank cars complying with TC/DOT 105J300W specifications-86 percent in single-unit tank cars complying with TC/DOT specification 112T340W or 112J340W-85 percent. 

Vinyl chloride is shipped as a liquefied compressed gas in cylinders, single-unit tank cars and TMU (ton multi-unit) tank cars, and in tank trucks and TMU tanks on trucks. For all these types of containers, it is required that all parts of valves and pressure relief devices in contact with the contents of the container must be of a metal or other material (suitably treated if nec-... 

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