Nocember I#SI
materials Two new railroad freight cars transport dry, granu€aror powdered solids in bulk with the same efficiency that a tank car carries liquids
of track mileage, the railroads in America are almost one and one half times as large as they were 50 years ago, and with that growth, technological improvements of great importance have been made. Today, no other country in the world has a railroad system nearly as large or as well equipped as that of the United States. This system carries nearly 70% of all freight traffic. Freight cars constitute an important part of railroad equipment. Approximately 2,125,000 railroad freight cars are in operation and, of these, about 300,000 are privately owned-that is, not owned by the railroads. Among the privately owned cars are a considerable number of special design including nearly 150,000tank cars. Others are refrigerator, stock, poultry, covered hopper cars, and miscellaneous types. Although the tank car of today consists principally of a horizontal tank on a wheeled carriage, it is a great improvement over the first tank car which was put into service more than 85 years ago. Tank cars usually carry liquid materials, but in many instances they are used for slurries, greases, gases, and free flowing solids. The Association of American Railroads lists 29 classes of tank cars. The classes vary in construction material, loading and unloading devices or apparatus, safety valves or vents, construction and pressure rating of the tank, insulation, and other features. A large percentage of the tank cars are classified as general service cars, which means that they may be used for many different commodities that do not require extraordinary equipment. The majority of cars in this class are of 8000 and 10,000 gallons capacity; carry 4000 or 6OOO gallons. The flexibility in this class
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N TERMS
November 1951
has been enhanced by compartmentalizing individual tanks to permit the loading of several grades or types of materials. As a general rule the tanks are fabricated of open hearth steel plate which is quite satisfactory for a vast number of product$. Where meticulously clean tanks are required or where corrosion problems must be overcome, several types of coatings have been successfully used. Special tank cars, of which there are not many, have made possible bulk rail transportation of products that otherwise have to be handled in special containers. Insulated cars and pressure cars with several combinations of safety devices, loading and unloading features, and other apparatus, are being used for shipments of chlorine, ethylene oxide and helium, for examples. Obviously, the handling problems of these three materials are quite dissimilar but, owing to unceasing work on the part of tank car builders, producers of the products, and special committees, these are only three of the list of approximately 500 different products that are currently hauled in tank cars. I n other fields, significant progress has been made also. General American Transportation Corp. and the Fuller Co., working closely together, developed a freight car that carries dry, granular or powdered products in bulk with the same efficiency that a tank car carries liquids. The copyrighted name of this car is Trans-Flo. The car appears to be the economical, efficient answer to the problem of shipping flour, cereals, and other products that previously had to be packed in bags, barrels, or drums. Not only does this car prevent contamination of the transported material, but it also reduces the loading
and unloading detail to an efficient laborand money-saving level. Twelve separate hoppers are built into a framework of steel sideand-end members of this new compartmented car. The product to be shipped is loaded through hatches on the roof. These hatches, an inner one which includes a special filter device and an outer one which hermetically seals the compartment, offer positive protection against contamination or tampering. On arrival a t its destination, the lading is removed pneumatically from the bottom of each hopper. The tendency of the commodity to bridge and pack does not present a problem in this car. In tests it was found that by filling the car hoppers (closed containers) completely and thereby eliminating air space above the load, where the only source of objectionable condensation would exist, the sticking and bridging of the material did not occur, Flour, starch, dehydrated milk products, and similar pulverized materials of low hygroscopicity are good insulating materials, but their atmospheric air content at loading density is small. Pneumatic unloading has proved highly successful. Depending, of course, on the density of the commodity, the car has a cubic capacity equivalent to 55 to 65 tons of pay load compared with an average box car pay load of 30 to 50 tons. In addition t o the features which qualify this car for transporting edibles, it appears to be a,n attractive innovation economically: Loading is direct from the source of production or storage where a screw (Continued on page 164 A )
INDUSTRIAL AND ENGINEERING CdEMISTRY
153 A
Materials Handling
Materials Handling
conveyor and chute take the product into the car. The average estimated loading time is 3 hours. If we assume a load of 60 tons, this would be equivalent to loading the net weight of 1200 bags at 100 pounds each. The average box car, we will assume, would be loaded with 800 bags, equivalent to 40 tons net weight of product. We would estimate the man-hours required to load 800 bags at 12 to 16. Add to that time the usual time required to handle bags in the plant, to fill the bags, to remove old dunnage, sweep out and install freshdunnagein a box car, and clean up after all these operations, and you will find the approximate time to compare with the estimated 3 man-hours required to load the Trans-Flo car which contains 50% more pay load. Moreover, the cost of the containers and the freight on them, plus shrinkage, is saved. Unloading details may be compared in very much the same way. An estimated average of 4 manhours is required to unload the new car, whereas, the bags must be removed from the box car, stacked in storage, and emptied and disposed of before the product reaches the processing operation. Again clingage and wastage occur, and it takes time and work to clean up after the unloading procedures.
Transportation Corp. is helping to regain this business for the railroadu. In cooperation with the Evans Products Co., they have developed the General American-Evans D-F (damage and dunnage free) car.
We have mentioned that the Trans-Flo car is particularly attractive for certain clean products. But, for many other commodities, the old familar covered hopper cars are entirely adequate. Obviously, there is a tremendous amount of tonnage that cannot be shipped in bulk. Fine chemicals, pharmaceuticals, many food products, beverages, and other supplies must be packaged and are generally shipped in box cars. Large losses from breakage and damage in transit occur when ordinary box cars are used for their transportation. The conventional freight car is, moreover, a slow means of transportation; in 1947 the average car miles per serviceable car was slightly less than 50 miles per day. There fore, trucks have become competetive with the railroads for this type of traffic, on a time basis if no other. Again, however, the General American (Continued on page 156 A ) 154 A
In this car the available loading space has been increased 50T0 through an increase in length of only 25%. High speed, balanced suspension trucks, which are designed for maximum protection against shocks, both vertical and lateral, special underframe capable of cushioning longitudinal bumping, and built-in devices that Becure lading positively and are universally adaptable, make it possible to utilize the full cubic capacity of the car. Side doors are 8 feet wide to permit easy entrance for loaded power lift trucks. The floor is steel with added reinforcement to support heavier loads safely and to prevent costly loading delays caused by broken floor boards. Tho steel floor is coated with a nonskid mastic which prevents slippage of lift truck wheels. The construction of this car is such that it will maintain its stability at passenger train speeds and, if it is desired that it be used in passenger head-end service, signal and steam lines may be added. It is expected that this improvement over the ordinary box car will effect a reduction in losses in transit and decrease dunnage costs; it increases pay load and is faster, thereby allowing a higher mileage utiliaation. The few cars discussed here are important because their development is an indication that progress in railroading has been and still is being made with a view toward meeting some problems that are confronted in the transportation phase of materials handling. Aekmswkdgment
The author appreciates the cooperation of the General American Transportation Corp. in supplying information for this discussion. Correapondenoe oonoernlng thin oolumn will be forwarded promptly it addressed to the author.
e/o Editor, INDUSTRIAL AND ENGINBEBIlva ISTBT,1155-16th St.,
CHEM-
N.W.,Washington 6, D. c . 156 h
