TRANSPORTATION OF FISHERY PRODUCTS 311 



pipe coils on the ceilings and walls. The pipes are cooled by the primary re- 

 frigerant ("Freon-12") or by brine. This is often referred to as the "grid" system. 

 All the equipment connected with the refrigeration of ships is usually of 

 standard design for ready replacement and repair. However, all pipes, coils, fan 

 casings, and other steel parts must be hot-dipped, galvanized, or otherwise treated 

 to protect them from the salty atmosphere. 



Transportation by Rail 



Commercial fishery products are transported by rail almost entirely in insulated 

 cars, called refrigerators or reefers in Canada and the United States. These are 

 essentially "ice boxes on wheels," insulated with from 2 to 5/2 inches of hairfelt, 

 aluminum foil, or "Fiberglas" and cooled by means of ice or ice and salt mixtures 

 carried in tanks suspended from the ceiling or placed in the ends of the car. 

 Those cars with tanks along the ceiling are called overhead or roof-tank cars 

 and those with the tanks in both ends are called end-bunker cars. 



Fresh (unfrozen) fish are shipped mostly in express refrigerators of either 

 the overhead or end-bunker types. The fish are packed in ice in boxes and the 

 car itself is serviced with a salt and ice mixture in order to minimize the melting 

 of the ice surrounding the fish. The concentration of salt in the mixture depends 

 upon the season and the ambient temperature, and in no case does it completely 

 prevent the melting of the ice around the fish. The melt from the ice carries with 

 it slime, dissolved proteins, and salts from the fish, all of which are food for 

 bacteria. This nutrient solution saturates the exposed parts of the interior of the 

 car and often gains access to the insulation. As time passes decomposition sets in 

 and gives rise to objectionable odors. Thus cars that have been used for the ship- 

 ment of unfrozen fish are easily identified and are often rendered useless for other 

 food products. 



Frozen fish move mostlv by freight refrigerators since they are less perishable 

 in the frozen state and time, therefore, is a less important factor. The fish are 

 usually boxed just before shipment, although bulk fish are also shipped, or the 

 shipment may be mixed bulk and boxed. Before loading the car is precooled for 

 from 12 to 24 hours with ice and salt in the proportions 30 pounds of salt to 

 100 pounds of ice. Some shippers use lower concentrations of salt, but this is not 

 good practice. When the car has been properly precooled, the fish are loaded as 

 expeditiously as possible by hand truck, conveyors, or fork trucks. After loading, 

 the bunkers or ice tanks are "topped off" or reiced to capacity with the same 

 proportion of ice and salt vised in the precooling. 



The End-Bunker Car. At present the most popular refrigerator car in the United 

 States is the end-bunker car, of which there were about 110,000 out of a total of 

 approximately 135,000 of all refrigerator types at the end of 1947. The size that 

 seems to be most favored is the 40-foot car, insulated with about 3 inches of 

 hairfelt. This car, when fitted with end bunkers and bulkheads, has a loading 

 space approximately 34 feet long. The bunker capacity is from 5 to 7 tons of ice 

 which is loaded through hatches in the roof. All end-bunker cars are equipped 

 with floor racks and the walls are cleated or cross-stripped when boxed com- 

 modities are shipped to permit the circulation of air. Air circulation in these cars 

 is longitudinal and, when induced by convection only, results in rather unequal 

 temperatures throughout the loading space, the highest degree being in the 



