REFRIGERATION OF FISH 



561 



pipes with traps at the bottom for discharge of brine. To allow cir- 

 culation of cold air, there is an aperture about 1 foot wide at the top 

 and bottom of the partition between the bunker and the body of the 

 car. A heavy wire screen prevents the ice from falling through these 

 openings. When the bunkers are charged with ice, or ice and salt, 

 the cold air flows from the bunker to the car, through the lower 

 opening, and is replaced with warm air from the car through the 

 upper. 



For dunnage the floor of the car is provided with heavy slat boards 

 mounted on 2 by 4 timbers. These floor racks often are hinged down 

 to prevent their removal from the car. Where " permanent " floor 

 boards (slats nailed directly on the floor) are provided circulation 

 is insufficient, and frozen fish may be partially defrosted. 



Cars vary in all their dimensions. Table 14 shows the dimensions 

 and capacities of several American and Canadian refrigerator cars. 

 If the dimensions of these cars were standardized, it would be pos- 

 sible to standardize boxes for more economical packing, but as it is 

 shippers must pack as best they can, often with much waste space. 

 Pan-frozen fish usually occupy about 4 cubic feet per 100 pounds when 

 boxed. The minimum car shipment is 24,000 pounds. In the larger 

 cars as much as 33,000 to 35,000 pounds, or even more, can be packed. 



Table 14. — Inside dimensions of some refrigerator cars 



Railroad 



Michigan Central 



N. C. &St. L___ 



New York Central _ 



Do.... 



Canadian National 



Canadian Pacific 



Soo Line 



American Refrigerator Transit 



Grand Trunk Pacific! 



Fruit Growers' Express 



Length 



Feet 

 33 

 29 

 39 

 28 



138 

 34 

 32 

 33 

 33 

 33 



Inches 

 

 1 



11 

 9 



9% 

 

 3 

 4 

 2 

 



Width 



Feet 



Inches 

 4 

 2 

 5 

 4 

 2 

 7 

 

 4 

 1 

 3 



Height 



Feet 



7 

 7 

 7 

 7 

 7 

 6 

 7 

 7 

 6 

 7 



Inches 

 7 

 3 



2M 



Capacity 



Cubicfeet 

 2,084 

 1,721 

 2,518 

 1,718 

 2,713 

 1,943 

 1,849 

 2,105 

 1,719 

 2,042 



1 Equipped for connection in passenger trains. 



Usually the cars are refrigerated by packing the ice chambers 

 with cracked ice and salt. The capacity of the bunkers is from 

 6,000 to 7,500 pounds of ice each, or 12,000 to 15,000 pounds for the 

 car. Salt is mixed with the ice in the proportion of 10 to 15 pounds 

 of salt to 100 pounds of ice, this figure being referred to as " per- 

 centage." Thus, 10 pounds of salt to 100 pounds of ice is referred 

 to as " 10 per cent " salt. (A true 10 per cent mixture would, of 

 course, be 10 pounds of salt to 90 pounds of ice.) In winter the 

 10 per cent mixture is used. Some shippers increase the proportion 

 to 12 per cent in spring and 15 per cent in summer. Other shippers 

 use a 10 per cent mixture all year round. For oysters, which require 

 a cool temperature above freezing, a 5 per cent mixture is used. 

 Winter shipment, of course, is most satisfactory, as summer ship- 

 ments, especially in the more southern latitudes and in warm periods, 

 sometimes partially defrost and lose their glaze. The drainage 

 valves remain open, so that the brine formed flows off. 



