THE WHALING INDUSTRY 



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to fill the cooker and cook the blubber, and must be carefully watched to prevent 

 damage to the oil. The 2 doors are bolted tightly shut at time of cooking, and 

 the whole digester is insulated with a special jacket to prevent loss of valuable 

 heat. 



The latest method for rendering blubber is the continuous rotary digester. This 

 is an enormous horizontal cylinder with precookers at each end and an oil sepa- 

 rator attached. Inside there is a rotary drum with perforations and baffle plates. 



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(.Courtesy U. S. Coast Guard) 

 Fig. 33-4. Whale carcasses are flensed on deck of factory ship. 



Large chunks of blubber are placed in the precookers. When the pressure rises in 

 the precooker, the material falls automatically into the digester, and is then quickly 

 and efficiently broken up into oil, water, and graks by the live steam and the 

 mechanical action of the rotary drum. The entire fluid brei passes over to the 

 separator under pressure during the digestion, and the oil is separated there by 

 an ingenious gravity arrangement. The huge precookers can be filled as fast as 

 the material is digested, which is from 2 to 4 hours per filling. The whole process 

 is continuous, and with the help of agitation the temperatures and pressures 

 remain low enough to give a good quality of oil. This continuous rotary apparatus 

 is standard equipment on all modern factory ships, and is gradually beginning to 

 replace the old vertical, batch, pressure, grid digesters at shore stations. However, 

 they are expensive and require a large amount of raw material to make up for 

 the cost of their installation. 



Hogging and mincing blubber will aid in digestion, and is necessary in the 

 case of open-cooking. In the continuous rotary digester hogging is unnecessary 

 because disintegration is accomplished by the rotating drum with baffle plates. 

 Blubber is tough and cannot be minced in the ordinary slaughterhouse prebreaker, 



