FISH MEAL AND OIL 



475 



this hollow central shaft is also provided with a series of steam nozzles; these are 

 located between the turns of the conveying screw and are connected to a steam 

 supply through stuffing boxes at its ends, which permits the injection of live 

 steam directly into the upper part of the moving mass of fish. The speed of the 

 screw can be regulated so that the conditions of cooking are adjusted to the fish. 



{Courtesy Edw. Renneburg and Sons Co.) 



Fig. 22-4. Continuous live steam cooker with feed screw, choke screw and thermal con- 

 trols. This size cooker has a capacity of more than 15 tons of raw fish per hour. 



This type of cooker has a smaller shell, about 8 feet long and 1 foot in diameter. 

 The shell is attached to the discharge end, which is a little lower than the main 

 cylinder and either at right angles or parallel to it. This is designed to keep the 

 steam from escaping. After passing through the cooker the mass of cooked fish 

 drops into the smaller cylinder and is carried thi-ough by a screw conveyor. A 

 homogeneous and thoroughly cooked product, containing a 75 or 80 per cent 

 mixture of water, oil, and fish protein, is thus delivered to the press by the cooker. 



Continuous Screw Press. A common form of continuous press is composed of 

 a heavy steel screw, enclosed in a cylindrical screen. The pitch of the screw flights 

 become progressively smaller as it approaches the discharge end of the press. The 

 cylindrical screen is heavily reinforced at frequent intervals. The screw is 

 machined to fit closely into the cylinder, and is driven by heavy gears. 



The hollow screw shaft is provided with a number of small steam nozzles be- 

 tween the convolutions of the pressing helix, and is fitted with a suitable stuffing 

 box at each end for connecting up with a high-pressure steam supply. This ar- 

 rangement permits jets of live steam to be forced directly into the cooked mass 

 while under heavy pressure in the machine. Live steam serves to prevent clogging 

 and likewise maintains the material at the necessary high temperature for maximum 

 oil extraction during the pressing operation. 



The discharge end of the machine is fitted with a special adjustable pressure- 

 regulating device, by which the rate of discharge and the size of the outlet can 

 be varied to suit the character and condition of the material being handled with- 

 out stopping the press or interfering with its operation. This feature is of great 



