510 MARINE PRODUCTS OF COMMERCE 



pipe-line between the outlet from the grinder and the pump to minimize the amount of 

 rock and tramp iron introduced into the gear pump. A shear pin of suflBciently small 

 diameter is often advisable to protect the pump in case such solid materials do travel 

 that far. Valves on the liver pipe-line should be self-cleaning and nonclogging. 



"Cooking tanks may be fabricated of wood or iron, depending on the desires of the 

 processor and the availability of material. As an example of the relative cost in the 

 Seattle area for tanks of approximately the same dimensions and of 1,000 gallons capacity, 

 those made of iron cost approximately $100 and those of wood cost $65. If heating is to be 

 direct steam, the only cost, other than piping, valves, etc., might be for an automatic 

 steam controller at $50-$ 100 per tank to regulate the temperature of the cook at the 

 desired temperature. If cooking is accomplished by indirect steam heating, there wdll be 

 the added cost of pipe coils. Agitation may be by a portable electric mixer, a fixed side- 

 entrance stirrer, or a stirrer fixed on top of the tank and driven by a chain or belt ac- 

 tivated by suitable shafting and gears. Portable stirrers are available in various horse- 

 power ratings and motor speeds. One brand of stirrer having a 1/2-liorsepower motor and 

 operating at 1,750 revolutions per minute costs approximately $185. The same brand 

 with a /2-horsepower motor costs approximately $110. 



"Several variations in the application of centrifugals for the separation of fish-liver 

 oils are in use by the processors. If the steaming process is used on a small scale, it is 

 possible to get fairly high oil recovery by allowing tlie material in the cooker tank to 

 settle until the upper or oil layer separates before it is drawn ofi^ to be processed in the 

 oil purifier or centrifuge. An imperforate basket centrifuge may also be used to separate 

 the liquid constituents from the solids prior to the final purification of the oil. For larger 

 operations the entire contents of the tank are first passed through the sludger centrifuge 

 to remove the wet oil from the solids; the wet oil is then finished in the purifier centri- 

 fuge. 



"There are two principal manufacturers of the centrifugals now being used in the fish- 

 liver oil industry. Each company manufactures the 3-phase or sludger-type machine, 

 designed to accomplish the continuous preliminary separation of the cooked or digested 

 liver material into ( 1 ) an emulsion of oil, water, and fine solids and ( 2 ) a sludge of 

 water and coarse solids. The larger centrifuge of this type has an approximate capacity 

 of 1,500 to 3,000 gallons of liquor per hour. The actual performance will be determined 

 by the character of the material to be separated, and there may be some variation in 

 capacity from one lot of material to another. The sludger of this capacity range costs 

 $6,000 to $8,000, depending on whether stainless steel construction or standard equip- 

 ment is ordered. 



"The second machine — the oil purifier or polisher — is designed to recover the oil in 

 a marketable form from the oil-water-fine solids emulsion of the sludger-type centrifuge. 

 These purifier machines are available in several sizes. The approximate costs for the 

 usual industrial models are $1,800, $2,400, and $3,500. 



"Centrifuges may require a rather large supply of hot water for satisfactory perform- 

 ance, especially if the sludger machine is used. Therefore, there should be provision 

 for an adequate supply of water at 180-190° F (82-88° C). 



"The boiler capacity required for liver processing varies considerably with the process 

 and plant equipment, but a rough estimate would be 10 boiler horsepower per 1,000 

 gallons of cooker capacity. Boiler costs are dependent on type and local rates. A 10- 

 horsepower boiler suitable for a fish-liver plant should cost approximately $500. 



"Plants processing large amounts of livers will need a gear pump to move the oil from 

 the centrifuge to the tanks used for storage or for blending and mixing. A portable stirrer 

 or other agitator is required for these tanks, and steam coils are usually desirable to 

 warm the oil sufficiently to facilitate mixing in case it has become viscous or partly solid 

 at lower temperatures. 



