—The chilling or cooling of water is accomplished in two ways, by the introduction of ice or the cooling of the water or by submerging pipes in the tanks, and circulating chilled brine or ammonia gas through the pipes, same being a part of the refrigerating system. In the latter case the pipes should be covered by a removable screen to prevent fats attaching to the pipes.
FIG. 54.—KETTLE FOR MELTING FATS FOR OLEO OIL.
Melting.
—The fat when hashed is passed to an open top water jacketed kettle of the type shown in the illustration, [Fig. 54].
Just previous to beginning to hash the fat into the kettle the stirrer is placed in motion. The water in the jacket is heated up to a temperature of about 180° F.
When the kettle is partially filled and as the fat accumulates, it will collect and hang to the stirring gear. To meet this condition the stirring gear is arranged to rise vertically on the shaft by lifting and assistance of the counterweight attached to it. The fat is removed by the use of a paddle, the stirrer lowered and started in motion. The fat is mixed with a large paddle so that the melting oil at the sides and bottom of the kettle is freely intermingled with the partially melted fat.
The mass gradually assumes a murky yellow appearance as the oil is made free. The man in charge of melting uses a bath thermometer constantly and regulates the temperature of the water in the jacket by the admittance of cold water to chill it or steam to warm it so that the temperature of the melting oil does not exceed 156° F. It usually takes 1¹⁄₂ hours to properly melt the contents of a full kettle. When the melting is complete the stirrer is raised out of the oil and allowed to remain raised while the oil is settled.
Settling the Oil.
—When the oil comes to rest about twenty pounds of fine salt is scattered over the surface, thrown in moderate handfuls so as to sprinkle the entire surface. This salt in settling clears the oil by carrying down the floating fibre by mechanical as well as chemical action. The oil usually has a scum on top and this is gently skimmed off and saved as a bottom for the next kettle. After settling about fifteen minutes the oil is run off by gently lowering the hinged pipe, the oil as de-canted is passed to the clarifier.