When the pure oil is run as low as can be conveniently done without carrying off any scrap of settlings, the oil laying on the surface of the water and sediment in the bottom is passed to some receptacle and sent to the pressure tanks. The kettle is well scrubbed, made clean and the skimmed bottoms deposited ready for filling again with hashed fat.
FIG. 55.—SETTLING KETTLE FOR OLEO OILS.
Clarifiers or Settling Kettles.
—Each kettle is provided with two clarifying or settling kettles. These are cone-shaped tanks in which the oil from one melting kettle is deposited. The oil is allowed to stand as long as possible in a quiet state and the sediment or fibre collects in the bottom of the cone. This is withdrawn at the bottom at frequent intervals so as to free the oil from sediment and dirt. The temperature of the oil carried in the clarifiers is 140°, kept uniform by use of warm water in the jacket.
After settling the oil about two hours it is drawn to the seeding trucks. Cotton flannel bags are usually put on over the outlet pipe so as to strain the oil and collect any floating pieces of tissue that would otherwise pass to the seeding truck.
Scrap Vat.
—A vessel which requires attention and in which the yield in the oil house can be very materially increased and improved by proper handling is the scrap vat. After the vat is melted and the oil siphoned off, the balance or residue in kettle is drawn out of the bottom into the scrap vat, which is located directly under the melting kettle. This kettle should be kept full of hot water at a temperature of about 130° F., and when the scrap is dropped in the oil will immediately come to the surface; this should be skimmed off promptly, for if it is allowed to lie in the scrap vat a bad flavor will result and it will then have to be sold as an inferior grade of oil; but if skimmed as stated this strong flavored feature may be avoided.
When through melting for the day, the steam should be turned on the scrap vats to bring them up to a temperature of 190° to 200° F. This will release any fat yet remaining in the scrap, which should be skimmed and used for a lower grade of oil, as it will have a strong flavor. The balance of the scrap is then sent to the tank house, where it is cooked under pressure and the remaining oil taken out.