Care of Electric Metal Pot
The contact points on the thermometer and the magnetic switch should be kept clean and free from corrosion. Use No. 00 sand-paper. (Never use emery cloth or paper.) Dirt and corrosion are electrical insulators, and if these contacts become dirty, electrical contact may not be made when the temperature reaches 550 degrees F.; the magnetic switch will not open and the crucible heaters will continue to increase the temperature of the metal until the fuses are blown; the dynamic thermometer permanently injured, or the heating units burned out. When the temperature reaches above 550 degrees, the metal is too hot, causing back squirts. When the metal has cooled, the contacts, owing to the dirt, will not operate, and the metal will continue to cool until it can not be used. The contact points should be cleaned about once each two weeks.
The hole in the hollow tube connecting the bulb and the flattened coil spring of the dynamic thermometer is very small and care must be taken that the tube is not injured when feeding metal to the pot, or that no sharp bends are made in it, as it will close the hole and interfere with the proper working of the thermometer.
Occasionally some of the parts such as the heaters, thermometer, or the wiring inside the pot may become damaged and will have to be replaced. In ordering the new parts for replacements, be sure to specify the voltage being used and the serial number of the pot. This number plate can be found on top of the pot cover.
It is seldom that both crucible heaters will be burned out at the same time, so if your pot is a 100 to 125-volt equipment, and one of the crucible heaters tests open or grounded, and must be removed and replaced, the metal in the crucible may be heated by the crucible heater that is in good condition; but if your pot is 200 to 250-volt equipment, and one of the crucible heaters must be replaced, it will be necessary to melt the metal in the crucible with a blow torch before either crucible heater can be removed. It is not necessary to remove the metal from the pot. Merely keep the metal agitated while melting it with the blow torch.
Frequently a heating unit is burned out by a little metal splashing on the terminals, causing a gradual short circuit. This trouble can be eliminated by wrapping the heater terminals with asbestos tape.
When cleaning the contact points on the dynamic thermometer, it is necessary to remove the cover by taking out the two long flat head screws. This cover should be examined for small particles of metal before replacing.
To remove and replace a damaged wire in the pot, fasten another wire securely to one end of it, grasp the other end with a pair of pliers and pull. The new wire will be pulled in as the old one is removed.
Rubber covered wire or slow burning wire is not satisfactory. A special wire with a special grade of insulation should be used.
If it becomes necessary to remove the dynamic thermometer, heat the metal in the crucible to operating temperature and then turn the main switch off. Disconnect the thermometer wiring and dip out the metal to below the level of the thermometer bulb. Take off the pot cover and remove the two screws fastening the thermometer case to the bracket. Grasp the case with the hand and the bulb with a pair of pliers and raise up and out. Be very careful at all times not to damage or break the bulb or hollow wire which contain the mercury; to do so will cause trouble in regulating the heat.
Replace the thermometer while the crucible is hot. See that the bulb does not project out from the casting so as to interfere with the insertion of ingots of cold metal. Press the tube firmly but carefully into place over the edge of the crucible, being careful not to injure it. Fasten the case to the bracket and reconnect the wiring and put on the cover.
All the pot adjustments on the electric pot are the same as on a gas pot.