TAPPING-OUT AND STOPPING-UP FURNACES, ETC. 95
pulled out, in which movement, should any difficulty be experienced, a device as seen at P, Fig. 18, is used, which by sledging on the end of the wedge shown, backs the bar out of the notch. Sometimes, instead of the device shown, a stout ring will be used, and by inserting" the wedge as shown a similar result is insnred. This device is a simple affair, and should suggest to many founders a remedy for difficulty often experienced in pulling back bars driven into the breast, tuyeres or slag-holes of a cupola.
After a bar has been removed from the notch, the metal generally flows out with a fair speed, but should lumps of dross or fuel impede its passage, a smaller bar than the one used to tap it is generally inserted in_ the notch-hole, and by working it up and down the passage is eventually cleared so as to permit the flow desired. It is not infrequent that the metal rushes out with too great speed, often coming with an unexpected burst, so as to strike the " keeper" with u spreading sheet of rushing metal if he is not continually on his guard. After a furnace has been tapped and the iron commences to flow well, a cover composed of fire brick held in an arch shape by a cast iron bracket casting is swung by means of an iron arm close up to the furnace front at the cooler V, Fig. 18, and let rest on the edge of the trough shown. Any space between this cover and the furnace shell is closed by means of sand being thrown around this section. This cover prevents the metal and slag from blowing" up against the shell of the furnace and burning it out.
An arrangement which is generally used at every hand-tap to assist in lessening the force of the stream is a stopper, as seen in Fig. 22. The end W, being*an when it can be tapped at the regular notch. It is often surprising how rapidly, as about 75 per cent of the heat generated from the solid fuel is utilized. This is attained where one ton of coke will produce one ton of iron; and Sir........................ 2,720 "