Metallurgy Of Cast Iron

TAPPING-OUT AND STOPPING-UP FURNACES, ETC. 97
ramrned down as far as it is possible with the rammer rod just described. After as much clay is pressed downward with these rammers as is found possible, then a round stick about 3 inches in diameter at the small end and 3 % inches at the top, having a ring to prevent the sledging splitting the timber as seen at Fig. 20, is inserted into the notch and driven with two sledg-es down to the bottom, thus driving the dross and. clay back into the crucible, as far as possible, to make a solid filling of clay in the notch at its bottom.. This method of packing having been performed half -way up the notch, the packing stick is removed, the blast started, and the balance of the notch is then filled with clay packed with hand rammers. A stream of liot blast is now turned on the top of the notch and the clay grouting used to coat the iron trough, so that at the next tap there will be no dampness to start a "boil."
The above description is one plan of hand-stopping a furnace, but lately a machine has been designed to be worked by steam forcing out a stopper,* by which a furnace can be stopped at any part of a tap without shutting off the blast.
Many furnaces are now using stopping machines. They prove valuable in many ways, especially in permitting a more steady blast, and which gives a greater output and more uniform grade of metal and greatly lessens the chances for scaffolding due to a more steady heat being maintained in the furnace. It is said that all users of these stopping machines praise them very highly, and it now looks as if it would not be long before all furnaces would adopt them in their practice,
* Patented by S. W. Vaughn, Johnstown, Pa. two shovelfuls of clay toss it into the notch-hole, the clay is then quickly 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 "