Slag Launder Build Up 106
Keeping the slag launders free of buildup is a constant chore for the slag tappers. Because the slag launders are water cooled slag will start to harden along the edges of the flow and build up over the top creating tunnels thru which the slag will flow. Many factors can determine the frequency and difficulty level of removing this buildup called a slag shell. Things such as slag level in the furnace, chemistry, mineral content and temperature determine the viscosity and "stickiness" of the slag which, in turn, determines the rate of flow and how quickly a shell builds up. On average the launder lids must be opened once every 3 or 4 pots and the launder quickly cleaned, most often while the slag is still running. A 6' long steel bar known as a skym-bay bar is used to break up the shell so the flow can wash it into the Kress pot. If the shell is heavy and/or hard or the flow is not sufficient to move it when broken up, such as you see here, the shelling must wait until the hole is closed whereupon the launder is "dry shelled" because the shell becomes brittle when cooled and is easier to break up and push into the pot.