Proceedings of Association of Iron & Steel Electrical Engineers Volume 10 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 Excerpt: ...but to anyone contemplating building a large electric furnace, I believe I could give some things beforehand. One refers to the electrical contact on top of electrodes. Certain conditions arise there that a mechanical engineer in designing, without really consulting with an electrical engineer, will slip up on, and that is the electrodes get hot, consequently the cap gets hot, and when it cools off the same contraction is not procured and nine times out of ten the moment the electrode cools off and the cap cools off, there is a loose connection. Now, there is practically the same thing on the short end. That does not seem very much, but just so much that when starting up the second time, in place of having the arc in the furnace there is a hot top on the electrode, so there is one thing in a large furnace one would be up against. In a small furnace, probably in a 2 or 3-ton furnace, that trouble would not be experienced. On a large furnace it is necessary to cool the opening for electrode, and put in a cooler around the top similar to that used in a blast furnace. It can easily be seen what happens there. On a large furnace a large electrode is used--we use them as high as 18 in. in diameter. That means the electrode cooler was several hundred pounds in weight. With a larger furnace it means that the top of the furnace had to carry the cooler. The moment the furnace became hot the top expanded, and when it cooled off it came down. Quite frequently the top of the furnace would fall in. These conditions do not occur in a small furnace. I can speak of the large furnace more particularly, because I do not know anything about the small furnace. On the large furnace, with large electrodes, it was necessary to lift the electrodes clear out in order to clear the fu...