MODERN BLAST FURNACE PRACTICE 93 



aro placed a minimum distanco apart (vortioally), usually 

 just far enouj:;li to allow the proper space for the thickness 

 of the socket plates and the depth of the bosh bands. As 

 we leave this rep;ion of intense heat and aj)proach the top of 

 the bosh, the plates are gradually spaced further apart. A 

 circular feed line carrying; water at 10 to 30 pounds pressure 

 supplies the legs or manifolds placed at each column. The 

 water is conducted from these manifolds to the lowest row 

 of plates and allowed to ascend through the series, finall}' 

 discharging into the water trough. Above the mantle plate 

 it is desirable to use a gravity feed instead of pressure. 

 The hearth is protected by a hea\^' steel jacket cooled by a 

 water spray, or a cast iron jacket built up in sections each of 

 which carries a coil of pipe through which the cooling water 

 circulates. With the increased l)0sh life it was found neces- 

 sary to protect the brick work forming the throat of the fur- 

 nace in order that both top and bottom might die together. 

 In some instances water cooled blocks have been used for 

 this purpose, but this seems a needless refinement, since a 

 scries of cast iron plates properly arranged will furnish all 

 needed protection for this portion of the furnace. 



The scope of this article will scarcely permit more than 

 a reference to the hot blast stoves of the modern furnace ; with 

 these the evolutionary process has been chiefly one affecting 

 size rather than one causing any radical changes in former 

 well known designs of the regenerative type. Some of the 

 recent stoves have been built 21 feet in diameter and 118 

 feet high. 



In the case of the modern blowing engine we find the 

 poppet, slide, and piston valves of the steam cylinder replaced 

 by the Corliss. The modern engines are of the vertical cross- 

 compound condensing type, as illustrated by the Tod engine 

 built for the National Steel company. The diameter for the 

 high pressure c^dinder of these engines is 54 inches, that of 

 the low 102 inches, giving a volumetric ratio of 3.57. The air 

 cylinders, w^hich are tandem to and above the steam cylinders, 

 are 108 inches in chameter; the common stroke is 60 inches. At 

 160 pounds steam pressure and 26 inches vacuum, these en- 

 gines will develop 5,000 indicated horsepower when running at 



