AMERICAN INDUSTRIES SINCE COLUMBUS. 



47 





fcX^i 



very thick lining of the best fire-resisting material. At the bot- 

 tom of the converter is a chamber called a " tuyere-box," from 

 which a number of " tuyeres " made of baked fire-clay pass up- 

 ward through the lining of the vessel. 



The " converter " is hung upon " trunnions " (much as cannon 

 are), through one of which the blast is conveyed to the " tuyere- 

 box " ; these trunnions rest 

 in "bearings " which, in some 

 of the earlier converters, 

 were on the top of tall iron 

 stands (the base of one of 

 such stands is seen in Fig. 

 57) firmly bolted to founda- 

 tions of masonry ; but in 

 more modern constructions 

 these bearings are supported 

 by iron girders sustained by 

 columns, or masonry piers 

 are carried up of sufficient 

 height to receive them. The 

 air blast being carried 

 through the hollow trun- 

 nion permits the turning of 

 the vessel upon its bearings 

 without interrupting the 

 blast by so doing ; this turn- 

 ing is in modern practice 

 generally effected by some 

 adaptation of hydraulic ma- 

 chinery, and occasionally by 

 " worm " or " spur " gearing 

 as shown in Fig. 58. The 

 pressure of blast used was 

 at first four to five pounds, 

 but this was soon increased 

 to eight, and, although there are still a few converters blown at 

 this pressure, in the larger establishments a blast of twenty to 

 twenty-five pounds is usually employed. Why such pressures are 

 used, involving very heavy and expensive machinery and an ex- 

 cessive amount of power, is not evident, as no better or cheaper 

 steel can be made thereby. 



The operations for making steel are as follows : The converter, 

 after having been newly lined, is thoroughly heated by means of 

 a coke fire built therein, and urged by a blast through the tuyeres; 

 when the lining is sufficiently hot, the converter is emptied, suffi- 

 cient blast being used to blow out all the dust, etc. The vessel is 



Fig. 57. Section of a Bessemer Converter. 



