Polytechnic Association Proceedings. §17 



relative efficiency of iron and cast-steel boilers. 



An important series of experiments, to ascertain the comparative 

 evaporating power of iron and steel boilers, were lately made by 

 G. Stuckenholz, at the rolling mills of Messrs. Funke & Elbers, of 

 Hasfeu, Prussia. The two boilers were each five feet in diameter 

 and thirty-fom* feet long — constructed to stand five atmospheres 

 " over " pressure. One was made of wrought iron and the other 

 of soft ca«t-steel. The thickness of the„ sides in the cylindrical por- 

 tions of the iron boiler was 0.50 of an inch, and of the cast-steel 

 boiler 0.33 of an inch. Each boiler had a heating surface of 293 

 square feet and twelve square feet of grate surface. Both were 

 new and had never been before heated. They were set alike in 

 brick work, one above the other, but entirely separated by masonry; 

 the gaseous products of combustion passed through a single flue 

 underneath each boiler, and passed directly into the same chimney. 

 At first both boilere were filled, and fires were kept under them for 

 several days in order to dry the brickwork, after which the fires 

 were extinguished and the boilers emptied and cleaned. Each 

 boiler then received exactly 712 cubic feet of feed- water at thirty- 

 five degrees C. temperature; the man-holes were closed, and the 

 water was heated to the boiling point; again the fires were put out, 

 and all the ashes and coals taken away. From this point the boilers 

 were fired afresh, and fed with weighed fuel; the man-holes, hith- 

 erto kept closed, were how opened to allow the steam to escape, 

 and the firing was so well regulated, by means of dampers, that the 

 velocity of the escaping steam — measured by List's Velocimeter — 

 ■was the same in each boiler. The temperature of the gases from 

 the fire was measured, at a point six feet from the rear end of 

 «ach boiler, by Gauntlett's Pyrometer, and found to vary from 340 

 degrees to 380 degrees C. 



After consuming on each grate 3,150 pounds of coal of the same 

 quality, the cinders of which were burned over and over again, the 

 fires were put out and the man-holes closed. On the following day 

 the remaining water of the boilers, showing a temperature of thirty- 

 five degrees C, was let out through the emptying tube, situated at 

 the lowest part of the boiler, and measured by means of a hydrome- 

 ter adapted to the tube. The iron boiler showed 387 cubic feet, 

 and the steel boiler 331 cubic feet of the remaining feed- water. 

 Therefore, the water evaporated in the iron boiler was 712 — 387 

 =325 cubic feet, or 20,065 pounds; and that evaporated in the 

 steel boiler was 712 — 331=381 cubic feet, or 23,523 pounds. 



[Inst.] 52 



