in the estimation of these particulars. Further, in order properly to represent working conditions, the rate of combustion of the fuel throughout the trial must be the same as that intended to be used in ordinary working, and the duration of the test must be sufficient to include proportionately as much cleaning of fires as would occur under the normal working conditions. The tests should always be made with the kind of coal intended to be generally used, and the records should include a test of the calorific value of a sample of the fuel carefully selected so as fairly to represent the bulk of the coal used during the trial. The periodic records taken are the weights of the fuel used and of the ashes, &c., produced, the temperature and quantity of the feed-water, the steam pressure maintained, and the wetness of the steam produced. This last should be ascertained from samples taken from the steam pipe at a position where the full pressure is maintained. In order to reduce to a common standard observations taken under different conditions of feed temperatures and steam pressures, the results are calculated to an equivalent evaporation at the atmospheric pressure from a feed temperature of 212° F. (J. T. Mi.)
Trials of Various Types of Marine Boilers
Description of Boiler. | Grate Area sq. ft. |
Heating Surface sq. ft. |
Duration of Trial Hours. |
Coal burned Per sq. ft. of Grate per Hour. |
Air Pressure in Stoke- hold— Inches of Water. |
Chimney Draught— Inches of Water |
Water Evaporated per ℔ of Coal. |
Water Evapor- ated per sq. ft. of Heating Surface. |
Thermal Units per ℔ of coal. |
Efficiency of Boiler %. | ||
Actual. | From and at 212° F. | |||||||||||
℔. | ℔. | ℔. | ||||||||||
Ordinary cylindrical single- ended; 3 furnaces; 155 ℔ working pressure; closed stokehold system.* | 81 | 2308 | 25 | 14.2 | Nil | 0.36 | 8.56 | 10.26 | 4.26 | 14,267 | 69.7 | |
” | ” | 24 | 13.9 | ” | 0.50 | 8.84 | 10.33 | 4.32 | 14,697 | 68.0 | ||
” | ” | 9 | 30.3 | 0.81 | 0.39 | 7.93 | 9.27 | 8.46 | 14,686 | 61.4 | ||
” | ” | 812 | 29.1 | 0.65 | 0.32 | 8.84 | 10.34 | 9.05 | 14,612 | 68.4 | ||
Ordinary cylindrical single- ended; 3 furnaces; 210 ℔ working pressure; closed ashpit, Howden system.** | 63.2 | 2876 in boiler, 766 in air heaters | 13 | 20.6 | In Ash- pit 1.53 | 0.58 | 11.30 | 12.33 | 5.14 | 14,475 | 82.3 | |
Niclausse water-tube; 160 ℔ working pressure. | 46 | 1322 | 8 | 12.8 | Nil | 0.20 | 8.41 | 10.15 | 3.75 | 14,680 | 66.9 | |
” | ” | 8 | 21.9 | ” | 0.20 | 8.01 | 9.40 | 6.11 | 14,760 | 62.1 | ||
” | ” | 37 | 20.2 | ” | 0.29 | 7.62 | 9.00 | 5.44 | 14,600 | 60.5 | ||
Niclausse water-tube; 250 ℔ working pressure. | 34 | 990 | 9 | 14.0 | 0.10 | 0.23 | 8.77 | 10.50 | 4.17 | 14,640 | 69.8 | |
” | ” | 9 | 22.0 | 0.27 | 0.23 | 7.68 | 9.06 | 5.74 | 14,640 | 60.4 | ||
” | ” | 90 | 15.4 | Nil | Not asce- rtained | 7.61 | 9.08 | 4.00 | 14,630 | 59.9 | ||
Babcock water-tube; 3316 in. tubes; 260 ℔ working pressure. | 36 | 1010 | 9 | 13.0 | ” | 0.26 | 9.31 | 11.02 | 4.30 | 14,590 | 73.2 | |
” | ” | 9 | 20.0 | 0.18 | 0.20 | 8.58 | 10.11 | 6.13 | 14,590 | 67.0 | ||
” | ” | 90 | 14.5 | Nil | Not asce- rtained | 8.09 | 9.53 | 4.18 | · · | 63.1 | ||
Babcock water-tube; 11316 in. tubes; 270 ℔ working pressure.*** | 62 | 2167 | 28 | 18.4 | ” | 0.45 | 8.94 | 10.61 | 4.61 | 14,520 | 70.7 | |
” | ” | 24 | 19.2 | ” | 0.47 | 8.93 | 10.59 | 4.82 | 14,390 | 71.1 | ||
” | ” | 12 | 20.5 | ” | 0.42 | 9.42 | 11.04 | 5.41 | 14,080 | 75.8 | ||
” | ” | 7 | 28.9 | 0.50 | Not asce- rtained | 8.54 | 9.88 | 6.91 | 14,390 | 66.3 | ||
” | ” | 30 | 19.9 | Nil | 0.38 | 10.11 | 12.00 | 6.01 | 14,530 | 79.9 | ||
” | ” | 29 | 27.1 | 0.66 | 0.23 | 9.96 | 11.67 | 8.05 | 14,630 | 77.1 | ||
Belleville water-tube with economizers; 320 ℔ working pressure. | 44 | 910 in boiler; | 2412 | 15.8 | Nil | 0.36 | 9.65 | 11.46 | 4.94 | 14,697 | 77.2 | |
” | 447 in econo- | 24 | 17.4 | ” | 0.39 | 9.33 | 11.00 | 5.30 | 14,805 | 71.8 | ||
” | mizer; | 11 | 19.8 | ” | 0.43 | 9.39 | 11.03 | 6.38 | 14,578 | 73.3 | ||
” | 1357 total. | 8 | 27.2 | ” | 0.39 | 8.28 | 9.79 | 7.78 | 14,611 | 65.0 | ||
Yarrow water tube; 134 in. tubes; 250 ℔ working pressure. | 56 | 2896 | 26 | 16.9 | Nil | 0.31 | 9.57 | 11.45 | 3.12 | 14,750 | 75.0 | |
” | ” | 26 | 18.2 | ” | 0.31 | 9.37 | 11.33 | 3.30 | 14,500 | 75.7 | ||
” | ” | 25 | 21.3 | ” | 0.31 | 8.83 | 10.45 | 3.63 | 13,500 | 75.2 | ||
” | ” | 30 | 35.4 | 0.53 | 0.26 | 8.82 | 10.59 | 6.04 | 14,430 | 70.9 | ||
” | ” | 8 | 41.9 | 0.86 | 0.31 | 8.24 | 9.94 | 6.69 | 14,500 | 66.3 | ||
” | ” | 8 | 33.7 | 0.31 | 0.30 | 8.39 | 9.93 | 5.47 | 14,680 | 65.4 | ||
” | ” | 8 | 39.8 | 0.82 | 0.24 | 8.85 | 10.43 | 6.81 | 14,530 | 69.5 | ||
Dürr water-tube; 250 ℔ working pressure. | 71 | 2671 in boiler, 140 in super- heater; 2811 total. |
26 | 16.1 | Nil | 0.39 | 7.95 | 9.50 | 3.24 | 14,500 | 63.8 | |
” | 26 | 17.7 | ” | 0.30 | 7.06 | 9.28 | 3.43 | 14,620 | 61.7 | |||
” | 25 | 21.1 | ” | 0.31 | 7.62 | 9.08 | 4.05 | 14,650 | 60.3 | |||
” | 7 | 33.8 | 0.70 | 0.36 | 7.72 | 9.29 | 6.59 | 14,570 | 62.7 | |||
” | 8 | 26.7 | 0.33 | 0.35 | 7.86 | 9.26 | 5.30 | 14,320 | 63.1 | |||
” | 8 | 34.6 | 1.11 | 0.20 | 8.02 | 9.53 | 7.02 | 14,230 | 64.8 | |||
” | 22 | 34.8 | 0.73 | 0.16 | 6.84 | 8.06 | 6.02 | 14,430 | 54.0 | |||
” | 24 | 29.9 | 0.35 | 0.12 | 7.62 | 9.00 | 5.75 | 14,240 | 61.2 | |||
” | 20 | 19.9 | Nil | 0.21 | 7.30 | 8.33 | 3.66 | 14,240 | 58.6 |
* In the first three trials no retarders were used in the tubes. In the last trial retarders were used. |
** In this trial retarders were used in the tubes. |
*** The first four trials were made with horizontal baffles above the tubes; the last two trials with the baffling described in the text. |
Boiler Making
The practice of the boiler, bridge and girder shops may here be conveniently treated together, because similar materials and methods are employed in each, notwithstanding that many points of divergence in practice generally relegate them to separate departments. The materials used are chiefly iron and steel. The methods mostly adopted are those involved in the working of plates and rolled sections, which vastly predominate over the bars and rods used chiefly in the smithy. But there are numerous differences in methods of construction. Flanging occupies a large place in boilermaking, for end-plates, tube-plates, furnace flues, &c., but is scarcely represented in bridge and girder work. Plates are bent to cylindrical shapes in boilermaking, for shells and furnaces, but not in girder work. Welding is much more common in the first than in the second, furnace flues being always welded and stand pipes frequently. In boiler work holes are generally drilled through the seams of adjacent plates. In bridge work each plate or bar is usually drilled or punched apart from its fellows. Boilers, again, being subject to high temperatures and pressures, must be constructed with provisions to ensure some elasticity and freedom of movement under varying temperatures to prevent fractures or grooving, and must be made of materials that combine high ductility with strength when heated to furnace temperatures. Flanging of certain parts, judicious staying, limitation of the length of the tubes,