469
OF ENGINEERING FORMULÆ.
Elephant Boilers—erm tinned.
Weight (in Cwts. per Hokse-power) of Elephant
' Boilers as usually made in France.
Horse- power. Diameter of Boiler. Diameter of Heater. Effective pressure in Atmo- spheres.
3 4 6 6
feet. feet. cwt. cwt. cwt. cwt.
10 to 20 2-62 1-64 .2-74 3-23 3-73 4-20
15 „ 25 2-95 1-80 2-86 3’50 4'01 4-57
20 „ 40 3-28 1-9? 3-12 3-73 4-33 4-94
30 „ 45 3'61 2’16 3-30 3-96 4’65 5-20
The disadvantages of the “Elephant” boiler are the un-
equal expansion of boiler and heaters, and the deposit of
sediment on the portions most exposed to the flie.
Belgian Rule for the Thickness of Boileh Plate.
1) = Diameter of boiler in feet.
P = Effective pressure of steam in atmospheres.
t = Thickness of plate in inches.
For plates directly exposed to the fire, t = -0216 DP +'12
„ beyond the fire .. .. t — *018 DP + -08
„ not heated by the fire .. t — ‘0144 DP + -04
„ the same, double riveted, t =z -0115 DP + '04
„ mild steel .. .. .. .. t = '0069 DP + ’04
Experiment on Comparative Performance of Boileks.
Water evaporated at 32°'i per lb. of coal .. .J Mean temperature of > gases.. ) Volume of air consumed) cube ft. per lb. of coal/ Diameter of boiler, feet Diameter of flues or| heaters, inches ..) Length of boiler in feet Number of flues ori heaters J Description of Boiler.
Lancashire. “ Elephant.” Fairbairn “ 1 ive Tube.’*
8-20 511° 186 6-56 27-5 25’75 2 7-95 510° 189 3-74 20’0 29-5 3 8-51 387° 227 3-75 27-5 25-75 2