Steam:
Its Generation and Use

SIZES OF CHIMNEYS WITH APPROPRIATE HORSE-POWER BOILERS. The following table has been computed by means of the formulæ on page 60, and will be found useful for ready reference Height of Chimneys. 5° ft :|öoftjyoft| 80 ft.J 90 ft.I: TOO Commercial Horse-Power. 18 21 24 27 3° 33 36 39 42 48 54 60 66 72 78 84 9° 96 35 49 65 84 25 38 54 72 92 141 27 41 58 78 t25 152 183 216 62 83 107 133 163 196 231 3” 363 5°5 ”3 208 245 33° 427 539 658 792 182 219 258 348 449 565 694 835 995 1163 ’344 ’537 36S 472 593 728 876 1038 1415 i6t6 IRON CHIMNEY STACKS. In many places, notably in iron works, iron stacks are preferred to brick chimneys. Their efficiency for the same dimensions is somewhat higher because there is no infiltration of air as through brick-work. The cuts on the mar- gin of this page show the stacks of the Pennsylvania Steel Co., at Sparrow’s Point, Md. These are lined with brick their whole height and are bolted down to the base so as to require no stays, though in this case they would be suffici- ently stable from their own weight. A good method of securing such bolts to the stack is practiced by the Pencoyd Iron-Works, Pa., and is shown in detail in the annexed figures. On page 61 is a cut of a similar stack, at the Bird Coleman Furnaces, Cornwall, Pa. stacks require to be kept painted to prevent rust, and generally, where not bolted down, as here shown, they need to be braced by rods or wires to surrounding objects. With four such braces attached to an angle iron ring at % the height of stack, and spreading laterally at least an equal distance, each brace should have an area in square inches equal to 1-1000 the ex- posed area of stack (dia. X height) in feet. 444 8-ins de-dia.^t- 389 503 632 776 934 1107 1294 1496 X720 3 gon, and 28 for a round chim- ney. Thus a square chimney 748 918 1105 1310 1531 i77o 2027 551 692 849 1023 1212 1418 1639 1876 '6 981 1181 1400 i637 1893 2167 Effective I Area, square ft. 1 Actual Area, square ft. | Side of i 1 square of 1 jap’roximatej o-97 z.77 16 i-47 2.41 2.08 3-M 22 2.78 3-98 24 3-58 4.91 27 447 5-94 30 5-47 7.07 32 6-57 8.30 35 7.76 9.62 38 io-44 12.57 43 I.3-5I >5-9° 48 16.98 19.64 54 20.83 23-76 59 25.08 28.27 64 29-73 33 18 7° 34-76 38.48 75 40.19 44-18 80 46.01 50-27 86 Iron well Stability, or power to withstand the overturning force of the highest winds requires a proportionate re- lation between the weight, height, breadth of base, and exposed area of the chimney. This relation is expressed in the equation C^- = IV, b in which d — the average breadth of the shaft, h = its height; b = the breadth of base; all in feet; W — weight of chimney in lbs., and C= a co-efficient of wind pressure per square foot of a. This varies with the cross- section of the chim- ney, and = 56 for a square,35 for an octo- Holding down Bolts and Lugs, of average breadth of <8 ft., 10 Pencoyd Iron Works. ’----------1------—- feet wide at base and 100 feet high, would require to weigh 56 X 8 X 100 X 10 — 448,000 lbs. to withstand any gale likely to be experienced. Brick work weighs from 100 to 130 lbs. per cubic foot, hence such a chimney must average 13 inches thick to be safe. Around stack could weigh half as much, or have less base. 170 i lide dia.f 62