Steam:
Its Generation and Use

by the remainder, the result is the height in feet. Or, by formula : a6-'.9) To find the maximum efficient draft for any given chimney, the heated column being 600 I*., DIAGRAM OF DRAFT AND CAPACITY OF CHIMNEY. temperature. It will be seen that practically nothing can be gained by carrying the temper- ature of the chimney more than 350° above the external air at 6o°. To determine the quantity of air, in pounds, a given chimney will deliver per hour, multiply the distance in inches, at given temperature, on the diagram, by 1000 times the effective II 50 100 150 200 250 300 3Ö0 400 and the external air 62°: Multiply the height above grate in feet by .007, and the product is the draft power in inches of water. The above diagram shows the draft, in inches, of water for a chimney 100 feet high, under different temperatures, from 50° to 8oo° above external atmosphere, which is assumed at 6o°. The vertical scale is full size, and each division is of an inch. It also shows the relative quantity, in pounds of air, which would he delivered, in the same time, by a chimney under the same differences of Chimney for 1260 H. P. of Babcock & Wilcox Boiler, at Bird Coleman Furnace, Cornwall, Pa. area in square feet, and by the square root of the height in feet. This gives a maxi- mum. Fric- tion in flues 000 050 700 750 800 and furnace may reduce it greatly. The external diameter of a brick chim- ney at the base should be one-tenth the height, unless it be supported by some other structure. The “batter” or taper of a chimney should be from fg to inch to the foot on each side. Thickness of brick work: one brick (8 or 9 inches) for 25 ft. from the top, increas- ing brick (4 or 4^ inches) for each 25 ft. from the top downwards. If the inside diameter exceed 5 ft. the top length should be 1 bricks, and if un- der 3 ft. it may be % brick for ten feet. 61