Document redJXX9n8aE8Qydz4Bm57XZRJ

American Society of Heating and Ventilating Engineers Guide, 1929 engineer and must be well built to sustain such a heavy load and the height is such as to produce considerable draft to offset unfavorable weather conditions, etc. Chimneys in this class produce about 0.00945 in. of theoretical draft per foot of height in zero weather with 600 deg. in the stack. Chimneys recommended foj larger boilers 15 to 250 hp. may be pro portioned in accordance with the report made by a joint Committee of the Table 3. Chimney Sizes for Low Pressure Heating Boilers and Warm Air Furnaces Warm Air Furnacb Capacity in Lbader Pips Sq. In. Steam Boiler Capacity Sq- Ft. OF Radia tion Hot Water Heater Capacity Sq. Ft. of Radia tion Nominal Dimen sions of FireClay| Lining In. Rectangular Flue Actual Inside oiDimensions Fire Clay Lining In. Actual Area Sq. In. Effec tive Area Sq. In. Round Flue Inside Diameter of Lining In. Actual Area Sq. In. Height in Ft. from Grate- 790 1000 590 690 900 900 1100 1700 1940 2130 2480 3150 4300 4600 5000 5570 5580 6980 7270 8700 9380 10150 10470 11800 14700 17900 973 1140 1490 1490 1820 2800 3200 3520 4090 5200 7100 7590 8250 9190 9200 11500 12000 14400 15500 16750 17250 19500 24300 29500 8)4x13 13x13 8)3x18 13x18 18x18 20x20 20x24 24x24 7x11)4 11)4x11)4 6)4x16)4' 11)4x16Yi 15)4x15)4 17)4x17)4 17x21 21x21 24x24* 24x28* 28x28* 30x30* 28x32* 81 70 127 99 110 100 183 156 248 195 298 234 357 278 441 576 380 672 468 784 531 900 616 896 635 10 12 15 18 20 22 24 27 30 33 36 79 2C 113 3&29* 177 254 314 380 452 573 707 855 1018 Dimensions below are for unlined rectangular flu?s. American Boiler Manufacturers Association and Stoker Manufacturers Association and approved by these organizations. The sizes are given in Table 4. Chimneys for Oil Fuel.'--The requirements for stacks for oil fuels are entirely different from those connected to coal-fired boilers, as there are certain losses through the boiler proper that are eliminated. Gas tem peratures entering the stacks are lower for a given capacity, and the volume of gas is less than with coal. The cross-sectional area of the stack may therefore be less. In most instances this may safely be taken as i From Marks- Mechanical Engineers Handbook. 152 Chapter VI--Chimneys w ______ __ ____ -- V..A.C ivouiu ue iurnisnea lor coal-hred boilers. In determining the height, care must be taken to design a stack that will give a sufficient draft for the maximum requirements of the boiler, but not more. In this way the efficiency is safeguarded, and the danger of a draft such as to pull through too large an excess of air is eliminated. Table 4. Height of Stack for Average Installations (Sea Level) Average Draft Losses vnth Forced Draft Stokers Per Cent Rating. ...... .. Draft Furnace....................... Friction Loss (Boiler)............ Friction Loss (Breeching)... . Total Draft Reauired............ Height of Stack (Ft.) . 100 0.15 0.18 0.10 0.43 80 112 200 0.15 0.65 0.10 0.90 145 250 U. 15 0.9 0.10 1.15 178 300 0.15 1.20 0.10 1.45 220 Diameter of Chimney in Inches for Horizontal Return Tubular Boilers Nominal H. P. 15 20 25 30 35 40 50 60 75 90 100 115 125 150 175 200 210 225 250 - 100% Rating 13 14 16 17 18 19 20 21 23 25 26 27 28 30 32 33 34 35 36 150% Rating 14 16 18 19 20 21 23 24 26 28 29 31 32 34 36 38 38 40 41 200% Rating 17 18 20 21 22 23 25 27 29 31 33 34 35 38 40 43 44 45 47 Stack in Feet--For Sea Level and 60 DEG. fahr. Outside Temp. Assumed Fric tion Loss in Stack 0.1 in. pkr 100 ft. Draft at Base of Stack 0.12 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 100% Rating 21 26 35 43 52 60 69 78 86 95 104 112 150% Rating 22 28 37 46 56 . 65 7484 93 102 112 121 200% Rating 25 30 41 51 61 71 81 91 101 111 122 132 Rating............ Efficiency_ CO,...... ......." 100% 65% 8% 150% 65% 9% 200% 63% 10% Stack Temp, deg. fahr... ............ Lbs. of Gas............... Friction loss through boiler varies according to construction. 450 500 550 85 77 73 'For Furnace Draft.--Allow 0.15 for forced draft. . For Natural Draft 0.35 in. or higher should be used depending upon rate of combustion and fuel used. For Breeching Friction Loss.--AUbw 0.05 in. for each right angle bend and 0.1 in. per 100 ft. of length. . Chimneys for still greater horsepowers are given by Tables 5 and 6. Table 7, adapted from one calculated by C. R. Weymouth (Trans. A. S.M. E., Vol. 34, 1912) and based on actual test data, will be found to give satisfactory results under the assumed conditions as given for stacks with oil-burning boilers. ... i53