Document BvRroYOMnQ52ze9VxDqgmq804

504 CHAPTER 35 1959 Guide Table 2 ....SBI Net Rating Data for Tab/e 2 Steel Boilers--Oil-fired* SBI Hoi Rating Steam SqR (t) Btvh (2) Water Btuh <31 SBI Crow Output Bhd> Minimum Furnace Yohtme Cu Ft Minimum Heating SqFI (4) 15) (5) 275 320 400 550 66,000 77,000 96,000 132,000 74,000 87,000 108,000 149,000 99,000 115,000 144,000 198,000 2.5 2.9 3.6 5.0 16 19 24 32 700 900 1100 168,000 216,000 264,000 189,000 243,000 297,000 252,000 324,000 396,000 6.4 8.2 10.0 41 53 65 1&0 1500 1800 2200 2600 3000 312,000 360,000 432,000 528,000 624,000 720,000 351,000 405,000 486,000 468,000 540,000 648,000 594,000 702,000 810,000 792,000 936,000 1,080,000 11.8 13.6 16.4 20.0 23.6 27.3 77 88 106 129 153 177 3500 4000 4500 5000 ' 840,000 960,000 1,080,000 1,200,000 945,000 1,080,000 1,215,000 1,350,000 1,260,000 1,440,000 1,620,000 1,800,000 31.8 36.3 40.9 45.4 206 236 265 294 * Stoker-Firedand Gm-Fired SBI Net Riling not peeler thin oil-fired rating. Hind-Fired Net RBI Riling (Steam) turt treater than 14 times the square feet of heeling garface. height, and the draft in the stack are all subject to the limits established in the code. Tests are ran using anthracite coal of standard specification. Bituminous coal and coke ratings are the same as for anthracite. For automatically-fired boilers, the number of boilers of a series to be tested, the flue gas temperature and analysis, the minimum overall efficiency, the draft loss through the boiler, and the heat, release in the combustion chamber are sub jected to limitation by the code.1 Oil-flred boiler ratings are established by tests using gun-type oil burners and commer cial grade No. 2 fuel oil. Stoker-fired ratings are based on the Gross / = B = R Output obtained by oil-fired tests. Gasfired ratings for boilers having gross outputs greater than 300,000 Btu per hour, where no A.QA. Rating is published, are based on the Gross I = B = R Output obtained by oilfired tests. Gas-fired ratings for boilers having gross outputs less than 300,000 Btu per hour, where no A.GA. Rating is published, are established by gas-fired tests with atmospheric, aingle-port-type burners using natural or manufactured gas or a mixture of these two gases. The A.GA. Output Rating of a gas-designed boiler may be used in determining the Net I = B = R Rating. The Net / = B -- R Rating is determined from the Gross I = B -- R Output by applying specified Piping and Pickup Factors which range from 2.36 to 1.40 for hand-fired boilers, and from 1-56 to 1.288 for automatically-fired steam boilers, and from 1.333 to 1288 for automatically-fired hot water boilers. In all cases, the factor decreases as the boiler size in creases. Table 5 is abstracted from the 19511 = B -- R Boiler Rating Tables in the.code and illustrates the relationship be tween Net I = B = R Rating and Gross I ~ B -- R Output. The American Gas Association rates gas designed boilers at 80 percent of the A.GA. Input Rating. These ratings are Table 3 .... SBI Gross Output and SBI Net Rating Data for Table 3 Steel Boilers SBI Grow Output Btuh Water Bluh SBI Net Rating] Steam Bluh Steam Sq Ft 99,000 115.000 144.000 198.000 252.000 324.000 396.000 504.000 648.000 792,000 1,008,000 1,260,000 1.512.000 1.800.000 74.000 87.000 108,000 149.000 189.000 243.000 297.000 378.000 486.000 594.000 756.000 945.000 1.134.000 1.350.000 66,000 77.000 96.000 132.000 168.000 216,000 264.000 336.000 432.000 528.000 672.000 840.000 1,008,000 1,200,000 275.000 320.000 400.000 550.000 700.000 900.000 1,100,000 . 1.400.000 1.800.000 2,200,000 2,800,000 3,500,000 4,200,000 5,000,000 Table 4 .... Minimum Stack Dimensions for Table 3 Oil-Burning Boilers and Boiler-Burner Units Rectangular Round Firing Rate Nat Over Gph 2.1 3.5 5.3 7.7 11.5 15.0 21.0 26.0 Nominal Dimension* Ind.** Inside Dimensions of Liner lnd"* Firing Rate Not Over Gph inside Ola of Liner Inches 8X8 8 X 12 12 X 12 OX X 6X 6mtf X x 1m0K 1.3 1.8 2.5 6 7 8 12 X 16 16 X 16 16 X 20 9H*X 13M 13>4 X 13K 13 X 17 4.7 5.6 7.0 10 11 12 20 X 20 16X X 16M 20 X 24 16H X 20H 12.0 19.0 15 18 determined by performance tests' described in the A.GA. Approval Requirements for Central Heating Appliances. The Mechanical Contractors Association of America has adopted a method, based on their physical characteristics, for rating boilers that are not rated in accordance with the SBI or I =? B = R Codes. Ratings are expressed on a Net Load basis in square feet of steam radiation. The MCAA has also adopted a Testing and Rating Code for Boiler-Burner Units.* The purpose of this Code is to pro vide a basis of rating commercial sizes of steel heating boilerburner units fired with oil or gas fuel. This code allows a higher rating than is permissible under the SBI Code. A gross output is established with certain limiting factors ap plying to flue gas temperature, carbon dioxide, efficiency, and quality of steam. This output is divided by 1.5 to determine the net rating. BOILER EFFICIENCY The term efficiency, as used for guarantee of boiler per formance, is usually construed as follows: I. SoUd Fuels. The efficiency of the boiler alone is the ratio of the heat absorbed by the water and steam in the boiler per Heating Boilers, Furnaces, Space Heaters 505 Nand*RrW labie 5....i = B = R Boiler Rating Table* Aotomatic-Fired ' Net l-B-R Rating Output StMj" water Steam MBh 1 MBh 2 Sq Ft 3 Piping and Ptdurp 4 Time Avail- Fuel" wo Last, Maximum Height* Minimum Area6 Gross Output Hr Ft Sq la. MBh 5 6 76 Nett = B " R Rating Steam MBh 9 MBh 10 Sq Ft 11 Piping and Fidaip Factor Water Steam Minimum Maximum Stack AOowoble Area6 Draft two Sq In. In. W.G.6 12 13 14 15 57 218 359 489 614 735 854 970 1083 1192 1298 1401 1502 1599 1726 1849 1968 2086 2197 2307 2415 2470 2605 2738 2874 3024 3192 3360 4032 4704 5376 6048 6720 24 100 2.360 96 400 2.268 168 700 2.139 240 1000 2.039 312 1300 1.967 384 1600 1.914 456 1900 1.872 528 2200 1.837 600 2500 1.805 672 2800 1.774 744 3100 1.744 816 3400 1.717 888 960 1056 1152 1248 1344 3700 4000 4400 4800 5200 5600 1.091 1.666 1.634 1.605 .1.577 1.552 1440 1536 1632 1680 1800 1920 6000 6400 6800 7000 7500 8000 1.526 1.502 1.4S2 1.470 1.447 1.426 2040 2160 2280 2400 2880 3360 8500 9000 9500 10000 12000 14000 1.409 1.400 1.400 1.400 1.400 1/400 3840 4320 4800 16000 18000 .20000 1.400 1.400 1.400 7.50 6.32 5.73 5.32 4.99 4.73 4.49 4.34 4.24 4.15 4.07 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 29.0 36.5 42.0 46.0 49.0 52.0 54.5 56.5 59.0 61.0 63.0 64.5 66.5 68.0 70.0 71.5 73.0 74.5 76.0 77.5 79.0 79.5 81.5 83.0 85.0 87.0 89.0 91.5 99.0 106.5 112.5 118.0 120.0 50 37 50 146 54 251 82 352 no 451 135 547 160 642 185 736 207 829 231 920 253 1011 275 1101 296 315 337 358 376 393 1189 1278 1394 1509 1624 1739 409 425 438 446 464 481 1858 1978 2102 2164 2318 2473 497 _ 515 535 555 634 712 2628 2782 2937 3091 3709 4328 789 4946 863 5564 900 6182 28 no 188 264 338 410 482 552 622 690 758 828 892 960 1056 1152 1248 1314 1440 1536 1632 1680 1800 1920 2040 2160 2280 2400 2880 3360 3840 4320 4800 24 96 168 240 312 384 100 400 700 1000 1300 1600 1.333 1.333 1.333 1.333 1.333 1.333 456 528 COO 672 744 816 1900 2200 2500 2800 3100 3400 1.333 1.333 1.333 1.333 2.333 1.333 888 960 1056 1152 1248 1344 3700 4000 4400 4800 5200 5600 1.333 1.331 1.320 1.310 1.301 1.294 1440 1536 1632 1680 1800 1920 6000 6400 6800 7000 7500 8000 1.290 1.288 1.288 1.288 1.288 1.288 2040 2160 2280 2400 2880 3360 8500 9000 9500 10000 12000 14000 1.288 1.288 1.288 1.288 1.288 1.288 3840 4320 4800 16000 18000 20000 1.288 1.288 1.288 1.560 1.525 1.492 1.466 1.444 1.424 1.408 1.394 1.382 1.369 1.359 1.349 1.339 1.331 1.320 1.310 1.301 1.294 1.290 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 1.288 50 50 50 52 73 95 115 135 155 173 192 211 230 249 274 297 318 339 359 377 395 405 426 446 467 486 504 522 596 668 740 810 877 0.044 0.058 0.072 0.084 0.096 0.108 0.118 0.130 0.141 0.152 0.162 0.172 0.183 0-192 0.206 * Extracted Irom Rating Table in 1951 edition of I -- B - R Toting and Entire Cod* for L*xc Prorurt Coot Iron Seating BotUrt. b To be speofied in catalog. ' Maximum stack height wtucb majr be shown in catalog. pound of combustible burned on the grate, to the calorific value of 1 lb of combustible as fired. The'combined efficiency of boiler, furnace, and grate is the ratio of the heat absorbed by the water and steam in the boiler per pound of fuel as fired, to the calorific value of 1 lb of fuel as fired. 2. Liquid and Gaseous Fuels. The combined efficiency of boiler, furnace, and burner is the ratio of the heat absorbed by the water and steam in the boiler per pound or cubic foot of fuel, to the calorific value of 1 lb or cubic foot of fuel, respec tively. The following efficiencies apply to current designs of boilers operated under favorable conditions at their gross output ratings. Some older boilers, designed primarily for hand fir ing, may have lower efficiencies when automatically-fired. Anthracite, hand-fired................................... 60 to 75 percent Bituminous coal, hand-fired.......................... 50 to 65 percent Stoker-fired..................................................... 60 to 75 percent Oil- and gas-fired ...........................................70 to 80 percent Higher efficiencies for hand-fired bituminous coal may be obtained by careful firing of either a regular or a smokeless boiler. RATING OF BOILERS In referring to boiler rating, it is necessary to know the hggre on which the rating has been established in order to understand the exact meaning of the term. The following example will illustrate the meaning of three ratings which might be established for the same boiler. Assume that an installation has the following loads deter mined in accordance with the section Selection of Boilers: Net Load............................... 1000 sq ft of steam radiation Piping Tax................................. 200 sq ft of steam radiation Design Load............................. 1200 sq ft of steam radiation Pickup Allowance.................... 240 sq ft of steam radiation Maximum or Gross Load-- 1440 sq ft of steam radiation