Document GKxoz9zyxRb6J2G94Rv3gpMLr

American Society oj Heating and Ventilating Engineers Guide, 1934 3300 Btu per sq ft per hour for hand-fired boilers and 4000 Btu per sq ft . per hour for mechanically fired boilers when operating at designed load2. When operating at maximum load2 these values will run between 5000 and 6000 Btu per sq ft per hour. Boilers operating under favorable conditions at the above heat transfer rates will give exit gas temperatures that are considered consistent with good practice. ,TESTING AND RATING CODES The Society has adopted three solid fuel testing cqdes, a solid fuel rating code and one oil fuel testing code. A.S.H.V.E. Standard and Short Form Heat Balance Codes for Testing Low-Pressure Steam Heating Solid Fuel Boilers--Codes 1 and 2--^(Revision of June 1929)3, are intended to provide a method for conducting and reporting tests to determine heat efficiency and performance characteristics. A.S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers--Code No. 3--(Edition of 1929)3 is intended for use with A.S.H.V.E. Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers4. The object of this test code is to specify the tests to be conducted and to provide a method for conducting and reporting tests to determine the efficiencies and performance of the boiler. The A.S.H.V.E. Standard Code for Testing Steam Heating Boilers Burning Oil Fuel5 *is intended to provide a standard method for Con ducting and reporting tests to determine the heating efficiency and per formance characteristics when oil fuel is used with steam heating boilers. The Steel Heating Boiler Institute suggests a single number dimensional, rating in the S.H.B.I. Code for the Rating of Low-Pressure Heating Boilers by Their Physical Characteristics3. BOILER OUTPUT Boiler output as defined in A.S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers (Code No. 3) is the quantity of heat available at the boiler nozzle with the boiler normally insulated. It should be based on actual tests conducted in accordance with this code. This output is usually stated in Btu and in square feet of equivalent heat ing surface (radiation). According to the A.S.H.V.E. Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers, the performance data should be given in tabular or curve form on the following items for at least five outputs ranging from maximum down to 35 per cent of maxi mum: (1) fuel available, (2) combustion rate, (3) efficiency, (4) draft tension, (5) flue gas temperature. The only definite restriction placed on setting the maximum output is that priming shall not exceed 2 per cent. These curves provide complete data regarding the performance of the boiler under test conditions. Certain other pertinent information, such as grate area, heating surface and chimney dimensions is desirable also in forming an opinion of how the boiler will perform in actual service. 2For definition of design load and maximum toad see pages 337 and 338. See A.S.H.V.E. Transactions, Vol. 35, 1929. Also Chapter 42. See A.S.H.V.E. Transactions, Vol. 36, 1930. Also Chapter 42. See A.S.H.V.E. Transactions, Vol. 37. 1931. Also Chapter 42. See Rating of Heating actions, Vol. 36, 1930). Boilers by Their Physical Characteristics, by C. E. Bronson (A.S.H.V.E. Trans 336 Chapter 25--Heating Boilers The output of large heating boilers is frequently stated in terms of boiler horsepower instead of in Btu per hour or square feet of equivalent radiation. Boiler Horsepower: The evaporation of 34.5 lb of water per hour from and at 212 F which is equivalent to a heat output of 970.2 X 34.5 = 33,471.9 Btu per hour. Equivalent Evaporation: The amount of water a boiler would evaporate, in pounds per hour, if it received feed water at 212 F and vaporized it at this same temperature and at atmospheric pressure. It is usually considered that 10 sq ft of boiler heating surface will pro duce a rated boiler horsepower. A rated boiler horsepower in turn can carry a design load of from 100 to 140 sq ft of equivalent radiation. It is apparent, therefore, that 1 sq ft of boiler heating surface can carry a design load of from 10 to 14 sq ft of equivalent radiation, or somewhat more if the boiler is forced above rating. The application of these values is discussed under the heading Selection of Boilers. BOILER EFFICIENCY The term efficiency as used for guarantees of boiler performance is . usually construed as follows: 1. Solid Fuels. The efficiency of the boiler alone is the ratio of the heat absorbed by the water and steam in the boiler per 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 thewater and steam in the boiler per pound of fuel as'fired to the calorific value of 1 lb of fuel as fired. 2. Liquid Fuels. The combirted efficiency of boiler, furnace and burner is the ratio of the heat absorbed by the water and steam in the boiler per pound of fuel to the calorific value of 1 Jb of fuel. Solid fuel boilers usually show an efficiency of 50 to 75 per cent when operated under favorable conditions at their rated capacities. Infor mation on the combined efficiencies of boiler, furnace and burner has resulted from research conducted at Yale University in cooperation with the A.S.H.V.E. Research Laboratory and the American Oil Burner Association7. For general information on heating efficiencies see Chapter 29. S-- --ELECTION /OspF nBvO-MILi EroRcS Estimated Design Load: The load, stated in Btu per hour or equiv alent direct radiation, as estimated by the purchaser for the conditions of inside and outside temperature for which the amount of installed radiation was determined is the sum of the heat emission of the radiation to be actually installed plus the allowance for the heat loss of the connecting piping plus the heat requirement for any apparatus requiring heat con nected with the system (A.S.H.V.E. Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers--Edition of April, 1932). The estimated design load is the sum of the following three items8: 1. The estimated heat emission in Btu per hour of the connected radiation (direct, indirect or central fan) to be installed. TSee A.S.H.V.E. research papers entitled Study of the Characteristics of Oil Burners and Heating Boilers, by L. E. Seeley and E. J. Tavanlar (A.S.H.V.E. Transactions, Vol. 37, 1931), and A Study of Intermittent Operation of Oil Burners, by L. E. Seeley and J. H. Powers (A.S.H.V.E. Transactions, Vol. 38, 1932). . n33o7i