Document LoEzNNxmKMvwd0V5n46xjr2Ez

Heating Ventilating Air Conditioning Guide 1939 are arranged in multiple on the boiler face, from two to five burners each boiler. "| The larger installations are nearly always started with a hand torch $ and are manually controlled, but the useof automatic control is increasing I and completely automatic burners are now available to burn the two I heaviest grades of oil. Nearly all of the smaller installations, in schools 1 churches, apartment houses and ,the like, are fully automatic. '| Because of the viscosity of the heavier oils, it is customary to heat them ii before transferring by truck tank. It also has been common practice to* preheat the oil between the storage tank and the burner, as an aid to I movement of the oil as well as to atomization. This heating is accomplished J by heat-transfer coils, using water or steam from the heating boiler, and I heating the oil to within 30 deg of its flash point. | Unlike the domestic burner, units for large commercial applications frequently consist of'atomizing nozzles or cups mounted on the boiler front with the necessary air regulators, the pumps for handling the oil; and the blowers for air supply being mounted in sets adjacent to the boilers. In such cases, one pump set can serve several burner units, and 1 common prudence dictates the installation of spare or reserve pump sets. Pre-heaters and other essential'auxiliary equipment also should be in stalled in duplicate. - Boiler Settings As the volume of space available for combustion is the determining factor in oil consumption, it is general practice to remove grates and extend the combustion chamber downward to include or even exceed the ; ashpit volume; in new installations the boiler should be raised to make added volume available. Approximately 1 cu ft of combustion volume; should be provided for every developed boiler horsepower, and in this ! volume from 1.5 to 2 lb of oil can properly be burned. This cor- _ responds to a maximum liberation of about 38,000 Btu per cubic foot per | hour: There are indications that at times much higher fuel-rates may be ' Automatic Fuel Burning Equipment This in turn suggests that the value of 38,000 Btu per cubic satisfactory. ht adjusted according to good engineering judgment. ' foot per ujte care should be taken to keep the gas velocity below 40 ft For best ^yhere checkerwork of brick is used to provide secondary air, P^T^artice calls for about 1 sq in. of opening for each pound of oil p hour. Such checkerwork is best adapted to flat flames, or to fired Peflames Jj,at can be spread over the floor of the combustion chamber. c/uca bricking of a large or even medium sized boiler for oil firing is 6 rtant and frequently it is advisable to consult an authority on this importa essential-in'combustion' chamber design is to provide SU "st flame impingement upon either metallic or firebrick surfaces. jl/p111 facturers of oil burners usually, have available detailed plans for ijapting their burners to various types of boilers, and such information Should be utilized. The Combustion Process Efficient combustion, as previously indicated, must produce a clean flame and must use relatively small excess of air, i.e., between 25 and 50 oer cent. This.can be done only by vaporizing the oil quickly, completely, and mixing it vigorously with air in a combustion chamber hot enough to support the combustion. A vaporizing burner prepares the oil, for combustion, by transforming the liquid fuel to the gaseous state through the application of heat. This is accomplished before the oil vapor mixes with air to any extent and if the air and oil vapor temperatures are high and the fire pot hot, a clear blue flame is produced. There may be a deficiency of air as shown by the presence of carbon monoxide (CO) or an excessive supply of air, depending upon burner adjustment, without altering the clean, blue appearance of the flame. An atomizing burner i.e., gun and rotary types is so named because the oil is mechanically separated into very fine particles so that, the surface exposure of-the liquid to the radiant heat of the combustion chamber is, vastly increased and vaporization proceeds quickly. The result of such practice is the ability to burn more and heavier oil within a given com bustion space or furnace volume. Since the air enters the fire pot with the liquid fuel particles, it follows that mixing, vaporization and burning are itll occurring at once in the same space. This produces a luminous instead of a blue or nori-luminous flame. In this case a deficient amount of air is indicated by a dull red or dark orange flame with smoky flame tips. An excessive supply of air may produce a brilliant white flame in some cases or, in others, a short ragged flame with incandescent sparks flashing through the combustion space. While extreme cases may be easily detected, it is generally not possible to distinguish, by the eye alone, the finer adjustment which competent installation'requires. Certain tests indicate that there is no difference in economy between a blue flame and a luminous flame if the position, shape and the per cent of excess air of both flames are about the same. Furnace or Combustion Chamber Design The furnace or combustion chamber may be defined as that- part of a boiler or conditioner in which combustion is established. With burners requiring a refractory combustion chamber the size and shape should be in - accordance with the manufacturer's instructions. It is important that 223