Document kmbJrVw5jMmZvEX97p91RGLMb

360 CHAPTER; 17 1949 Guide fire can be increased-to give almost any desired control characteristic within the, range of the burner. The majority of vaporizing burners are manufactured in sizes up to one gallon per hour input. Most vaporizing ' burners are limited to use with No. 1 fuel oil having a maximum end point of 625 F and a minimum A.P.I. gravity of 35 deg. A barometric draft regulator is required to maintain the recommended drafts A draft of not more than 0.06 in. of water column is recommended for most natural draft .burners. When burners are equipped with me chanical forced draft, a slightly lower chimney draft can be used: A burner of this type is illustrated in Fig. 17. Vaporizing burners are adaptable to water heaters, space heaters, and furnaces.,. Some types have also been applied successfully to conversioii installations.' 'The heat output is in the range of requirements for the average or small home.... The modulating1,flame allows simple manual control by regulation of a metering valve and simplifies the control equipment. Quiet com bustion and the absence: .of moving parts .contribute to quiet operation ' when the'heating device is located in .the living quarters. hi'.;;:.-i.-.i '-'.s; . * : j. Fio.17. Vaporizing Pot-Tite Buhner -.- `-.-r--- ; . . .. Automatic Fuel Burning Equipment 361 The ability to operate on natural draft and gravity feed of the fuel,makes possible the use of these burners where electric current is not available or is unreliable. However, most furnaces are thermostatically controlled and many are provided with mechanical draft. Oil-Fired Boiler and Furnace Units A number of types of specially designed oil-fired boiler-burner and furnace-burner units are available. Various locations of burners will be noted in such units; some having the combustion chamber and burner at the top, some at the bottom, and some at the center of the appliance. One type of boiler-burner unit is shown in Fig. 18. The coordinated design of boiler (or furnace) and burner elements insures the optimum in operating characteristics, and the maintenance of balanced performance. This type of equipment usually has more heating surface, better flue proportions and gas travel than conventional boilers or furnaces. Some of the better conversion installations, however, may equal the..unit type in performance....-- " Operating Requirements for Oil Burners The U. S. Department of Commerce in conjunction with the oil burner and heating appliance industries has established commercial standards for conversion burners and burner-appliance units which cover installation, construction and performance tests4. -Combustion Process Efficient, combustion must produce a clean flame and use a relatively small excess of air, i.e., between 25 and 50 per cent. This can.be done only by vaporizing the oil quickly and 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 by the application of heat before the oil va.. por 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.