Document XO6me2181JMkDmEbjg4GdOp24

|W 336 CHAPTER 14 li! For burning rates from 100 to 1200 lb coal per hour 1950 Guide S - 0.03 B + 24 where ll w=. minimum setting height, inches, measured from dead plates to crown sheet for steel boilers. For cast-iron boilers height may be l B. B = burning rate coal per hour, pounds. Standards for minimum firebox dimensions and base heights have been formulated by the Stoker Manufacturers Association as shown in Fig. 11*. In considering these recommendations, it should be understood that they show the average recommended minimum. ' There are many factors affecting the proper application of stokers to various types of boilers and furnaces, and, in certain instances, setting height or firebox dimensions shown in the standards may be modified without impairing performance. Such modification rests with the experience of the installer, or designer, Automatic Fuel Burning Equipment 337 or hot water heating system, a piping and pick-up factor of 1.33 is com monly used in sizing the stoker, but this factor should be increased at times due to unusual conditions. Controls The heat delivery from the stoker of the smallest household type to the largest industrial unit can be regulated accurately with fully automatic controls. The smaller heating applications are controlled normally by a thermostat placed in the building to be heated. Limit controls are supplied to prevent excessive temperature or pressure being developed in the furnace or boiler, and refueling controls are used to maintain ignition during periods of low heat demand. Automatic low water cut-outs are recommended for use with all automatically-fired steam boilers. (See Chapter 38.) DOMESTIC OIL BURNERS An oil burner is a mechanical device for producing heat automatically from liquid fuels. Two methods are employed for the preparation of the Fig. 11. Suggested Minimum Fibbbox Dimensions and Base Heights* * For reference in selecting or designing boilere end fomeces for stoker firing. Dimensions shown are for net inside clearance at grate level using coal with heating vahieof not less thaniireferred certain conditions smaller fireboxes wifi permit satisfactory performance but these dimensions are preferred normal minimums. with a particular stoker, the type of fuel used, and the construction of the boiler or furnace. Installation of stokers (particularly smaller sizes) from the side of the boiler or furnace will sometimes facilitate clinker removal. Rating and Sizing Stokers The capacity or rating of. small underfeed stokers is usually stated as the burning rate in pounds of coal per hour. Codes for establishing uni form methods of rating anthracite and bituminous coal stokers have been adopted by the Stoker Manufacturers Association*. The Association also has adopted a uniform method of selecting stokers that is published in convenient tables and charts2. The required capacity of the stoker is calculated as follows: Load (Btu per hour) Heating value of coal (Btu per pound) X over-all efficiency of stoker and boiler or furnace Stoker burning rate required (pounds of coal per hour) In determining the total load placed on a stoker-fired boiler by a steam oil for the combustion process; atomization, and vaporization. The simpler types of burners depend upon the natural chimney draft for supplying the air for combustion. Other burners provide mechanical air supply or a combination of atmospheric, and mechanical. Ignition is accomplished by an electrical spark or hot wire, or by an oil or gas pilot. Some burners utilize a combination of these methods. Continuously operating burners may use manual ignition.. Burners of different types operate with luminous or non-luminous flame.. Operation may be inter mittent,. continuous with high-low flame, or continuous with graduated flame. CLASSIFICATION OF BURNERS Domestic oil burners may be classified by type of design or operation into the following groups: pressure atomizing or gun, rotaiy, and vapor- izing or pot. These are further classified as mechanical draft, and natural draft. Pressure Atomizing . (Gun.Type) Gun type burners may be divided into two classes, low-pressure, and high-pressure atomization. In the first group, a mixture of oil and primary