. Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . event disturbance of the brick work by the endwiseexpansion and contraction of the boiler. Grate Surface. The number of square feet of gratesurface required depends upon the size of the good rule and one easy to remember is to make thelength of the grates equal to the diameter of the width, of course, will depend upon the construe- BOILER SETTINGS AND APPURTENANCES 33 tion of the furnace. If the fire brick lining is builtperpendicular, the width of grate will be about equalto
. Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . event disturbance of the brick work by the endwiseexpansion and contraction of the boiler. Grate Surface. The number of square feet of gratesurface required depends upon the size of the good rule and one easy to remember is to make thelength of the grates equal to the diameter of the width, of course, will depend upon the construe- BOILER SETTINGS AND APPURTENANCES 33 tion of the furnace. If the fire brick lining is builtperpendicular, the width of grate will be about equalto the diameter of the boiler. On the other hand, ifthe lining is given a batter of three inches, starting atthe level of the grate, then the width will be reducedsix inches. It is customary to allow one square footof grate surface to every 36 sq. ft. of heating distance of the grate-bars from the shell of theboiler varies from 24 to 28 in., according to the dimen-sions of the boiler. Insulation. All boilers should be well protectedfrom the cooling influence of outside air, if economy. M CLAVES GRATES. of fuel is any object. The tops of horizontal boilersshould be covered with some kind of heat insulatingmaterial, or arched over with common brick, leaving aspace of two inches between the boiler and the resulting saving in fuel will far more than com-pensate for the extra expense in a very short cracks in the side and rear walls should be care-fully pointed up with mortar or fire clay. One sourceof heat loss in return flue boilers is short circuitingfrom the furnace to the breeching, caused by thearches over the fire doors becoming loose and shaky,and allowing considerable of the heat to escape directlyto the stack instead of passing under the boiler and 34 ENGINEERING through the tubes. Another bad air leak often occursat the back connection when the arch rests whollyupon iron bars imbedded in the side walls. This leak,as has already been noted, is c
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