MAPLE SIRUP PRODUCERS MANUAL 



61 



Cinder till, may have 

 I" fire brick facing 



Combustion chamber 

 Insulating fire brick 

 (2800° F, ) 



— Cinder brick 



Firebrick, 

 zS'V X 4'/2" X 9" 



LONGITUDINAL SECTION T i i T T I i CROSS SECTION 



Chart ;^.— Arch and firebox for oil-fired evaporator. 



cinder block except for the top section, which is 

 3V2-inch bricks to provide a 2-inch supporting 

 surface for the pans and project IV2 inches 

 beyond the pans. If the arch is made to the 

 exact outside dimensions of the pans, the sup- 

 porting wall of the arch would cover too much 

 of the underpan surface (3V2 inches on all sides). 

 A large loss of heating surface would result. 



The height of the ai'ch is governed by the size 

 of the combustion chamber, which in turn is 

 governed by the size of the burner (see table 5) 

 and the size of the evaporator. For a 5- by 12- 

 foot evaporator, the height of the arch should 

 be 46 inches (chart 12). The arch should elevate 

 the pans 46 inches or more above the floor level 

 to permit the use of gravity flow of the sirup in 

 successive operations. If the arch raises the 

 pans too high, especially when multiple evapo- 

 rators are used, a catwalk can be installed; or 

 the combustion chamber of the arch and the 

 burner can be built in a pit. 



Firebox and (.ombustioii Chamber. — The 



entire open space enclosed by the arch under 

 the pans is the firebox. Better results will be 

 obtained if it contains a combustion chamber 

 (see chart 12). The function of this chamber is 

 (1) to provide a hot radiating surface and (2) to 

 utilize the hot, incandescent surface to vaporize 

 and insure complete combustion of the oil. 



For maximum efficiency, the size of this com- 

 bustion chamber must conform to minimum 

 dimensions that are related to the nozzle size of 

 the burner. These dimensions are given in table 

 5. A rule-of-thumb relation between combus- 

 tion chamber and nozzle size is that there 

 should be a floor area of 90 square inches for 

 each gallon per hour of rated nozzle capacity. 



The distance between the top of the combus- 

 tion chamber and the bottom of the pans (di- 

 mension D of chart 12) is important for two 

 reasons: (1) The ball of burning oil should be far 

 enough below the "cold" pan surface to prevent 



