Temperature Control Below the Load s

Temperature control below the load(s) depends on load piece location. If a product is placed on the hearth, the top-to-bottom temperature difference will never be uniform, and the magnitude of the top-to-bottom AT will depend on the following variables  

Every effort should be made to position loads on piers or stools (preferably of low mass construction), especially for load pieces more than 4 in. (0.10 m) thick. Material more than 6 in. (0.15 m) thick should never be placed on the hearth unless the distance between centerlines of the pieces is at least twice the product thickness. Under no circumstance should pieces be piled on top of one another. 

To assure a low temperature difference across the furnace width, T-sensors must be located on each side of the furnace. One sensor should be 1 to 3 in. (25 to 75 mm) above the pier in the wall opposite the burner(s) that controls the fuel input, with the combustion air flow held constant. When the furnace arrives at setpoint, the other sensor (in the burner wall at the same elevation) will be within 6°F (3.3°C) of the opposite wall temperature. (See fig. 6.23, also refer to figs. 2.21 and 3.26.) 

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