Calibration 



Each retardant was calibrated to determine its total flow rate, lateral pattern uniformity, 

 and usable flow rate . 



Total Flow Rate 



Flow rates were measured at tank pressures between 3 and 21 p.s.i. , and at five orifice 

 sizes of 5/64 to 11/64 inch, by timing the discharge of 1 gallon of each retardant and converting 

 the information to gallons per minute . 



Lateral Pattern Uniformity 



We achieved optimum uniformity of retardant amount at all points across the 18-inch tray 

 width by: (1) spraying each retardant for 10 seconds into plastic ice cube trays arranged across 

 the spray chamber floor to intercept the spray, using varied nozzle heights and the array of 

 pressures and orifices described above in Total Flow Rate (also see fig. 2); (2) weighing each 

 tray; and (3) after examining results, choosing the nozzle type, nozzle height, and tank pressure 

 that produced the best pattern for each retardant across the usable 18-inch span. 



Figure 2. --Pattern calibration. 



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