The NFPA Std 11, Sect.10.5.3 requires that “the distance from the monitor to the furthest extremity of protected area forward of the monitor shall not be more than 75% of the monitor throw in still air conditions.” Does anybody know what was the basis/rationale for this requirement? I suspect the intent was to provide some safety margin for the opposing wind that reduces jet throw.
Current proprietary vendor correlations are based on actual data. They can reliably predict trajectory of the fire monitor jet for both water and foam for a specified inclination angle, monitor elevation, and opposing wind speed. Would the above NFPA requirement still be applicable for the situation where a fire monitor is designed using such correlations to cover target area with conservatively specified velocity of the opposing wind? In other words, wouldn't application of this requirement create excessive margin for the monitor throw already taking into consideration wind velocity?
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