photo.jpg

Operating with fog nozzles, particularly on smaller-diameter hoselines, may result in inadequate nozzle pressures and flows, especially at upper stories of a standpipe zone. Although fire department pumpers might be able to increase the pressures in the stand-pipe, it might not be of much value. It...

Operating with fog nozzles, particularly on smaller-diameter hoselines, may result in inadequate nozzle pressures and flows, especially at upper stories of a standpipe zone. Although fire department pumpers might be able to increase the pressures in the stand-pipe, it might not be of much value. It might not even be possible. The standard Class A pumper is rated to deliver one-half of its capacity at 250 psi. That is just barely sufficient to operate a fog nozzle between the 21st and the 30th floors (100 psi nozzle pressure plus 5 psi loss per floor, plus friction loss in the handline, ceiling supply lines to the siamese, and the standpipe itself). As additional lines are stretched from other standpipe outlets, pressures within the system are likely to drop still further, thus demonstrating the value of a nozzle