If Fog Streams Lack Reach, Try Changing to Straight Streams
departments
The Volunteers Corner
Like some other equipment on fire apparatus that tend to be forgotten because they are seldom used, straight tip nozzles sometimes remain on the pumper when the fire dictates their use.
We are so successful in using fog nozzles in interior attacks that when the volume of fire forces us into an exterior attack, we continue to use our fog nozzles through force of habit. There are times when a fog pattern is desirable during an exterior attack, but there are other times when the fire condition makes a fog stream utterly useless. Sometimes we unconsciously concede the need for a solid stream by adjusting the fog nozzle to the straight stream position.
Unfortunately, adjusting a fog nozzle to the “straight stream” position does not result in the application of a solid stream. The water passes through the peripheral opening and then comes together at the apex of the water cone to form what might be labeled a poor man’s “solid” stream a few inches from the end of the nozzle. Because this stream is developed outside rather than inside the nozzle tip, the fog nozzle’s straight stream lacks the cohesive bulk and carrying qualities of the true solid stream.
Stream destroyers: If you look for it, you can see what happens to a fog stream many times when it is directed at a large volume of fire. As the fog cone enters the heavy fire area, the fog makes an upward curve and rises with the flames instead of penetrating them. This is the serious effect that the thermal updraft has on the usefulness of the fog stream.
An adverse wind can also blunt the usefulness of a fog stream. According to the direction of the wind opposing the stream, the fog cone will be blown off the intended trajectory. No matter which direction the fog cone takes under the influence of an opposing wind, the result is a shortening of the stream reach. When this happens, little or no water may be reaching your target in the fire area.
You will do well to remember this when smoke makes it impossible to see the end of the fog cone near the fire. At a structural fire emitting a heavy volume of smoke, I saw a good fire stream coming out of a fog tip on a ladder pipe and angling into a brisk wind. As I took a photo of the ladder pipe stream, the smoke lifted for an instant without my noticing it in the camera viewfinder. Therefore, I was surprised when I later looked at the color slide and saw that the fog stream, under the influence of the wind, made a U-turn as it neared the building roof.
Training exercise: You don’t have to wait for the next large fire to compare streams from fog tips and straight tips. Lay out a couple of 2 ⅛ -inch hand lines and put a fog tip on one and a straight tip on the other. Select a straight tip that will provide the same gpm as the fog nozzle. Place the two nozzles side by side and provide your normal pressures at each nozzle. Then stand off to one side so that you can compare the reach of the solid stream with the reach of the fog stream at not only the “straight stream” pattern, but also at the 30, 60 and even 90-degree fog patterns.
The ideal time to do this is when you have a noticeable wind condition. Then change the positions of the two streams so that you can compare them with the wind striking them from the front, rear and each side. Even without any wind, you will be able to see that the straight tip delivers a greater volume of water at a longer distance than a fog tip.
Keep in mind that this reach capability is an important characteristic only when it is needed. The fog stream has superior extinguishing capability when you can put the fog where it can effectively reduce the fire heat. When either the wind or the thermal updraft keeps the bulk of the fog stream from reaching the fire, then use of a straight tip is the alternative that will provide a longer stream reach to hit the fire.
Master streams: The hand line stream comparison can be extended to master stream equipment. Using streams of the same flow rate, compare the reaches of fog tips and straight tips on deluge sets, deck guns, ladder pipes or elevating platform monitor nozzles. Monitor your engine pressures and determine the pressures at the tips so that you know the same gpm is flowing from each tip. Also, use your standard nozzle pressures so that your comparisons will relate to fireground reality.
While you have master st ream equipment in operation at a drill, continue by comparing the ranges of all the straight tips you carry and show that at the same nozzle pressure, the greater the volume of water flowing, the greater the reach—with or without wind.
With both hand lines and master streams, the participants in these stream comparisons will learn first hand that the man controlling the nozzle is in the worst position to evaluate the stream. This will help nozzlemen understand why an officer standing behind them or off to one side has to give directions from time to time to actually put the stream where the nozzleman only thinks it’s going.
To put water where it is needed under adverse conditions, every pumper should carry 1, l 1/8 and 1 1/4 -inch straight tips in addition to the usual fog tips. Every apparatus with master stream equipment should carry an assortment of straight tips. The sizes range from 1 1/4 to 2-inch and at least three of the sizes most useful to a department should be carried.
