©Copyright Task Force Tips, Inc. 2004 - 2017 LIU-330 November 16, 2017 Rev08
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The nominal fl ow of the eductor is the sum of water plus foam concentrate when set at 6%. The eductor should always have its rated
pressure at the inlet. The water fl ow does not change with diff erent percentage settings; however, the inducted foam concentrate will
change when the percentage setting is changed. Therefore, the total fl ow exiting the eductor is lower at 1/4% than at 6%. Longer
hose lengths can be used when proportioning rate is less because less work is needed to move lower total fl ows.
6.0 NOZZLE SELECTION
Eductors work with any nozzle whose gallonage is equal to or larger than eductors’. However, if a larger gallonage nozzle is used,
the reach of nozzle and the proportioning rate of the eductor will be compromised.
Fog-type nozzles have the greatest reach in the straight stream position. The fi nished foam is produced as the stream projects
forward, and the greatest expansion is at the end of the stream. While straight stream gives maximum reach, it can also splash
fl ammable liquids if not carefully applied. The stream impact can be softened by defl ecting the stream off nearby objects. The stream
can also be trimmed to a 10-15 degree pattern which gives good reach and creates a softer “snow-fl aking” eff ect at the end of the
stream.
The expansion ratio is the amount of fi nished foam produced compared to the volume of foam concentrate/water solution used to
generate the foam. For Example: A 10:1 expansion ratio will produce 950 GPM (3600 l/min) of fi nished foam from a 95 GPM (360
l/min) nozzle. Non-aspirated automatic nozzles can produce expansion ratios of 6-8:1 when measured at the end of the stream. By
maintaining a constant nozzle pressure, automatic nozzles keep the velocity of the stream high. Large amounts of air are pulled into
the stream and mix with the foam concentrate/water solution as the stream leaves the nozzle.
Air-aspirating devices, such as the TFT FOAMJET, allow a wider selection of foam concentrates to be used, and can produce a better
quality of fi nished foam. Air-aspirating attachments will, (1) improve the 1/4 drain time, (2) produce a more uniform bubble structure,
(3) improve the burn back resistance of the fi nished foam, and (4) the foam blanket is visibly thicker. This thicker foam blanket has
better vapor suppression and is longer lasting than foam from non-aspirated nozzles. The fi nal expansion ratio and, therefore, the
amount of fi nished foam, depends on the type of foam concentrate being used.
WARNING
The nozzle must be operated fully open to prevent excessive back pressure which will prevent
foam pickup. Lack of foam can result in injury or death.
The following tables list the compatibility between eductors and nozzles. NOTE: A 75 psi (5 bar) nozzle will result in lower nozzle
pressure and shorter stream reach.
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