©Copyright Task Force Tips LLC 2010-2021
9
LIU-360 October 14, 2021 Rev05
7.0 MAXIMUM HOSE LAY
The maximum hose lay is based on the back pressure. Pushing the foam solution through the hose and eductor causes back pressure
on the eductor exit. If the back pressure on a 200 psi (14 bar) nozzle is over 130 psi (9 bar) the eductor will not work. If the back pressure
on the 150 psi (10 bar) eductor is over 80 psi (5.5 bar), the eductor will not work.
Elevation loss adds to the back pressure when the nozzle is higher than the eductor. For each foot in vertical height, there is 0.4 psi
elevation loss.
The eductor can be used with or without a monitor. The maximum hose lays and elevations change due to the different friction losses in
the monitors. To use in a permanent installation with another monitor, calculate friction loss in pipes and elevation changes to determine
correct setup.
To calculate back pressure, add the nozzle pressure, hose friction loss, monitor appliance loss if present, and elevation pressure loss
together. The sum must not exceed 130 psi (9 bar) or 80 psi (5.5 bar) depending on the model. The Go/No-Go pressure gage on the
outlet of the unit indicates acceptable back pressure levels. Should the gage show a pressure in the No-Go (red) range, shut down the
line and change the line setup to lower the pressure.
Friction loss varies with different brand hoses. Determine the friction loss of your own hose. The nominal flow of the eductor is the sum
of the water plus the foam concentrate when set at 6%. The eductor should always have 200 psi (14 bar) at the inlet unless otherwise
specified on the eductor body. The water flow does not change with different percentage settings; however the inducted concentrate will
change when the percentage setting is changed. Therefore, the total flow exiting the eductor is lower at 1/2% than at 6%. Lower flow rate
reduces nozzle pressure and hose friction loss. Longer hose can be used when proportioning rate is less because less work is needed
to move less foam concentrate.
8.0 NOZZLE SELECTION
Eductors work with any nozzle whose gallonage is equal or greater than that of the eductor. If a nozzle with a larger gallonage is used,
the reach of nozzle and the proportioning rate of the eductor will be compromised.
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 finished foam. The final expansion ratio and, amount of finished foam, depends on the type of foam concentrate being used.
8.1 NOZZLE COMPATIBILITY
The following table lists the compatibility between eductors and nozzles.
Table 8.1
WARNING
Excess back pressure causes loss of foam flow resulting in risk of injury or death from an
ineffective stream.
• Verify that adequate foam flow is established and maintained.
• Do not exceed the maximum back pressure.
NOTICE
Low pressure 150 psi (10 bar) eductors are compatible only with 55 psi (4 bar) nozzles.
WARNING
Excess back pressure causes loss of foam flow resulting in risk of injury or death from an
ineffective stream. Operate the nozzle fully open to prevent excessive back pressure.
350 SERIES EDUCTORS
Nozzle Name Nozzle Model # Water Flow
Setting GPM
Nozzle
Pressure PSI
Multi-Expansion
Foam Attachment
Max-Force
MD*2A
100-500
100 or 55
FJ-MX-MD
MD-ERP-*2A
MD-ER-*2A
Max-Matic
MD*8A
100-500
100 or 55
FJ-MX-MD
MD-ERP-*8A
MD-ER-*8A
MD*7A
80
Max-Flow
MD*4A
100-500
100 or 55
FJ-MX-MD
MD-ERP-*4A
MD-ER-*4A
