DRAFT
TM 5-4210-249-13&P-1
0003
FOAM SYSTEM
An around-the-pump foam system is used. System includes an eductor in the line from the pump discharge to
pump intake. Eductor uses a venturi effect to create a vacuum, which draws foam agent into the water stream. A
metering valve is placed in the foam line to control injection percentage. Foam is injected into the foam line that will
pump foam agent at a percentage set by a metering valve to all discharges.
Foam agent system is broken into two (2) halves: Class A foam and Class B foam. One is an "automatic" valve
(multi-metering valve). The other is a manual metering valve. Multi-metering valve is used for the two (2) turret
discharges and four (4) ground sweeps, all of which are controlled in the personnel cab. When each respective
discharge is opened, a signal will be sent to the multi-metering valve to open the corresponding port, which will
have an orifice sized to inject foam at a preset rate, for a pre-determined flow. It is important to note that the roof
turret and bumper turret must be run at the same flow every time. The bumper turret must be operated at 250
GPM (946 l/min). The roof turret must be operated at 500 GPM (1,893 l/min). A manual metering valve is used for
side and pre-connect discharges, and is located on pump operator's panel. This valve is operated by pump
operator, depending on percentage and flow requirements. If flow changes at any point, metering valve must also
be adjusted.
Intake pressures higher than 5 psi (34 kPa) are not allowed. To facilitate operating from either a hydrant or from
relay pumping, an automatic tank refill will be used. When water level in tank falls below a certain predetermined
level, refill valve will open. When water tank is full, refill valve closes. This system allows vehicle to pump
continuously from water tank with accurate water/foam concentration levels.
In order to enable simultaneous use of pre-connects and turrets, pressure reducing valves are used on pre-connect
lines. Pump will need to maintain a pressure of 210 psi (1,448 kPa) for optimum turret flow and reach. Pressure
reducing valves are provided to reduce driver side A and B pre-connects operating pressure to a more manageable
pressure of 150 psi (1,034 kPa). 2-1/2 in. (6.4 cm) discharges are not equipped with pressure reducing valves.
A two-tank selector is located inside personnel cab and at pump operator's panel.
Foam system engagement controls are located inside personnel cab and at pump operator's panel.
CREW CAB
A four-person crew cab is located separate from personnel cab. The crew cab doors open to 90 degrees from
closed position to allow safe and fast access for crew members in full MOPP gear.
Seats of crew cab are SCBA type. Seats have a recessed area in each backrest for mounting a SCBA holder with
a "knock-down" bracket and collision resistant holding strap that secures a one-hour SCBA provided for each crew
member. Provided with every SCBA seat is a padded backrest insert, which can cover SCBA cavity to improve
seating comfort when SCBA bottles are not installed in recessed areas. All seats are furnished with three-point
shoulder type seat belts with automatic retractors.
Roof of crew cab is equipped with a split-type roof hatch. The roof hatch is used to access pump operator's panel
and can also be used for escape. When the split-type roof hatch is opened, it allows operator a 360-degree field of
view. Both split-type roof and pump operator's panel cover are secured by a latch when closed, and are released
manually to provide additional safety during operations. Floor of crew cab is equipped with drain holes that allow
draining of free standing water on cab floor.
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