Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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For Eighting fire in which liquefied products are
burning for e~ample, use is often made of foams which are
generally produced by the addition of an emulsifier to water
under pressure. Various forms of apparatus for adding an
emulsifier to a fluid have been proposed in the art, in particular
for adding the emulsifier to water flowing in a conduit under
the action of a pump. For example the addition of emulsifier
to water may be effected by means of a "GiEfard" injector
which utilises or converts the energy taken from the head of
flowing water, to produce a vacuum phenomenon which causes the
emulsifier to be drawn into and mixed with the water, but this
results in the disadvantage of a pressure drop in the flow;
to compensate for this, it is necessary to use energy levels
which are excessive relative to the use thereof, hence resulting
in a lack of flexibility which permits this apparatus to operate
only over a very narrow operating range. In a second kind of
apparatus, the Giffard injector is arranged on the water pump
between the inlet and the outlet, but the resulting recycling
phenomenon produces a power loss which must be compensated for
by the power of the pump and the drive motor, in any case,
this leaves only an operating range of from 50 to 100% on the
discharge of the pump, with the system not operating properly
below this range, even taking account of a pressure difference
of for example 5 bars between the pump inlet and the pump
discharge. Another kind of apparatus uses a metering and
proportioning device which reacts on the differential dynamics
oE the water head and the emulsifier, the emulsifier being
carried ~rom an emulsifier storage tank to the metering and
proportioning device by means of a pump.
In this apparatus, the metering and proportioning
device is a static system which has two sets of valves which
are open and closed in the rest position and which become
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blocked in those positions if the emulsifier solidifies in
the device. In addition, the emulsifier must be injected
into the proportioning device at a pressure which is higher
than the water head by for example two bars. This assembly
is also delicate and requires motors, which is a disadvantage
because such motors will not always operate simultaneously.
In the three kinds of apparatus mentioned above, a
common feature is the lack of operating flexibility, namely,
that it is not possible, under the best conditions, with very
good apparatus and optimum adjustments, to be able to use
then in a functional range outside the limits of from 50 to
100 % of the fluid flow.
An object of the present invention is to overcome
the above disadvantages and to increase the operating flexibil-
ity of the apparatus, making it possible to use the full
performance of a pumpf at from 0 to 100~. Another objet is
to provide for the addition of an emulsifier, with a minimum
preset relative value, over a range of adjustment.
In apparatus according to the invention, a nozzle
is disposed at the inlet or intake side of the pump, the
conicity and diameter of the nozzle being adapted to the
performance characteristics of the pump; disposed within
the nozzle is a central tube which is displaceable axially
therein and whose diameter is adapted in dependence on the
one hand on the maximum required flow rate of the emulsifier
and on the other hand on the maximum flow rate or output of
the pump. When the pump is not in operation, the tube is
completely inserted into the noæzle while when the pump is
at maximum output, the tube is disposed totally outside of
the nozzle. Thus, the position of the tube will depend on
the output flow rate required from the pump and the relative
value of the amount o emulsifier to be added to the fluid
\
flow.
The translatory movement of the tube may be controlled
by a valve disposed at the outlet or discharge side of the pump.
This valve is normally held closed on its seat when the pump
is in a rest condition, anc~ opens in dependence on the output
flow rate of the pump; by way of a connecting assembly, this
valve displacement controls de displacement of the tube relative
to the nozzle. The tube-valve connecting assembly may be of
any suitable construction, and adjustment of the the relative
1~ value of the amount of emulsifier added is achieved by acting
on the above-mentioned connecting assembly.
Figure 1 is a diagrammatic view of a first embodiment
of the apparatus, on a pump,
Figure 2 is a detail view of the apparatus of
Figure 1,
Figure 3 is a diagrammatic view of a second embodiment
of the apparatus, on a pump,
Figure ~ is a view of the apparatus mounted on a
conduit.
; 20 Reference îs made to Figure 1 which shows the apparatus
1 according to the invention, which is disposed at the inlet or
suction side of a pump 2 with axial inlet and outlet. The ~ -
apparatus 1 includes a nozzle or restriction portion 3 in the
flow conduit, the nozzle comprlsing a convergent-divergent
portion 4, the conicity and diameter of which are adapted to
- the performance characteristics of the fluid flow and tllus of
the pump 2, providing a venturi effect. Disposed within the
nozzle 3 is a central round tube 5 comprising a divergent end
portion 6 which is co-operable with the divergent portion 4
of the nozzle 3. The diameter of the tube is adapted in
dependence on the maximum flow rate of emulsifier to be added
to the flow of fluid through to nozzle 3 and the maximum output
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flow rate of the pump 2. The tube 5 is mounted so as to be
displaceable axially within the nozzle 3.
Disposed at the outlwt or discharge side of the
pump 2 is an output flow-responsive control valve 7 which is
urged to a closed position against its seat 8 by a spring 9.
A rod 10 of the valve 7 is displaceable to control displacement
of the tube 5 within the nozzle 3, by means oE a connecting
assembly 11. This assembly comprises an inner cable fixed
at respective ends to the valve 7 casing and to a casing portion
adjacent the nozzle 3, and an outer cable cover connected to
the rod 10 and the tube 5 and displaceable on the inner cable,
as shown.
In the embodiment illustrated, fluid such as water
id passed into the nozzle 3 by a conduit 12, and the emulsifier
is introduced through the tube 5n
When the pump 2 is operating, water flowing in the
conduit 12 is discharged by the pump 2 and acts against the
valve 7 which is thereby lifted away from its seat 8. The
movement of the valve 7, transmitted by its rod 10 and the
cable assembly 11, acts on the tube 5 for delivering the
emulsifier, whereby the tube 5 is axially displaced within the
nozzle 3 relative to the divergent portion at 4. The extent of
axial displacement of the tube 5 is proportional to the output
of the pump 2. It should be noted that such displacement of
the tube 5 is assisted by the fact that, when an increased pump
output is required, the pump 2 will increase its suction effect
and will thus promote the axial displacement of the tube 5
thus making it possible to achieve quicker and vir~ually
instantaneous reaction of the apparatus to the change in
operating condition.
Pre~adjustment of the emulsifier flow rate through
the tube 5 is effected by acting on the connecting assembly,
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that is to say, by adjusting the length of the cable assembly
11. For a given output of the pump, such adjustment varies
the position of the divergent end portion 6 of the tube 5
relative to the portion 4 of the nozzle 3. For a given output
of the pump 2, the peripheral speed of the water flowing around
the divergent end portion 6 of the tube 5 increases, as the
flow section between the divergent end portion 6 and the portion
4 of the nozzle 3 becomes smaller. In consequence, for a given
pump output, if the portion 6 is retracted to the bottom of the
cone of the portion 4, a larger amount of emulsifier will be
injected, whereas if the tube 5 with portion 6 is pushed in the
other direction, less emulsifier will be injected into the water
flow.
Figure 2 is a detail view of the apparatus diayram-
matically shown in Figure 1. Figure 2 does not show the pump,
but it shows the main components of the apparatus, namely the
tube 5 for delivering the emulsifier which opens at its divergent
portion 6 within the convergent-divergent portion 4, the valve -
7 for controlling thetube, which valve is held on its seat 8
by the coil spring 9, and the connecting cable assembly 11
which is fixed by a bracket to the tube 5. Figure 2 also shows
a device 13 for pre adjusting the basic flow rate of emulsifer,
comprising a handwheel 14 for acting on and thus varying the
length of the cable 11. It will be understood that this wheel
device 13 may be replaced by other suitable means, for example
by a hydraulic control arrangement~
Figure 3 diagrammatically shows another embodiment
of apparatus according to the invention, which is generally
the same as that shown in Figure 1 except that the valve 7 is
mounted at the periphery of a rotary flow pump 20.
- Figure 4 is a diagrammatic view of another embodiment
of the apparatus according to the invention, mounted on a
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conduit 30. In this embodiment the water flows through conduit
30 and into a chamber 31 comprising an outlet conduit 32 forming
a downstream-divergent portion 33. Conical end portion 36 of
an axial tube 35 is displaceable within the divergent portion
33. The tube 33 is controlled in its axial movement by the
valve 37 which is disposed at the outlet end of the conduit 32
and which is heldclosed on its seat 38 by a spring 39; the
valve 37 is thus disposed at the outlet or downstream of the
divergent portion 33. In the Figure 4 embodiment, the valve
37 controls displacement of the tube 35 by means of a sliding
rod 41. In this embodiment also, when the wa~er flow rate
through the conduit 31 is increased, the effect of this is to
encourage the axial movement of the tube 35 which is subjected
to a differential pressure, and this makes it possible to have
a substantially zero inertia in the response of the tube
movement.
