Through the pump foam system

Apparatus and method for in-line inducting additive into a fire fighting flow line before the pump, including automatic regulating of water flow.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates to fluid additive supply systems for fire fighting 
equipment, and in particular to systems for adding foam concentrate into a 
water stream used for fire fighting operations. 
2. Description of Related Art 
Fire fighting mechanisms typically include a source of water (the primary 
fire fighting fluid) connected to a water pump that supplies water via a 
conduit (fire hose) to a discharge device (hand held nozzle, monitor, 
sprinkler system, foam chambers, etc.). 
It is often desirable to have a mechanism that can supply an additive, such 
as foam concentrate, into the water stream. Foam is useful in 
extinguishing certain types or classes of fires, particularly flammable 
liquid fires. The additive supply mechanisms may have a metering device 
that allows the introduction certain percentages of foam to water, termed 
proportioning, to be varied (i.e. 1%, 3%, 6% foam to water proportioning 
are the most common). 
There are numerous systems on the market that supply additives into water 
streams. The majority of these systems are in fixed installations or 
permanently mounted in fire fighting apparatus such as a fire truck. Such 
apparatus for foam proportioning are discussed and disclosed, for 
instance, in U.S. Pat. No. 4,436,487. Many of these systems require the 
use of foam concentrate additive pumps for forced injection. These pumps 
may be, for example, either positive displacement or centrifugal type. 
Such systems designed for foam proportioning are complicated and very 
expensive. 
Alternatively, the basic design and principle of a venturi device can be 
used to "induct" or "educt" foam concentrate into the primary water stream 
Venturi mechanisms use primary liquid flow to create a pressure drop 
across an orifice. The pressure drop forms a partial vacuum into which 
fluid or gases will flow if permitted. Additives supplied in the vicinity 
of the venturi mechanism will be pulled into the partial vacuum created. 
A close relative of the present invention is termed an "around the pump" 
foam system. These systems involve the use of jet pumps and/or eductors 
together with a pump. The "around the pump" foam system is setup as 
follows (FIG. 1). The fire fighting apparatus connects a pressurized water 
source such as from a fire hydrant 1 to the suction inlet side 6 of the 
water pump 2 via a water conduit line 7. A further water conduit line 8 
attaches to the discharge outlet side of the water pump 2 and connects to 
a deployed downstream fire fighting fluid delivery device such as for 
example a hand held nozzle 3, fixed nozzle termed a "monitor", or a 
sprinkler system. An auxiliary conduit 10 from the discharge outlet side 9 
of the water pump is connected to a jet pump and/or eductor 4. The 
discharge conduit 11 from the jet pump and/or eductor 4 is attached to an 
auxiliary connection on the suction inlet side of the water pump 12. Once 
water flow is established, the auxiliary discharge conduit 10 supplies 
water to the inlet of the jet pump and/or eductor 4. The water passes 
through a pressure drop area. The additive 5 is drawn from a suction port 
inlet 13 that is connected to the device in the low pressure zone that is 
created by this pressure drop. The additive is entrained by the operating 
water stream of the jet pump and/or eductor. The entrained foam 
concentrate mixing together with the jet pump and/or eductor operating 
water stream is then injected into the auxiliary connection 12 on the 
suction side of the pump 2. The total solution than passes through the 
water pump where a pressure increase is effected. Once adequately 
pressurized, the water/additive solution is then directed into the 
deployed downstream fire fighting fluid delivery device 3. The "around the 
pump" foam system can either be installed as a fixed installation on the 
water pump apparatus or can be deployed portably. 
Some inherent problems associated with the "around the pump" foam system 
are as follows. The ability for the system to operate is based on the 
performance of the jet pump/eductor. The jet pump/eductor must have the 
energy (discharge head pressure) to inject the entrained foam into the 
pressurized system of the water pump. The available energy is based on the 
style of the jet pump/eductor and the operating water pressure supplied to 
the inlet of the jet pump/eductor, the amount of additive picked up, and 
the discharge velocity of the homogenous fluid mixture(i.e. operating 
water and additive). As a rule jet pumps inducting a high relative percent 
of additive fluid have discharge capabilities of approximately 30% of 
inlet pressure. Full in-line eductors inducing a low relative percent of 
additive have discharge capabilities of approximately 65% of inlet 
pressure. In the relevant fire fighting systems of the present invention, 
additive pick up is normally approximately 1.8-15 gpm (gallons per minute) 
(based on different eductor models with flow capabilities ranging from 
30-250 gpm at 6% proportioning). 
Once the pressure on the inlet side of the water pump exceeds the discharge 
head pressure, the proportioning of foam will either decrease or totally 
cease, usually the latter. Thus, if the supply water conduit to the pump 
system inlet has an inlet pressure exceeding the discharge capabilities of 
the jet pump/eductor, as is often the case, a manual control valve will 
need to be adjusted, such valve is installed between the water supply and 
the inlet side of the water pump. The port through the valve will be 
reduced to adjust the water pressure at the pump inlet so as to not exceed 
the discharge head capabilities of the jet pump/eductor. 
Inlet water pump pressure variation is usually caused by the increase or 
decrease in total volume through the water pump. Once the manual control 
valve is adjusted for the determined flow, any deviation of flow will 
cause a variation in pressure. Many times this variation is enough to 
exceed the capabilities of the jet pump/eductor and causes system failure. 
Volume variations are normally due to the opening and closing of the 
downstream water stream delivery devices. Thus, the water pump operator 
must constantly monitor the discharge water volume and adjust the manual 
control valve accordingly. Without this constant adjustment the inlet 
water pressure to the pump will either be in excess of the jet pump 
system, or will not have adequate volume to supply the discharge 
requirements, resulting in cavitation. 
Another deficiency in the current "around the pump" foam system relates to 
fluctuation in the percentage of additive concentrate. The fluctuation is 
due to changing water volumes created by the opening and closing of the 
downstream fluid delivery devices. Once the desired amount of concentrate 
is selected, the volume of concentrate added is fixed at the optimum 
proportioning level. If the volume of water passing through the water pump 
changes and the amount of additive remains the same than the percent (it 
additive will vary immensely. An example of this is as follows. 
Example 
A fire apparatus is set up as described earlier utilizing "around the pump" 
technology. Two hand-lines are deployed from the apparatus each flowing 97 
gpm water and 3 gpm foam concentrate for a total of 200 gpm water/foam 
solution. The most common proportioning of foam concentrate added to a 
water stream delivery device is 3%. If one of the lines is truncated 
without making the proper adjustments to the jet pump/eductor then the 
single hand line left in operation will now be proportioning water/foam 
solution at the rate of 6%. The proportion of foam to water may be 
critical to optimum performance of the foam with respect to the 
peculiarities of the fire being fought. In order to maintain an "around 
the pump" foam system performing adequately the operator must constantly 
monitor the volumes and pressures of all the liquids involved with the 
system. 
SUMMARY OF THE INVENTION 
The invention disclosed herein comprises both apparatus and method 
dedicated to the regulated supply of fire fighting additive, particularly 
foam concentrate, to a fire fighting water stream. A system for the 
addition of foam concentrate comprises a pressurized water supply source, 
an in-line venturi/modulating valve assembly, an additive source, an 
in-line fluid pump drive and one or more terminal foam/water delivery 
devices. Together these form a "through the pump foam system" or "TTP foam 
system." 
In a preferred embodiment, the "in-line venturi/modulating valve assembly" 
of the subject invention comprises a flow regulation valve, a sensor of a 
pilot valve for measuring an indicia of pressure downstream of the flow 
modulation valve, and at least one venturi mechanism for the induction of 
foam concentrate. In a preferred embodiment, the sensor measures water 
pressure and the pilot valve is biased to reflect venturi mechanism 
discharge pressure. In a preferred embodiment, a sensor associated with a 
pilot valve governing the flow modulation valve mounted proximate to an 
in-line venturi mechanism senses downstream line pressure and adjusts the 
fluid backpressure acting on the water stream such that proportioning is 
to be maintained at desired levels despite changes in line pressure. 
The venturi/modulating valve assembly uses the motive force of the 
pressurized water source for foam eduction and is placed in the system 
upstream of the pump drive used to increase pressure after flow through 
the in-line venturi/modulating valve assembly. Fluid line pressure lost in 
passage through the "venturi/modulating valve assembly" is increased by 
the subsequent fluid pump which then transmits the fluid to a downstream 
terminal fire fighting solution delivery device. In such a manner 
recirculating foam additive/water mixture through the pump in the manner 
of "around the pump" systems is avoided. 
In an alternative embodiment, the "in-line venturi/modulating valve 
assembly" includes at least two venturi mechanisms, one suitable for high 
flow and one suitable for lower flow. Diversion of the motive flow to the 
high or low flow venturi is made through a diversion valve. 
The invention combines the simplicity of venturi foam additive eduction 
with the higher performance capabilities of strictly pump driven systems 
but offers important advantages over the existing "around the pump" 
combination. The "through the pump foam system" described herein allows 
for simple and consistent foam proportioning without the constant 
monitoring of pressure and flows. 
The invention also comprises a method for producing fire fighting foam that 
includes supplying a water stream from a pressurized water source through 
fluid conduit, modulating the water stream pressure through the use of a 
modulation valve, inducting fire fighting additive into the modulated 
water stream through the use of a venturi mechanism, pressurizing the 
foam/water stream and discharging the pressurized water additive mixture 
through a terminal fire fighting delivery device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In a normal operations illustrated in FIG. 3 the "venturi/modulating valve 
assembly N", also termed "TTP foam assembly", is installed between water 
supply M and the inlet side P.1 of a water pump P. As the supply water 
passes through the "venturi/modulating valve assembly N" the water supply 
pressure is automatically adjusted to meet preset pressure requirements. 
These preset pressures are designed to be below the maximum discharge head 
capabilities of the jet pump G. See also FIG. 2 The jet pump G is located 
within the "venturi/modulating valve assembly N". A small volume of water 
(high pressure) is bypassed through the modulating valve providing 
adequate pressure and water volumes to operate the jet pump G. Several 
sensing lines monitor the pressures on the inlet L and down stream side I 
of the water modulation valve. As the demand for water supply is 
increased, the sensing lines will detect the decrease of water supply 
pressure on the down stream side of the "venturi/modulating valve 
assembly". This decrease in pressure triggers the modulation valve D on 
the "venturi/modulating valve assembly N" to open allowing for a higher 
volume of water to enter the pump until the pressure of the downstream 
water supply matches the preset pressure of the "venturi/modulating valve 
assembly" as shown on FIG. 6. As the demand for water supply is decreased 
the sensing lines will detect the increase of water supply pressure on the 
down stream side of the "venturi/modulating valve assembly". The increase 
in pressure triggers the modulation valve on the "venturi/modulating valve 
assembly" to close and decrease the amount of water entering the pump 
until the pressure of the down stream water supply matches the preset 
pressure of the "venturi/modulating valve assembly" as shown on FIG. 5. 
This modulation occurs automatically to assure that the inlet pressure of 
the water pump will never exceed the discharge head capabilities of the 
"venturi/modulating valve assembly". 
The unit control valve C of FIG. 2 allows the operator to select the mode 
of operation of the "venturi/modulating valve assembly". In automatic mode 
the unit will perform as described above, adjusting water pressures as 
required. In the open mode the modulation valve will open completely 
allowing for maximum flow through the unit without any modulation. In the 
closed mode shown in FIG. 4, the modulation valve closes completely 
preventing water from passing through the "venturi/modulating valve 
assembly" (the jet pump or eductor motive flow will still be allowed to 
pass through the system in the closed mode). 
As the water from the high pressure side A enters the inlet B of the jet 
pump nozzle G, the jet pump nozzle converts the pressure of the jet pump 
operating water into a high velocity stream. As the high velocity stream 
enters the low pressure area of the jet pump, the low pressure area allows 
for a liquid additive to be educted into the low pressure area. The jet 
pump operating water entrains the water additive and the solution flows 
into the mixing area of the "venturi/modulating valve assembly" 
Water additive proportioning can be established by several means as 
follows: 
Method One: Automatic modulation: 
Located at the inlet of the additive jet pump it provides for a positive 
and automatic means of proportioning. Pressure sensing lines are used to 
monitor pressure drop across an orifice located in the mixing chamber of 
the "venturi/modulating valve assembly". Based on the differential 
pressure across the orifice total volumes can be sensed. One of the 
sensing lines connects directly to an additive modulation valve. The 
second sensing line is attached to a pressure amplifier. From the pressure 
amplifier the sensing lines terminates into the additive modulation valve 
opposite sensing line 1. lines. The additive modulation valve reacts 
accordingly as the pressure differential across the orifice in the mixing 
chamber varies. This additive modulation valve at the inlet of the 
additive jet pump allows for precise automated metering of the correct 
volumes of additives into "venturi/modulating valve assembly". 
Method Two: Variable Metering Valve: 
Located at the inlet of the additive jet pump it provides for positive and 
manual means of proportioning. The variable metering valve utilizes a 
characterized ball valve to provide additive proportioning over a wide 
range (0 gpm--maximum jet pump pickup). The variable metering valve is 
designed with a positive off feature. Once the water flow is established 
on the system the operator selects the volume of additive to be introduced 
into the system. The volume of additive is positive and constant and will 
not vary unless reestablished by the operator. 
Method Three: Fixed Orifice: 
Location of a fixed orifice at the inlet of the additive jet pump provides 
for a fixed means of proportioning. This method by far is the simplest of 
the earlier mentioned methods. It is designed for operations that will be 
utilizing set water flows with no variances. 
Method Four: Remote Jet Pump: 
Located away from the inlet of the additive jet pump provides for positive 
and remote means of proportioning. Remote Jet Pump proportioning utilizes 
a separate independent jet pump. The independent pump can be located a 
considerable distance away from the "venturi/modulating valve assembly". 
Independent jet pump operating water is supplied by an external 
pressurized source. Proportioning Methods Two and Three can also be used 
in conjunction with the independent jet pump. A fluid conduit is attached 
to the discharge side of the independent jet pump. The fluid conduit then 
terminates at the additive suction side of the "venturi/modulating valve 
assembly". Since the independent jet pump is truly discharging into a 
vacuum area, the two jet pumps can be located a great distance apart. 
Once the correct volume of additive is introduced into the water stream. 
the solution enters the mixing chamber of the "venturi/modulating valve 
assembly". The total solution than passes through a downstream fluid pump 
where a pressure increase occurs. Once adequately pressurized by the pump. 
the water/additive solution is then directed into a fire water delivery 
device. 
In a preferred embodiment of the "TTP foam system" of the present invention 
as shown on FIG. 3, a "venturi/modulating valve assembly" N is installed 
between a pressurized water supply M and the inlet side P.1 of a fluid 
pump P. The pressurized water supply is provided for example, either as 
central line pressure as is supplied by a water hydrant, or pressure 
created by pumping water from a water supply such as a tank, reservoir, 
natural water body, etc. As the supply water passes through the 
"venturi/modulating valve assembly" N the water supply pressure is 
detected by pressure sensing lines and the water flow passing through the 
"venturi/modulating valve assembly" N is automatically adjusted via a 
modulating valve to meet preset pressure requirements. These preset 
pressures are designed to be below the maximum discharge head capabilities 
of a jet pump or eductor functioning as the venturi mechanism. A desired 
volume of additive originating from an additive source O enters via an 
additive port into the pressure adjusted water stream within the 
"venturi/modulating valve assembly". The additive together with the water 
which educted it into the fluid path is discharged into the 
"venturi/modulating valve assembly" N. The combined solution than passes 
through a fluid conduit into a downstream fluid pump P where a pressure 
increase is effected. Pump P can be a standalone pump or can be the pump 
on a fire truck. The subject invention can enable an ordinary municipal 
fire truck lacking a foam proportioning system to efficiently educt and 
apply foam. Placement of a fluid pump in a location downstream from an 
inline venturi mechanism enables eduction and adequate pressurization 
without having to recycle foam additive together with water as in the 
"around the pump" system. Once adequately pressurized by the pump P, the 
water/additive solution is then directed out of the pump outlet P.2 and 
passes via fluid conduit R to a terminal fire fighting solution delivery 
device Q. Terminal fire fighting delivery device Q can be for example one 
or more of a fire fighting nozzle, fixed monitor, sprinkler system, 
floating tank rim seal fire protection system, tank foam port, etc. 
The "venturi/modulating valve assembly" disclosed herein comprises a 
combination of an in-line venturi mechanism together with flow pressure 
detection and regulation of the water passing around the venturi itself 
such that a desired flow pressure is maintained without the short comings 
of prior art systems. Without this regulation, increased water pressure 
such as occurs when a downstream delivery device is terminated, might 
cause the venturi to cease operation. Conversely, without pressure 
regulation and modification, decreases in pressure flowing around the 
venturi such as when terminal delivery devices are opened may either 
result in hysteresis or undesirable increases in foam proportioning. 
In a favored embodiment of the "venturi/modulating valve assembly" of the 
subject invention, depicted on FIG. 2, pressurized supply water enters 
"venturi/modulating valve assembly" at water inlet A. A jet pump G 
comprises the venturi mechanism. The jet pump G of the preferred 
embodiment is located within the body of the "venturi/modulating valve 
assembly" as shown on FIG. 2. An example of such a jet pump is Model 
2.0JP60 made by Spectrum Manufacturing (P.O. Box 1359, Mauriceville, Tex. 
77626). In a most prefered embodiment, the motive stream for operating the 
jet pump enters jet pump water inlet channel B and is passed through the 
center of the modulating valve D via a channel B through the modulating 
valve D. However, it is contemplated that the channel carrying the motive 
flow for the jet pump could pass through the modulating valve in a 
peripheral location as well or could be diverted around the modulating 
valve. 
In an alternative embodiment as shown on FIG. 7, the "venturi/modulating 
valve assembly" further includes a plurality of venturi mechanisms. At 
least one the venturi mechanism T is suitable for relatively high flow 
rate while the other venturi mechanism U is suited for lower flow rates. 
The motive fluid for the venturi mechanisms is diverted by a valve V to 
either the high or low flow rate venturi as circumstances require. 
To return to FIG. 2, one or more pressure sensing lines respective to 
pressure control or pilot valves monitor the pressure of the main volume 
of fluid flowing through the venturi assembly. This is the fluid passing 
around or past the venturi mechanism opening into which the motive fluid 
of the venturi carrying additive ultimately empties. In a most preferred 
embodiment, a pressure sensing line is located on the down stream side I 
of the water modulation valve D. An example of a modulating valve/pressure 
sensing pilot valve combination able to perform this dual detection and 
flow regulating function is Pressure Reducing Inbal valve Series 700-R 
(MIL, P. O. Box 1786, Holon, 58117 Isreal). It is contemplated that any 
type of pressure sensing device and associated flow regulating device may 
be used to carry out the purpose of flow and pressure regulation of the 
main water stream respective to the venturi mechanism. 
As the demand for water supply varies, the control valve pressure sensor 
will detect the variation of water supply pressure on the down stream side 
I of the modulating valve. This increase or decrease in pressure triggers 
the modulation valve D on the "venturi/modulating valve assembly", by 
virtue of the pilot valve J, to open or close allowing for a higher volume 
of water to flow through the "venturi/modulating valve assembly" and enter 
the downstream water pump, until the pressure of the downstream water 
supply matches the preset pressure of the pilot valve associated with the 
"venturi/modulating valve assembly" shown on FIG. 6. As the demand for 
water supply settles, the pilot valve will stabilize the modulation of 
water through the modulating valve. A sensed increase in pressure triggers 
the modulation valve D on the "venturi/modulating valve assembly" to close 
and decrease the amount of water entering the assembly until the pressure 
of the water supply proximate the venturi discharge matches the preset 
pressure for the pilot valve as shown on FIG. 5. This modulation occurs 
automatically to assure that the pressure of the water pump will never 
exceed the discharge head capabilities of the venturi mechanism in the 
assembly. 
The unit control valve C shown on FIG. 2 allows the operator to select the 
mode of operation of the "venturi/modulating valve assembly". In automatic 
mode the unit will perform as described above, adjusting water pressures 
as required. In the open mode the modulation valve to open completely 
allowing for maximum flow through the unit without any modulation. In the 
closed mode shown on FIG. 4, the modulation valve closes completely 
preventing water from passing through the "venturi/modulating valve 
assembly" (the jet pump or eductor motive flow will still be allowed to 
pass through the system in the closed mode). 
As the water from the high pressure side enters the jet pump motive flow 
channel B channel at inlet A of the "venturi/modulating valve assembly". 
the pressure of the jet pump motive fluid is converted into a high 
velocity stream. As the high velocity stream enters the low pressure area 
of the jet pump G, the partial vacuum formed allows for a liquid additive 
to be pulled into the low pressure area. The jet pump motive fluid 
entrains the water additive and the solution flows out through 
water/additive discharge H of the "venturi/modulating valve assembly". 
It is contemplated that additive proportioning can be established by 
several alternative means such with either an automatic or variable 
metering valve, a fixed orifice or together with an additional remote jet 
pump. In a preferred embodiment, additive passes through inlet E and 
enters a variable metering valve F, before the additive inlet S of the 
water additive jet pump 1 which provides for positive and manual means of 
proportioning. The variable metering valve utilizes a ball valve to 
provide additive proportioning over a wide range (0 gpm--maximum jet pump 
pickup). The variable metering valve is designed with a positive off 
feature. Once the water flow is established on the system the operator 
selects the volume of additive to be introduced into the system. The 
volume of additive is positive and constant and will not vary unless 
reestablished by the operator. 
Virtually any type pump able to increase the line pressure after the 
water/foam solution leaves the "venturi/modulating valve assembly", 
including for instance displacement pumps or centrifugal type pumps, could 
be used with the subject invention. In the preferred embodiment, a 
centrifugal pump is used. 
In a typical application, flexible portable fire hose is used to provide 
the fluid conduit line connecting elements of the invention. However. it 
is also contemplated that rigid or fixed fluid conduit may be used to 
provide connections between the source of pressurized water, the 
"venturi/modulating valve assembly", the downstream pump and the terminal 
applicator equipment. Either flexible or rigid conduit may be used to 
permanently install the subject invention in critical locations such as a 
refinery or tank farm. It is contemplated that connections may be made 
into the fluid conduit line such as for example to introduce additional 
additives or to provide for flushing of the line. 
FIG. 2 illustrates the operation of unit pilot valve J. Modulated pressure 
sensing line I senses water pressure downstream of the sleeve or tube 
valve, not shown. Pilot valve J is preferably spring biased to reflect a 
preset desired water pressure proximate the discharge of the venturi 
mechanism. High pressure sensing line L uses the motive force of the 
entering water to expand the tube or sleeve valve to modulate water flow 
through the housing. Unit control valve C alternately permits high 
pressure water to expand the sleeve within the modulating valve or to vent 
to atmosphere as controlled by pilot valve J. 
The foregoing disclosure and description of the invention are illustrative 
and explanatory thereof, and various changes in the size, shape, and 
materials, as well as in the details of the illustrated system may be made 
without departing from the spirit of the invention. The invention is 
claimed using terminology that depends upon a historic presumptive 
presentation that recitation of a single element covers one or more, and 
recitation of two elements covers two or more, and the like.