WO2008156522A2

WO2008156522A2 - Swirl methods for blanketing a tank with foam to combat fire or hazard, particularly for alcohols or the like

Info

Publication number: WO2008156522A2
Application number: PCT/US2008/005320
Authority: WO
Inventors: Dwight P. Williams
Original assignee: Williams Fire And Hazard Control, Inc.
Priority date: 2007-04-30
Filing date: 2008-04-25
Publication date: 2008-12-24
Also published as: WO2008156522A3

Abstract

Methods for blanketing a tank containing a flammable/combustible liquid, and in particular hydrophilic liquids, polar solvents, alcohols or ethanols or the like, with foam, including landing primary nozzle footprints) proximate to, or on, downwind inner tank wall portions, the trajectories streaming generally with the wind over upwind tank wall portions and rebounding off of downwind inner tank wall portions at an acute angle, less than perpendicular, thereby inducing a general swirl foam run pattern.

Description

Title: Swirl Methods for Blanketing a Tank with Foam to Combat Fire or Hazard, Particularly for Alcohols or the Like Inventor: Dwight P. Williams

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority to co-pending US Application Serial No. 60/926,937, filed 4/30/2007, entitled Methods for Blanketing a Tank with Foam to Combat Fire or Hazard, inventor Dwight P. Williams, the contents of which are also hereby incorporated herein by reference in their entirety. FIELD OF THE INVENTION

The field of the invention lies in methodologies for blanketing a large tank of a flammable/combustible liquid with foam, including in particular, blanketing a tank of a polar solvent, an alcohol or ethanol or the like, utilizing techniques including landing foam on or proximate to inner tank wall portions and creating a swirl pattern of foam run. BACKGROUND OF THE INVENTION

Flammable/combustible liquid fuels are stored in large industrial tanks with diameters of 125 feet to 300 feet or more. Techniques have developed for fighting fires and addressing hazards of fire in such tanks, in particular as disclosed in the instant inventor's prior patents and applications. (See US Patent Nos. 5,566,766, 5,913,366, 6,065,545 and 7,048,207; US Application Nos. 09/569,178, 10/081,419, 10/147,647, 10/380,750, 11/196,882, 1 1/659,934,

11/292,776, 10/568,520 and 10/572,292; PCT Application No. PCT/US06/ 30070.) The techniques include blanketing the fuel surface with foam.

Today polar solvents including alcohol, ethanol or the like fuels are stored in such tanks. ("Alcohol" and/or "ethanol," as used herein, should be understood, for simplicity's sake, to include blends containing at least 15% alcohol or 15% ethanol. A "blend," as mentioned, should also be understood to include liquids containing 85% or more alcohol or ethanol, again for simplicity's sake. Thus, when an "alcohol" tank or an "ethanol" tank is referred to, it should be understood to include an alcohol blend tank or an ethanol blend tank; and when a "blend" is referred to, it could include all alcohol or all ethanol.) For extra security against fire, polar solvent fuels such as alcohol or ethanol or the like are typically stored in tanks with a fixed roof and/or a floater roof. However, a series of events can cause a fixed roof to be largely blown off and/or a floater to largely sink. Such events can then lead to a fully engaged, full surface tank fire of the alcohol or ethanol, or to at least the hazard of such. It is important, thus, to understand and develop effective methods to blanket the surface of polar solvents, alcohols and ethanols and the like, with foam, taking into account the unique characteristics of these liquids or fuels.

Ethanol is a prime example of water soluble alcohols and comprises a polar solvent fuel. Ethanol, as stored today in large tanks in a relatively pure form or as blended with other hydrocarbons, can present unique and hitherto unappreciated fire hazards. This is due, at least in part it is believed, to hydrophilic properties.

A fully engaged, full surface tank fire of a polar solvent, an alcohol or an ethanol or the like, has been discovered to present novel extinguishment problems in that the plunge of the stream delivered by a type three device (over the wall from outside the tank) into the polar solvent unexpectedly appears to remove the bite from the foam. Initial foam collapse does not ensue as with other fuels.

Solutions to this novel problem, discussed below, have been surprisingly determined to have further possible benefits for even traditional fires, or hazards of fires, involving traditional hydrocarbon fuels such as gasoline.

The instant inventor has tested and demonstrated that ethanol and the like fuels behave differently. A fully engaged tank fire of such fuels has significantly different characteristics than gasoline, crude or various other traditional hydrocarbon fuels when attacked in a traditional manner with foam from type three devices. These differences adversely affect foam blanketing techniques. The first key factor appears to be that polar solvents, alcohol, ethanols or the like, tend to absorb or draw out water from the fire fighting foam. This is particularly critical during a plunge of a type three applied foam stream over a tank wall to the surface of the liquid. Such plunge and resulting loss of water can render the foam significantly less useful in its capacity to cool, significantly less useful in its capacity to run, and significantly less useful in its capacity to form a foam blanket over the surface of the liquid. These are key fire extinguishing features of the foam. The techniques traditionally employed for blanketing traditional flammable/combustible liquid tank with foam using type three devices, in particular techniques utilized for extinguishing a fully engaged full surface gasoline tank fire, include staging appropriately sized primary nozzle(s) upwind of the tank and landing more or less centered footprint(s) of foam in the tank. The approximately centered footprints have a size vis-a-vis the tank such that the foam, given historically expected foam run, is predicted to cover and blanket the tank surface with foam within minutes. Nozzle(s) are traditionally staged at what is called the six o'clock position, the upwind position, to throw foam over the tank wall at approximately the 5 o'clock to 7 o'clock tank wall position, and to land footprints) of foam more or less centered in the tank. (The upwind position of a tank should be understood to be somewhat of an approximation in practical situations. This upwind position, however, is commonly designated as the "6 o'clock position" with respect to the tank walls.) Nozzles and footprints are pre-selected such that experimentally determined foam run is predicted to carry the foam to all tank wall portions within a reasonable period of time, e.g. within a few minutes, given predicted foam life. Landing approximately centralized footprints with primary nozzles is taught by the instant inventor in US patent No. 5,566,766.

As background information, storage tanks now have diameters of 300 feet and more, with standard heights of 50 to 60 feet. The range for the leading edge of the foam thrown by primary nozzles is at least 200 feet and may run up to 350 feet or 450 feet or more, depending on nozzle size, for large scale master stream nozzles discharging in an essentially straight stream pattern (which optimizes range) with adequate supplies of pressure and water. (Discharge patterns are chosen to optimize range because safety dictates that the staging of the primary nozzle be as far back as possible from the tank. A minimum staging distance of about 150 feet is preferred today. Staging distances of about 100 feet are possible if necessary.) Preferred footprint dimensions thrown from such primary nozzles, assuming nominal head pressure conditions can, run from about 90 to 140 feet in length, with a width of about half the length. In general landing footprints exhibit an oval-type shape.

Primary master stream nozzles discharge a stream that comprises a liquid, typically water, and a foam concentrate which, at discharge, typically has not yet fully expanded into foam bubbles. A significant amount of the expansion of the liquid into foam can occur during transit and/or upon landing.

Landing a footprint of foam from a large primary master stream nozzle, discharged in essentially a straight stream pattern, results in an initial significant "plunge" of the liquid/foam into the fuel upon landing. With gasoline and various other historic hydrocarbon fuels, the foam rises to the surface subsequent to the plunge with no significant deterioration or adverse effects from the plunge. The momentum of the throw plus the foam run tends to carry the foam from an approximately centered footprint to back tank wall portions and, by reflection and rebound, to side and front wall portions. Foam is typically relied upon today to run about 90 to 100 feet toward the back tank wall (in direction of the throw) and to run about 80 to 90 feet toward the front and side tank walls The instant inventor has discovered, however, that plunging a liquid/foam stream from a master stream nozzle into water soluble alcohol fuels, or polar solvent fuel blends, and particularly into ethanol, unlike the case with gasoline and traditional hydrocarbon fuels, does have a significant adverse effects on the resulting foam. During the plunge of a liquid/foam stream into an alcohol or polar solvent fuel or ethanol or the like, apparently the fuel tends to draw out and absorb significant amounts of water from the foam, leaving significant adverse effects. The capacity of a foam to run can be significantly diminished. The capacity of a foam to carry water to coo! can be significantly diminished. The capacity of the foam to form a film blanket over the tank surface can be significantly diminished. An ethanol fire, in fact, might not be extinguishable at all using traditional type three techniques applied to gasoline. The instant inventor, in response to his above discovery, has tested and developed novel techniques for blanketing a tank of fuel, such as a polar solvent, an alcohol or an ethanol or the like, with foam from staged type three primary nozzles. The novel technique disclosed herein includes the staging of primary nozzle(s) generally upwind of the tank, that is, generally in the 6 o'clock position, (say from the 4 o'clock to the 8 o'clock position) wherein the nozzle stream(s) pass over tank wall portions in the 4 o'clock to 8 o'clock range, preferably in a trajectory generally parallel with the wind, as before. The trajectories may be moved laterally with respect to the tank (and slightly forward in the wind direction if desired,) more than previously, such that the thrown foam passes over tank wall portions between approximately the 4 o'clock and the 5 o'clock tank wall position, or the 7 o'clock to 8 o'clock tank wall position. Preferably the foam lands on, or proximate to, downwind wall portions in the 1 o'clock to 4 o'clock position, or the 8 o'clock to 11 o'clock position. Preferably, the stream(s) is/are staged and aimed such that the stream(s) target roughly either a 2 o'clock position or a 10 o'clock position. Further, for hydrophilic alcohols such as ethanol, a significant and substantial portion of a stream's footprint should land on, should impact on, and should rebound at an acute angle off of, the inside tank wall portions themselves, the outage. That is, preferably the stream should rebound off of the downwind inner tank wall outage itself, above the level of the liquid, at approximately either a 1- 3 o'clock or 9-11 o'clock position.

(It should be understood throughout the specification, including drawings and claims, that a symmetrical analog exists. For simplicity's sake, this symmetrical analog may not be explicitly mentioned each time, but should be understood as inherent and implied. For instance, in one case a counter clockwise swirl is induced and in the symmetrical analog, a clockwise swirl is induced.)

It has been determined, including by testing, that the process of landing stream(s) from primary nozzle(s) proximate to or against or on inner tank wall portions, at an acute angle thereto, has several beneficial effects. Some of the beneficial effects are especially useful in regard to hydrophilic alcohols. These beneficial effects include: (1) the impacting itself against and on the inner tank wall portions further agitates the foam, creating a more expanded foam, and the more expanded foam can skate more easily across tank surfaces and land more softly, with less subsequent plunge. (In fact, the type three application proximates a type two application.) (2) As landing significant portions of a stream's footprint against inner tank wall portions significantly reduces the degree of the plunge of the liquid foam into the tank fuel, this reduces the apparent absorption or drawing out of water from the foam by a plunge into a hydrophilic liquid. (3) Surprisingly, foam as a whole appears to run significantly further in a swirl pattern in a tank than when landed in a centered position within a tank. In regard to the latter point, an acute angle of attack of the trajectory of thrown liquid foam up to or against or on inner tank wall portions imparts a swirling movement and momentum to the rebounding foam, swirling the foam in either a counterclockwise, or for the symmetrical analog, clockwise, run pattern around inner tank wall surfaces, as well as migrating toward the center. A slight crosswind vector can enhance the angle of attack. It has been surprisingly discovered that this swirl movement and momentum, aided it is surmised by the fact that part of the running foam that is on the surface and against the tank wall itself is shielded from the fire, results in a foam run as a whole that extends over a significantly longer distance than the foam run experienced from foam thrown into a center portion of the tank. Experiments and testing indicate that a swirl foam run can carry at least twice as far. This may amount to at least one half to three quarters of the way around inner tank wall portions of even relatively large tanks, and as well to the center of the tank. Such a run in even a large tank can create initial foam collapse.

The inventor further teaches herein, to the extent possible, subsequent to initial foam collapse, (which is extinguishment of at least 50% of the surface fire,) staging react line(s) and nozzle(s) about the tank, preferably at the 9 to 6 o'clock position and possibly also, or alternately, at the 1 o'clock position (remembering to apply symmetrical positions for the symmetrical analog.) The react lines and nozzles can direct their streams either toward the tail of the swirl pattern foam run, adding to and enhancing the swirl pattern movement and momentum, and/or directly toward unblanketed surface areas of the tank, which might be counter to the foam swirl run direction. In the case of hydrophilic alcohols, ethanols and the like, the react lines should also land their footprints significantly and substantially on and against inner tank wall portions themselves above the liquid level, on the inner tank wall outage, to minimize the plunge.

The staging of react lines can depend upon many factors, such as how a tank is behaving under environmental conditions, the equipment available, the size of the tank, the tank chemicals, the tank location with respect to its surroundings and the wind and weather conditions. Given the above and the run of the foam actually achieved in the tank from the primary nozzle(s), react lines are preferably placed at approximately the 6 to 9 o'clock position and/or also at about the 1 o'clock position, (and the symmetrical analogs.) As above discussed, in the former case the react lines direct stream(s) of foam against inside tank wall portions in the direction of the swirl foam run such that the new foam run augments the tail end of the general swirl pattern of foam run established by the primary nozzle(s), thereby assisting to run foam all the way around the tank and back to the initial approximately 1 to 4 o'clock position. Alternately and/or in addition, react line(s) can be staged at approximately the 1 o'clock position and direct foam back to inner tank wall portions around the 2 to 3 o'clock positions to rebound directly onto areas of the liquid surface to which the foam has not yet been carried by the swirl pattern. (Again, the symmetrical analog exists.)

It is possible that an ethanol or similar fluid tank fire can only be extinguished with the above techniques. Subsequent to discovering that ethanol tank fires are best extinguished using the wall impact and swirl foam run technique, discussed above, augmented by react lines where possible, the instant inventor further discovered that the swirl pattern foam run has some good applications and advantages for traditional flammable/combustible fuels, e.g. for the traditional hydrocarbon fuel fires such as gasoline. Testing indicates that a swirl pattern foam run appears to extinguish a traditional flammable/combustible fuel fire in approximately the same time as the centered footprint method. However, in the case where supply head pressure to the primary nozzles deteriorates below nominal, the swirl pattern can have an advantage. Were head pressure supplied to the primary nozzle(s) to deteriorate to the extent that the range of the nozzle, for a centered footprint, would not enable the foam run to reach back wall portions of the tank at all, (and deterioration of supply head pressure occurs unfortunately too frequently,) in such case applying the same foam targeted on and proximate to the 1 to 4 o'clock position and utilizing a resulting swirl pattern of foam run might reach the back wall, blanket a substantial portion the surface with foam and achieve initial flame collapse. (Symmetrical analog exits.) Also implementing a swirl pattern may permit personnel equipment to be staged approximately up to 30% further back from the tank itself. And a swirl pattern might better reach fire under any curled wall portions, when the heat of the fire curls the tank walls inward.

To take a specific example, as mentioned above, testing has shown that foam run from a footprint landing in the center of a tank of ordinary fuel is generally limited to about 100 feet in the forward direction, the direction of the throw toward the back wall, and to about 80 feet to 90 feet in the side and rearward direction from the throw, e.g. toward the side and front of the tank or the 3, 6 and 9 o'clock positions. Testing has indicated that foam running around tank walls in a swirl pattern has a capacity to run significantly longer, possibly 200 to 300 to 400 feet.

The following example, thus, illustrates a possible beneficial consequence of the instant invention when head pressure is lost in a traditional hydrocarbon fire. The example is illustrated in Figure 5. (Only one primary nozzle is shown in Fig. 5 for simplicity.) In the instant example, assume a loss of head pressure causes the design range and footprint of the nozzle of Figure 5 not to be achieved. Assuming two primary nozzles staged 150 feet from a 300 foot diameter tank, staged at the 6 o'clock position, the two primary nozzles would nominally be expected to throw centralized footprints about 130 feet long with a leading edge range of 360 feet. Given nominal foam run, this should be sufficient to run foam to the back, front, and side walls of the tank. However, were a significant less of head pressure to occur, such as due to other necessary draws on the water supply, the resulting in a footprint might be only 100 feet long with a leading edge range of only 300 feet. In such a case, foam run from the centralized footprint patterns likely would not reach back tank wall portions. Staging the primary nozzles laterally and slightly forward toward the tank 4 o'clock position, (yet still remaining 150 feet from the tank,) and aiming the leading edges of the footprints toward the inner tank wall 2 o'clock position, would allow the primary nozzles to be staged approximately 30 feet further forward, measured in the direction of the wind. The 100 foot long footprints could still be landed largely inside of the tank with their leading edges toward the tank 2 o'clock position. Testing indicates that the resulting swirl pattern of foam run, going around inner tank wall surfaces, should run significantly farther than 100 feet and should in fact achieve at least initial flame collapse in the above circumstances. After achieving initial flame collapse, react lines and react nozzles could be staged, hopefully for example around the 9 o'clock position, aiming their streams over the tank wall at approximately the 6 to 8 o'clock position, to hasten complete flame collapse and complete the blanketing.

Thus, the instant invention, even in the case of traditional flammable/combustible liquids, has advantages. Flame collapse may be achievable in essentially the same period of time as with a centered footprint pattern approach but a safeguard exists for achieving flame collapse if nominal nozzle head pressure deteriorates and thus range and footprint size significantly diminish, or when the tank walls curl inward. (An obvious corollary exists for the situation where tank dimensions simply exceed the capacity of the available primary nozzles.)

Note: in regard to the co-pending application herein incorporated by reference, to the extent any conflict exits between the disclosure there and herein, the disclosure herein is to govern. SUMMARY OF THE INVENTION

To recap, alcohol fuels, such as ethanols or blends thereof, appear to significantly absorb water from liquid/foam during a landing plunge, as foam is applied over a tank wall from primary nozzles staged outside of the tank to combat a fire or a hazard (type three attack.) The instant inventor has developed and discloses inventive techniques to combat this situation. Testing further indicates that the invention has application and value in the cases of traditional flammable/combustible liquids, as the invention offers a technique possibly advantageous in the case of loss of nominal primary nozzle head pressure, or in the case of tank dimensions challenging primary nozzle design capacity, or in the case of tank walls curled inward by heat.

The invention includes landing leading edges of footprint(s) of foam at or near or on the 1 o'clock to 4 o'clock inner tank wall positions, (or alternately the 11 o'clock to 8 o'clock position) including landing the foam on the fuel and/or landing the foam significantly and substantially on the inner tank wall portions themselves, the outage. Foam run therefrom assumes a swirl pattern. The angle of intersection of the stream trajectory with the inner tank wall should not be perpendicular, in order to create a counter clockwise (or clockwise) swirl pattern with the rebounding foam. (Again it is to be understood that symmetrical analogs exist.)

Specifically for alcohols and the like, such as ethanol, what could amount to an unacceptable loss of water from the foam during a landing plunge of the foam liquid into the fuel can be alleviated by throwing a significant and substantial portion of the footprint(s) of liquid foam against inner tank wall portions themselves, against inner tank wall outage. Rebounding the foam off of the inner tank walls creates larger foam bubbles, through agitation, and lessens the extent of the plunge of the foam when it hits the fuel surface. To the extent that there is insufficient outage of tank walls above an alcohol fuel level, initially, it can be noted that the alcohols burn off at a rate of one foot to one and a half feet per hour. The alcohol further can be drawn down in the tank. Both processes create inner tank wall surfaces, or outage, off of which the foam can be impacted and rebounded.

The instant invention includes methods for blanketing a large industrial tank surface with foam, including inducing a swirl pattern. The method includes staging one or more primary nozzle for a type three attack generally upwind of the tank and directing one or more foam stream trajectories therefrom over approximately 4 o'clock to 8 o'clock tank wall portions. (The 6 o'clock tank wall position represents the general upwind position.) The foam stream trajectory is preferably directed such that a straight trajectory would intersect downwind inner tank wall portions between approximately a 1 o'clock to 3 o'clock position or an 11 o'clock to 9 o'clock position and at least 5 degrees off perpendicular. The method includes landing the foam stream on or proximate to (within 50 feet) said downwind inner tank wall portion such that foam run from rebounding off of inner tank wall portions at an acute angle assumes a swirl pattern on the surface of the tank liquid. (It should be understood that if the foam is landed on or proximate to inner tank wall portions, not every element of foam will literally touch the tank wall. Some foam closer to the center of the tank will simply rebound off of foam further from the center of the tank.) In preferred embodiments the tank liquid includes a hydrophilic liquid and the landing includes landing the foam stream substantially on inner tank wall portions. In further preferred embodiments the foam stream is directed generally parallel to the wind and over 4 to 5 o'clock, or 7 to 8 o'clock, tank wall portions.

Preferred embodiments include, subsequent to achieving initial claim collapse, staging at least one react line and nozzle on the tank wall to complete or speed the blanketing. BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiments are considered in conjunction with the following drawings, in which:

Figure 1 illustrates a primary nozzle staged to direct its stream generally in the direction of the wind (from 6 o'clock to 12 o'clock position) over tank wall portions between approximately the 4 o'clock and 5 o'clock positions, and landing onto and/or proximate to inner tank wall portions between approximately the 1 o'clock and 3 o'clock positions. Figure 1 also illustrates a resulting counterclockwise swirl pattern of foam run around inner tank walls and toward the center as well as potential locations for react lines and nozzles. (It should be understood that the symmetrical analog exists, in regard to the 7 and 8 o'clock wall portions and

11 and 3 o'clock positions, and a counter clockwise swirl.)

Figure 2 illustrates landing a footprint of a primary nozzle substantially on inner tank wall outage, between approximately a 1 and 3 o'clock position. A nozzle is discharging its stream in the general direction of the wind and over tank wall portions between approximately the 4 and 5 o'clock position. (While the footprint is landing predominantly or substantially against inner tank wall portions, some of the footprint lands on the liquid. Preferably substantially all of the footprint lands on the outage, if possible.)

Figure 3 illustrates the geometry of landing a footprint from a 6000 gpm primary nozzle on and proximate inner tank wall portions at the 1 o'clock to 3 o'clock position, the tank being a 200 foot diameter tank, as well as the potential positioning of react lines.

Figure 4 illustrates alternate geometry for landing a footprint of a 6000 gpm primary nozzle substantially all against inner tank wall portions of a 200 foot diameter tank, either proximate a 12 o'clock position or proximate a 1 to 2 o'clock inner tank wall position. Figure 4 illustrates that less leading edge range for the footprint is required for the 1 to 2 o'clock landing pattern.

Figure 5, discussed above, compares landing a centralized and a less centralized footprint in a tank under nominal and diminished head pressure conditions.

Figure 6 illustrates geometries of a tank and foam streams and rebound angles for streams targeted at approximately a 1:30 o'clock tank wall position. The drawings are primarily illustrative. It would be understood that structure may have been simplified and details omitted in order to convey certain aspects of the invention. Scale may be sacrificed to clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 illustrates tank T having within it a polar solvent blend PSB. WD indicates wind direction, which generally, conventionally defines a clock face on the tank. Clock face position 6 o'clock is the upwind position. Clock face position 12 o'clock is the downwind position. Wind, of course, can be variable. The downwind position can not be precise or exact in practice, but is generally accurate.

In the embodiment of Figure 1 only one primary nozzle N is shown as staged, for simplicity. Actually a plurality of primary nozzles might be staged, clustered about the N or upwind position. Also, the symmetrical analogue is not shown, for simplicity. It should be understood.

Primary nozzle N is shown staged outside of tank T (a type three application) such that its trajectory is generally parallel with wind direction WD. The nozzle is staged such that its trajectory passes over tank wall portions at the general 4 o'clock to 5 o'clock position. The nozzle preferably lands its footprint of its foam generally on and/or against inside tank wall portions. For hydrophilic fuels, the liquid foam should be landed significantly and substantially on inner tank wall portions themselves, above the liquid level in the tank, between the 1 o'clock and 4 o'clock position, or 11 o'clock and 8 o'clock position. (Substantially indicates at least over 50 %.) Preferably almost 100% of the effective footprint is landed on the outage. Preferably the footprint or footprints are targeted to land between approximately the 1 o'clock and 2 o'clock, or 11 o'clock and 10 o'clock, position. This is illustrated more particularly in Figure 2 wherein FP illustrates in dashed lines a footprint. A heel of the footprint is landing on the liquid surface PSB. However, a significant and substantial portion of footprint FP is landing against inner tank wall portions of tank T between approximately the 1 o'clock and 2 o'clock position. In Figures 1 and 2 foam run direction arrows FRD illustrate that the foam will tend to rebound off of tank wall portions at an acute angle and move counterclockwise along and around the tank in the direction of arrows FRD, in a counter clockwise swirl pattern. Figure 1 illustrates the swirl pattern of the foam rebounding from inner tank wall portions and tending to cover the center.

As Figure 1 illustrates, foam landed against inner tank wall portions at approximately the 1 o'clock and 2 o'clock position forms a swirl pattern, illustrated by foam run indicators FRD, and testing indicates that a foam blanket will relatively quickly cover a significant portion of the surface of the tank. Presuming that there was a full surface tank fire in tank T, foam blanket F indicated in Figure 1 should at least create initial flame collapse (collapse of at least 50% of the fire.)

Preferably, after initial flame collapse, react lines and nozzles could be staged on or about tank

.T. Figure 1 illustrates two preferred positions for staging react lines and nozzles about tank T.

One position is at approximately the 9 o'clock position on the tank. The react line and nozzle staged at the 9 o'clock position will send foam against inner tank wall portions at approximately the 7 o'clock position. This foam will augment the foam run created by the primary nozzle and should assist in carrying foam run all the way around the tank to the 1 to 2 o'clock position.

Alternately, or in addition, a react line and nozzle might be staged at approximately the 1 o'clock position, as illustrated in Figure 1. This nozzle sends foam against inner tank wall portions back at the 3 o'clock position, rebounding off the tank wall onto areas having the least foam blanket created by the swirl. (Again, a symmetrical analog possibility is to be assumed.)

Such techniques discussed above should assist in blanketing a surface of tank T with foam. The system is designed to create an effective foam blanket and to do so in a cost effective period of time. It should be understood in the above that the primary nozzle(s) stream(s) need only be directed approximately parallel with the wind. Circumstances, convenience or necessity could dictate a divergence from strict parallel.

It should be understood that in certain circumstances advantage could be taken of a reliable wind. A primary nozzle could be stationed more around toward a 3 o'clock position, for instance, aiming its trajectory to an extent crosswind, such that the force of the wind together with the throw of the trajectory lands the footprint proximate to, or on, tank wall portions in the

12 to 3 o'clock position. Such would be analogous to the curved trajectory of a golf ball in a high wind environment. Alternately, a nozzle could be stationed at approximately the 7 o'clock position sending its trajectory across toward the 1:30 to 2 o'clock position. The wind would be expected to bend the trajectory somewhat creating a greater acute angle of impact of the trajectory against inner tank wall portions. The actual impact area of the footprint, taking into account the wind factor, could be closer to the 1 o'clock position.

Figure 1 also illustrates react lines set at the 2 to 3 o'clock and 10 to 9 o'clock positions directing foam streams to the inner tank wall between the 3 to 5 o'clock areas and the 7 to 9 o'clock areas. Preferably foam would be applied by react lines to impact the inner tank wall outage as well as to create a swirl effect.

Figure 3 illustrates one geometry for practicing the instant invention in a 200 foot diameter tank with 6000 gpm primary nozzle. The nozzle is shown throwing a 120 foot footprint with a leading edge range of 400 feet. The geometry of Figure 3 illustrates staging the primary nozzle such that the footprint is landed proximate to and/or on inner tank wall portions at approximately the 1 to 3 o'clock position. Figure 4 illustrates a comparison of landing a footprint from a 6000 gpm nozzle in a 200 foot diameter tank (1) against back tank wall portions, at approximately the 12 o'clock, or 11 to 1 o 'clock, position, and (2) against side tank wall portions at approximately the 1 to 2 o'clock position. Landing the footprint against inner tank wall portions between the 11 to 1 o'clock position does not yield a swirl foam run pattern. Landing the footprint against tank wall portions at approximately the 1 to 2 o'clock position results in an advantageous swirl pattern of foam run. Testing has indicated that the swirl foam pattern covers a tank at least as rapidly with foam as a centralized foam landing pattern, with the foam landed on the tank wall portions. Figure 5, also discussed above, illustrates how loss of head pressure (creating dimensions

A' and B') for a nozzle that was nominally adequate (dimensions A and B) to blanket a tank with foam could be countered by the instant technique with a result that would still likely blanket a tank with foam, utilizing the advantageous foam run of a swirl pattern. It can be seen that it takes less leading edge range to effectively land a footprint proximate the 3 o'clock position than it takes to effectively land a centralized footprint, where effectively means having a run to adequate to run at least to rear portions of the tank and while fire fighting personnel are able to remain at a safe distance from the tank.

Figure 6 illustrates a tank T with a 200 foot diameter. The radius from the tank center O to the tank wall is 100 feet. The nozzle is assumed to have a 450 foot maximum range, which is about top range. Figure 6 assumes that the nozzle lays a footprint with a 120 foot length. Given margin for error with the nozzle, in order to land substantially all of the footprint on inner tank wall portions, the nozzle should be staged no further than approximately 300 feet away from the targeted inner tank wall portion. W indicates the wind direction and wind vector. A clock face is drawn on tank T with the 12 o'clock, 1 o'clock, 1:30, 2 o'clock, 3 o'clock, 4 o'clock, 4:30, 5 o'clock, 6 o'clock, 7 o'clock, 7:30 and 8 o'clock positions indicated around the tank wall. The 6 o'clock position is the upwind position. Lines A and B indicate radial lines from the tank center out through the 7:30 and 12:30 o'clock positions respectively. In Figure 6 assumes that nozzles will be staged somewhere between the 4:30 and 7:30 o'clock radial tank positions, indicated by lines A and B. Line C indicates the upwind downwind axis of the tank running from 12 o'clock to the center and to the 6 o'clock position. Position D indicates a position 100 feet up wind of the 6 o'clock tank wall position. A footprint could be thrown along the center line C from the position D and substantially all of the footprint, or the effective footprint, could be expected to land on the outage of the inner tank wall centered around the 12 o'clock position. The foam would tend to run equally both clockwise and counterclockwise as well as to the center. A swirl pattern is not created.

If the trajectory of the nozzle at point D is re-aimed slightly, across wind toward the 1 :30 o'clock position, in fact, the nozzle could be moved back a further approximate 20 feet away from the tank, which is a safety advantage. Further, the trajectory now will strike the back tank wall portion on or around the 1:30 position at an acute angle and be bound from the back wall portion at an acute angle. The new trajectory is indicated by line F and the rebound trajectory is indicated by line FR. Line G illustrates an analogous situation if the nozzle were stationed at point E which is 150 feet from the tank wall. When realigned from direction C to direction G the nozzle at point E could be moved backwards for safety to point I and land the same amount of foam on inner tank wall portions. The rebound direction of the foam from trajectory G will be approximately the same as FR.

In Figure 6 a nozzle originally located at location D could alternately be moved sideways to location L. The nozzle location L can send his trajectory K substantially parallel to the wind and strike downwind inner tank wall portions at approximately the 1:30 o'clock position, or centered about the 1 :30 o'clock position. The rebound direction of the foam landing on inner tank wall portions on or around the 1:30 position would be illustrated as line KR. Rebound lines JR, FR and KR should all three set up swirl patterns. Rebound line JR comes from moving the nozzle at location D over to location M, more or less opposite the 7 o'clock position. Location M in fact could illustrate simply a second nozzle located at location M. The trajectory of the nozzle at location M is also centered about a rear downwind inner wall portion on or about location 1:30 on the tank. Rebound trajectory JR reflects the primary direction of rebound of the foam thrown from a nozzle at location M along trajectory J towards the 1 :30 position. This rebound direction is slightly acute. It could be further pointed out that the nozzle located at position L can be located approximately 30% further away from the tank wall, radially, than the nozzle at location D. Yet the nozzle at location L can throw substantially all of its effective footprint against inner downwind tank wall portions centered about the 1:30 position. (It might be mentioned that with any nozzle, including nozzles with the tightest and best defined footprints, some foam is lost through fall out traversing the trajectory to the target footprint landing site. Probably 10% of the foam is lost and does not reach the final footprint. Hence it is well recognized that the effective footprint always has some fall out or foam loss.)

A nozzle located at position D is 300 feet from the back wall 12' o'clock position. This nozzle could throw all of its footprint against the back wall. However, with a trajectory that is essentially perpendicular to the back wall portions, the foam will not rebound such as to create a swirl pattern around the tank surface. Preferably the nozzle staged at location D would aim its footprint against the 1 :30 position on the tank wall. With such aim the nozzle in fact could be moved back to position H which gains approximately 20 feet of further safety for the personnel and equipment. The foam following trajectory F from location H would have a rebound direction of FR. The foam in general that would create that trajectory in general would create a swirl pattern of the foam on the surface of the tank. Position E shows a staging of a nozzle 150 feet away from the tank and position I indicates that that nozzle too could be moved a safer distance away from the front wall of the tank if it aimed its trajectory at the 1 :30 tank wall position. In both cases the nozzle could throw its full footprint against the inner wall of the tank assuming nominal conditions. Location L and trajectory K indicate the nozzle positioned at D moved laterally. Trajectory K remains essentially parallel with the wind. Trajectory K passes over the tank wall before the 4 o'clock and 5 o'clock position and also targets landing its footprint on the wall at the 1 :30 position. The rebound angle for trajectory K is indicated by line KR, and rebound direction KR will create a swirl foam run pattern on the tank surface. Alternately again the nozzle at D could be moved to position M and again target with a trajectory the 1:30 position on the tank wall. The rebound direction of trajectory J from position M would be rebound direction JR as indicated. Even trajectory KR can produce a swirl pattern.

In the embodiment of Figure 6, of course, the nozzle could be staged both at location D and location L and location M.

The foregoing description of preferred embodiments of the invention is presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to the precise form or embodiment disclosed. The description was selected to best explain the principles of the invention and their practical application to enable others skilled in the art to best utilize the invention in various embodiments. Various modifications as are best suited to the particular use are contemplated. It is intended that the scope of the invention is not to be limited by the specification, but to be defined by the claims set forth below. Since the foregoing disclosure and description of the invention are illustrative and explanatory thereof, various changes in the size, shape, and materials, as well as in the details of the illustrated device may be made without departing from the spirit of the invention. The invention is claimed using terminology that depends upon a historic presumption that recitation of a single element covers one or more, and recitation of two elements covers two or more, and the Jike. Also, the drawings and illustration herein have not necessarily been produced to scale.

In the following claims "large industrial tank" means a tank of 100 foot diameter or greater. "Proximate," when used with "landing a foam stream proximate inner tank wall portions," means an edge of the foam stream lands within at least 50 feet of inner tank wall portions.

Claims

CLAIMS What is claimed is:

1. A method for blanketing a large industrial tank surface with foam, including inducing a swirl pattern, comprising: staging one or more primary nozzles for a type three attack generally upwind of trie tank; directing one or more foam stream trajectories therefrom over approximately 4 o'clock to 8 o'clock tank wall portions, wherein a 6 o'clock position represents the upwind position, such that a straight trajectory intersects downwind inner tank wall portions between an approximately 1 o'clock to 3 o'clock position, or 11 o'clock to 9 o'clock position, and at least 5 degrees off perpendicular; and landing the foam stream on or proximate to said downwind inner tank wall portion such that foam run rebounding off of inner tank wall portions at an acute angle creates a general swirl pattern on the surface of the tank liquid.

2. The method of claim 1 wherein the tank liquid includes hydrophilic liquid and the landing includes landing the foam stream substantially on inner tank wall portions.

3. The method of claims 1 or 2 that include directing the foam stream in a trajectory generally parallel with the wind over 4 o'clock to 5 o'clock, or 7 o'clock to 8 o'clock, tank wall portions.

4. The method of claim 3 that includes landing the foam stream substantially on inner tank wall portions between the 1 to 3 o'clock position or between the 9 to 11 o'clock position.

5. The method of claims 1 or 2 that includes landing the foam stream substantially on inner tank wall portions between the 1 to 3 o'clock position or the 9 to 11 o'clock position.

6. A method for blanketing a large tank of a hydrophilic liquid with foam, comprising: staging at least one primary nozzle generally upwind of the tank; directing a foam stream therefrom over approximately 4 o'clock to 5 o'clock tank wall portions, or 7 o'clock to 8 o'clock tank wall portions, in a trajectory generally parallel with the wind; and directing the foam stream substantially against inner tank wall portions above the surface of the liquid, at approximately a 1 o'clock to 3 o'clock tank wall position or an 11 o'clock to 9 o'clock tank wall position.

7. The method of claim 6 wherein the hydrophilic liquid includes alcohol.

8. The method of claim 6 wherein the hydrophilic liquid includes ethanol.

9. The method of claims 1 or 6 that includes achieving initial flame collapse and subsequently staging at least one react line and nozzle at approximately at a 9 o'clock to 6 o'clock position, or 3 o'clock to 6 o'clock position, and throwing foam from such at least one react line and nozzle substantially against inner tank wall portions at approximately a 7 o'clock to 3 o'clock position, or a 5 o'clock to 9 o'clock position.

10. The method of claims 1 or 6 that includes achieving initial flame collapse and subsequently staging at least one react line and nozzle at approximately a 1 o'clock to 2 o'clock tank wall position, or 11 o'clock to 12 o'clock tank wall position, and throwing foam from such react line and nozzle substantially against inner tank wall portions at a 6 o'clock to 2 o'clock position, or a 6 o'clock to 10 o'clock position.

11. The method of claims 1 or 6 that includes creating inner tank wall outage by burning off tank liquid and/or by drawing down tank liquid.

12. The method of claims 1 or 6 wherein a foam stream trajectory from at least one primary nozzle passes over tank wall portions at approximately a 4 o'clock to 5 o'clock position, or 7 o'clock to 8 o'clock position, and targets an inner tank wall portion at approximately a 2 o'clock position, or a 10 o'clock position.

13. A method for blanketing a tank of a flammable/combustible liquid with foam, comprising: staging at least one primary nozzle generally upwind of the tank; directing a foam stream therefrom over tank wall portions in a trajectory generally parallel with the wind and aimed at approximately a 1 o'clock to 2 o'clock tank wall position, or a 10 o'clock to 11 o'clock tank wall position; and landing the footprint on and/or proximate to said aimed at inner tank wall portions.

14. The method of claim 13 wherein a foam stream trajectory from at least one primary nozzle passes over tank wall portions at approximately a 4 to 5 o'clock, or 7 to 8 o'clock, tank wall position.

15. The method of claim 13 that includes achieving initial flame collapse and subsequently staging at least one react line and nozzle at approximately a 9 o'clock to 6 o'clock tank wall position, or a 3 o'clock to 6 o'clock tank wall position, and throwing foam from such at least one react line and nozzle proximate to and/or on inner tank wall portions at a 7 o'clock to 3 o'clock position, or a 5 o'clock to 9 o'clock position.

16. The method of claim 13 that includes achieving initial flame collapse and subsequently staging at least one react line and nozzle at approximately a 1 o'clock to 2 o'clock position, or a 10 o'clock to 11 o'clock position, and throwing foam from the at least one react line and nozzle proximate to or on inner tank wall portions at approximately a 6 o'clock to 2 o'clock position, or a 6 o'clock to 10 o'clock position.