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"Reducing Risk and Saving Lives & Property"
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"Reducing Risk and Saving Lives & Property" |
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WHITE PAPER PRESENTED AT THE AVIATION FIRE JOURNAL'S 3RD ANNUAL CONFERENCE - LAS VEGAS 8-10 MAY 2006 MULTI-AGENT DELIVERY TECHNOLOGY & THE FIRE TETRAHEDRON For years the Fire Industry has been (in the backrooms of various research labs) trying to enhance the fire suppression process through the development of new and improved agents and delivery systems. Looking back over the past 50 years what have we accomplished? After using water since the beginning of time, from the fifties on, we have seen the advent of dry chemical powder, foam, the of the Fire Tetrahedron, the use of halogenated (clean agent) gases, compressed air foam (CAF), and multi-agent delivery technology. Over the past several years various mechanical means of getting the agents inside the fire envelope more effectively (extendable reach booms, etc.) have been developed. An indictment on our Industry politics is the fact that:
A mini-awakening occurred in the mid-nineties when along with the acceptance of CAF, the HydroChem® nozzle was developed (entrainment of dry chemical powder within a water stream) to improve the ability to get the dry chemical agent through the fire wall from safer distances. The Multi-Agent delivery technology was being developed (our topic today) and the beginning concepts of using mechanical means to improve firefighter safety (extendable booms, etc.). The most emphasis was placed (within the ARFF community) on apparatus design to reduce roll-over, and improve response time. This being driven by our ancestral compact with water! Our goal of carrying ever increasing amounts of water/foam at faster rates to the scene and then delivering them at higher flow rates to longer distances from a variety of different nozzles and extensions was met through the consumption of almost all our Industries R&D dollars. Our goals in this area, in large part were accomplished. As a result we saw the cost of apparatus skyrocket during this period, driven by the costly improvements in chassis design to improve safety. We now see 4000 gallon apparatus operating like Indy cars! Our Industry should pat itself on the back --- I think? We can now do all this in record time carrying more water/foam SAFER! We now have a 21st century apparatus carrying and delivering essentially 18th & 19th century agents. Let me explain. As previously listed, there are several agents that have been developed and improved over the past 100 years that have superior fire suppression capabilities when compared to water or water/foam. In fact, if you rate the agents on their fire suppression capability you will find water at the bottom of the list. The list would look something like the following going from best to least effective. These ratings are based on Optimum Delivery and by Unit Volume. 1. clean agents 2. dry chemical powders 3. compressed air foams (CAFS) 4. water/foam 5. water (most available, most familiar, lowest cost/gallon excluding infrastructure) We should probably talk about the new term ‘EFFECTIVE DELIVERY’. Each agent has an OPTIMUM PRESENTATION within the HEART of the FIRE that will result in the most EFFICIENT FIRE SUPPRESSION (both in time and agent used). We also need to understand or at least review the concept of the FIRE TETRAHEDRON. Back in the late sixties, Walter Hessler (noted fire scientist) introduced the fire world to the concept of the FIRE TETRAHEDRON. In that concept, the fire was made up of four parts, not the three parts as thought with the fire triangle. Hessler put forward the science to back up his theory that the fire actually included a fourth part which was an uninhibited chemical chain reaction. So the fire tetrahedron (three sided pyramid) said that in order for fire to exist, all four of these components of the fire had to exist simultaneously. If one of the four was missing or removed, the fire would go out or could not exist. The four components of the FIRE TETRAHEDRON are as follows:
And is represented by the following:
Now that we have reviewed the important terms let’s look at the effective delivery of each of the major agents and their reaction or reactions with the FIRE TETRHEDRON MODEL.
Since we all understand water, let us start there. WATER: Water’s most effective fire suppression mode is small droplets. Water is typically delivered via a stream which is the most ineffective way to delivery water for fire suppression. Water absorbs the heat or energy of the fire through the creation of steam. The smaller the water droplets, the faster steam is created, the quicker the fire energy can be removed and the fire goes out. We have known this for years and have been working on ways to deliver small water droplets (smaller the better) through the fire wall and into the heart of the fire from a safe distance. Small droplet creation is all about increasing exponentially the amount of water surface area that is being exposed to the heat or energy of the fire. With small size comes the difficulty of delivery. As you decrease the size of the water droplets exponentially increasing the fire suppression effectiveness, you are also exponentially decreasing its ability to be thrown with any force safely, thereby forcing the firefighter ever closer to the fire, exponentially increasing his/her safety risk. On a graph, water in relation to fire suppression capability (droplet size) and increasing fire safety risk (firefighter standoff) would look something like this:
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NEW DEFINITION: FIREFIGHTER STANDOFF is the maximum distance a firefighter is from the fire wall to enable the agent to penetrate the firewall. Therefore, in summary water needs to be small droplet but that creates a safe delivery problem and because of this, water is typically streamed using a variable nozzle which has an effective delivery of water of only 10% max and less than 5% when streamed. This may begin to explain why we need to carry so much water to the scene! DRY CHEMICAL POWDER Let’s look at dry chemical powder which was the next agent to come onto the scene 100 years ago. In the lab, dry chemical powder has shown the capability to absorb incredible amounts of heat or energy or bind immense amounts of free oxygen on a by weight basis. For example, one pound of mono ammonium phosphate can absorb the same amount of heat as 100 gallons of water (laboratory conditions). The dry chemical powder optimally should be around 25 micron in size (talcum powder like). The smaller the particle (greater surface areas exposed) the more effective the agent. And like small water droplets, small 25 micron dust has a delivery problem (See Graph above). For years dry chemical powder could only be cast about 25 feet as dust, carrying very little energy to enable penetration of a fire wall of any intensity. Dry chemical, though, has proved its value in small fire extinguishers that effectively delivery the agent into small, low intensity or cold fires. No commercial delivery method had been developed to allow the safe use of this superior agent on intense fires safely until the nineties. We will revisit this topic later. In summary, dry chemical powder (probably our best fire suppression agent) looks very similar to water except that dry chemical powder by weight and volume has exponential fire suppression capability. Different types of dry chemical powder attack different parts of the fire TETRAHEDRON MODEL. ‘ABC’ powder absorbs the heat or energy of the fire through the creation of an ‘ENDOTHERMIC REACTION’ within the fire and secondarily has a chemical chain reaction inhibition property. ‘PURPLE K’ is a heat absorption agent that also binds the free oxygen available to the fire process causing the fire to starve of oxygen. FOAM Now let’s look at the introduction of foam and its evolution, contribution, and fire tetrahedron effect. There are too many types of foam and would require to much time and space to properly address in this paper. Therefore, we will summarize the foam effects in the fire process primarily discussing the AFFF and Class ‘A’ varieties. Class ‘A’ foam typically is used as a wetting solution to allow the water to stick around longer at the fire scene creating the opportunity to rob the fire of more energy through the cooling of the fuels and creation of more steam before it continues its journey down the street. AFFF foam is designed to create a vapor barrier over the top of any fuel, separating the fuel phase (vapor) from the heat and oxygen phases of the fire process. Foam characteristics can be varied depending on the situation/circumstance and product used, and range from very light (large bubbles) to very dense (small bubbles). Foam is delivered to the fire via the water stream. While throw distance has not been a major issue with foam deployment, the means of application (where, when, and how) has changed over the recent years. In summary foam is an excellent agent to isolate the fuel source from the fire process. Its’ major drawback is that it has to use water as its carrier and is typically delivered at high rates at ever increasing pressures requiring huge amounts of water. Its’ other draw back is that it can be easily contaminated causing early barrier breakdown. COMPRESSED AIR FOAM (CAFS) In the mid eighties, the concept of compressed air foam (CAF) was introduced. By injecting compressed air into the water/foam stream within the apparatus, the foam volume could be greatly expanded (sometimes by factors of 10’S) greatly increasing the effectiveness of the foam blanket. In other words, introducing compressed air into the water/foam stream can increase foam coverage by 150% or more from the same amount of water and foam. For example: Using 3% foam – 97 gallons of water and 3 gallons of foam concentrate make 100 gallons of foam solution. By introducing air into the water/foam stream the following results can be attained:
This means that on a 3000 gallon vehicle: 3000 gallons of water, 105 gallons of foam concentrate equaling 3105 gallons of proportioned foam can produce: · A non-aspirated nozzle can achieve 12,420 gallons of finished foam. · An aspirated nozzle can achieve 31,050 gallons of finished foam. · An using CAF can achieve up to 62,100 gallons of finished foam. You would think this would have been adopted by the industry immediately, but it wasn’t until the mid nineties that it started getting traction. Today, CAF is widely used but is still not in published standards. CLEAN AGENTS Now let’s look at the last class of agents – CLEAN AGENTS—which have been typified by Halon 1211. Clean agents (halogenated or not) have been around for many years and their fire suppression function is to stop the uninhibited chemical reaction between the other elements of the fire tetrahedron (fuel, oxygen, heat). These agents are typically described as clean agents as they leave no residue in their fire suppression process. Clean agents have been widely used in room flooding situations like computer rooms and the like to suppress the fire yet not damage the sensitive equipment. However, in doing so certain human effects (like lack of oxygen) can come into play that have restricted its use and application. However, the environment (ozone) effect has impacted these agents use the most. Halon 1211 (the best of the best in this class) was removed from commercial use in 1992 by the EPA. It has been replaced with several ‘SNAP’ listed clean agents like Halotron® 1 (FAA APPROVED), DUPONT FE36® and many others with varying fire suppression capabilities, human effects, ozone and green house gas ramifications.
Data provided by Dupont The FAA set the standard for use of a clean agent many years ago. This was based on some testing that indicated the agent (then HALON 1211) should be delivered at a rate of 5 lbs per second and had to be thrown 25 feet. As good as HALON 1211 was, the cost of deployment was enough to minimize its use and acceptance except in very special cases. Halon within ARFF has been replaced with Halotron® 1. The delivery rate has not been changed but the cost have gone up. You get the picture. For an average engine nacelle fire it takes about 30 seconds to extinguish using the existing delivery technologies. That means you will use 150 lbs. of Halotron® or between $1500-$2500 of agent. It should be noted that Halotron® only has to be about 7% of the atmosphere to cause fire extinguishment. So why do we use so much? Good question? We’ll try and answer that later. All clean agent materials are a liquid when deployed. They, within a short distance, all have a relatively low boiling point and flash to a gas when exposed to the atmosphere. The effective deployment of the clean agent requires that the gas or vapor be within the fire envelope or heart of the fire. Current delivery technology can only deploy the agent about 25 feet. Most of these agents are loosely bound chemical chains that are easily influenced by other materials. Clean agents typically don’t like water. Testing using water as a carrier have not proved effective in improving the delivery or the agent’s effectiveness. Deploying clean agents under super high pressure can cause the chemical chains to break apart (super decompression), destroying any fire suppression capability. Needless to say, the agent although extremely sensitive, can be a very effective fire suppression tool when effectively deployed inside the fire envelope. So ‘EFFECTIVE DELIVERY’ means we must deliver
In short this tells us, that if we are to ever effectively deliver these agents, we must develop better delivery systems. Delivery systems that can defeat the PHYSICS of throwing small particulate (low masses) long distances without compromising each agents fire suppression capabilities. MULTI-AGENT DELIVERY TECHNOLOGY From this goal the Multi-Agent delivery concept was born. The theory that attacking all sides of the fire tetrahedron simultaneously would result in immediate fire suppression and knockdown—Maximizing firefighter Standoff and Agent utilization. There have been several attempts to solve these very difficult delivery problems. For example, the Williams Company came up with the idea of entraining the dry chemical powder within the water stream to allow greater standoff for the firefighter and to penetrate the fire front with the dry chemical powder. On its face this is a conundrum in that the concept of delivering dry chemical wet raises a few questions. The concept (HydroChem® nozzle) caught on and is now widely used in the Industry. The HydroChem® nozzle does allow the delivery of the dry chemical powder to much longer distances. Distances that could not be attained before. However, it is not a very effective delivery method for dry chemical powder. Entrainment of dry chemical powder in a water stream creates a slurry. The ability of the dry chemical powder to interact with the heat of the fire is dependent on the water flashing off the dry chemical powder before it reaches the ground. Unfortunately, by the time this can occur the vast majority of the dry chemical has been carried to the ground by the water stream. It has been estimated that less than 5% of the dry chemical powder is actually consumed by the fire. This, as small an impact as it is, was still orders of magnitude better than anyone had been able to do before. Another compromising issue with this delivery technology is that if water/foam was being used as the dry chemical carrier the foam blanket was then contaminated by large amounts of the dry chemical powder within it –reducing its vapor barrier capabilities. The technology incrementally improved the fire suppression process (especially with 3 dimensional fires) and the Industry adopted this technology and rightfully so. PULSE DELIVERY® TECHNOLOGY About the same time as the HydroChem® delivery technology was being introduced another technology based on the delivery of dry chemical powder was developing. This NEW DELIVERY CONCEPT was based on PULSE DELIVERY® of the dry chemical powder. Pulse Delivery® being the ability to produce small packets of dry chemical powder at and within the nozzle and propel them at near mach 1 speeds out of the nozzle. The packets would then assume the mass of the packet and when combined with the velocity at the nozzle would give it force to not only travel longer distances but do it with enough force to penetrate a commercial size fire wall from a safe distance. This technology, developed by Phoenix Fire Systems, proved to be able to throw the DRY dry chemical powder to over 90 feet over three times the current capability. The packets proved not only to be robust enough to carry enough force to travel long distances and still penetrate the fire wall, but proved delicate enough for the fire wall penetration to disrupt the packet allowing the dry chemical particulate to bloom within the fire envelope exposing all its surface area to react with the heat or energy of the fire—allowing almost instantaneous fire knockdown and suppression.
Third Party Testing Results THROW RANGE TESTING Phoenix® Pulse Delivery® & QuadAgent® Technology Performed by Tyndall AR FF Research Laboratory Dec 2004
*Could not measure width but could measure throw distance. AF declined to publish throw distance at 20 degrees elevations even though precedent had been previous set with other competitive products that also could not measure width/FFOD. ALL TESTED UNDER NO WIND CONDITIONS INSIDE A HANGER. The Pulse Delivery® technology requires a high pressure delivery technology which starts back at the apparatus. This high pressure (typically twice the existing technology pressures) allows for trouble free delivery from the storage tank, requires none of the typical weekly/monthly fluffing of the dry chemical powder, and allows delivery for the first time through 15O feet of bundled hose line. The dry chemical Optimum Delivery Problem was bridged! This primary delivery solution for dry chemical powder proved the solution for a clean agent as well. Phoenix Fire Systems understanding the sensitivities of the clean agent chemical compounds first tried to entrain the clean agent within a water/foam stream. The results were not promising as the gains in fire suppression times did not offset the economic cost of deploying the clean agent with the water/foam stream. Understanding that dry chemical powder is essentially INERT and that there would be no chemical or physical interaction between the two agents if combined, Phoenix Fire developed the technology to entrain small amounts of a clean agent within the dry chemical stream as it passed into the dry chemical nozzle. They chose small amounts (rather than the recommended 5 lbs. per second) because it only takes small amounts to create the necessary atmosphere to inhibit the chemical reactions of the fire tetrahedron. This development worked beyond their own expectations. They not only could now deliver the clean agent vapor within the dry chemical stream to over 90 feet – some three times the standard expectation—they could do it OPTIMALLY. The testing also proved that smaller amounts of clean agent (1 lb. per second), when more effectively delivered can extend the throw distances to over 42 feet and still achieve the desired results.
Third Party Testing Results THROW RANGE TESTING Phoenix® Pulse Delivery® & QuadAgent® Technology Performed by Tyndall ARFF Research Laboratory Dec 2004 Test performed indoors (no wind conditions)
*Could not measure width but could measure throw distance. AF declined to publish throw distance at 20 degrees elevations even though precedent had been previous set with other competitive products that also could not measure width/FFOD. ALL TESTED UNDER NO WIND CONDITIONS INSIDE A HANGER. The CLEAN AGENT OPTIMUM DELIVERY problem was Bridged! Well what about water? Unfortunately the small droplet water delivery problem is still an open issue. A lot of people and groups are trying various ways to solve it. The Air Force is trying an ULTRA-HIGH PRESSURE TECHNOLOGY (1500 psi) to overcome the delivery problems of small droplet water. And while they are making incremental progress the real solution has yet to surface. The high pressure technology was based on high pressure water pump that have been developed over the past several years. You have seen them mounted on the back of the John Deere Gator by the Air Force. While the technology has some application, its primary driver appears to be the ability to PUSH the fire off the fuel as much as delivering small droplets into the heart of the fire. The larger machine that was built and tested by the Air Force again appears to have, as its primary driver, the ability to PUSH fire from the fuel as much as introducing small water droplets to cause fire extinguishment. The larger apparatus is very dangerous at those pressures, both internally and externally to the machine, and if it is eventually commercialized it will most like come in some other form and delivery technology. At least they are trying! QUADAGENT® DELIVERY TECHNOLOGY Phoenix, without a solution to the delivery of water, focused on how best to deliver 1) Water (existing technology), 2) Water/Foam and 3) CAF OPTIMALLY in combination with the optimal or OPTIMIZED DELIVERY of dry chemical and clean agent. Their answer was to marry the water, water/foam & CAF technology in PARALLEL DELIVERY with Pulse Delivery® dry chemical powder technology and clean agent delivery technology so as to minimize the amount of Cross Contamination of the agents – Thus the QUADAGENT® DELIVERY TECHNOLOGY. The development of the Pulse Delivery® Technology for dry chemical powder and the entrainment capability with a clean agent allowed for the partnership with the parallel complimentary delivery of water, water/foam, and CAF (Yes I said COMPLIMENTARY). This allowed for the first time, all sides of the FIRE TETRAHEDRON to be attacked simultaneously and effectively causing immediate fire suppression and knockdown. All of which go to increasing FIREFIGHTER SAFETY or STANDOFF and MAXIMISING the FIRE SUPPRESSION CAPABILITY of all on-board agents. In ARFF terms this means using the Pulse Delivery and entrainment of clean agent for fire extinguishment and using the water, water/foam and/or CAF to create a vapor barrier and introduce further cooling if necessary. This technology development should cause the industry to pause and at least begin to rethink their approach to fire suppression. The Industry currently uses large volumes of water/foam/CAF delivered at high rates to overwhelm the fire and separate or push the fire off the fuel thereby stopping the fire process. This approach requires enormous amounts of water/foam/CAF to accomplish suppression. If fire suppression is accomplished one can only hope that enough agent is left to provide a defense against re-ignition! Hopefully, we can now see a way to better utilize the on-board water/foam/CAF. Using it OPTIMALLY is the KEY. And that is as a VAPOR BARRIOR AND DEFENSE AGAINST re-ignition. Using water/foam/CAF as our primary fire extinguishment tool has driven us to our current apparatus. The real questions that we need to answer are: Now that we have all this new technology in our apparatus chassis that allow for INDY type arrivals safely, can we put the fire out any faster? If we can’t or can show only marginal improvement in the fire suppression process because we got there a few seconds earlier are all these new safety developments worth the cost to the flying public and our firefighters who have to attack the fires and often are put at extreme risk! The Air France incident in Toronto should be our wake up call! Here we had all known assets on site within 52 seconds or so! Great Job! A lot of off-sight assets were at or near the incident scene before the plane caught fire. All the passengers safely evacuated themselves from the plane prior to the plane catching on fire with only minor injuries! Only to then watch as we (I say ‘we’ broadly here) fail to put the fire out and in disbelief see the plane burn to the ground in front of all these expensive assets. There are lots of reasons for this occurrence, the biggest is, though, the fact that we are still basing our fire suppression technology on our ability to force the fire or fuel pool into ever smaller areas so that we can get to a point at which we can simply overwhelm the fire and separate the fuel from the fire itself. This technique works great on a 100 foot diameter pit of water that is covered with JP fuel with a simulated aircraft in its center. This type of testing arrangement facilitates the very technology that we use and allows for what happen in Toronto. How many planes have ever landed within a 100 foot diameter pool of water and spilled its fuel into it? Is none the right answer? Pushing fuel that does not glide on water is a completely different animal. The result was witnessed in Toronto. Enough opinion, let’s get back to the facts. We have spent a lot of time talking about what I have defined as ‘EFFECTIVE DELIVERY’ and ‘STANDOFF SAFETY’. As most of you know the Phoenix Pulse Delivery & QuadAgent Technology was tested in 2004 at Tyndall ARFF Research Laboratory for the FAA. These tests have resulted in an FAA MEMORANDUM AND ENGINEERING BRIEF #71 creating a temporary modification to standard (M.O.S.) for the Industry to use while 150-5220-10C & -19 are revised. This NEW STANDARD Resulted from this testing at Tyndall. The Memorandum and Engineering Brief #71 are attached. Here is the FAA testing data from Tyndall that caused this Engineering Brief to be published. The following is the FAA’s Testing of the Phoenix® Pulse Delivery® / QuadAgent® Technology at the Tyndall AFB ARFF Research Laboratory as compared against previously tested Twin/Tri-Agent technologies. These tests took place in late February and early March and again in early December 2004. The comparative data for all other twin/tri agent technologies were taken from released test documentation performed and released by the FAA and include the testing of both typical twin agent parallel stream nozzles (variable and straight foam) and the HydroChem® nozzle (entrainment of dry chemical powder in the water stream). The following graphs will show comparisons of fastest and average extinguishment times as recorded by AFCT. Since the Tyndall ARFF firefighters had no previous training in the effective utilization of the Phoenix® Pulse Delivery® / QuadAgent® technology the firefighters went up a rather steep learning curve as can be seen by viewing all tests in sequence. Therefore, the fastest times should be more representative of an experienced ARFF firefighter with the Phoenix® Pulse Delivery® / QuadAgent® technology, therefore discounting the average times. The fastest times are expected to match up well with the final report from the FAA. Here are the resulting comparative results: 3-Dimensional Engine Fire in 30' water ring
100' Diameter water covered pit with aircraft simulator
Summary of Phoenix® Pulse Delivery® / QuadAgent® technology ONLY on the 100' diameter pit
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This
first chart is a comparison of the technologies on a
3-Dimensional engine fire simulating a high intensity
tarmac or off runway incident. As you can see there is a
DIFFERENCE! The Phoenix® Pulse Delivery® /
QuadAgent® technology suppression times were on
average better than 4 times faster than the other twin/tri
agent technologies tested by Tyndall for the FAA.
This
chart posts the results on Tyndall's 100 foot diameter
water covered pit with aircraft simulator in its center.
This incident scenario is a real test of capabilities. As
you can see in the third column the Phoenix® Pulse
Delivery® / QuadAgent® technology extinguished
100% of all fire tests while the twin/tri agent
technologies using both variable and HydroChem nozzle
technologies only extinguished two-thirds of theirs.