Changing Gears (Part I)

by Admin 22. November 2011 08:03

“What’s in the water?” 

No discussion on Fire Suppression would be complete without delving into water. As I stated in the intro to this blog series, it is somewhat of an irony that good-ole H2O has maintained its place in the forefront of the Fire Service arsenal amidst all the other changes that have taken place. We will take a look at that and how it does what it does for us, so well. Comprised of 2 parts Hydrogen and 1 part Oxygen, water is the most common medium for combating fire. It has a multitude of properties which make it a firefighter’s choice for the job. First, it is very easily transported. The “bucket brigades” were our first “real” water delivery system for fighting fires of all sizes. Later, of course, it was learned that water could be easily forced through a conduit (i.e.- piping, hose, etc.) and sprayed, much easier than carrying bucket after bucket to the fire. We went through the era of hand-pumps, then steam-driven engines and finally came to rest on centrifugal pumps (which are still in use today). Although, many tried to find something better, nothing could replace the portability of water with another product. Second, water is available almost everywhere. Although our World (and even our body) is comprised primarily of H2O, I must concede that not “every” location has a good source of water (or at least plentiful enough to advantageous in a large firefight). We all understand that problem and many have adapted by employing Water Tenders as part of our fleet. However, notwithstanding, the availability (or lack thereof) of this precious commodity: water does not have to be “made” or “manufactured”. It is here for us already. It is not a “product” that we will have to “order” if/when we run out, while fighting a large fire. Command will simply call for more Tenders or an increase in the municipal water pressure/volume to a particular area. We can circumvent the problem of running out of water. It can be daunting, but it can be done. If you run out of foam, gel, dry chemical, etc., you are just out of luck until it can be shipped in from, oftentimes, a very distant location (and more often than not, not when you “need” it). So, we must still be proficient in the use of water for daily operations (no matter what additives we may choose to employ). Third, although, not often thought of in these terms, water it a great medium for the delivery of other products. Water can be used in a variety of ways to combat different types and classes of fire. However, the addition of Gel-producing agents, Foam surfactant or even dry chemicals can increase the effectiveness of water on Class A, B and D type fuels. (We will cover these additives in greater detail in later parts of the column.) By adding a foam concentrate to water and aerating the mixture, we can break the surface-tension of water and make it “lighter”, allowing it to float on products with a lower specific gravity than water itself. By adding Gelling products to water, we are able to produce medium retardants or suppressants with high-heat absorption capabilities. Due to the “anti-wetting” agents present in dry chemical powders, water can used as a delivery vehicle to provide more reach for the application of these products at a greater distance. Our constant friend, H2O, has made it readily available to work with other suppressant and protectant agents and thus has remained a valuable, irreplaceable resource. Lastly, the most desirable attribute that water has provided the Fire Service for hundreds of years, is its inherent ability to readily absorb heat. Air will only be heated by high heat and can, in fact, contribute to flame spread and intensity. Dirt, while being a natural product that can absorb “some” heat, can only effectively smother a burning product. With all of the aforementioned attributes considered, water is the only natural medium available that can absorb high heat and bring a burning fuel below its inherent ignition temperature. It can expand into steam, enveloping an enclosure, excluding the available oxygen required for open combustion. It can cool surfaces or the atmosphere equally well. For this reason, if not any other, water is still a firefighter’s greatest tool for Fire Control and extinguishment. While the bulk of the above points can hardly be argued, there is still one issue that is still debated on almost a daily basis (worldwide). How do you get the wet stuff on the red stuff? While I have my own opinion on this matter, I will attempt to be more objective and general in nature regarding this topic. It is not my intention to begin a war of the “nozzleheads” here but rather to educate and incite thought. Whether your department is using the latest, greatest, super-sonic TurboJet automatic nozzle, a variable-flow with a pistol grip, or a 15/16” smooth-bore; you are still putting the wet stuff on the red stuff! You can change nozzles. You can change what pattern you operate the knob in. You can do direct attack or indirect. We can go for reach and knockdown with a smooth-bore (or straight stream from a fog tip) or we can get up close and personal with a fog pattern. Everybody out there has a preference on how to attack a fire and an opinion on what method works best. I know I do and I stand by it! All of these variables can be changed but we need to consider what cannot be changed. We began this discussion on water and to water we shall return. No matter which method we choose to satiate our madness, there is one constant that cannot be ignored. The game is still “water vs. fuel”! Why is it that pump operators, DO’s, and MPO’s, or whatever your department choses to call them, have to be so proficient in what they do? Answer: They have to ensure the proper GPM is provided to effectively fight the fire! It’s not enough to merely make wet stuff come out of the end of the hose. It has to be in the correct volume to be able to absorb the heat that the fire is producing. If you provide a fog nozzle with the pressure that it requires to operate optimally (usually between 50-100psi) and then do not set the GPM flow high enough to provide adequate heat-absorption capability, then you are fighting an uphill battle and the fire will maintain the high ground. We have all learned, in Rookie school, what a BTU is and that it takes a defined amount of water to absorb a defined amount of heat, right? Well, that principle has not changed. What HAS changed is the fuel package. Instead of the natural product fires we fought, through most of the last century, we are now fighting synthetic product fires. The difference from 8000btu’s/lb. vs. 21000btu’s/lb. is the reason we have changed our nozzle designs and capabilities. The properties of water have never changed. We still require it to absorb heat, only now we have to dispense more of it to accomplish the same end-result. We could spend hours debating whether small droplets of water or large streams extinguish fires. It has been debated (heatedly) for years. Can a fog stream absorb heat? Absolutely. Can a solid stream absorb heat? Yes, Sir. Can we go into a half-involved warehouse fire with a 1.75” hand-line, just because we have a smooth-tip and good technique? Only if you want to either be embarrassed or die young. We still have to choose the correct size line and appropriate flow to combat the fire, whatever it may be. In making the calculation of what will work the best or what flow to use, you just have to remember the basics of “water vs. fuel”. When heated past 212oF, it will begin to turn to steam. The higher the heat level is, the faster the water will break down. The smaller the droplet, the faster it will reach its maximum heat absorption capability. Knowing that some of our water will not make it to the seat of the fire (which is where the “real” problem is), we need to make certain we are flowing the necessary GPM to defeat the fuel. Am I saying that a smooth-bore is the only way to fly? Absolutely not. What I am saying is this: You have to plan your tactics well and ensure that you do not allow that allure of the newest toy to detract from what you know is needed to fight the fire at hand. Smooth-bore nozzles have their own limitations as well. However, that being stated, I do not wish to get into a debate on the topic of nozzle choice. It’s all about the water! Hopefully, this has been a mind-jogger for you and has made you think of how much of a valuable player water still is. No matter how much technology changes or what advances we make in the way of water additives, we still have to be very savvy in the use of our oldest ally. My next topic of discussion will be Foams. Until then take care of yourselves and your brothers and sisters on the fireline.


Categories: FireIce | GelTech Solutions