The Right Amount of “Wet Stuff”Two Benchmarks for Water Delivery on the Modern Fireground
By Paul Spencer
The world of a modern-day engineer has changed, and many of us are struggling to keep up. Fires that used to go out relatively easily are now challenging us more than ever. The fuels involved in residential structure fires are changing along with fire behavior, forcing us to develop greater fire flows to achieve the same basic knockdown. In many places we’re also arriving with fewer firefighters in the first-in engine, so the engineer may have to perform their tasks with an SCBA on as part of the designated “two-out” crew.
Put simply: The benchmarks that have defined good pump operation for a very long time are not quite hitting the mark as they once did.
Yesterday’s performance benchmarks for engineers are no longer sufficient. Today's engineers must be prepared to deliver greater fire flows with fewer resources. Photo courtesy John Miller
So in this new world, we must ensure we’re getting absolutely everything out of every resource we bring to the fire. From an engineer’s standpoint, that means delivering 100% of the capacity of every appliance pulled from your engine. Photo courtesy John Miller
Draw a line on the discharge gauge of every preconnect showing the exact pressure on the gauge necessary for that particular nozzle and hose load to achieve its design flow. Photo courtesy John Miller
Use a digital flow meter attached to a hydrant water supply and flow each preconnect, one at a time, until you find the exact discharge pressure for all your preconnects. Photo courtesy John Miller
The ability to maintain a good pattern and reach over a wide range of flows (gpm) is the trademark of an automatic nozzle. Photo courtesy John Miller
No matter what nozzle the firefighter is holding, we can evaluate the fire stream in terms of pattern, reach, flow in gpm and nozzle reaction force. Photo courtesy John Miller
In an article in the April issue of FireRescue
(“Delivering the Impossible,” p. 52), I explained why yesterday’s performance benchmarks for engineers are no longer sufficient, and I outlined four new benchmarks for us to shoot for when at the pump panel today:
1. Get beyond just “making water.” You must not only deliver water to the nozzle, but also deliver the correct amount so that the nozzle can achieve its peak flow, helping to ensure the success of the firefighters holding on to it.
2. Deliver the correct volume of water to the second handline without the first handline noticing any change in its fire flow.
3. Know and communicate how much water you are currently flowing (in gpm) and how much more water is available in your water supply (in gpm or minutes of fire flow).
4. Receive multiple water supplies simultaneously into your fire engine under varying pressures and/or vacuum while remaining in complete control of where the water goes.
This article will detail the steps necessary to successfully achieve the first two benchmarks with ease at every fire. With full control of each of your discharges and an understanding of the flows they’re producing, it’s then possible to begin to accomplish the next two benchmarks (which will be addressed in a future article). In short, you need to gain control of your discharges first, then you can begin to gain control of your intake manifold.
Why is all of this important today? Because the fire still has to go out, even though we have fewer of everything in today’s economy. Fewer firefighters have to flow more water more efficiently today to get the same result while at the same time not increasing our own personal risk. So in this new world, we must ensure we’re getting absolutely everything out of every resource we bring to the fire. From an engineer’s standpoint, that means delivering 100% of the capacity of every appliance pulled from your engine. You should be able to achieve the flows for which your nozzles were designed every time, from every nozzle pulled during the attack phase of every structure fire. This is not possible without a complete understanding of the nozzles on your fire engine.
In practical terms, if the attack crew pulls a 150-gpm nozzle into the fire, then 150 gpm of water should come out of it when it’s opened. The same goes for any other nozzle with any other flow rating. How do you achieve this in the dead of night when concentration may not be ideal? Tip: Draw a line on the discharge gauge of every preconnect showing the exact pressure on the gauge necessary for that particular nozzle and hose load to achieve its design flow. Remember:
An identical preconnect loaded on the opposite side of an engine sometimes requires up to 20 psi of additional pressure, so each individual preconnect must be tested. To make life even easier, write the gpm the nozzle will be flowing at that pressure directly onto the gauge at that line.
What this really means is the first performance benchmark for the modern fire engineer is easily achievable by simply opening up the valve and throttling up until you hit the line. At that point the nozzle firefighter will be receiving exactly what they were expecting, and you as engineer will know exactly how long your tank will last or how much water you will need from your water supply.
I’ll get to how to put those lines in the correct place in a moment, but first, let’s review the next benchmark of the modern-day fire engineer. On many larger fires, a second handline is pulled and supplied. With the exact pressure necessary for the second preconnect drawn on its pressure gauge, the engineer simply opens the valve up enough to bring the discharge needle up to the line. It doesn’t get any easier than that. Add up the two flows in gpm, and you have the combined fire flow.Nozzle Evaluation
As a firefighter, chances are you didn’t personally select the nozzles carried on your engine. The only choice you may have about nozzles is which one to pull off the engine into a fire. As the engineer, our job is clear: Deliver the water to the nozzle the attack crew pulled. If it was the big nozzle, they’re expecting big water. They would have picked a small nozzle if they wanted small water. An engineer’s job is about customer service: Our customer is the firefighter who just ripped that nozzle off of our fire engine and is running into that fire.
Ultimately, what nozzle pattern, how big a droplet of water it produces or what surface the water is bounced off of is really a discussion for firefighters holding the nozzle. As the engineer, we know the fire goes out when the critical flow is applied to cool everything below its combustion temperature. Enough wet stuff and the fire goes out; it doesn’t really matter what nozzle is used so long as there’s a trained firefighter holding on to it and they flow the right amount of water onto the right place.
So why are there so many different types of nozzles? I could ask the same question about why there are so many choices of cars to buy. One might hope there’s more thought put into the function rather than image of both—well, I’m going to quit while I’m ahead. The bottom line: Don’t comment on what car your neighbor drives or what nozzle is on the end of their hose. Just do your job and pump the necessary water into your hose so the nozzle attached to it produces a functional fire stream.
No matter what nozzle the firefighter is holding, we can evaluate the fire stream in terms of
· Flow in gpm
· Nozzle reaction force
There are additional bells and whistles, but these are the critical design parameters/performance characteristics for nozzle comparison.
If you look at any printed information about your nozzle from its manufacturer, it will clearly state what gpm it is supposed to deliver. The gpm of the nozzle should be known to all and be a pre-agreed upon gpm that we are going to deliver flawlessly. If it’s a 150-gpm nozzle, then let’s put 150 gpm into it for the attack phase of the fire.
That’s not to say we can’t pump something a little different to accomplish a different task. If my attack team pulled a “room and contents” preconnect into a two-story stick-frame residential and within seconds I hear a “mayday” called with a firefighter through the floor with a fully involved cellar fire, I want instant options. One option: If attack calls for “max flow,” I can throttle up the pump to deliver near blitz line flows from that nozzle as it’s shoved through the hole in the floor while still maintaining its pattern and reach characteristics. Note: This is a practiced evolution and the “max flow” is carefully worked out ahead of time on all preconnects.OK, So What Pressure?
In my earlier years, I would use really impressive formulas to carefully calculate the theoretical discharge pressure for a preconnect. Today, there’s an endlessly easier and more accurate method of determining pressure.
Use a digital flow meter attached to a hydrant water supply and flow each preconnect, one at a time, until you find the exact discharge pressure for all your preconnects. The flow meter is very portable, accurate and absolutely easy to use. It’s also possible to achieve similar results with a little less accuracy by using the flow meter found on many newer fire engines that have a foam injection system. There’s a paddle wheel flow sensor that registers water flow in gpm, and so long as it is calibrated, the results are accurate enough for the job. If the preconnect you’re trying to set up is on this system, it doesn’t get any easier than that.
If the flow meter is in the water supply, say on a water supply engine that’s supplying the engine testing its nozzles, then every preconnect can be identified very quickly. Remember: The flow test will only be accurate if the exact same hose and nozzles are kept together on their particular discharge. Is That the Best We Can Do?
It’s a little funny, but in many departments the fire engine is replaced more often than the nozzles. I’ve supplied water to nozzles that were older than I am (and I have my fair share of gray hair), and I can tell you that nozzles definitely don’t get better with age. If the process of becoming efficient with your equipment makes you curious about how a different nozzle would work for you, then look around. I’ve worked with a number of engine companies where the best nozzle on the engine was the spare kept in the engineer’s compartment. As a firefighter, I respond to a fire to put it out. I want a nozzle in my hands that delivers the water I need on target for the fire to go out now!
When flowing nozzles, make sure to flow them all and compare them fairly, using the same criteria, which include:
· How far in feet the stream holds its shape before breaking apart. Remember the environment we use them in and try to envision that fire stream reaching all the way in to the seat of the fire.
· How much water in gpm the nozzle successfully delivers on target.
· How much work it takes—both for the pump to get the rated flow of water to the nozzle (discharge pressure) and for the firefighter to hold on to it (nozzle reaction force). Nozzle engineering and construction play a very large part in this.Who’s In Control?
Water control is a very important topic. Who exactly is in control of the water is in many ways decided by the construction of the nozzle. Yes, all modern nozzles have a shut-off valve, but once it’s open, who exactly is in control of the water?
The firefighter on the tip controls the pattern, right? Only if there’s enough pressure and volume in the line to develop the pattern. Have you ever seen a nozzle with a bad pattern, reach or flow? If the shut-off has only two positions (open and closed) then really, control of the water is at the pump panel discharge valve and pump throttle.
If the fire doesn’t go out when the wet stuff is put on the red stuff, it’s the result of an ineffective fire stream poorly supplied by the engineer—or the wrong nozzle was pulled. Ultimately, it’s the firefighter in the smoke who decides whether the fire attack they just made was successful. If the fire doesn’t go out with a nozzle delivering its designed flow, then it’s time to get a bigger nozzle or change tactics.
There are two different types of nozzles: those with ball valves and those with slide valves. Ball valves create turbulence in the water flow. The problem: This turbulence breaks apart the pattern and reach of the nozzle if it is not opened completely. If the nozzle has a ball valve, the engineer is in control, and they must be on their toes to ensure that a functional fire stream is created.
There are nozzles on the market that put control of the water in the hands of the firefighter holding onto the nozzle. These nozzles use a slide valve that doesn’t create the turbulence associated with ball valves. If you look at these nozzles closely, you will see detents that hold the shut-off in many different positions between open and closed. When using nozzles with slide valves, the firefighter is in control. The engineer supplies adequate pressure for the nozzle’s design flow; however, the firefighter on the nozzle decides how much water they actually take. Pattern and reach are always maintained over many different volumes of flow (gpm).Automatic vs. Fixed
The ability to maintain a good pattern and reach over a wide range of flows (gpm) is the trademark of an automatic nozzle. Automatic refers to a feature inside of the nozzle that makes automatic adjustments internally to maintain a constant nozzle pressure at the tip, ensuring good pattern and reach. It’s really no different than a high-tech spring-loaded thumb over the end of a garden hose. Without the automatic feature, there’s a very narrow window of pressure where the nozzle will have ideal performance; with the automatic feature, the window is very large. For automatic nozzles with ball valves, the engineer throttles up or down through the window of pressure; for nozzles with slide valves, the firefighter at the tip throttles the bail open or closed through the window of pressure.
In the family of nozzles that are not automatics, that have a fixed flow, there are also adjustable gallonage versions. This means that there’s a fixed orifice or waterway that the water comes out of, but it’s possible to twist a ring just behind the pattern control that changes the orifice or water way to allow different flow volumes. Using adjustable gallonage nozzles requires extremely good communication between the firefighter on the nozzle and the engineer about what setting the nozzle is on. With separate lines on the discharge pressure gauge for every flow setting used on the nozzle, the engineer will be able to keep control of their pump panel. However, these nozzles pose a unique and frustrating challenge to engineers at the pump panel as they try to do all the other fun things like manifold management. I have experienced a firefighter, realizing their dial was twisted all the way down to garden hose flows, without notice abruptly spin it all the way up, increasing their flow and instantly putting my pump into cavitation. In short, these are not my favorite nozzles!Changing World, Changing Tactics
Our world has changed. Staffing on both career and volunteer engines is reduced in today’s economy. “Two in/two out” is putting more tasks on the “first-in” engineer and the fire is requiring much higher critical fire flows. On many engines, a 1¾" handline flows 250 gpm and a 2½" flows 500 gpm. Sometimes these flows are even delivered by a single firefighter on the line. That firefighter must be in control of that water for their own safety. We are in an era of the fire service where, in many places, minimum staffing requires that crews perform an exterior transitional knockdown and only then enter for overhaul.Example:
I frequently work with engine companies that are staffed with less than four firefighters and the next-in engine company takes what seems like forever to arrive. That puts an SCBA on the back of the engineer, who is now standing with a hose or a nozzle in their hand close to the front door as an integral part of the “two out” crew. There really isn’t anyone at the pump panel to call to for more water. (Note: I wouldn’t recommend this practice, but it’s a reality for many departments.) For efficient firefighting, the nozzle must have maximum flows and the firefighter holding on to it must be in control of how much water comes out of it. As a result, our crews use large automatic nozzles with slide valves in the hands of all of my firefighters.A Final Word
There seems to be no piece of fire equipment more passionately fought for or fought over than the nozzle. As engineers at the pump panel, our job is really very simple. No matter what nozzle is at the end of the hose, make sure the right amount of water comes out of it so the firefighter can put out the fire. Not too much, not too little, just the right amount. No air, no pressure spikes, just the right amount of water to produce perfect flow characteristics of each and every nozzle on the engine. Engineers play a large role in the ultimate delivery of the water that puts out the fire. Maintaining control of the pressure being delivered to the nozzles to ensure functional fire streams, no matter how many lines are pulled, is the hallmark of a good modern-day engineer.Paul Spencer began his emergency services career in 1983 with a heavy rescue company in the Washington, D.C., area. Over his 14-year career with San Juan Co. Fire #2 (Wash.), he held positions as rescue captain and station captain. With 20 years experience in the fire service as officer, instructor and technician, Spencer speaks about industry change and keeping our skills sharp. He is an IAFC member. Spencer can be contacted at: firstname.lastname@example.org.
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