By Paul Spencer
Published Friday, April 1, 2011
| From the April 2011 Issue of FireRescue
The engine rounds the corner arriving first-in to a heavily involved, two-story, stick-frame residential with flames and heavy black smoke pushing hard from every window. The owners are crying on the front lawn because everything they own is burning. The neighbors look on in horror as flames extend to the homes on either side.
The captain and the firefighter quickly stretch a 250-gpm 1¾" crosslay, hitting exposures and confining the fire to the building of origin, but they’re fighting a losing battle when it comes to attacking the actual fire. The engineer takes a nearby hydrant and quickly secures a water source, then stretches a 200', 2½" blitz line up to side A of the building of origin. He drops the blitz line and tells the captain, “I’ve got 500 gpm on the blitz, but that’s it for the 750-gpm hydrant.” The captain yells back, “I want the deck gun at 1,250-gpm transitional across side A, first floor, then second.” The engineer calls back “OK, but only for one minute, then you’re back to handlines at 750 gpm.”
The firefighter follows the engineer back to the engine and hops up to the deck gun, swinging it around toward the house. The engineer unleashes a 1,250-gpm wall of water through the deck gun that the firefighter directs into every hole that’s spewing flames from side A. The second-in engine arrives to see a huge cloud of steam venting from every orifice in the house. They stretch a line as the first team goes in to overhaul with the 1¾" line.
“Not possible,” you say? Firefighters have been taught for a long time that it’s just not possible to flow 250 gpm from a 1¾" or 500 gpm from a 2½" blitz—at least, not with control, let alone with a single-firefighter evolution while standing. Engineers reading this are saying, “Only in your dreams can a deck gun flow 1,250 gpm from a single hydrant that only supplies 750 gpm.” For many engine companies, that may be the case; however, that’s not because it’s not possible.
Would you like to know how some engine companies do it, and possibly add some new techniques to your tool box?
Measuring Pump Operator Performance
For a very long time, the fire service really only had three performance measures for the position of engineer/pump operator/chauffeur:
- Was the fire engine safely spotted into the correct position on the fireground?
- Did we “make water” in a timely manner?
- When sitting around the kitchen table talking shop, did our answer to every question somehow include a complex algebraic formula that included pi, and could we calculate it in our head?
Times have changed. Much more is being asked of the engineer. Hose crews continually want higher and higher flows to meet the ever-increasing fire flows caused by plastic-fueled fires. These demands, if not met by proficient engineers, can easily lead to fires not being put out in a timely manner, or worse yet, significant damage to our fire engines.
It goes almost without saying that delivering the fire engine safely to the fire scene and spotting it correctly is a driver/engineer/chauffeur benchmark. As long as firefighters keep getting killed on the way to incidents, we must continually stress that this is an absolutely mandatory and clear-cut benchmark that far exceeds all others. However, I’d like to suggest four additional benchmarks that address the needs of the modern fireground.
1. Pump the correct pressure for the chosen nozzle: After a safe arrival and proper positioning of the apparatus, our first true task or performance benchmark is to pump the correct pressure so we can deliver the flow of water that the nozzle was designed for. We can’t really get away with simply making water show from the nozzle anymore.
The attack team pulled that nozzle for a reason. If they wanted a different flow, they could have pulled one of the other nozzles. That’s not to say that if the hose team gets themselves into trouble we can’t pump a different pressure to make the nozzle do something a little different (e.g., maximize flow for better knockdown or protection, reduce flow during overhaul or mop-up). In today’s fire engines, it really is much easier than you might have ever imagined to identify the exact pressure for every preconnect without ever remembering a single mathematical formula.
2. Pressure balance the discharge manifold: When standing at the pump panel, the next performance benchmark is whether we can deliver the correct pressure to the next handline pulled from the engine, without the crew on the first handline ever knowing anything has changed. The key: Balancing discharge pressures by opening valves only as far as necessary to deliver the correct pressure. Proactive preloading (aka setting the relief valve) of the older pressure relief valves or using the computer governors on modern engines makes pressure balancing much easier.
3. Balance both manifolds for peak efficiency: We never really could technically “make water.” Every single drop we pushed out of the nozzles first came into the pump through the hollow metal box we call the intake manifold. Both intake and discharge manifolds have many holes with valves attached to them that we need to control if we want to effectively deliver functional fire streams. Simply put: If 750 gpm is coming into the intake manifold, then a maximum of 750 gpm can be delivered from the discharge manifold.
Tip: A good engineer doesn’t keep secret the fact that the water supply is delivering 750 gpm and the attack crew is only using 250 gpm. If the fire isn’t going out right away, then it’s really helpful to let someone know that you have 500 gpm in your supply and you would gladly provide it to someone who wants it.
4. Manage the intake manifold: The fourth benchmark is intake manifold management. It’s a practical result of our crews continually wanting more, more, more, as well as the fact that with minimally staffed crews, many departments are using a transitional attack strategy. In suburban or rural areas, we must work incredibly hard to build an effective water supply. Many times, water is coming at us from a number of different directions simultaneously (e.g., tank water, supply lines, front/side suction), and we simply must effectively manage the intake manifold to be able to deliver the critical fire flow necessary to put the fire out—now, not in an hour after the fuels have burned down to whatever we are squirting.
So how did our engineer deliver 1,250 gpm out of a deck gun if only 750 gpm was entering the intake manifold from the hydrant? The short answer is 500 gpm came from the engine’s water tank simultaneously. With good pressure management, it’s possible to pull from both sources at the same time.
As engineers on the pump panel, we learned early on that it’s critical to maintain a positive pressure in the soft hose coming from the hydrant, otherwise it can potentially get pulled right into the impeller of the pump, causing damage. This rule should not be broken; doing so not only jeopardizes the pump and hose but also the underground water main.
The art of this attack comes from the lessons learned from the classic tactic of tandem pumping. Look back over a driver/operator textbook and you can find a description of how an engineer would adjust the hydrant without turning it off so the steamer cap could get pulled from the pump without the cap rocketing off and killing someone. For this evolution, we apply the same principal to the valve on the pump panel instead of the hydrant.
A Little Homework
Once you understand the four new benchmarks for engineers, it’s time to look at the specific tactics involved in each one. In future articles on Fire fighterNation.com, I’ll discuss these skills in greater detail. For now, however, here’s a few things to get you started:
- Determine the gpm rating and flow pressures for the nozzles on your preconnects. Sometimes you may have to do a little research to find the information, but it’s out there.
- Determine whether your nozzles are smooth-bore, stacked tips or combination fog nozzles. Note whether they’re fixed- or adjustable-gallonage or automatic. Details like a nozzle’s ability to spin a wheel and change flows from booster flows to blitz line are critical for the engineer.
- Also look at the shut-off valve and determine whether it’s a common ball valve or a slide valve with multiple detents.
- As you’re reviewing your nozzle inventory, look for the closest digital flow meter. If your newer fire engine has a foam injection system on it, chances are there’s a flow setting where you can see your flows in gpm. You might have to go as far as a neighboring department, but chances are there is a flow meter not too far away.
- Take careful notes on all of this information. You’ll need it when applying the four benchmarks.
Oh, and by the way, for those of you who think these are “city” skills, you’re not off the hook. Many of the more advanced pump operation skills are common in rural operations. That 1,250-gpm transitional attack could just as easily have been supplied by a 500-gpm relay balanced with a 750-gpm tank to pump flow rate out of your water tank, or even your basic drop tank.
Urban or rural, career or volunteer, all engineers have a fundamental responsibility on the fireground. Setting benchmarks that reflect the challenges of today’s fires can help us all meet that responsibility.
A Note about Nozzles
The fire service has long debated the merits of smooth vs. fog, fixed flow vs. automatic. The reality: A design team of real engineers looked at three things as they were designing your nozzles:
- Delivered over what distance; and
- Carrying what gpm of water.
It’s a simple truth: Our blitz nozzles have 500 gpm written on them, and a digital flow meter confirms that they can deliver such flows with grace and style.
An Important Safety Note
As pump operators, we can easily destroy our fire pumps in very quick order. Likewise, we can hammer a water system so hard we literally drive it out of the ground. The advanced performance benchmark and skill set presented in this article require true mastery of fire pump operations and represent the art of advanced fire engine pump engineering. Please follow your department’s standard operating policies and procedures and only attempt new procedures on the drill ground, exercising the necessary precautions so as to not hurt anyone or damage any equipment.
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