Fireground hydraulics has been around all of my life(pushing 60). Just like CPR, it has changed through the years. My question is , do you really use it. I was an engineer for 28 years,I understood how the use the formula, and never did use it on a fire. Reason being, in the heat of the battle and without a calculator it was impossible to use. Besides that without the GPM part of the equation it can't be used . I found that a pump chart designed from actual flow tests worked bet. Why does it still exist? Teachers of this math even tell you that you will never use it. Don't we have enough to learn in this job. What do you think?
You need it for a couple of reasons (perhaps not at the entry level MPO, though):
1. To make plans, test alternatives, and come up with new tactics.
2. To deal with unusual water supply issues.
I'm personally a fan of teaching firefighters to handle large flows, and teaching the MPOs to throttle up until they run out of supply, pump, or engine. Make the pump do the work, and use it to its fullest.
Mother nature is quite clear that smooth bore, combination nozzle, or CAFS applications actually matter very little. It is all about the ability to accurately apply gallons per second into the fire space. She cares little that we know math, can pass an engineer test, or show up with a shiny 2000 gpm capable engine. What does matter in the real world is a sound knowledge of fire flow capabilities on a handline, or blitzline and how best with limited staffing we can meet or exceed the needed fire flow for the BTUs being generated in the fire.
Having said that, let's argue about nozzle reaction, smooth bore streams, or low pressure hose handling characteristics...
I'm in partial disagreement -- the last FE magazine had a nice article about handline selection, and apparently nozzle type DOES mean something. I'd have to believe that CAFS adds something to the equation, though I've never used it myself.
But, that being said, it IS a matter of putting the wet stuff on the red stuff, and doing it with enough water to overwhelm the fire.
You know Paul, I'm going to have to partially side with you on this one. If you are doing planning like Sean suggests, then you absolutely need to pre-plan water supply needs that includes making sure you are not expecting too much from an engine and/or fire protection system.
But... when you are talking about the fireground, it can't get any simpler (my opinion) because all you have to do is put the engine in pump, get water flowing and as long as there is water flowing through the nozzle, the interior guys will ask for more or less pressure. An experienced fire engineer can simply step on a discharge line and have a pretty good idea, again for initial attack handheld attack lines. You can follow all the hydraulics in the world but I always figured it was a better idea to just talk to your crew and adjust the pressure as needed.
If you need big water, then bumping up from 1.75 to a 2.50 inch hoseline with TFT should be factored in, but again, start with lower pressures, talk to your crew and adjust as needed. For evolutions such as multiple stories, use of appliances or monitors, etc., then you have to go with using hydraulics to make sure you don't blow a hoseline or the person on the other end.
As far as having to memorize the hydraulics for these kinds of situations being too complicated to use in the heat of the fire... there is not that much stuff to memorize to handle the basic hydraulics you need to use. Plus, you should have at least a dozen flashcard scenarios with different examples to keep your skills and mental calculator sharp. Like anything, if you don't do it a lot, when the time comes to use it, you will feel overwhelmed. This is why we train on the fireground and at a desk in the firehouse.
It's what we do.
"Failure to prepare is preparing for failure, be prepared..."
I think it is still important to teach enough of it to help engineers understand the impact of changing certain variables such as hose diameter, hose length, nozzle pressure, appliance friction loss, etc. Who would think that increasing the hose diameter 1/2" from 2 1/2" to 3" could reduce friction loss by as much as two thirds? Or that increasing flow does not result in a linear increase in friction?
I agree that most adjustments are made based on direct feedback from the nozzle man but you should be able to anticipate that setting the pump for an 1 3/4 TFT pre-connect and a 2 1/2" smoothbore of the same length is going to be interesting to watch.
I can think of a relevant comparison in teaching SCUBA diving. We still teach new divers how to use the tables even though almost everyone uses a computer now. The reason is help new divers understand the relationship between time, depth and surface intervals and how they affect the body, not so they can memorize the table (which we emphatically tell them not to!).
In a larger, or career dertment I can see the engineer having the formulas down fowards and backwards, it is their job to operate the apparatus day in and day out. They should know every little detail of that rig and how it performs or if it has any quirks. In a smaller department that may not have assigned engineers, that may not pump all of the time I still feel that the formulas are important to understand the principles of pumping. However, not everyone will remember that training, this is where the basic principles come in and getting a close pressure off the bat and then relying on your crews is important. I am not saying that inexperienced people should be on the pump panel. Another tool for firefighters that may not pump on a regular basis is the infamous cheat sheet, a laminated chart showing the most common hose lays that your dept uses and the pressures they should be pumped at. While it will not fit every scene it is an added tool in the box, if kept within easy reach of the pump panel.
I found this to be a really awesome class. It made me look at my district in a whole new light. Where can I get the water that I need to put out a structure fire or a wildland fire. I live in the rurals where it consists of BLM land and farm land. I say teach on!
Paul, I disagree with you. When you say that you can't calculate friction loss without the GPM, my thought is,"but the pump operator always does know the GPM. There is no excuse for not knowing it. Also, while nobody precisely calculates friction loss on the fireground, there are mental shortcuts to get a proper pump pressure, but you need a sound basic knowledge of fire hydraulics to use whatever means you choose to determine a pump pressure.
After reading all the posts I realize that maybe I wasn't specific enough in my opening statements. When I talk about fireground Hydraulics what I mean is actually using the formulas such as FL = CQ2L. Alot of you talk about how Fireground hydraulics has helped in understanding water delivery. Great!!I am a firm believer in what ever works for you is the right thing to do. Great discussions and thanks for all the imput.
Hey firegeezer, I just read your post on the lineup sit. It sounds like your class was pretty good . You teach facts about water movement. Again the big issue I had was with the formulas themselves. I can tell you that after 28 years as a pump operator I totally understand everything you teach and it does make a big difference in knowing it. For me and me only the one exception was the formulas.
I think todays fire service sometimes makes things to complicated. We do so much except put the water on the fire. Look at some of the senerios on FFN. Very rarely will someone mention put the fire out. They talk about positioning, reponse time, walk around etc etc. Put how about the first engine lays a line and the crew tries to put the fire out.
I pumped large and small fires. Tandem Pumping and even pumped through. Never once did I think about a formula. I looked at my guages to determine what I had and what I needed. The only time there was trouble is when the officer wanted to do something crazy like use another hydrant on the same loop or system.
Maybe I'm a dinosaur admitely, but its really not that hard.