Friday, April 27, 2012

Firehouse Innovations

So this evening I meandered into the apparatus bay and found FF Nick Beck practicing with the water rescue throw ropes. He is taking an advanced swiftwater rescue course, and is brushing up for an upcoming session.

Recoiling the rope after the first throw, getting ready for the second throw.

Preparing to re-load the bag.

Here is the evolution on video: (the goal is two 50' throws in under 20 seconds)

video

He had a frustration, however - repacking the ropes was taking longer than he felt it should. What does he do when he is frustrated by a problem? He comes up with a solution! I enjoy having Nick on my company. He's a good man and a good fireman. He a problem solver. AND, he is quite the practical joker!

He took a coffee can - well, as I often refer to them, a coffee plastic. Yeah, that shows my age, as I remember when a coffee can was A CAN! Anyway, he cut down a side and then cut out the bottom. He rolls it around the rope and into the rope bag. Then, he simply hand+over-hands the rope into the bag, using small motions. When the rope clumps in the can, simply push it down into the bag.

Putting the rope in the can...

... putting the can in the bag...

... and loading the rope!

Close up of loading the rope.

After quickly reloading the rope bag, Nick quickly deploys the rope!

We practiced it behind the bay and found it to be quite a time saver. My genuine thanks to FF Nick Beck for: most importantly, showing us this technique, & for allowing me to photograph, video, and write about his little adaptation.

Thanks for reading.

Stay safe, and God bless.

Ken

Pump Operator Math, Part 2

The other day, I posted a blog about Pump Operator Math. It has occurred to me that I didn't cover as much as I should have, and for that I apologize. I freely admit that I got busy and that I prematurely (keep your mind out of the gutter) posted it before it should have been.

Ok, so the other day I listed several factors:





  • hose size
  • length of hoselay
  • needed fire flow
  • nozzle type
  • nozzle flow rating
  • nozzle operating pressure
  • friction loss
  • elevation pressure loss OR gain
  • appliance loss
  • standpipe friction loss
  • sprinkler connections


  • But I didn't cover them all. I stopped at friction loss.

    Oops. My bad.

    So, let's talk about Elevation Loss (or gain) which in the formulas is represented by EL. Science has proven that for every ten feet of elevation, there is a pressure difference of 4.34#, but in the fire service, we like to try to keep things simpler, so we rounded up to 5#/10ft. If you are pumping up a hill, you will loose five psi for every ten feet of elevation. Conversely, if you are pumping down a hill, you will gain five psi for every ten feet of elevation. Fairly simple, isn't it.

    Now for street applications. For this example we are pumping a 2.5" line that is 200ft flowing 250 GPM through a standard fog nozzle which operates at 100 psi, so the standard pump pressure is 125 psi. The house is on a slight hill, and is about ten feet above the roadway. We'll need to add 5 psi, so we're now pumping at 130psi. Say this fire is on the second floor of the house - we'll need to add another 5 psi, so now we're up to 135 psi.

    What if that house was down the hill? I'd ask how far down. Say, for example, the house is 30 ft below the road we parked our pumper on, but the fire is on the second floor. Ok, 125 psi - 15 psi + 5 psi = 115 psi. Not too confusing, is it.

    Ok. Let's move on to Appliance Loss (AL in the formulas). Appliance losses are caused by using varuios appliances in your set-up. They cause additional turbulence within the appliances themselves that rob flow by increased friction. Wyes, siamese connections, and water thief valves are common examples. Other appliances are master stream devices (deck guns, fly-pipes, and portable monitors).
    • AL for Wyes, Siamese, & Water Thief's: Flow < 350 GPM, AL = 0
    • AL for Wyes, Siamese, & Water Thief's: Flow > 350 GPM, AL = 10 psi
    • Master Stream Applilances: AL = 25 psi
    Ok, so, now we are told we have to pump a fly-pipe. At my FD we have simplified it: for the aerial's water pipe system, the elevation, friction loss, and appliance loss is 80 psi. This was figured at full elevation. We don't reduce it if the aerial is not at full elevation. What's the worst thing that'll happen - with no EL, more GPM will flow and the fire will go out faster - I'm good with that! So, we add the nozzle pressure (80 or 100, depending on the nozzle that is on the pipe) to the 80 and pump it at either 160 or 180 psi. That's not counting the friction loss from the pumper to the inlet; we'll hafta add that in, too.

    For sprinker systems, at my FD, our SOP is we pump them at 150 psi at the panel. Period. We don't have any high-rise buildings, but do have several mid-rises. The prescribed 150 psi will handle anything we have. If any readers out there have experience pumping sprinkler systems in high-rise buildings, please leave a comment on how your FD covers this.

    On standpipe systems, we need to do a little more thinking. For starters, what is the expected flow rate that you'll need to support? You'll need to pump your supply line(s) properly to overcome friction loss for that flow. For the standpipe system itself, at my FD we figure 25 psi for the friction loss. I was told in a class many moons ago that this figure comes from the "propeller-heads" and to accept it. Ok - who am I to argue? ;^) If the crews are operating above ground level, we'll need to remember to add 5 psi for each floor above the ground. (Standpipe PDP = FL (to the connection) + FL (standpipe system) + EL + FL (attack hose) + NP).

    Did I miss anything? Probably. But, I feel better now, having covered more of the basics.

    FWIW, here's are the coefficients for the most common sizes of fire hose:
    • 3/4"   =  1100
    • 1"      =    150
    • 1.5"   =     24
    • 1.75" =     15.5
    • 2"      =       8*
    • 2.5"   =       2
    • 3"      =       0.8**
    • 4"      =       0.2
    • 5"      =       0.08
    (* - 1.5" couplings; ** - 2.5" couplings)


    Remember, we need to know the flow desired before we can figure friction loss. Fog nozzles have their flow ratings stamped on them.

    The formula to figure GPM for solid tip/smooth bore nozzles is GPM = 29.7 x d2 x sqrtNP. The 29.7 is another propeller-head constant; the d2 is the square of the diameter of the nozzle tip; and the sqrtNP is the square root of the nozzle pressure. FWIW, the three common nozzle pressures are 100, 80, and 50 psi. Their square roots are 10, 8.94, and 7.07, respectively.

    While I am practically giving you the answers to a lot of this, I want you to work SOME of it out! At least I'm giving you the tools!

     While it may LOOK intimidating, it really isn't. Remember, these things are built by people. You can do it! I have faith!

    Monday, April 23, 2012

    Pump Operator Math

    As is tradition at my FD, we just completed another round of annual promotional exam testing for positions of Captain, Engineer, and Inspector. Every year we study, cram, take classes, what ever, all for the chance at scoring good enough to get on the promotional list.

    This got me to thinking...

    I've been an Engineer at CJC for several years now; six years since being permanently promoted, nearly seven if you count the nine months I was temporarily promoted. I've also had experience operating pumps and aerials at St. Joe Fire and at Camdenton Fire, as well as a few part time fire department jobs I worked at over the years. I think I get the job done - well, at least I haven't had too many complaints for over- or under-pumping a line. (The one under-pumping complaint I can think of as I write this was attributed to a kink in the line, which I handled shortly after the attack began.)

    I actually have been studying pump operations since I was about ten or eleven years old, when my dad was a fireman on the Brookfield Vol. Fire Co. in Brookfield, CT. One Saturday after we got the yard work done I asked him how he knows what to pump the fire hoses at. He asked me if I wanted the short or long answer. I said to hit me with the short answer, and he said, "150 & pump." I guess I looked genuinely confused, cuz he was grinning when I asked exactly what that means. He then said it appears I want the long answer, and for that, perhaps a trip to the firehouse was in order. We spent the afternoon up there, and he taught me the theory of FL and why we need to know what we are going to flow, and even set up some demonstrations for me using one of the pumpers and a pitot gage. I was hooked!

    Over the years, I have had the honor of helping younger members study for the upcoming exam. Lately, the exams cover less of the math and more of the policies and SOGs at our department. I can't complain, although, in my less-than-humble opinion, knowing the math - by this I mean KNOWING IT COLD - is the bread and butter of pump operating. Yes, engineers do other jobs too, like running aerials and other support apparatus, however, this post will be confined to the general topic of pump operating.

    Why is pumping a line at the proper pressure important? The answer seems simple enough - so you can supply the proper flow to the crew and they can then put the fire out in a quick, safe, and orderly manner.

    While that answer is seemingly simple enough, there are several factors a pump operator must consider:
    • hose size
    • length of hoselay
    • needed fire flow
    • nozzle type
    • nozzle flow rating
    • nozzle operating pressure
    • friction loss
    • elevation pressure loss OR gain
    • appliance loss
    • standpipe friction loss
    • sprinkler connections
    • pumping an aerial fly-pipe (at my FD we pump it at either 160# or 180#, depending on which truck we are dealing with, due to their nozzle types)
    Quite a lot to think about, ain't it - especially when you are the driver of a pumper arriving at a well established fire in a large apartment building at double-dark-thirty.

    Hose size - by this I am referring to the internal diameter of the hose. Each size has its own friction loss properties. The length of the hose lay also effects the friction loss. So does the flow of water through the hose.

    What type of nozzle are you pumping to? For handlines, a smooth bore is generally pumped at 50 psi; if pumping a master stream appliance with a smooth bore tip on it, you pump it generally at 80 psi. A standard fog nozzle operates at 100psi. However, there are several models of fog nozzles available now that operate at lower pressures, such as 80 psi, 75 psi, and 50 psi. Confused yet? It's ok, so am I sometimes. Just try to relax, remember to breathe, and think it through, one step at a time.

    Ok, so now let's talk friction loss. The formula is: FL=CxQ2xL. "C" is the hose "Coefficient", also referred to as the "Constant" or the "C-Factor". It doesn't matter really, it is the same thing. It just depends on who is teaching the class you are taking. Basically we have to trust that the taped-glasses wearing, pocket protector using, propeller-head types know what they are doing (they do) and they have spent years coming up with this stuff. "Q2"is the GPM (flow, in gallons per minute) divided by 100. "L" is the length of the hose line divided by 100.

    Wow... if THAT ain't a mouthful...

    Ok. Now we need to know what we are flowing. The fog nozzles on my engine company are rated for 200 GPM @ 100 psi of nozzle pressure (aka: NP). The nozzles on my FD's truck company are rated for 150 GPM @ 50 psi NP. (Frankly, I wish we had those fog nozzles too, along with a good set of smooth bore nozzles, but we don't, not yet.) See what I meant about what type of nozzle and what operating pressure they work at? Just two different companies in the same department with drastically different nozzles. FWIW, there is another engine company at my FD that has the same nozzles my company does. Both pumpers are water pumpers. There are two other engine companies that are CAFS pumpers, and they have TOTALLY different nozzle types. We'll skip that for now.

    Our SOG's call for an initial attack line to be able to flow 160 GPM. This is easily attainable with our 1.75" lines. Now begs the question, But Ken! You just said your engine company's nozzles are rated for 200 GPM @ 100 psi! How do you pump it for 160 GPM?"  I'm glad you asked. I simply figure the friction loss for the length of line for 160 GPM, then add 100 psi to it for the NP.

    (For those of you keeping score, that means for 160 GPM I pump the 150' lines at 160 psi and the 200' lines at 180 psi. For the 200 GPM, I pump the 150' lines at 190-195 psi and the 200' lines at 210-215 psi. Both of my engine's 2.5" preconnects are pumped at 125 psi to start, which is 250 GPM.)

    So, is this exactly 160 GPM? No, it's not. But it's worked for me for years when pumping this style of nozzle. I should note that where obvious larger flows are needed, I pump it at the higher pressure for the 200 GPM. If this doesn't work, then it's time to consider larger lines & master streams. You may ask, Well, Ken, how can you KNOW what you are flowing when you think you're flowing 160 GPM? We can hook up to a calibrated flow meter and then we will KNOW what we are flowing. We don't have one, though, so we're good with shooting from the hip.

    Here is a chart of the FL in 1.75" hose for various flows:
    • 100 GPM = 15.5 PSI/100 FT
    • 125 GPM = 24 PSI/100 FT
    • 150 GPM = 35 PSI/100 FT
    • 160 GPM = 40 PSI/100 FT
    • 170 GPM = 45 PSI/100 FT
    • 180 GPM = 50 PSI/100 FT
    • 185 GPM = 53 PSI/100 FT
    • 200 GPM = 62 PSI/100 FT
    • 210 GPM = 68 PSI/100 FT
    • 250 GPM = 96 PSI/100 FT
    Here is a rule for FL - in any size hose - that I want you to tuck away for potential future use:

    WHEN THE FLOW RATE DOUBLES, THE FRICTION LOSS INCREASES FOUR TIMES!

    Look at the flows of 100 & 125 GPM, their respective FL #'s are 15.5 & 24 PSI for every 100 ft of hose you are pumping through. Now look at the 200 & 250 GPM - their FL #'s are 62 & 96 PSI for every 100 ft of hose you are pumping through. Why is this important? Well, I have seen some folks out there throughout my career who incorrectly presumed that since a nozzle is stamped for, say, 200 GPM at 100 psi, that you only had to pump the line at 100 PSI, no matter how long the lay was. They were seriously underpumping lines - making it inherently UNSAFE for the crews, and frequently being told to increase the pressure by crews using the lines.

    A little off topic, but still related and very important - the 1.75" hose line, while it is capable of flowing high flows, is a very squirrelly line to handle when you kick up the GPMs and have higher nozzle pressures. We can discuss more on this later. (Or, feel free to contact me and I'll be happy to share my thoughts.) My point is, if you are going to flow higher flows, either use lower pressure nozzles or larger lines, or both.


    Here is a chart of the FL in 2.5" hose for various flows:
    • 200 GPM = 8 PSI/100 FT
    • 210 GPM = 9 PSI/100 FT
    • 225 GPM = 10 PSI/100 FT
    • 250 GPM = 12.5 PSI/100 FT
    • 265 GPM = 14 PSI/100 FT
    • 300 GPM = 18 PSI/100 FT
    • 325 GPM = 21 PSI/100 FT
    • 350 GPM = 25 PSI/100 FT
    • 400 GPM = 32 PSI/100 FT
    • 500 GPM = 50 PSI/100 FT
    • 750 GPM = 113 PSI/100 FT

    Here is a chart of the FL in 5" hose for various flows:
    • 250 GPM = 0.5 PSI/100 FT
    • 500 GPM = 2 PSI/100 FT
    • 600 GPM = 3 PSI/100 FT
    • 700 GPM = 4 PSI/100 FT
    • 750 GPM = 4.5 PSI/100 FT
    • 800 GPM = 5 PSI/100 FT
    • 900 GPM = 7 PSI/100 FT
    • 1000 GPM = 8 PSI/100 FT
    • 1250 GPM = 12.5 PSI/100 FT
    • 1500 GPM = 18 PSI/100 FT
    • 1750 GPM = 25 PSI/100 FT
    • 2000 GPM = 32 PSI/100 FT
    While there are other common sizes of fire hoses within the United States Fire Service, these are the sizes used at my FD, and are what I am familiar with.

    Okay, that's enough for one day. Thanks for reading. Any questions, please feel free to contact me.

    Stay safe, and God bless you.

    Ken