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  • Engine/Pump Match

    How do you determine the size engine needed for a given GPM pump?

    Example, how big of an engine do you need for a 1500 Single Stage?

  • #2
    When you write your RFP ( request for proposal ) which I would recommend over a tender, specify the minimum horsepower such as 350 hp. I would not go below 350 hp. With a Cummins ISL 350, you can get an engine brake which is far superior to an exhaust and will cost you much less in the long run then a trans retarder, which will eat your trans.
    I would be more concerned with the terrain in your district then the hp to run the pump. I believe even an ISC 330 would run a 2000 GPM pump.

    Comment


    • #3
      Hale has a "Pumps/Engine Recommendation Database" you can look at. I would think Watersous would have one, too, but I couldn't find it (didn't really look that long, though).

      Comment


      • #4
        Pumping is a horsepower function, whereas moving down the road requires torque at the outset, then horsepower (and torque) to keep up road speed. There is a generic formula for making the pumping calculation. I had it at one time, but if I still do, it's buried deeply in notes from years past. I do remember that when we were spec'ing our 1989 Duplex/Quality, we found that it would take somewhere around 226 hp at the pump input shaft to handle a 1500 gpm pump. After allowing for all of the parasitic losses, it worked out that the minimum engine hp would be about 350.

        Working backwards through that, I was able to determine that our 430 hp engine in our recently ordered Spartan/Toyne could handle a 2000 gpm pump, but not a 2250. An applications person at Waterous Co. confirmed it. It would take something on the order of 460 hp to handle a 2250.

        Stay safe out there, everyone goes home!

        Comment


        • #5
          And those would be just minimums of course, always get more than you need. While a 350HP will run a 1500GPM, get at least a 400. Always go to the next size up. The more HP and torque available the less the motor will be straining, i.e. working itself up for a mechanical failure. Spec a size bigger and you'll be building a truck to go at least 20 years.

          Same reason I don't recommend less than a 1500gpm pump.
          Brian P. Vickers
          www.vickersconsultingservices.com
          Emergency Services Consulting
          Westlake VFD - Houston, TX
          Proud Member IACOJ - Redneck Division

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          • #6
            Obviously if you can afford the "big bore" engines,Series 60, Cat C-13 or Cummins M11, then go for it. You can never have too much hp or torque as mentioned before. We have an old '86 Mack, 285 hp with a 1500 gpm two stage which has no trouble at all passing the capacity test to this day. In fact I just tested it last week.
            Horsepower and torque go hand in hand. You request how much Hp you want, not how much torque you want. For a given hp rating, the engine will produce "X " amount of torque at a given rpm. That's just the way it goes. Sure there are different torque and hp curves, but don't even think about trying to spec that.

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            • #7
              CE11,Time was that was a truth.Like everything else we deal with the rules are changing.Speaking only for the pumps I know(Hale)you can,today,drive more pump(GPM)with less HP than ever before.I know this is also true of Waterous but I am much less familiar with their pumps.Vanisle,again not quite a "in stone"statement on HP/torque ratings.Let's examine the Cummins line since you brought it up.ISL vs ISM,both a 350 HP motor.But that's where the similarities stop.ISL is for all practical figuring a 9 liter motor at if I remember correctly some where around 950 Ft lbs torque.The ISM is an 11 liter motor and can produce upwards of 1200 ft lbs torque depending on how you set it up.Time was not so long ago that Cummins were 855 cubic inch engines that produced HP from 160-180 to 500 hp.Same block,just different innards.Now EVERYBODY's doing it,so many engine choices and sizes that it literally boggles the mind.And the hard and fast rules of yesterday's truck speccing are changing faster than we can adapt.For fire service use,I personally favor an 11 liter or bigger engine with a HP rating of at least 375(400 preferred).But that's me,I find "big power"saves you money in total cost of ownership.Others may disagree. T.C.

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              • #8
                Our new engine has a 400 hp Cummins with a 1500 gpm HALE single stage pump. You may also want to spec a heavy duty 4000 EVS trans that will out last a smaller 3000 EVS tranny !... 20 years down the road.

                Comment


                • #9
                  Originally posted by Rescue101
                  CE11,Time was that was a truth.Like everything else we deal with the rules are changing.Speaking only for the pumps I know(Hale)you can,today,drive more pump(GPM)with less HP than ever before.I know this is also true of Waterous but I am much less familiar with their pumps.Vanisle,again not quite a "in stone"statement on HP/torque ratings.Let's examine the Cummins line since you brought it up.ISL vs ISM,both a 350 HP motor.But that's where the similarities stop.ISL is for all practical figuring a 9 liter motor at if I remember correctly some where around 950 Ft lbs torque.The ISM is an 11 liter motor and can produce upwards of 1200 ft lbs torque depending on how you set it up.Time was not so long ago that Cummins were 855 cubic inch engines that produced HP from 160-180 to 500 hp.Same block,just different innards.Now EVERYBODY's doing it,so many engine choices and sizes that it literally boggles the mind.And the hard and fast rules of yesterday's truck speccing are changing faster than we can adapt.For fire service use,I personally favor an 11 liter or bigger engine with a HP rating of at least 375(400 preferred).But that's me,I find "big power"saves you money in total cost of ownership.Others may disagree. T.C.
                  An ISL is 9 liters and can be ran up to 400 hp and 1250 ft lbs.

                  An ISM is 11 liters up to 500 hp and 1550 ft lbs.
                  FTM - PTB

                  Comment


                  • #10
                    General rule of thumb for hydraulic horsepower is:

                    (P x Q)/1714 P being pressure in PSI and Q being flow in gallons per minute. If you really feel like getting precise, figure in efficency.


                    Example
                    (150 X 1500)/1714 = 131.27 hydraulic horsepower
                    (250 x 750)/1714 = 109.39 hydraulic horsepower

                    You can use this to figure up the horsepower you need, aling with efficency and a few other equations, but i don't have my books handy to tell you what they are.

                    General rule of thumb, take the 132 HHP, multiply it by 2.5, and that gives you the minimum engine horsepower to start with. (132 x 2.5 = 330)
                    Service is the rent you pay for having space on earth.

                    Comment


                    • #11
                      BV.You are so right.After I posted that(from memory,I know better),I found a good article in one of the new trade mags on the 07 engines in which Cummins partially addressed this issue.I'll stand by my other statement though,the rules are changing. T.C.

                      Comment


                      • #12
                        Originally posted by HFRH28
                        General rule of thumb for hydraulic horsepower is:

                        (P x Q)/1714 P being pressure in PSI and Q being flow in gallons per minute. If you really feel like getting precise, figure in efficency.


                        Example
                        (150 X 1500)/1714 = 131.27 hydraulic horsepower
                        (250 x 750)/1714 = 109.39 hydraulic horsepower

                        You can use this to figure up the horsepower you need, aling with efficency and a few other equations, but i don't have my books handy to tell you what they are.

                        General rule of thumb, take the 132 HHP, multiply it by 2.5, and that gives you the minimum engine horsepower to start with. (132 x 2.5 = 330)
                        I've been hunting around for my notes. As I remember, the formula I had was quite different but produced pretty much the same result. But even that would only be a guideline. VanIsle's 285 hp Mack (aka 300 Maxidyne) is an exception. It's one of a number that were hooked to 1500 gpm pumps. They were considered marginal when you got above 1250, but they did work. I think Mack preferred to keep them at 1250 and the 237 Maxidynes at 1000. I'll ask Harvey Eckart next time I see him.

                        That 300 Maxidyne was nothing short of amazing when they first hit the street in 1974. I had one in a '74 F-model that I bought used in 1977, and I ran it all over the U.S. When everyone else put 10 and 13 speed tranmissions behind their engine, the Maxidynes almost always used a five speed. I have to wonder if VanIsle's has a five speed stick or an Allison. The 5-speed (TRL107?) version and without air conditioning would have lower parasitic losses compared to some other engine/transmission combinations.

                        Having seen the transition from mechanically controlled engines to today's electronic engines has been nothing short of amazing. We're squeezing so much more power out of so much smaller engines than was ever imagined possible just a few years ago.

                        But TC, I gotta tell you this: I have total respect and admiration for down east common sense and ingenuity. It's been years, but I've been through enough of Maine and dealt with enough Mainers not to. Here though, we're dealing with some laws that never change. They're the laws of physics. You can understand the truth of that when you consider where those laws come from. Our understanding of them and our ability to make use of them constantly changes, but the laws themselves don't. It still takes X horsepower to move Y gpm at Z pressure.

                        Granted, our pumps are hydrodynamically more efficient and we gain a little there. But we keep adding stuff to the vehicle that robs the power before it ever gets to the pump input shaft.

                        Also, VanIsle, I agree that horsepower and torque are interrelated, but it's far from a lockstep relationship. Pull up the various Cummins and Cat curves (Detroit's too, if you can find them) and look at the variations. The curves on the smaller cube engines deteriorate more quickly, or peak out at higher rpm before falling apart. Maybe you can't spec the shape of the curve, but you can pick one that works. Flathead Fords have come and gone, but there still ain't no substitute for cubic inches.

                        Where's Birken???

                        Stay safe out there, everyone goes home!

                        Comment


                        • #13
                          chiefengineer11,

                          I completely agree with you, "there is no replacement for displacement", but not every dept can afford the chassis with the big bore engines. I believe that you should not spec less then a Cummins ISL, and ideally for a couple of extra bucks, get 400 hp. If you afford a Gladiator, Cyclone, Dash, Marauder etc. where the horsepower and torque are plentiful, then go for it! We do.

                          Getting back to our Mack, it has an Allison. And yes, those engines are amazing. Ours is in a MC model. Great trucks but a little tight inside wearing turnout gear. Our rescue is the same chassis, same driveline.

                          Since the Mack, everything was spec'd with 8V92's with 450 hp, then a Series 60 with 470 hp. The two we have in production have Cat C-13's with 485 hp and 1500 GPM pumps.

                          Oh, and the flathead Ford comment. I still have two Bickle Seagrave trailer pumps with flathead Fords and 500 GPM pumps. You should hear those babies scream!!

                          Comment


                          • #14
                            We run a mixed bag of L-10 and M 11's.If we get our TL I suspect we have to "pony up" a bit.Flatheads? My dad is one of the last surviving Flathead men still alive in the area.For a few years I drove the company wrecker,a '36 Ford with a whopping 100hp.It was amazing what you could haul with that truck.Couldn't stop it but you could haul a house.CE,I couldn't agree with you more.However technological advances are allowing us to bend if not break a few of the laws of physics.What was not possible ten years ago,now is.As I mentioned earlier,I prefer power in the 11 liter and larger for Fire service use.But I've found our discussions very valuable in planning for future purchases. T.C.

                            Comment


                            • #15
                              Originally posted by chiefengineer11
                              Where's Birken???
                              Learning from this thread.

                              We have very large hills and relatively small buildings. Thus, we seldom run into this issue. Our engines are powerful but we have not really found a need to go over 1250 yet. So they are just loafing when pumping for the most part.

                              Birken

                              Comment

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