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    Default Drafting question

    I have a question about the capacity of a pump when drafting. I've been told that pumps are rated for drafting at a 10' head. Will a 1500 gpm pump exceed it's rated capacity when drafting from a dump tank? And by how much? I've never had to do a pump test so I've never had to run a pump at capacity when drafting. I'm working on some drafting projects, so just looking to get some info to prepare for it.

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    Short answer is yes. If you have a large body pump. I have seen a 1250 pump do 2000 gpm. But there are many variables. Valves and plumbing strainers and hose. Using multiple inlets can also increase output. To realy know you will have to do some testing.

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    Pump manufacturers have to certify that the pump is capable of doing capacity at 150 PSI from a 10' lift up to an altitude of 2000' for up to 1500 GPM and 8' and 6' for 1750 and 2000 GPM. Most are capable to higher altitudes. So if you have the horsepower and chances are you are less than 2000' altitude you should have no problem pumping higher than the rated capacity.

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    Work done by Larry Davis and published in his Rural Fireground Water Movement indicates flows with a 1500 gpm pump at a 10 ft. lift should approach 1630 gpm. As others on this thread have indicated, there are many factors that can affect this. Pump casting size, care in machining and removing rough interior caused by sand casting, Hard Sleeve construction (smooth interior wall is essential), Number of 10 ft. sections, strainer design, etc. etc. However using your example and making a rough calculation, you should be able to reach 1790 gpm with one section of hard sleeve and a regular barrel strainer. Low level strainers can add significant loss to a drafting operation at high flows. Part of the suction side equation is the effort it takes to accelerate the water into the suction sleeve. (inertia) The smaller the slot in the low level strainer, the more drop will be developed when trying to move large water volumes through that slot. This adds to the turbulence in the suction tube as well.

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    Question...if you are running from a dump tank filled by your own tenders/tankers.....are you still using a barrell strainer?

    If you are filling your tanker/tenders from hydrants....is there that much crap coming out that you need to use a strainer?

    If you are filling from a drafting location....is enough stuff passing by that strainer to warrant another strainer?

    Just a curious question....
    "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?

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    Just an example of physical limitations- My 1958 FWD Pumper was delivered with a pump rated @750GPM. In 1968, a third 2.5" discharge was added to the driver's side, obviously increasing discharge capability- However due to having 4.5" intakes that were never upgraded, I can only move approx. 900 at draft- no more! To this day she still carries the orginal 750GPM rating plate, I suspect this is why.

    She will of course move as much as can flow through her on a good hydrant.
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    Quote Originally Posted by johnsb View Post
    I have a question about the capacity of a pump when drafting. I've been told that pumps are rated for drafting at a 10' head. Will a 1500 gpm pump exceed it's rated capacity when drafting from a dump tank? And by how much? I've never had to do a pump test so I've never had to run a pump at capacity when drafting. I'm working on some drafting projects, so just looking to get some info to prepare for it.
    You are getting lots of good info from the other posts.

    Think of it this way, pump testing can have lots of variables. Discharges, intakes, lift, condition of pump etc, etc, etc.....

    To recreate any experiment, you must recreate all the variables the same way as the initial experiment. That is way the test must be set up the same way. You are trying to recreate the same data that the truck tested to at the time of it being made. You know it is in good shape when it can do the same flows at the same RPM's as when it was new. If it can not, then there are issues that need to be addressed.

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    Quote Originally Posted by Bones42 View Post
    Question...if you are running from a dump tank filled by your own tenders/tankers.....are you still using a barrell strainer?

    If you are filling your tanker/tenders from hydrants....is there that much crap coming out that you need to use a strainer?

    If you are filling from a drafting location....is enough stuff passing by that strainer to warrant another strainer?

    Just a curious question....
    Hey, if you do like I did and drop your handheld radio into the dump tank, you are glad for every strainer there is!

    Seriously, many older pumpers have the steamer strainers rusted out, and at least some of the time we are filling out of creeks. Also we operate on rather small (6" or less) water mains, and when you crack a hydrant wide open to fill a tanker, you frequently flush out considerable sediment. The residue in our dump tanks after use can attest to that.

    But broadly speaking, you are right. All that straining can be...a strain.
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    Good info guys, thanks a lot!!

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    My personal record for a 1250 GPM pump being driven by a 330 horse Cummins ISC is 2100 GPM at a draft. That is the highest we were able to keep it stable.

    We were able to reach 2300 GPM but if you sneezed or even thought about sneezing the pump would cavitate and lose prime.

    This was done with the engine nosed into a boat ramp with a 10' hard sleeve on the font intake and 20' of hard sleeve on each side intake.
    I can't believe they actually pay me to do this!!!

    One friend noted yesterday that a fire officer only carries a flashlight, sometimes prompting grumbling from firefighters who have to lug tools and hoses.
    "The old saying is you never know how heavy that flashlight can become," the friend said.
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    Quote Originally Posted by Bones42 View Post
    Question...if you are running from a dump tank filled by your own tenders/tankers.....are you still using a barrell strainer?

    If you are filling your tanker/tenders from hydrants....is there that much crap coming out that you need to use a strainer?

    If you are filling from a drafting location....is enough stuff passing by that strainer to warrant another strainer?

    Just a curious question....

    Trust me when I say you'll want a strainer attached, regardless. I've seen rocks dumped into drop tanks while doing water shuttles upwards the size of a baseball. How they got into the tanker/tender in the first place is beyond me but they did. We were drafting out of a quarry when it happened so that was probably the source but into the tanker itself, I'm not sure.

    I've also pulled suction hose off the intake of an engine a few times only to find good sized rocks up against and even stuck in the intake's strainer.

    All those times, I cringed as to the thought of how much damage could have happened to the pump had they made it past and into the impeller. Worse yet had they made it past to the nozzle while a crew was inside.

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    EastKY: The intake screen on most pumps is also a sacrificial anode made of Zinc or other electrically active dis-similar metal. It is supposed to be eaten away by the electrolysis when the pump is left standing in the wet condition. It is there to protect the other parts of the pump that would be corroded away. You are supposed to periodically replace this screen. If it is allowed to fail, pieces will become wrapped around the vanes of the pump due to water flow. If the pump is not back flushed to remove these pieces, eventually the pump will experience bearaing and packing failures due to the off balance condition (weight) added to one or more vanes. I have seen this happen when pumping high volumes through a deck gun. It resulted in a poor stream from the gun. Fortunately we were able to back flush both the shaper tube and the pump. The replacement of this strainer is supposed to be a regular maintenance item.

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    Quote Originally Posted by IronsMan53 View Post
    This was done with the engine nosed into a boat ramp with a 10' hard sleeve on the font intake and 20' of hard sleeve on each side intake.
    If you really wanted good flows, you would have nosed in a little further and just used a strainer on the front intake.

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    Right! But the Chief might have frowned upon that.
    I can't believe they actually pay me to do this!!!

    One friend noted yesterday that a fire officer only carries a flashlight, sometimes prompting grumbling from firefighters who have to lug tools and hoses.
    "The old saying is you never know how heavy that flashlight can become," the friend said.
    -from a tragic story posted on firefighterclosecalls.com

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    Quote Originally Posted by KuhShise View Post
    The replacement of this strainer is supposed to be a regular maintenance item.
    Right. We keep an eye on ours too...always gotta remind the fellers to open the keystone and check the things.

    They have them down in the sump area of some pumps too, don't they?
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    On engines with metal tanks. See this web site: http://www.firetechservice.com/index_files/Vol1Iss1.htm

    Many years ago our F.D. built our own tanker (tender) on a B-model Mack tractor. Tandem axle was removed, frame extended and springs beefed up to accept a square tank with a flat top. We discussed at length a coating that would protect the steel. A local painting contractor suggested a two part sprayed epoxy made from coal-tar. This eliminated any hauling of potable water due to the carcinogenic effect of the coal tar, but incidental exposure of firefighters was deemed to be an acceptable condition. The epoxy prevented any corrosion in the tank, but the bolts used to hold the top of the tank became the sacrificial elements and needed to be replaced about every three years. Amazing how the threaded ends exposed to the water were eaten down into needle thin points.
    Last edited by KuhShise; 04-01-2012 at 09:18 PM.

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