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  1. #1
    Forum Member Doorbreaker's Avatar
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    Default GPM question on LDH - NST adapters

    My dept. has been finally putting LDH in service. The current method to feed it on one engine is to connect two 25' 3" (w/2.5"couplers) lines to a Y -4" Stortz adapter. Works OK but a bit cumbersome. I have been looking at changing one of the pump outlets over to a 4" line to the rear (It's a Century ALF with a 2K pump so the capacity is there and I think it has a blocked outlet on it that is 4/5 in on top of the manifold)

    BUT I was also talking to a couple of other departments that have just screwed adapters right onto the 2.5" lines and claim they get just as much flow.

    Somehow I doubt that since your limiting the flow through the 2-3" pipe running through the rig, But how much of a reduction is it? That is the number I can't find. I know in most of the pump classes they claim reductions of flow for appliances but most of those are for same sized line. (IE 2.5 feeding a twin 1.5Y)
    Using flow calculations I get all screwed up because the distance is only 8 feet.

    Anyone want to come up with a real answer before I cut and gut the rig ??
    Thanks.


  2. #2
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    Quote Originally Posted by Doorbreaker View Post
    My dept. has been finally putting LDH in service. The current method to feed it on one engine is to connect two 25' 3" (w/2.5"couplers) lines to a Y -4" Stortz adapter. Works OK but a bit cumbersome. I have been looking at changing one of the pump outlets over to a 4" line to the rear (It's a Century ALF with a 2K pump so the capacity is there and I think it has a blocked outlet on it that is 4/5 in on top of the manifold)

    BUT I was also talking to a couple of other departments that have just screwed adapters right onto the 2.5" lines and claim they get just as much flow.

    Somehow I doubt that since your limiting the flow through the 2-3" pipe running through the rig, But how much of a reduction is it? That is the number I can't find. I know in most of the pump classes they claim reductions of flow for appliances but most of those are for same sized line. (IE 2.5 feeding a twin 1.5Y)
    Using flow calculations I get all screwed up because the distance is only 8 feet.

    Anyone want to come up with a real answer before I cut and gut the rig ??
    Thanks.
    You really need to do some testing. I've played around with pretty much the same thing but never to the point of generating good numbers. What little I've done convinces me that putting a true LDH discharge on will be more efficient from a flow and discharge pressure standpoint.

    If you use an adapter, it will work, but there will be friction loss involved. The question is, how much loss can you tolerate? As the GPM flow goes up, the loss will increase exponentially.

    There are several ways to test, but the one that really counts is how much water is coming out at the smoky end. So get out your smooth bore nozzle(s) and your pitot gauge. Borrow the kind of adapter you want to use from a dealer or someone. Get the water flowing and look at how hard you have to run the pump to produce the flow that you need.

    KuhShise, if he picks up on this, may very well have the numbers you need.

    I even made, and still have, something similar to what you're using. It's an unclappered siamese fed by two 7' lengths of 3-1/2" hose with 3" couplings. We don't use it any more because the engine that it was made for has been replaced with one that has an LDH discharge.

    Please let us know how you make out.
    Last edited by chiefengineer11; 11-04-2011 at 04:53 AM.

  3. #3
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    A bunch of "case study" type reports at http://gotbigwater.com/ that may be of interest including LDH and relay info.

    Look in "Big Water Info" check "previous events" as I recall seeing such there.

  4. #4
    Forum Member CaptOldTimer's Avatar
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    When we went to 4 inch LDH and before the pumpers were plumbed to connect LDH to discharge or intakes, we use several methods to supply the LDH.


    One was attaching a 2-1/2 X 4 LDH Adapter to the designated discharge. Discharge No. 4. It was the decided one city wide.


    We laid out 500 foot LDH to a portable Stang pipe with a 1-1/2 inch tip, 600 GPM, on the ground plate and flowed water to the pipe. We were very careful noting the compound and master gauges. We also used a pitio gauge at the nozzle opening to record flow pressure and converted it to GPM.


    We really didn't experience a lot of extra pressure at the pumper as we pumped that line using the correct hydraulic formula being used back then. Bottom line it worked well for what we wanted it to do.


    We also tried using Siamese's and that worked well, but remember it has to be all connected and the less you have to connect to better the operation will be and the chance of a muck up will be greatly reduced.


    We also used a three manifold in reverse. That is, run 2-1/2 hose into the manifold backwards and it would in turn come out the other side in the LDH line.


    Of course everything ordered after that, 1986, came in with the correct intakes and discharge for the LDH.
    Stay Safe and Well Out There....

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  5. #5
    Forum Member DeputyMarshal's Avatar
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    Quote Originally Posted by Doorbreaker View Post
    Anyone want to come up with a real answer before I cut and gut the rig ??
    It's been a while since I actually crunched the numbers and did the research but, back when we switched over to 5" LDH, we determined that a 2 1/2" hydrant outlet adapted up to 5" would typically yield as much or more water off of a single hydrant outlet as two 2 1/2" outlets wyed into 5".

    This seems counterintuitive until you consider that the hydrant outlet size itself isn't the limiting factor so much as the friction loss in the 2 1/2" hoses and the wye itself. Turbulence created in the hydrant when using two outlets is also a significant factor. But, that's not directly relevant to your situation where the smaller supply pipe lengths are very short AND already effectively accounted for in the pump's GPM rating as long as you are using the main, outlets directly off off the pump body.

    My gut instinct is that, using a single 2 1/2" outlet with an adaptor will feed a 4" line just fine and that any gain from using two 2 1/2" outlets into a 4" would be negligable if there is any gain at all.

    Quote Originally Posted by chiefengineer11 View Post
    If you use an adapter, it will work, but there will be friction loss involved.
    Keep in mind that the friction loss adapting from a smaller diameter to a larger one is virtually nil. A "true LDH discharge" only becomes an advantage if it's piped for LDH all the way back to the pump body. Realistically, you'll only get that if you spec it in the original purchase.
    Last edited by DeputyMarshal; 11-04-2011 at 11:17 AM. Reason: Added reply to second poster
    "Nemo Plus Voluptatis Quam Nos Habant"

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  6. #6
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    Quote Originally Posted by Doorbreaker View Post
    My dept. has been finally putting LDH in service. ...
    You're just now starting with LDH and someone decided on 4"?

  7. #7
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    Aside to CE-11 Pssst... Thanks for putting me in the middle.

    "It's a Century ALF with a 2K pump so the capacity is there" - Lets look at 4" line and a 2K gpm pump. Max pressure for the supply line is 200 psi and the ALF will do 1400 gpm at that pressure... So 14 squared times (K factor of ).2 = 39.2 psi (40) per hundred feet so the max usable lay will be only 500 feet. Beyond this lay you are waisting part of the purchase price for the 2,000 gpm pump. Changing to 5" line the 1400 gpm can be supplied out to 1500 ft. (14 squared/ 15 = 13 psi/100) Another thing this will do is get you max flow (2K gpm) a lot further. 350 ft. of 4" or 600 ft. of 5" at 2,000 gpm. (150 psi eng. press. at 100% capacity. And a lot less rpm at 150 psi than at 200 psi.

    Speaking of internal piping..The Hazen-Williams is the bible for pipe fitters and engineers, but converting it to something familiar to firefighters looks like this: Fl = K * Q * Q * L/100
    K for steel pipe - 2 1/2" = 4.1 3" = 1.65 & 3 1/2" = 0.75. Looking at 25 feet of 2 1/2" pipe at 1400 gpm we get 200 psi of loss. The same length of 3" drops to 81 psi, while 3 1/2 will be about 37 psi. What's that you say...We will never have 25 feet of pipe between the pump and the outside of the pump panel.... Well, except that every 90 deg. elbow creates about the equivalent of 15 feet of straight pipe. So a 2 1/2 outlet with 2 elbows between the pump and the outlet and 65 feet of pipe is the same as 35 feet of pipe with 2 elbows. (rear discharge)

    Trying to crank 2,000 gpm through 2 elbows of 3" pipe and standard 2 1/2" valve can easily equal 40 to 50 feet of 3" pipe. Running the numbers (20 * 20 * 1.65 * 40/100) = 264 psi of friction loss inside the pump panel. Choose an outlet with the largest valve available with the least number of elbows. Best case 3 1/2" pipe with 3 1/2" valve and one elbow We get an equivalent length of about 20 feet and at our 2,00 gpm could expect about 60 psi loss. (don't forget to include the elbow coming out of the top of the pump into the manifold) It is easy to see why specifying large diameter piping and valve is essential when buying a large pump for relay purposes.

  8. #8
    Forum Member DeputyMarshal's Avatar
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    Quote Originally Posted by fireinfo10 View Post
    You're just now starting with LDH and someone decided on 4"?
    I was consciously ignoring that part.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

  9. #9
    Forum Member Doorbreaker's Avatar
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    Up until it was donated we ran (and still run) twin 3" runs, up to 1000 feet. Now we have 900 feet on one rig and 1200 feet on the floor waiting for deployment. 4" is pretty standard for this area as well. Many of the other departments have been using it for years.

    No hydrants in the district and for years no real tanker shuttles either. All drafting and long distances to water.

    Now we have a tanker and most of the neighboring depts. do as well. But trying to get modern is a difficult option when we run on a shoestring and trying to overcome many years of willful neglect.
    I am trying to work out ways to make using it with limited manpower easier as well as flowing more water for the effort.

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    Quote Originally Posted by KuhShise View Post
    Aside to CE-11 Pssst... Thanks for putting me in the middle.
    Glad to do it, KuhShise! I know how you love those questions and problems. Actually, I try to stay with what I feel I know best. I realize that what we do, in reality, is applied basic physics. When it comes to the more advanced physics, I'm happy to defer to those with the more advanced knowledge.

  11. #11
    Forum Member Doorbreaker's Avatar
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    Thanks for all the info. Guess it's time to do some testing. The Alf was originally set up to work with an aerial ladder and LDH wasn't common at the time. My ideal water supply rig would be a 1500-2K pump, with a front mounted 5-6" suction straight shot into the pump. Out of the pump to a manifold with maybe a 2.5 out each side, one to the rear. And the main line plumbed straight back through a ball valve and a 4-5" Stortz. LOW hose bed for LDH with a motorized retriever. Set this on a 4X4 chassis and only carry the LDH and appliances needed to operate the rig.

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    I rode a 1979 ALF as we were changing over to LDH. The 2.5" discharges relied heavily fairly long runs of pipe, and we had problems attempting to get high volume flows through them. I believe your set up with a siamese will be your most efficient way to move the water. Our shop fabricated and installed an LDH discharge using a plugged outlet in the discharge side of the pump with a 4" valve and pipe.

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