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  1. #1
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    Default Friction Loss inside the Discharge Manifold - 3" vs 4" @ 1,500 GPM

    Brothers,

    When performing some driver training last week, we did some side-by-side comparisons of different trucks concerning high volume pumping.

    Both trucks were identical with one exception...
    One had a 3" discharge plumbed off the side of the discharge manifold...
    and the other had a 4" discharge plumbed off the top, yet still had two 90º bends in it.

    Here's a pic of the 4" off the top:


    You can imagine what the 3" looks like, it's identical to the 2½" facing the camera above, except it's 3".

    To test the resistance, we stretched a 100' of 4" hose to a ground monitor, and screwed on a set of pitot tips used to service testing. Using a 2½" tip @ 82 psi, we were flowing 1,509 GPM. Each truck was equipped with a pressure governor to maintain constant discharge pressure, and each discharge valve was left full open (not throttled at all).

    The 3" discharge had 90 psi of loss between the master gauge and the line gauge.
    The 4" discharge had 30 psi of loss.

    I knew there would be a difference, but not that much.

    Both were Hale Qmax pumps. Hale offers a 4" off the side, without the 90º bends, but the 4" port (2433 series flange) is optional, not standard, while the 4" off the top is a standard feature on all Qmax's. The side port is known as "port P" in Hale's literature. Hale rates the 3" at 1,500 GPM, and the 4" at 2,600 GPM.

    So, if you're specing out a truck, and you ever plan on pumping 1,500 GPM or more to another source through one line, abandon the 3", and embrace the 4" or larger for far less resistance.
    Last edited by txgp17; 03-10-2010 at 03:59 PM.
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    I salivate at your posts!

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    Interesting. I assume valve is a 4". Air operated or electric operated?

    Would be interesting to see what 4" plumbing with 3" valve (manual operator/much less expensive) can do.
    Last edited by neiowa; 03-14-2010 at 08:45 PM.

  4. #4
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    Quote Originally Posted by neiowa View Post
    Air operated or electric operated?
    Manually operated. It uses a handwheel driven worn gear actuator with a position indicator. They're on page 125 of Akron's present catalog.
    Quote Originally Posted by neiowa View Post
    Would be interesting to see what 4" plumbing with 3" valve (manual operator/much less expensive) can do.
    Not much better, the piping of the 3" we tested was less than 12" long total.

    Also, 3" discharge valves require slow close mechanisms just like 4" ones do.
    Last edited by txgp17; 03-15-2010 at 11:03 AM.
    The American people will never knowingly adopt Socialism. But under the name of 'liberalism' they will adopt every fragment of the Socialist program, until one day America will be a Socialist nation, without knowing how it happened. --Norman Mattoon Thomas, 6 time presidential candidate for the Socialist Party of America

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    Here's a few numbers to hopefully put things into perspective. Looking at Waterous Co.'s form F2117, Pressure Drop Though (presumably Waterous) Discharge Valves:

    3-1/2" valve is just over 3-3/4 psi loss at 2000 gpm. On this valve the waterway through the ball is 3", the entrance and exit tapers to/from 3" to 3-1/2".

    The 2-1/2" full flow valve (full 2-1/2" waterway through the ball) shows 4-3/4 psi loss at 1000 gpm. The curve does not go past there. Projecting the curve out you can see that it would be difficult to put more than about 1300 gpm through it at all. By comparison, the 3-1/2" valve shows just under 1 psi loss at 1000 gpm.

    The 2-1/2" standard flow valve (2" waterway through the ball) shows about 2-3/4 psi loss at 500 gpm and just over 4 psi at 600 gpm. Again, projecting the curve out it looks as if that valve would be hard pressed to move 700 gpm. The 2-1/2" full flow valve shows just a hair over 1 psi at 500 and the 3-1/2" shows about 1/4 psi for the same thing.

    I am presuming that this chart applies to the flows and losses through the valves only and does not take in pipe connections to and from them. But we can see that not skimping on valve sizes can improve water flow operations considerably.

    I know of one published writer who stated that hooking an LDH line to a 2-1/2" discharge with an adapter was an acceptable procedure. I beg to disagree.

    Also, anywhere that there is a sudden change in diameter, especially from larger to smaller, such as a pipe threaded into a flange or any other coupling device, eddy current losses can be expected. They can be pretty significant. That's in addition to losses through bends elbows, etc. It's easy to see that internal losses behind the pump panel can mount up in a real hurry. Paying attention to these when writing specs can pay off big time.

    I will have to echo a chief we had many years ago who said that all friction loss in hose lines could be calculated at 10 psi per 100 ft. He went on to say that 99% of the time it didn't really matter anyway. The same can be said for internal friction loss in the pump. What he didn't factor in was the remaining 1%. That's the one that gets you, and gets you when it matters most. So anything you can do to improve flow through your pump will be a big plus in the long run.

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    Quote Originally Posted by chiefengineer11 View Post
    Here's a few numbers to hopefully put things into perspective. Looking at Waterous Co.'s form F2117, Pressure Drop Though (presumably Waterous) Discharge Valves:

    3-1/2" valve is just over 3-3/4 psi loss at 2000 gpm. On this valve the waterway through the ball is 3", the entrance and exit tapers to/from 3" to 3-1/2".

    The 2-1/2" full flow valve (full 2-1/2" waterway through the ball) shows 4-3/4 psi loss at 1000 gpm. The curve does not go past there. Projecting the curve out you can see that it would be difficult to put more than about 1300 gpm through it at all. By comparison, the 3-1/2" valve shows just under 1 psi loss at 1000 gpm.

    The 2-1/2" standard flow valve (2" waterway through the ball) shows about 2-3/4 psi loss at 500 gpm and just over 4 psi at 600 gpm. Again, projecting the curve out it looks as if that valve would be hard pressed to move 700 gpm. The 2-1/2" full flow valve shows just a hair over 1 psi at 500 and the 3-1/2" shows about 1/4 psi for the same thing.

    I am presuming that this chart applies to the flows and losses through the valves only and does not take in pipe connections to and from them. But we can see that not skimping on valve sizes can improve water flow operations considerably.

    I know of one published writer who stated that hooking an LDH line to a 2-1/2" discharge with an adapter was an acceptable procedure. I beg to disagree.

    Also, anywhere that there is a sudden change in diameter, especially from larger to smaller, such as a pipe threaded into a flange or any other coupling device, eddy current losses can be expected. They can be pretty significant. That's in addition to losses through bends elbows, etc. It's easy to see that internal losses behind the pump panel can mount up in a real hurry. Paying attention to these when writing specs can pay off big time.

    I will have to echo a chief we had many years ago who said that all friction loss in hose lines could be calculated at 10 psi per 100 ft. He went on to say that 99% of the time it didn't really matter anyway. The same can be said for internal friction loss in the pump. What he didn't factor in was the remaining 1%. That's the one that gets you, and gets you when it matters most. So anything you can do to improve flow through your pump will be a big plus in the long run.
    That's all interesting information. I've got two questions for you, though. First, where can a guy find that form F2117? Second, at what pressure are they calculating the losses?

    While I think I see what you're saying, I'd argue the perception that you cant use LDH on a 2 1/2" outlet. You just have to use it the right way and know where and what the limitations are. If you're only going to get 1,000 or 500 GPM, depending on which valve, that's all you're going to get out of it. However, if you're laying a stretch of say 500' to pump through, you're going to get a lot more of that 500-1,000 GPM to the other end with LDH than you will with MDH.

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    We have some Hale 1,500 GPM. rated pumps that have a three inch full flow valve right of the end of the manifold and located on the officers side pump panel. They have a 5" storz adapter and will easily flow the capacity of the pump with around a 3-4 psi drop through the valve at 1,500 gpm.

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    Quote Originally Posted by Catch22 View Post
    That's all interesting information. I've got two questions for you, though. First, where can a guy find that form F2117? Second, at what pressure are they calculating the losses?

    While I think I see what you're saying, I'd argue the perception that you cant use LDH on a 2 1/2" outlet. You just have to use it the right way and know where and what the limitations are. If you're only going to get 1,000 or 500 GPM, depending on which valve, that's all you're going to get out of it. However, if you're laying a stretch of say 500' to pump through, you're going to get a lot more of that 500-1,000 GPM to the other end with LDH than you will with MDH.
    I'm sure Waterous Co. would be happy to provide one.

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    Default pressure losses in pipe fittings

    Actually, the picture shows three (3) 90 degree bends in the run. The first one is the turn from the manifold into the pipe and then the other two that are obvious. Pipe suppliers generally use an equivalent pipe length of 15 feet for each 90 deg. elbow, so there is an equivalent length of pipe in the engine of 45 feet plus the valve and straight piping. Using the Hazen - Williams formula the friction loss for just the elbows should be about 74 psi for the three inch at 1,000 gpm and about 18 psi for the 4 inch line. Adding in the losses for the droop snoot and the valve and your tests are right on target.

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    Quote Originally Posted by chiefengineer11 View Post
    I'm sure Waterous Co. would be happy to provide one.
    Catch - My apologies for the short answer. I had just come back from a run and was running behind to pick someone up to go the the Phila. Fire Museum for a time capsule opening.

    As I said, if Waterous still publishes that chart, I'm sure a phone call would produce one. (651) 450-5200. Option 4, I think, should get you to one of their service folks. Or, if you can provide me with a fax number, I'd be happy to fax mine to you, grease spots and all.
    Last edited by chiefengineer11; 03-15-2010 at 11:31 PM.

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    Quote Originally Posted by chiefengineer11 View Post
    Catch - My apologies for the short answer. I had just come back from a run and was running behind to pick someone up to go the the Phila. Fire Museum for a time capsule opening.

    As I said, if Waterous still publishes that chart, I'm sure a phone call would produce one. (651) 450-5200. Option 4, I think, should get you to one of their service folks. Or, if you can provide me with a fax number, I'd be happy to fax mine to you, grease spots and all.
    No apologies needed, I completely understand. I'll give them a holler and see if I can't get a copy. I didn't know if maybe I was missing where it was on their website or even if it might be somewhere in the owner's manuals somewhere.

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    Quote Originally Posted by chiefengineer11 View Post
    Catch - My apologies for the short answer. I had just come back from a run and was running behind to pick someone up to go the the Phila. Fire Museum for a time capsule opening.

    Have your ears healed yet?
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    Quote Originally Posted by Catch22 View Post
    No apologies needed, I completely understand. I'll give them a holler and see if I can't get a copy. I didn't know if maybe I was missing where it was on their website or even if it might be somewhere in the owner's manuals somewhere.
    I have not ever seen it anywhere else. I don't think it is even in the manual that I got when I went to their mechanics' school. I think I got mine from a long since retired person at Waterous.

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    Quote Originally Posted by FWDbuff View Post
    Have your ears healed yet?
    Wasn't him.

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