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  1. #1
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    Default Foam Eductor Question

    Well, might be a silly question but.... Always heard of a mismatched foam nozzle versus an eductor question. I was always under the impression that if there was a mismatch the finished foam product would stink.. We carry 95GPM eductors with 150 gpm nozzles. I thought that this would make for a lousy FFP. Friend of mine did some research and says that it dosen't matter, eductor will only allow for 95GPM and that as long as the nozzle flows higher than 95GPM it will make a good finished foam product. Reason being is that the eductor limits flow to 95 GPM, may not have as good a reach with lower GPM eductor but product will still be good. Any thoughts?


  2. #2
    MembersZone Subscriber fireslayer1237's Avatar
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    I would think that as long as your nozzel is an automatic nozzel it will not be a problem. considering it will account for the low gpm to creat the correct stream.
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  3. #3
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    Not automatic nozzles..are 150GPM at 50 psi fogs.

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    MembersZone Subscriber JHR1985's Avatar
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    Lots of times, even with mismatched eductors, you will still get a decent foam, just not its full potential. Automatic are notorious for this. They work but you take a 95gpm eductor with an automatic vs a actual 95gpm nozzle and the automatic stinks. Its not as discernable on a 1 3/4 line compared to a 2 1/2 eductor.

    Now, with a 150 gpm nozzle and your flowing foam through it, your not getting the full effect. That nozzle is made for 150 gpm. Anything less and the stream isnt as effective and neither is the reach. Also, its not pull as much air and the agitation of the foam isnt going to be the best.

    That being said.... yes it WILL still work and put the fire out. But, if you have a 95 gpm eductor, its just better to have a 95 gpm nozzle.

    Look at it this way. You take a 100 foot pre-connect with a fog nozzle on the end of it and you pump it at 100, not taking into effect the friction loss. Your nozzle still works and the fire will go out, but your not getting the stream, reach, or amount of water you need. Its the same principle with the eductor.

    And secondly, that eductor will flow more through it at a higher PSI. Thats why most of them give you the pressure range to pump it at. Any lower and the venturi effect wont work. Too much higher and I believe your sucking in more than you need.

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    I would think that using a 50 PSI nozzle that is rated for 150 GPM would result in a diluted foam solution.

    Most eductors require 200 PSI to develop the necessary pressure to create the venturi that draws foam through the eductor. Although the eductor would eat a significant portion of the pressure I would guess that the eductor is suppose to be mated with a 100 PSI nozzle. Using the 50 PSI nozzle would result in increased flow since it is a fixed gallonage nozzle. The increased flow would mean the foam concentrate would be diluted past the desired setting (3% for instance).

    To get a reliable answer (beyond my best guestimate) you should check with both the manufacturer of the eductor and the nozzle.

    While on this subject I recently operated at a semi-tractor fire that was carrying 6,000 gallons of unleaded gasoline. During the critique a representative from Marathon recommended that all FD’s should make it a habit of carrying ATC foam and apply it at the polar solvent rate due to the increased blend of Ethanol in gasoline. Just food for thought.
    Last edited by traumawave; 06-08-2007 at 06:59 PM.
    Anything less than excellent is unacceptable!

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    MembersZone Subscriber JHR1985's Avatar
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    While on this subject I recently operated at a semi-tractor fire that was carrying 6,000 gallons of unleaded gasoline. During the critique a representative from Marathon recommended that all FD’s should make it a habit of carrying ATC foam and apply it at the polar solvent rate due to the increased blend of Ethanol in gasoline. Just food for thought.
    I dun have the link but there is a thread in the main FF section that has to do with ethanol fires

  7. #7
    Forum Member Squad1LT's Avatar
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    You need to test it yourself to see if it works or not. I was on a fire awhile ago where the nozzle was mismatched from the eductor and the eductor wouldn't pick up any foam at all. So I would test it out not just take someone elses word for it. You need to match GPM.

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    MembersZone Subscriber ullrichk's Avatar
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    In order to test the setup yourself, just drop the pickup tube in a 5 gal. bucket of water. Using whatever setting is convenient use a stopwatch to clock the drain time of the bucket while you are flowing water. Do the math and you will have some idea of what your eductor is actually doing with this setup. (Keeping in mind that water is less viscous than foam and will educt more quickly than the real stuff -but water is cheap.)
    ullrichk
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    Forum Member gunnyv's Avatar
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    Your best bet to figure this out is probably to flow some into a pool and check the concentration with a refractometer or conductivity meter. Just because there are suds doesn't mean the finished foam has the quality to work effectively.

  10. #10
    MembersZone Subscriber JHR1985's Avatar
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    also, depending on your eductor, on lower settings it wont pick up water. Density and gravity issues are the problem. I think that is why the majority of eductors are set for around .5% to like 6. Granted, I flush mine all the time with water but its like 6%. On a 1 3/4 eductor, anything below .5% i believe wont be picked up. I'm like 75% sure on that but test it. I never did but who know's

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