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paulz
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# Posted: 22 Jun 2020 09:51am
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There's a term I've never used.. Yesterday I participated in testing the injection of foam into the water stream of our fairly new local small fire truck. Sometimes it worked well, sometimes it didn't.
300 gallon water tank, 10 gallon foam (it's like liquid dish soap), both above the centrifugal pump. The water feed pipe is about 3" diameter. The foam line is about 3/4", with an adjustment valve. It tees into the water pipe a foot prior to the pump.
Pump pressure is usually around 100 psi, output 50 gpm but both can vary quite a bit. Sometimes we got foam out the nozzle quickly, sometimes little or not at all. I'm wondering if, depending on these or other factors, the liquid foam is not being pulled into the water stream?
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FishHog
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# Posted: 22 Jun 2020 05:30pm
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I've done similar things over the years but foam injection was always after the pump. The faster water flow would suck in the injection liquid with no issues.
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paulz
Member
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# Posted: 22 Jun 2020 06:43pm
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Quoting: FishHog I've done similar things over the years but foam injection was always after the pump. The faster water flow would suck in the injection liquid with no issues.
I was just thinking the same thing this morning Fish! But I figured the people that built the rig must know what they are doing...maybe not.
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Irrigation Guy
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# Posted: 22 Jun 2020 07:40pm - Edited by: Irrigation Guy
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On our class A pumper there is an injection system but on our fire boat we use a Venturi with a pickup tube in the bucket of AFFF after the pump
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paulz
Member
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# Posted: 22 Jun 2020 09:19pm
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Thanks IG. Been doing a little reading on the subject, putting the foam in prior to the pump is apparently one way to do it, although after the pump seems to be the preferred way, using the venturi or some other methods.
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