Foam Lines

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Permalink Reply by Joe Heim on July 22, 2010 at 6:29am

Dave,

Can you use other a line larger than 1.5"?

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Permalink Reply by Christopher Drake on July 25, 2010 at 8:26am

Like Dave, we use 1 3/4 with an eductor with no problems. We also use the TFT ProPaks, which replace the nozzle at the end of a line with no eductor.

We've never had a need for anything larger than 1 3/4 line for foam ops.

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Permalink Reply by Joe Heim on July 25, 2010 at 8:32am

Dave & Chris,

Thanks for the info, we currently use 1.5" for our foam lines and discussing going to 1.75". The sticking point in the discussion was some of the firefighters didn't think we could go larger than 1.5" hose. The information is very much appreciated.

Stay Safe!!

Joe

Dave LeBlanc said:

From my knowledge, which is limited, as long as you can match the flow from the eductor, yes. The issue may be finding a 2 1/2 line that flows 125gpm. And then the other question would be if that is your target flow rate, why use 2 1/2.

We do it with 1 3/4 with no problem. And if you are pumping the eductor at 200 psi, you will make foam, the quality depends on matching the flow rates......

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Permalink Reply by William Hoehn on July 26, 2010 at 7:44am

Joe: The part of the Eductor/Nozzle combination that has not been mentioned here is the back-pressure issue. If you do the calculation for a 60 gpm eductor (1/2" throat) you will find that it takes about 70 psi across the eductor to develop the 60 gpm. This leaves 100 psi for the nozzle and the remaining 30 psi is for the friction loss in the 200 ft. of 1 1/2" hose between the eductor and the nozzle (actually about 18 psi friction loss). If you were to replace the line between the eductor and nozzle with 2 1/2" hose, then in theory it is possible to make the line longer since the friction in the 2 1/2" line at 60 gpm would be less than 2 psi. Also many foam equipment producers recommend that the nozzle be at the same or lower elevation as the eductor. Excessive pressure drop across an eductor does not cause a problem, since the eductor can not develope a pressure lower than the vapor pressure of the water, but too low a differential across the eductor will not bring the correct amount of foam solution into the stream. For anyone operating an automatic nozzle with an eductor, please be sure to instruct the nozzleman to fully open the nozzle bail to minimize back-pressure.

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Permalink Reply by Alex Sharp on September 17, 2010 at 4:29am

I guess I am confused. Out where I live almost all engines have built in foam systems. We have used the eductor in training for class B foams but not for class A. All of my departments engines have a built in foam system that will supply certain lines. This system usually is built for class A foam as the percentage only goes up to 1% in increments of .1%. We use this on all structure fires because of it being a surfactant. We also use this on all wildland fires.

Although I have used the eductor it has only been with 1 1/2" lines and only at 200'

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Permalink Reply by Tom Bradley on December 22, 2010 at 2:55pm

You can use 1.75" hose. The only difference will be the distance from eductor to nozzle can be longer. We use a 95 gpm eductor with 1.75" hose and can "theoreticly" use 250'. The most we use is 200' and have never had a problem. We also use automatic nozzles without a problem. You just have to have them ALL the way open.

If you have an around the pump proportioner you can flow foam out of every discharge. You could pump foam solution through 4" or 5" supply line to another truck hundreds of feet away.

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Permalink Reply by William Hoehn on December 22, 2010 at 4:17pm

Alex:  Your reply raised a little flag in my head.  With the EPA mandating ethanol in fuel as an extender...We can no longer expect to use standard class B foam on gasoline fires.  You must use AR-AFFF at 3%, but will get better results with 3% concentrate run at 6% on the eductor.  This occurs for two reasons..  First, The more concentrated the foam mixture the quicker the film / barrier will be created between the fuel and the foam.  Second, much of the AR-AFFF concentrate has higher viscosity than the regular class B foam of old.  This means that the size of the orfice in the eductor is too small to pass the 3% into the eductor since we are limited to 14.7 psi to push the concentrate out of the bucket.  We will also need to recognize that with a flowing fuel fire it becomes harder to get the barrier to form without being carried away on the flowing fuel.  There are some good suggestions being offered by the foam concentrate manufacturers, but incident commanders will need to consider doubling the calculations for concentrate before starting an attack on a particular fire.

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Permalink Reply by Alex Sharp on December 23, 2010 at 3:02am

William:  Thanks for letting me know that.  We have never used any type of class B foam on anything but training.  The only Class B foam that we used in training was going to be thrown out because of the age and it was a 3% - 6% AFFF foam.  I didn't even think about the ethanol used in the gasoline.  Without the AR-AFFF foam it would be very hard to suppress these new fires.  Especially the new flex fuel vehicles.  I ended up talking to a guy that has one and it will run on just ethanol or the ethanol gasoline mixture.  What about using FireAde?  I heard that it is not corrosive and is biodegradable and that it knocks out all parts of the fire tetrahedron by emulsifying the fuel.

 

Like I said, thank you for bringing this up.  It didn't even cross my mind.

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