04-13-2006, 05:40 PM #1
- Join Date
- May 2004
Foam with Low Pressure Fog Nozzles
Has anyone had any experience with using low pressure constant gallonage nozzles in a Class B Foam Operation? I am specifically using the Elkhardt Chief Low Pressure Nozzle 150gpm @ 75 psi.
04-13-2006, 09:27 PM #2
I had the probie for foam training yesterday, and downloaded the Akron eductor instructions on their website. They had a separate chart for using 75psi nozzles.
It took me 2 seconds with Google to find this, the product description for your nozzle-
It states that it works for AFFF and Class A foam.
04-14-2006, 12:54 AM #3
- Join Date
- Oct 2005
Is there a more specific part of your question?
If you're using an eductor, obviously the math will need to be adjusted (I hope you're not using an eductor!).
Most Class B foams we see are "film forming" and have two actions they can use: foam blanket and film forming. A few only use the foam blanket.
Film forming won't matter whether you're using a 100psi nozzle, 75psi, smoothbore, open butt, whatever. HOWEVER, the film is easily broken by protrusions -- such as brush or tall grass on a roadside. Works great on airport tarmacks, works great on tanks. Not the best solution for most municipal situations.
Foam blankets are much less susceptible to these "break through" problems (although you have to keep the blanket replenished). This means you need an aspirating adapter for the nozzle -- I don't know if the lower pressure makes a difference or not. As the foam drains, it forms the film.
An alternative is to run CAFS with film-forming Class B so as the mechanical foam blanket drains, it forms a film. Of course, you wouldn't use a fog nozzle at the end of a CAFS line that you want to maintain a foamy foam -- it'll work, but it will break down the foam texture, essentially stripping most of the air from the water/foam.
IMHO, most of us do not have situations to justify Class B foams in municipal operations -- we don't have the foam supplies, flow rates, and duration to extinguish and keep extinguished anything more than a pickup truck's tank full of gasoline.
As we see more of these high-capacity CAFS systems (like the 200CFM on many modern pumpers)...they can put out enough of a mechanical foam blanket with Class A to do an effective job on those smaller Class B fires and scale up to somewhat larger ones. The Class A foam via CAFS will make a nice, thick blanket to suffocate the fire. It doesn't have the residual film-forming properties, and the blanket will likely break down faster and thus need to be replenished at a higher rate than Class B. But with lower cost, typically lower percentages, and greater liklihood of nearby mutual aid with additional supplies...Class A CAFS is probably the best compromise.
If you have specific hazards, or the ability to invest and maintain the special supplies of Class B, that's great because they do perform better when used for what they're meant for! But it's a big committment. The State of CT has a fair number of foam trailers located around our state, which carry IIRC 600 gallons of 1% AFFF...somehow you know when it's time to replace stock, the state will be in another of it's perpetual budget crisises!
06-30-2007, 02:28 PM #4
- Join Date
- Jan 2003
we just recieved a new apparatus with a foam pro 2002 system.....Nozzles are Elkhart 4000-18 150gpm @ 50 psi.
Site says it is fine for them but i can't find what i need for the Foam Pro system......
Anyone using Foam Pro system with LP nozzles that can give some input!
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