Foam 101

[Remember585 815]

I know how water works, but when it comes to foam, I'm all washed up. Here's a few questions for everyone regarding firefighting foam.

1. What type (AR-AFFF, AFFF, Etc.) do you use?

2. What are it's uses?

3. How much do you carry?

4. Can you pump it from the rig or do you rely upon eductors?

5. Do you have any SOPs/SOGs regarding it's use?

6. Why do you carry what you carry?

All feedback and info is welcome, thanks.

[Alpinerunner 61]

1) AFFF

2) Flamable liquid fires. Basically any time water would spread the fuel around and you want smother instead of cool.

3) 4 5-gallon jugs

4) We can pump from the rig but would always use the eductor because the tank system gets gummed up if you don't rinse it out and maintain it

5) Unknown

6) If 20 gallons isn't enough, we're calling someone else.

A few more things I've learned about foam: Nozzle flow must match eductor flow. It may be required to gate down the nozzle to achieve the flow rate the eductor requires and to get good foam.

My question: I thought foam was pumped at 100 nozzle psi (fog), but I've heard that you need up to 200 psi. What is the correct pressure?

Edited April 1, 2010 by Alpinerunner

[FiftyOnePride 100]

1. What type (AR-AFFF, AFFF, Etc.) do you use? Class A in a Compressed Air Foam System.

2. What are it's uses? Structural, Vehicle, and other type fires.

3. How much do you carry? 30+ gallons at any given time.

4. Can you pump it from the rig or do you rely upon eductors? Pumped through the rig as aforementioned using a CAFS system.

5. Do you have any SOPs/SOGs regarding it's use? We do, I'll have to go get the specifics.

6. Why do you carry what you carry? Because it works, Foam directly deals with all three sides of a fire triangle. This, since we received our first foam truck in the mid 90's has worked. Only electrical malfunctions have really affected its use from what I can remember.

Once you put foam down, don't break the barrier by throwing water on top as well. I'll have more later...

[lalautze 35]

My question: I thought foam was pumped at 100 nozzle psi (fog), but I've heard that you need up to 200 psi. What is the correct pressure?

You need to provide nozzle pressure at the nozzle which sounds like you have 100psi fog nozzles. Eductors have high friction loss due to their design so it is very possible to have pump pressures of 150-200psi to get your needed 100psi at the nozzle. Check the manuals for the eductors you use, they should have a required intake pressure on them.

Our eductors are 150psi at the intake but depending on friction loss in the hose lay we can pump close to 200psi for a 100psi fog nozzle.

We have Class A Foam systems on our last 2 engines (25-gallon tanks) and a Class B AR-AFFF Foam Trailer (550-gallons). The Class A system does help with extinguishing typical structure fire and does a good job on vehicles and dumpsters too. The foam trailer is for all of the tanker trucks and trains we have going thru town. With a pipeline terminal we get everything from diesel to gasoline to aviation fuel plus this is Iowa so there is quite a bit of ethanol as well. The Class A systems are injection via computer and the Class B trailer we use eductors. No SOG for use of the Class A, we train to use it on everything but we do have a SOG for the Class B since you have to calculate how much foam you need for the given fire size, duration, etc.

[Alpinerunner 61]

You need to provide nozzle pressure at the nozzle which sounds like you have 100psi fog nozzles. Eductors have high friction loss due to their design so it is very possible to have pump pressures of 150-200psi to get your needed 100psi at the nozzle. Check the manuals for the eductors you use, they should have a required intake pressure on them.

Very good info! I'll have to check that out. I am surprised to hear of people using Class A foam and CAFS. I haven't heard of any departments using that around me. I've read about it being useful for protecting houses from wildland fires though. A class B foam trailer makes sense for your district.

[Remember585 815]

I also meant to ask what % is the foam you have and how did you decide to get it? Thanks.

[Bnechis 3,961]

I know how water works, but when it comes to foam, I'm all washed up.

You are not alone, I think that the majority of firefighters have never been taught what is truly needed for foam operations. After training and performing the calculations for ethonal based fires most FD's do not carry enough to handle a car fire.

A few more things I've learned about foam: Nozzle flow must match eductor flow.

Very True

It may be required to gate down the nozzle to achieve the flow rate the eductor requires and to get good foam.

If you gate down the nozzle you create a back pressure and the eductor will not pick up foam, so you get water without foam.

My question: I thought foam was pumped at 100 nozzle psi (fog), but I've heard that you need up to 200 psi. What is the correct pressure?

Most eductors require 200psi at the eductor, with a max of 200' of hose between the eductor and the nozzle. the friction loss of the hose and eductor will give you 100psi at the nozzle. This is general, you need to know what eductor psi requirements you have.

1) AR-AFFF 1-3%

2) Flamable liquid fires.

3) 4-5 5-gallon jugs per engine. Each engine has a 95gpm eductor, low & medium expansion TFT nozzles.

4) We do not have "prepiped" systems because they cost extra to install, cost a lot to maintain and almost never work (class when you need them (unless they have been perfictly maintained and exercised). As mentioned they get "gummed up" and I have seen many depts. fail to produce foam because of it. On engine 25 we have it pre set-up (not pre-piped) we have a gated wye on the front bumper with a short length that goes to an eductor. 200' of 1.75" hose and a foam nozzle. If you want foam, you stretch that line, spike a foam can (which is stored in the bumper) and charge the line. It cost nothing extra to set it up, nothing more to maintain and we can get foam as fast or faster than any rig with a "prepiped" system.

With 20-25 gallons per rig we can get 100-125 gallons on-scene quick, if that is not enough we can go to our back-up:

We stock another 30-60 5 gal pails in the fire stations and we just added (not inservice yet) a large flow system, which consists of the following:

3) 55 gallon drums of concentrate

1) Drum hand truck

1) pick-up truck with lift gate (mechanics)

1) Foam bin (like a dump tank for foam). Its on wheels has a drain bar (so 5 gal pails can be flipped and drain) and a spike (to rip open pails that are dumped in) it can support multiple eductors at one time as it holds about 50 gallons.

3) foam master stream nozzles with built in eductors and pick-up tubes (can work on any deck gun and pick up from the ground or foam bin).

3) 2.5" 500gpm eductors to supply ladder pipes and the tower ladder

1) Jet Ratio Controller - to supply a remote master stream device from upto 3,000 feet away from the foam supply. This way we can leave an unmanned monitor flowing foam.

[Remember585 815]

Thanks for the reply Barry. Is that the National Foam Liquid Gold 1/3 AR-AFFF I see? I was reading up on that, and it says that it almost has the same properties of a 3/6 concentrate.

I guess I could answer my own questions too...

1. AR-AFFF 1/3%

2. Flammable liquid fires, others requiring a blanket. (Recent uses included overhaul at structure fires)

3 & 4. E118 has 100 gallons via on board tank with all around pump capability. E119 & E120 have 15 gallons (3 pails)and required the use of Eductors (Akron-Brass Bypass). Additional foam stored at all 3 firehouses.

5. No SOG yet (work in progress)

6. E118 is "Chemical Engine Company," it's predecessor rig had a small foam tank as well. We carry the foam we do because of it's versatility in flammable fuel fires, as we have several gas stations, a large amount of trains carrying fuels and a 200,000 gallon above ground diesel tank in the Metro-North Harmon Yards. (If the latter ever catches fire, you can bet we'll be calling for more!)

[Alpinerunner 61]

If you gate down the nozzle you create a back pressure and the eductor will not pick up foam, so you get water without foam.

Most eductors require 200psi at the eductor, with a max of 200' of hose between the eductor and the nozzle. the friction loss of the hose and eductor will give you 100psi at the nozzle. This is general, you need to know what eductor psi requirements you have.

Thanks for the info. That is a great setup in the bumper! About the flow rate. Are you sure that's the case with all nozzles? I remember the eductor being rated for a specific flow rate (95 gpm) engraved from the manufacturer. Our variable flow rate (30-200?) TFT fog nozzles had to be gated down a click or two to get to that flow rate. I experienced this first hand, that at full flow the foam was poor, and when gated down the foam was significantly better. It's possible that we weren't pumping at a high enough pressure and that's why we needed to gate down. Thoughts?

[Bnechis 3,961]

Thanks for the reply Barry. Is that the National Foam Liquid Gold 1/3 AR-AFFF I see? I was reading up on that, and it says that it almost has the same properties of a 3/6 concentrate.

Yes and thats why we switched to it. It costs about 25% more, but each pail gives almost 100% more coverage since you dial down the %. Also means each rig carries 2x as much in the same space.

[Bnechis 3,961]

Thanks for the info. That is a great setup in the bumper! About the flow rate. Are you sure that's the case with all nozzles? I remember the eductor being rated for a specific flow rate (95 gpm) engraved from the manufacturer. Our variable flow rate (30-200?) TFT fog nozzles had to be gated down a click or two to get to that flow rate. I experienced this first hand, that at full flow the foam was poor, and when gated down the foam was significantly better. It's possible that we weren't pumping at a high enough pressure and that's why we needed to gate down. Thoughts?

TFT warns you not to gate down. Its about Presure (PSI) not flow. We have 95gpm, 125gpm and 500gpm eductors, they all require 200psi and thats what they flow if you give them that psi.

[wraftery 1,275]

A couple of points on foam that weren't mentioned:

1. For class B fires, do not begin a foam application until you have enough foam concentrate on scene to complete the operation. Otherwise you are wasting your time and foam.

2. Foam Is Not Foam! Not all foams are compatible. Make sure (espaecially in mutual aid situations) that only compatiblle foams are applied. Try talking to your mutual aid comrades before and, and buy compatible foams.

3. What was I thinking...Forget the second and third sentences in Point #2. FD's don't use logic like that. If Dept A buys foam, Dept B has to buy Better Foam, compatible or not.

4. If you want to dissolve the foam blanket AFTER the emergency is over, Try educting fabric softener and applying it to the foam blanket. Most foams are detergents and fabric softener breaks down detergent. Try it on your foam.

[Guest alsfirefighter]

In regards to the flow rates, it is the flow rate and required pump discharge pressure of the eductor that is important. Not the nozzle. Either way you control flow rate through your PDP not by gating a nozzle. All of the eductors that I have utilized in the field and teaching pump operator courses of varying manufacturers require 200 psi at the eductor to achieve the venturi needed to pull the foam. The easiest way to achieve this is by attaching the eductor direly to the discharge. If you can do it on the pump panel side this allows the pump operator also to keep the foam flowing. I have seen varying hose lengths that can or cannot be used, from 200' to 150'. Check with your eductors manufacturer info to find out. A couple of other things to point out:

1. If possible have an empty bucket to pour the foam into or open your first container enough so you can pour additional foam needed so you do not have to interrupt the flow of foam as you would if you have to keep removing the wand from container to container.

2. If you are on the nozzle, remember you are going to get water first, keep the stream away from the class B material until you have good foam.

3. For significant incidents, those of you carrying only a few foam containers, its not going to cut it. A leading expert in foam from Oklahoma State University in a foam course I attended recommended that if spec'ing an apparatus for foam with an around the pump proportioner that the minimum foam tank size you should be looking at if you have a hazard specific target should be 100 gals.