CAF FLOWS
Q – I was wondering if the gpm that CAFS is flowed at product flow, or water prior to the air and concentrate being added. For example, is flowing 70 GPM of CAFS the same as flowing 70 GPM of water.
A – The easiest way to explain your CAFS flow rate’s are in terms of “Rate of Consumption”. That is the amount of water consumed to create the desired “Foam Type” of CAF that is being discharged. The water consumption rate is the GPM that is displayed on your Foam Proportioner on the pump panel. The GPM is actually measured prior to the addition of concentrate, addition of compressed air and the expansion process via agitation within the propper size and length of hoseline. The final and fairly dramatic change is applied by the propper selection of Smooth Bore Tip bore sizes. Since all of the above mentioned items are variable and have an effect on the final discharge rate of “product” we always use the proportioner GPM flow rate displayed on the panel as our reference when setting our panel or discussing the rates of flow. Since the rate of flow and expansion is user variable it would lead to dangerous confusion on the fire ground to referrence or request flows based on what flow is coming out of the nozzle tip’s. As a gerneral rule of thumb most “Wet” CAF for interior fire attack is expanding in the hose at a rate of about 3 to 1. That is, about 3 gallons of finished foam bubbles are leaving the nozzle for every 1 gallon of water entering the CAFSystem. In relation to Naturally Aspirated Foam that is a very low expansion level, but that is the widely preferred level as the water is what’s doing the work, not the concentrate and not the air. The two former products simply enhance the physical characteristics of the water to absorb BTU’s as quickly as possible. Even at the lowest recommended interior flow rate of 80 GPM (measured at the panel !) you may still be generating (at 3:1 expansion) upwards of 270 GPM of finished foam bubbles that love carbon and BTU’s!
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FOAM CONCENTRATE
Q – I’m an Indonesian firefighter. We have portable CAFS but we can’t afford to refill our CAFS tank if it’s empty. Our vendor told us that their foam can use for Class Fire A,B,D,and K. Is it true? Or every Class fire needs specific foam for each fire? Can we use detergent for our CAFS tank instead Class A Foam? I’ve ever read that waste from pulp industry can used to be foam instead class A foam. Is it true? Underline, we need cheaper foam to our portable CAFS. Also, can you give me formula to make Class A Foam ourself, cause it’s too expensive for us. We need the cheaper one. Thank You!!
A – Many years ago some CAF units used “Pine Soap” which is a byproduct of the logging & paper industry. It was and still is a poor Class A concentrate and is NOT recommended. To my knowledge no departments use this anymore. Also, to my knowledge there are no acceptable, affordable or user friendly “Universal Foam Concentrates” currently on the market. They all have some down sides to there use and at this point we CAN NOT recommend any Universal Foam Concentrates. The use of commercial grade detergents is a common practice for training in some areas. The bubble structure of the detergent based CAFS usually doesn’t hold up to heat as well as a true Class A based firefighting foam. Also, these commercial detergents have not been tested to the USDA / U. S. Forest Service Qualified Product List standards, thus there is no way to know if they may harm your equipment through contamination or corrosion as well as the environment. They will work to a lesser level in CAFS, but be careful. For anything other than training, we urge caution. In summary, using good quality USDA / USFS approved Class”A” concentrate is the best bet for the safety of your personnel and the well being of your CAFS equipment and the environment.
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CAF IN COLD WEATHER
Q – Our department just took delivery and put into service a new Truck with the CAF system that we are very excited about. We were talking at shift change this morning and was wondering if and how cold to extreme cold temperatures will affect the foam performance and can it freeze up in the hoseline?
A – The use of CAFS in cold climates is on the increase and in some cases these locations would be classified as severe if not dangerously frigid. Currently, the most challenging locations that I’m personally aware of that are employing CAFS are Iqaluit, Nunavit Canada which is on Baffin island near Greenland. Yellowknife, in the Northwest Territories of Canada. Anchorage, Fairbanks and several smaller communities in Alaska, as well as several units in the province of Quebec. A CAFS engine was put into service at the Red Dog Mine (145 miles North of the Arctic Circle) in Alaska. Unlike water pumping apparatus that must keep a flow of water running at all times to prevent getting a solid “popsicle” in the hose line, CAFS lines don’t freeze into a solid mass since the bubbles are basically 33% air. Certainly freezing can occur, but the frozen product in the line is easily blown out due to it being a honey comb of crystals. Also remember that the air being injected to make the CAFS is compressed which results in it being heated via compression. The oil which the compressed air passes though generally runs around 180+ degrees F. Normal freeze prevention methods should be employed due to the fact that the foam bubbles are in the fire hose ONLY. Most importantly is the protection of the CAFS “Heat Exchanger” system which keeps the compressor oil temp within limits. This closed loop system is supplied with water from the pressure side of the fire pump and can’t be protected with anti-freeze. The only way to manage this water system is to drain it in freezing conditions and / or engage the compressor while sitting on the scene to generate heat and thus circulate the warm water through the heat exchanger circuit. Keep in mind that this water circuit is flowing water whether you are running the compressor or not. There is now way to isolate and drain just that portion of your fire pumping system! You MUST drain the whole pump and heat exchanger, or engage the compressor to heat the water being circulated through the heat exchanger circuit. A heat exchanger is a simple radiator and due to the small volume of water within it, it will be the first item to freeze up in the pump compartment. Even with this additional cold weather concern, the advantages to CAFS far out weigh the needed training and maintenance. An added advantage that most temperate climate natives don’t ever consider is weight. If the Compressed Air Foam has 33% less weight due to air displacement, does not the ice weight that builds up on and in structures weight 33% less?
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FOAM CONCENTRATE HEALTH
Q – Our firefighters use Class A foam. Do you know of any dangers/issues related to firefighter exposure to the foam, e.g. skin contact, inhalation, accidental ingestion? I just want our squad to be ready if we have to treat anyone for unprotected contact. For example, we’ve already had issues with accidental inhalation of dry chem.
A – Generally, Class A foams under normal conditions cause no inhalation issues, but might cause issues if ingested. Class A Foams are very similar to dish soaps and can cause drying of the skin if there is enough skin contact (similar to dish pan hands). Some Class A foams have no reportable contents and some do. The only way to be sure of any foam product is to secure a copy of the SDS and read what it has to say about health issues. Most of the major foam manufacturers have their SDS available on-line.
