As foam concentrate technology marches forward toward more environmentally friendly products, more and more discussions are taking place involving what to expect from an equipment and foam perspective related to changing over to new foams. While there are changes coming to improve our environmental responsibility, manufacturers are working hard to ensure that the best products are put in the hands of industry emergency response personnel worldwide. When we say “best products,” we mean systems that include both the foam concentrate AND the equipment components to mix the foam with the water and then add the air and agitation necessary to generate foam qualities suitable for extinguishment.
Because foams are changing, we naturally expect metering settings and proportioner orifices to change. This is because of viscosity differences in the foams. This is an expected requirement when changing any system to a new foam type—C8 to C6 to fluorine-free foam (FFF). Along with the metering adjustments, there are cleaning and flushing requirements necessary to ensure piping, tanks, and systems are made ready for a new foam. Depending on the foam you choose, minor additional changes associated with materials compatibility and nozzle types may be necessary.
Not to worry: Major equipment replacements or modifications are not necessary. Don’t panic!
The following information will hopefully be helpful in preparing your truck and equipment for your new environmentally friendly foam concentrate of choice.
Foam Concentrate Mixing Compatibility
The category of foam concentrate mixing compatibility spans all types of foams—C8, C6, and fluorine-free versions. The rule of thumb is: If it’s a different foam concentrate type or manufacturer, do not mix in storage containers, tanks, or piping. It may, and likely will, cause immediate changes in viscosity and fluid structure. If you are consuming foam concentrate while discharging foam solution, switching from one foam type or manufacturer to another through a proportioning system, eductor, pump, or nozzle is not a problem. It is recommended that the system be flushed with water for a short time after foam solution pumping. This will ensure that the piping is free of any mixture or old foam before filling the foam system with the fresh concentrate. Foam solutions and expanded foams of different types will work together and not degrade one another so long as they are being used properly and on the fire they were intended for.
Mixing compatibility concerning C8, C6, and new FFFs is largely unchanged. As usual, different foam concentrates are not recommended to be mixed because of chemical reactions that can be triggered, resulting in loss of firefighting effectiveness, thickening, or separation in the foam. This is true for mixing different manufacturers’ foams as well as mixing foams of different types from the same manufacturer.
There is usually no problem adding new foam of the same brand and product name to existing foam in your tank. The user should call the foam concentrate manufacturer with the product name and lot number to make sure he can top off his foam concentrate holding tank without damaging the existing foam concentrate before adding anything to his tank that is not exactly the same as the original. When in doubt, call the manufacturer.
Further, there are new C6 versions of many longstanding C8 foams on the market today. Not all of the newer C6 versions are compatible with their C8 parents. To avoid problems, contact your foam manufacturer for guidance prior to mixing C6 foams into older C8 foams.
To improve your environmental position or to comply with local code requirements, the best practice is to remove or use the C8 foam, completely flush and wash all components in accordance with the manufacturers recommendation, and then refill with either C6 formulation or FFF.
Take care so that during foam solution discharge the user understands that typical aqueous film forming foams (AFFFs), for hydrocarbon fuels, may have limited effectiveness for polar solvent fuels—perhaps for immediate use, but the foam blanket on the fuel may be unstable and not safe.
Equipment: Nozzles, Eductors, Components, and Proportioning Systems in General
When considering foam system performance impacts (proportioning), the general considerations are: Foam concentrates of different types and brands all typically have different viscosities or thicknesses. This affects the way orifices in proportioners, eductors, metering valves, or other devices are able to control the amount of foam concentrate that is metered into the water lines of a system.
For this reason, metering valves and orifices designed for use with different foam concentrates will likely require adjustment, orifice modification, or possible replacement. The hardware itself will be fine and will likely not require replacement.
In the case of fire truck proportioning systems that use metering valves, the metering valves will need to be recalibrated. In the case of flow-based systems, all flow meters measuring foam concentrate flow will need to be recalibrated and tested for accurate operation with the new concentrate. All external eductors that are used on trucks or tote trailers such as line proportioners, eductors, and pick-up nozzles, will need to have their orifices changed to suit the new foam.
Equipment manufacturers will be able to tell you how to adjust or what to change based on your system components.
Lastly, but just as important, look for agency listings as proof of performance for proportioners and components with the specific foam concentrates you intend to employ.
Strainer screens are always asked about when changing foams. In our opinion, when moving from C8 foams to C6 or FFF concentrate, you should not have to change your strainer screens unless the manufacturer of the foam recommends a specific mesh size that is different than your current screen or if you are moving to a foam concentrate that is drastically different in viscosity.
Foam nozzles have not been found to need changes either. Aside from adjusting or changing restricting orifices in self-educting nozzles, you should not need to change nozzles when changing from C8 to C6 foams. In short, unless you are going to fluorine-free, you should not need to change nozzles. If you are switching to a fluorine-free concentrate, don’t worry! There are many aspirated foam nozzles, both handheld and on fixed monitors, available on the market today. Consult your foam concentrate manufacture for guidance on the best nozzle to use.
Be assured that you may need to change some orifices or metering valve settings or nameplates to bring your system into spec, but that should be all. Expect to conduct a complete proportioning test to confirm that all flow meters and settings are doing their jobs as expected when switching to a different foam concentrate. Simply put, if you don’t calibrate your foam system, it may use too much or too little foam concentrate, causing you to fight fires with uncertain effectivity and to not be as efficient with your foam concentrate consumption.
No change or adjustment is required for foam pumps.
Differences Between Using the Old Foams and New Foams
When changing from C8 to C6 foam concentrates, there is no difference in basic application rates according to the National Fire Protection Association. Some C6 versions have maintained a full complement of UL listings as C8 versions. It is important for you to consult your manufacturer and check agency Web sites for listings when in doubt.
When changing to the new FFFs, because of their newness on the market, there are generally limited listings, especially in the polar solvent fuel categories. The number of listings will increase as time progresses and manufacturers continue development.
FFFs may have higher application rates on polar solvents than C8/C6 alcohol-resistant foam concentrates, mainly because of the lack of the fluorinated ingredient. Further, some FFF concentrates are listed for fresh water use only. Make sure to check product listings and labels to avoid this pitfall. Seawater can render incompatible foams ineffective when fighting fire, thus putting personnel and property at risk. Since FFFs do not contain fluorosurfactants, firefighting using nonplunging techniques using aspirated foam nozzles is recommended.
The Fire Apparatus Manufacturers’ Association (FAMA) is committed to the manufacture and sale of safe, efficient emergency response vehicles and equipment. FAMA urges fire departments to evaluate the full range of safety features offered by its member companies.
National Foam contributed information and data for this article.