Guide to Eductor Proportioning with New SFFF Formulations

As the fire service transitions to Synthetic Fluorine Free Foam (SFFF) concentrate, there are several concerns to be addressed. It is well known that the finished foam from these new formulas does not act in the same manner as Aqueous Film Forming Foams (AFFF). Formulation differences also mean that the viscosity of SFFF concentrates varies widely which may create differences in how each concentrate educts.

To address these issues, TFT conducted testing with common SFFF concentrates to determine if the current TFT eductors available were able to proportion each one correctly.

The purpose of this paper is to explain the process we used, reveal our findings, and explain the changes to our foam eductor line of products.

Foam Concentrate Testing Setup

To begin, our engineering team conducted research and spoke with our domestic and international sales teams to find the most popular SFFF concentrates available.

From these recommendations, we acquired ten foam concentrates:

Ansul NFF
BioEx ECOPOL
Fomtec ERS
Fomtec ULTRA ARC
Phos-chek
Solberg Versagard
Universal Green
Avio Green
Dr. Sthamer vaPUREx LV ICAO
Dr. Sthamer vaPUREx AR 3/3

Our testing evaluated foam concentrate proportioning using three different eductor flow rates. We used the following equipment for testing:

125 GPM, 95 GPM, 60 GPM foam eductors
125 GPM, 95 GPM, 60 GPM, 225 LPM (@11 Bar), and 450 LPM (@10 Bar) foam eductors with modifications
Foam concentrate

Flow meters to measure water flow during testing
Scale for weighing foam concentrate

Testing Method

Eductor Proportioning

To complete testing, our team built a testing stand with a scale. This allowed us to weigh the foam concentrate before, during, and after proportioning with an eductor.

Testing was completed in an enclosed test tank where water flow could be carefully controlled. Some factors, like ambient temperature and weather could not be controlled but were documented with the testing data. Tests were also conducted on days within a specific temperature range to ensure test results were not affected by temperature differences. Foam concentrates used during various temperature and weather conditions did not have significantly different results between tests. We do not believe weather or temperature factors influenced the data.

Our goal was to determine the percentage of foam concentrate picked up educted during these tests. To do so, we used calculations based on the weight difference of the concentrate over time paired with our knowledge of the water flow for that time.

This was done by placing the container of concentrate on a fast-reading scale prior to starting the test. Then, the foam concentrate was educted where water flow and change in weight were monitored over time and fed to a single programmable logic controller (PLC). The inlet pressure, back pressure, water flow rate, and concentrate pick up were allowed to stabilize before each test began. At the conclusion of each test, the PLC was programmed to calculate the proportioning rate of the eductor based on flow rate, weight difference, and time.

Results

After testing and evaluating the data, it was shown that all of the tested foam concentrates worked well with our eductors.

Testing revealed that the differences in proportioning were due to the viscosity, or thickness, of the foam concentrate as it moves. The tested concentrates are shear-thinning, meaning they become more liquid as they move. This makes it difficult to predict how different concentrates will behave because they may be the same viscosity when still but become a different viscosity during movement.

This difference caused some foam concentrates to educt slightly richer than th acceptable range according to NFPA standards. It is important to note that most of our tested foams use a 3% setting. We did tests with one concentrate with a setting for 6% and completed adjustments to the eductor in accordance with those results.

Conclusion

The changes in foam concentrate formulation require a response from firefighting equipment manufacturers to ensure their products work well with the new SFFF concentrates. Proper proportioning is key to creating high-quality firefighting foam and one of the first pieces of the foam system that needs to be evaluated.

Starting with eductors, TFT completed thorough testing on ten popular foam concentrates available to the fire service.