Effective Use of On-Board Foam Delivery Systems

A glance at the recent deliveries of many fire apparatus reveals that more and more fire departments are purchasing on-board foam delivery systems. Although it’s great to see departments embracing change and moving forward with their water enhancement, we have to ask if they are making the change with all of the necessary knowledge. When a department purchases an apparatus with an on-board foam delivery system, are they doing adequate research to ensure their delivery system is compatible with their concentrate?

While conducting research for my recent National Fire Academy (NFA) Executive Fire Officer Applied Research Project, it became apparent to me that the majority of departments purchasing on-board foam delivery systems are not taking the time to ensure their delivery system is compatible with their concentrate. This can create a serious safety hazard when the on-board foam delivery system doesn’t work in the manner it’s expected.

System Compatibility
As part of an Executive Fire Officer Applied Research Project, a survey was created to gather data to examine the compatibility of on-board delivery systems with concentrates. In the survey respondents were asked to provide the make and model of their foam system and the brand of foam/wetting agent being utilized. The provided answers clearly showed a lack of knowledge by many agencies utilizing on-board foam systems.

Only 22% of the responding agencies could provide the make and model of their on-board delivery system and the brand of foam/wetting agent being used by their department. One agency reported that they did not know what concentrate they utilized because it ‘arrived from their logistics division unmarked. Another agency reported that they buy what agent is the best price at the time, not a particular brand. Regarding their Class A foam, another department reported that, “it doesn’t matter; major brands are all the same.”

Concentrate Percentage
The research examined the recommended percent concentrate required by the manufacturer and the viscosity of 30 different foam/wetting agent concentrates; it also looked at the manufacturer-recommended minimum and maximum delivery percent and maximum centipoise of 23 concentrate delivery systems.

Centipoise is the measure of the viscosity of a liquid. The centipoise of a liquid is generally dependent on temperature; in regards to simple liquids, the lower the temperature the higher the centipoise, and the higher the centipoise the slower the liquid moves. As a general rule when dealing with on-board delivery systems, the higher the concentrate centipoise, the harder it can be to move the concentrate through the foam delivery system.

The research revealed the manufacturer-recommended concentrate percentages varied greatly from concentrate to concentrate. The recommended delivery percentages of examined concentrates ranged from a low of 0.10% to a high of 6%. The viscosity of the examined concentrates varied from a minimum of 2.2 centipoise to a maximum of 5,700 centipoise.

The delivery systems varied greatly in the percent concentrate and the maximum centipoise of the concentrate they are capable of delivering. The delivery percentages varied so much from system to system that some were not compatible with many of the concentrates examined. The research also revealed there are many on-board foam systems only capable of delivering fixed percentages of concentrate with a wide margin of error for the percentage concentrate they deliver.

The delivery capabilities of the examined systems varied from a maximum of 1,000-1,600 centipoise.Numerous manufacturers’ maximum centipoise couldn’t be located during the research process.

Do the Research
If your department utilizes an on-board foam delivery system, it’s important to take the time to research the compatibility of the delivery system with the concentrate being utilized. This should include taking the time to determine the manufacturer-recommended delivery percentages for all classes of fires approved for the concentrate. In addition to the delivery percentage, you should research the viscosity of the concentrate and the temperatures your agency encounters. The majority of the concentrates examined only reported their concentrate viscosity at 77 degrees F. This temperature can be much warmer than many departments experience for extended periods.

Once the needed delivery percentages and viscosity have been determined, research should be conducted on the delivery system to determine if it can effectively deliver the concentrate. If it is determined the delivery system isn’t compatible with the concentrate, consideration should be given to switching the concentrate to one the system can properly deliver.

When purchasing a new apparatus, a lot of heartache and costly repairs can be avoided by conducting research on the compatability of the concentrate and delivery system being considered. Note: NFPA 1901 provides a section to guide departments in ensuring their concentrate is compatible with their delivery system. Investing time in researching your delivery system and concentrate will be an investment that pays dividends when your enhanced water stream is needed.