John Ottesen, Founder and CEO of Fomtec, explains why advising on real world design and applications means gathering data from testing beyond the “standards”
I have memories of sitting through many presentations and training programmes when the Senior R & D Chemist would pronounce to the audience that “the role of the R & D Chemist is to develop foam concentrates to pass a test”.
Perhaps this seems like a strange thing because surely the foam concentrate is being developed to be an effective firefighting agent? Of course, the two are not mutually exclusive because the role of the test is to determine if a particular foam concentrate is an effective firefighting agent, or perhaps more correctly how effective.
Bottom line the function of any test is to provide a measure of the performance of the foam concentrate.
As fire performance testing needs to be repeatable, cost-effective and controllable the biggest question with any test protocol is the scalability from the test protocol to the real world e.g. does a 4.5 m2 test pan accurately reflect a full surface fire on a 120 m storage tank.
In an ideal world, we would test each mission or application under real-world conditions but this is just not realistic so in setting up a test procedure we need to take into account scalability and the ability to make any test repeatable, cost effective and representative of the mission or application.
Test procedures are usually devised by standards committees or stakeholders in a particular industry and (perhaps) correctly due to the difference in missions or applications a number of different test procedure exist.
Common test procedures relating to Class B foams include UL 162, FM 5130, EN 1568, which are geographic in nature, and ICAO, IMO 1312, LASTFIRE and US MIL SPEC which are more application specific.
For the end user the difference in the procedures between these test standards may leave them wondering why the folks writing these test standards don’t appear to talk to each other and agree on some of the variables.
Safety margins
The test fires are relatively small and are typically performed with application densities that are set at a level above the critical application density, but below what design standards define as design densities.
The difference between test density and design density is our safety margin.
The question is what variables are these safety margins supposed to cover?
Variables that we need to consider include: different fuels; ambient conditions; water quality; aging of the foam concentrate; type of discharge device; physical differences between the test pan and the real-world fire; difference between foam qualities achieved in test and those in real world; compatibility with dry chemicals and other agents; and operator technique.
Safety Margins for PFAS-containing foam concentrates are backed by 50+ years of experience and data and design standards such as NFPA 11 or EN 13565-2 incorporate these safety margins within their application design.
As we transition to SFFF’s we are seeing different approaches to performance testing from the various testing authorities such as UL, FM, ICAO, EN as well as a completely new US Mil Spec for fluorine free foam.
As stated the test standards must have repeatability as well as relevance to the mission that the foam will be used in and it is this mission specific element that requires that we move outside the standard testing to find the limits of performance, and have data to support recommendations.
The first variable – the fuel(s)
From when we first started using foam, we had to address the issue of water miscible and water immiscible fuels which lead to foams suitable for hydrocarbon fuels and what became known as “alcohol resistant” foams which could be used on both water immiscible and water miscible fuels.
This remains the case with SFFF’s although typical formulations from most manufacturers are alcohol resistant type.
Beyond the type of foam, we have used reference fuels to represent groups of chemicals i.e.
Heptane for “hydrocarbons”, Acetone for “ketones” and IPA for “alcohols”.
In the latest version of FM 5130 for SFFF, FM has introduced approvals for hydrocarbons based on the flash point and vapour pressure relative to heptane, and also for fuel blends – such as gasoline.
Fomtec totally supports this approach and to date has tested with Jet A-1, Hexane, Hexane blends, Plant based hydrocarbons, and different gasoline blends.
With the water miscible fuels the situation is even more complicated because of the sheer number of different chemicals.
Again it is totally impractical to test every chemical because of the numbers but also because of life safety issues with some chemicals.
Fomtec experienced difficulties early on when we looked at performance with MEK and Ethyl Acetate as both these chemicals are what we at Fomtec describe as “foam destroyers”.
Fomtec approach to water miscible fuels
MEK was the catalyst for Fomtec to initiate another data driven project.
Over a two-year period Fomtec tested more than 200 chemicals in a laboratory environment where the comparison data relative to physiochemical characteristics has allowed Fomtec to develop an analytical modelling tool that looks at gel creation and foam destruction.
This data was then compared to the data available for fire test results to verify the correlation to fire performance.
The tool now allows Fomtec to review a client’s fuels and predict the performance of the Enviro foams without having to fire test.
We have proven a high reliability with the tool but still some fuels fall outside the prediction range and we then still need to resort to the lab scale testing that was used to develop the tool.
The Holistic Approach – How it applies in testing?
Foam Qualities (FQ) of Expansion Ratio and 25% drain time have always had an impact on the fire performance of a firefighting foam, and now that with an SFFF we are totally reliant on the foam blanket to suppress and extinguish knowledge of the range of foam qualities that will achieve the mission is critical data.
The issue with single point data as achieved with the EN 1568-3 and -4 testing is that we have fire performance data for one test nozzle, at a set pressure and flow rate generating one expansion ratio and 25% drain time point.
Even with the proposed update of this test standard the current draft/discussion documents only address Expansion Ratio variation which we feel is a missed opportunity.
Fomtec believes that the approach from UL and FM for topside type II and type III testing is more appropriate as the foam qualities used for testing are required to match those achieved with real world discharge devices.
Many have observed and commented on the different test densities applied with SFFF’s compared to AFFF’s, but it should be noted that application density and application duration with SFFF’s is the same as non film forming fluorinated foams such as FP.
UL has also made a further change with SFFF’s and that now listing with type II devices such as foam chambers and foam makers MUST be carried out as a separate test to the type III direct application test used for hose and monitor nozzles.
Foam that is fire tested with various foam qualities captured from real world discharge devices during testing at minimum and maximum flows and inlet pressures, take this critical variable out of the equation and turn it in to a KNOWN VARIABLE that the safety margin does not need to account for.
Similarly, the safety margins applied by some design standards cannot compensate for a complete lack of data related to foam qualities and non aspirating discharge devices.
Beyond “Standard” testing
Whilst many of the variables that impact the performance and safety margins can be tested within the standard fire performance tests by using different fuels, water, foam qualities, discharge devices (foam-water sprinklers) correlation to mission specific requirements and always evaluating the correlation between the standard tests to much larger real world are important data necessary for the transition away from PFAS containing foams.
Fomtec believes as an industry we all have a responsibility to test to obtain the data and at Fomtec we are increasing the resource of time and money that we allocate to such testing.
Over the last 12 months this testing has included:
- Testing our Enviro USP with standard sprinklers at approximately 14m height on Jet Fuels to verify application density as ALL hangers are higher than the approximate 4.5m test height under UL.
- Setting up a 12 head test grid and pan in association with GESIP and LASTFIRE to test aspirated heads in a loading rack fire with 3,000 litres of gasoline and application density of 0.16 gpm/ft2 (6.5 lpm/m2).
- Participation with LASTFIRE to test Enviro USP for large fires with handlines and a simulated full surface tank fire with an over-the-top type III application method on gasoline.
- Testing Enviro foams on the 13m diameter test pan at IRIS in Beaumont, Texas at both 0.08 gpm/ft2 and then at NFPA 11 minimum recommended application rate of 0.16 gpm/ft2
Data not opinions
It’s a mantra for us at Fomtec but we have a continuing responsibility to the industry to provide accurate information and this requires data from meaningful test programmes.
The Enviro Programme hit 3,000 fire tests a few weeks ago and we will continue to commit the resources to add data going forward so that we verify that the Safety Margins remain valid and achievable in the real world.
