Cathy Longley

How much foam is enough for a High Hazard Flammable Train?

Blog Post created by Cathy Longley Employee on Aug 29, 2017
The Fire Protection Research Foundation (FPRF), the research affiliate of NFPA, has released a report on Foam Application for High Hazard Flammable Train (HHFT) Fires for the first responder community. Trains with a continuous block of tank cars loaded with a flammable liquid are typically defined as HHFT. Incidents are low frequency, high consequence response scenarios but given that the transport of crude oil and ethanol by rail allows for greater geographic flexibility and the ability to pivot with market needs, first responders along rail lines need to understand the dynamics of an HHFT derailment.  
When it comes to HHFT fires, fuels can flow, pool, saturate and burn for days. Situations are complex and can quickly evolve into major conflagrations. Heat can also cause thermal stress to surrounding railcars, resulting in heat-induced tears, pressure relief venting, and other causes of tank car failure. 
This FPRF foam application study looked at HHFT fire event data and fire suppression information; and took into account available literature, first responder and technical response, and post-incident analysis. Foam usage information was collected from 12 different HHFT incidents that involved ethanol, crude oil, petroleum, denatured alcohol, and/or a combination of fuels. During the incidents between 7 and 39 cars derailed, and weather conditions ranged from severe cold weather to extreme heat. The foam concentrate usage ran from 0 to 2,520 gallons; 0 to 2,200,000 gallons of water were used. 
The research shows that applying water to cool the involved tank cars is a vital initial tactic and that first responders should only apply foam after railcars have been properly cooled and after a tactical action plan has been developed. The study also concluded that a first responder’s awareness about HHFTs will affect the overall outcome, duration, and severity of an incident; and that proper knowledge of HHFT derailments and incident training will go a long way in helping firefighters respond to the call. 
Class B firefighting foams are the industry standard for fighting liquid-pool-type fires or hazards. First responders typically refer to an area-based method defined in NFPA 11, the Standard for Low-, Medium-, and High-Expansion Foam to calculate foam application rates and the quantities needed. However, considering the complex, three-dimensional, and potentially high obstructed and limited access nature of these fires, questions exist about the values estimated using NFPA 11 foam calculation with these applications. Specifically, three-dimensional flowing fuel fires are extremely challenging to extinguish using solely Class B foams. The report identifies that the values determined using the “area-based” method need to be verified through comparison with actual incident data and applicable research. The data also illustrated that water usage (for cooling) is equally important as foam usage when mitigating these types of incidents. 
The HHFT research project was conducted as a follow-up to an earlier study on “Enhancing Incident Commander Competencies for Management of Incidents Involving Pipeline and Rail Car Spills of Flammable Liquids” that indicated more information was needed on foam usage. That project showed that foam operations typically fell into two different operational environments: to extinguish fire in the early phases of a flammable liquid spill or to control a fire after the size and intensity of the fire have greatly diminished. Relative to HFFT Incidents, there was a lack of research and findings on the quantity of foam and water used during incidents. Until now.