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Foam & E-10

For many years, methyl tert-butyl ether (MTBE) was the oxygenate of choice for reformulated gasoline. MTBE was very soluble in gasoline, forming a stable blend with physical properties consistent with conventional gasoline. MTBE was also found to contaminate groundwater. For this reason, it was removed from the nation’s reformulated gasoline pool. It shall be interesting to see if this transformation affects class “B” firefighting Foam tactics. It has been suggested that the “Ether” family responds in much the same way as the “alcohol” family. In so far chemically, the relationship between the interstitial interfaces of Firefighting finished Foam and these two families may remain the same, there have been some interesting characteristics that affected power-boat owners as well as posing concern for motor vehicle owners.

The original school of thought upon the creation of exotic fuels and AR-AFFF Foam was to increase the percentage of draw usage from 3% to 6%. Since then and with much better technological advancements, these Foams are now able to conquer fuel or alcohol fires while both being drawn into the solution at 3%. This of course was calculated and tested at the MTBE additives, as they were (at the time) thought to be the answer to all our problems. One wonders if the change in vaporization from MTBE to alcohol additives will change this equation once again.

MTBE itself had numerous challenges to the Foam Industry, many of which have been corrected by the evolving technology and the release of the new product from National Foam labeled “Universal Gold” created for the 3% setting delivery. MTBE’s low surface tension inhibits AFFF film formation lengthening fast knockdown times. MTBE also had a high vapor pressure as in its pure form, topped out at 4.65 RVP @77 degrees Fahrenheit. The blending grade was further elevated to between 7.8-10.5 RVP. Additionally, MTBE has a long flammable range from 1.6%-8.4%. Another issue was agitation; MTBE had the tendency to emulsify with AR-AFFF foam solutions when agitated. With agitation during a continuing spill/release, post ¼ drain time solution mixtures resulted below the interface of Foam and flammable liquid.  Pre-“Universal Gold” AFFF’s had extreme difficulty with film formation and as a result, never achieved UL listings, even at higher application rates.

Switching to E-10 (alcohol & gasoline blend) brought some unintended consequences, not the least of which was the process called cooling-induced phase separation or (CIPS), and a process by which typically 1 to 3 percent and potentially 8 percent of the fuel can precipitate to the bottom of the tank. Here’s how it works:

Ethanol is soluble in gasoline only if the alcohol is very dry. Unfortunately, the mixture is hygroscopic, meaning, to draw water from the air. In addition, the blend can become unstable when the temperature drops with the change of seasons. During the day, as the temperature rises, ethanol’s vapor pressure increases markedly. In fact, E-10 begins to boil at a mere 95 to 105 degrees Fahrenheit. (MTBE gasoline, by comparison has a far more stable vapor pressure.) These rapid changes in vapor pressure effectively act as a pump, drawing more humid air into the tank every night.

In addition, E-10 is an active absorbent. A half-full tank will become moisture saturated within 30 to 90 days, depending upon the temperature range and humidity. (Unless there is a leak, MTBE can collect water only from condensation, which is usually caught by a fuel/water separator in motor boat engines.) In passenger vehicles, unless the vehicle is only used once every 30-90 days, this issue should be eliminated.

In E-10, the solubility of water decreases with temperature—0.6 percent is soluble at 85 degrees, but only 0.4 percent at 32 degrees—and when the solubility drops due to cooling, a portion of the water drops out of suspension, along with six times its volume in ethanol.

Tips for Storage of Ethanol Fuel in water-craft use

Run only the highest-octane gas for your last tank-ful of the season, burning as much E10 out of the tank as safely possible to negate ethanol's affinity for water absorption.

 If completely emptying the tank is not practical (empty tanks can increase fire risk), then fill the tank with non-E10 gas, leaving 10 percent room for expansion.

Carefully stabilize the remaining fuel (check engine manufacturer for recommended stabilizer) and run the engine long enough so the stabilized fuel can circulate through the entire fuel system.

When commissioning, fill the tank with high-octane fuel. Check fuel- water separators consistently. Have spare separators on board.

There have been multiple issues with long term storage in vessels with various materials used for fuel tanks. Additional corrosion, formulation of “gunk” materials inside the tank which can be drawn into engines causing more “issues” as well as other problems is seen. To prevent motor vehicle issues, it would be advisable to check with your mechanic regarding possible “issues” for your automobile.

As far as hazardous materials incidents are concerned, an increase of the “all-in-one 3%” Foams to the older 6% setting cannot harm, and possibly increase personnel safety, at least until “newer” results become official standards for operations on flammable liquid spills.

Careful review of my other posted articles on Foam hazardous material response demonstrate this issue is worth your response groups consideration.

                                                                Haz Mat Mike

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