Handle ethanol with care
Published: 11 June, 2009
With an increasing demand for E5 petrol and B5 diesel it is important to be aware of the differences when it comes to an emergency. The Energy Institute’s Guidance for the storage and handling of fuel grade ethanol at petroleum distribution installations contains a highly useful firefighting section – IFJ reproduces some of the highlights here.
Ethanol is soluble in water and can therefore be extinguished by dilution. However, laboratory tests have shown that dilution of more than 500% is required to achieve extinguishment.
The flashpoint of ethanol/water solutions increases with increasing water concentration as shown in Table 4, but is still within the EI’s definition of a Class I product, even when water content is increased to 70%, and a Class II product at up to 90% water content.
Thus, it is generally impracticable to rely on dilution of ethanol as the extinguishing strategy apart from minor shallow spills. However, it is also recognised that in some cases addition of relatively small quantities of water to ethanol/gasoline blends can bring about phase separation which precipitates the alcohol and water to the bottom, leaving the gasoline intact and thus permitting extinguishment as a conventional gasoline fire with conventional foams.
Again, the approach would only be applicable in situations where the alcohol content was low and the overall fuel quantity small.
Alcohols and other water miscible fuels require special foam for effective extinguishment. Multi-purpose foams are types that can extinguish fires in both hydrocarbon and water miscible fuels.
They are often referred to as “alcohol resistant” foams because alcohols are the most common water miscible fuels.
Multi-purpose foams are available in both protein and synthetic generic types and some fluorine-free foams have also been shown to be suitable for water soluble fuels using relatively gentle application techniques.
Work in the 1970s and 1980s using the US Federal Fire Test Specification OF 555C as the basis for testing, showed that some good quality standard foams could be used under certain application conditions with gasoline having ethanol content up to 10% (E10).
A report to this effect was published by the API in 1985 – Evaluation of fire fighting foams as fire protection for alcohol-containing fuels. More recent work using a different fire test (UL 162 Standard for safety foam equipment and liquid concentrates) has clearly shown the importance of foam quality and application technique. A poor quality standard foam or poor or inappropriate application technique will not give effective extinguishments. Although a good quality standard foam can be used on E5 and E10 a more efficient foam attack will be achieved with a multi-purpose foam. For ethanol content greater than 10%, a multi-purpose foam must be used. If a standard foam concentrate is to be used for ethanol blends then the user should seek confirmation through validated test data which establish application rates that the foam is suitable for the blend using the application method used on site.
With any foam on any fuel, greater effectiveness and efficiency are obtained with “gentle” application of the foam rather than forceful application which tends to pick up fuel and cause foam destruction. In most real situations, totally gentle application is not possible.
Some multi-purpose foams are used at different concentrations for hydrocarbons and for water soluble fuels. For example, a particular foam may be used at 3% concentration on hydrocarbons but 6% on ethanol, and different application rates of foam solution might apply.
Overall, with the introduction of ethanol or gasoline/ethanol blends especially those greater than 10% ethanol, there may be a need to change the foam concentrate used on site, alter its percentage pick-up rate and increase application rate (and hence additional concentrate will be required to maintain system run times and alternative nozzles and/or foam piping may be required).
Ultimately, the only way to check the necessity of this is through the foam concentrate manufacturer by seeking independently verified test data. It should be noted that with the increase in storage and use of ethanol, foam manufacturers are putting increasing efforts into testing and development of foam concentrates so the latest information should always be sought on application rates and acceptable application methods. Application rates of foam solution are normally significantly higher than those for hydrocarbons, but this depends very much on the foam concentrate. It is always advisable to seek independently validated test data to establish what application rate is applicable for any particular foam concentrate.
It has already been noted that foam monitors are generally not an efficient means of extinguishing deep fuel fires involving ethanol due to the forceful application technique although increased application rates can be successful in some cases. Subsurface applications should not be used with any currently available foams. Semi-subsurface application (see EI Model Code of Practice Part 19) can be used but the associated maintenance and testing issues mean that it is not a preferred method. The most appropriate system is a fixed-foam pourer system designed and installed in accordance with a recognised standard such as EN 13565-2 Fixed firefighting systems – foam systems or NFPA 11 Standard for low-, medium-, and high-expansion foam. The foam pourer should be a type that directs the foam against the tank wall so it runs down the inside of the tank shell and is consequently applied as gently as possible.
