Firefighting foam concentrates – the constant evolution: Part 1
In the last decade there have been many advances in foam for firefighting. Since 2001 the multinational 3M ceased to manufacture surfactants and fluorinated AFFF foams due to the ban on PFOS (perfluorooctyl sulfonates), a flurry of development has been carried out by manufacturers of fluorinated derivatives and foams.
The ban of PFOS required by an European and American Regulations, the decreasing of chains length (from 8 to 6 carbon atoms) in the fluorinated materials to reduce precursors of PFOA, the different proposals to limit the PFOA levels or even the regulation on the use of halogenated organic compounds in some countries have made the market of foams for firefighting very dynamic with changes on legislation, development of new products, etc. in the last decade. The fluorine-free foams (Fluorine Free, 3F, FFF) have become very important in recent times, in some cases even as substitutes for AFFF agents, being the subject matter of controversy and discussion in all international forums.
In addition to new formulations and types of foam, new testing standards have been developed and modified seeking test conditions as representative as possible of the real risks. Examples of this are the widely accepted protocol LASTFIRE tests as a requirement of foams in the petroleum industry or changes in the ICAO standard for airports. The European standard EN-1568, has been revised in 2008 and it has introduced new test fuels with respect to 2001 version; a new revision is on approval process and it will be published soon.
New fuels have gained importance in recent times, such as ethanol or gasoline with polar solvents as additives (e.g. the ethanol itself, MTBE, ETBE, etc.) which converts one specific type of hydrocarbon fuel in a complex mixture of hydrocarbons and polar solvents whose behaviour in contact with a foam solution has special features that should be taken into consideration.
The use of CAFS (Compressed Air Foam System) and the use of electronic foam proportioning systems have been a major technological breakthrough in the industry of fire fighting. These systems are more efficient and allow a precise control of dosage, even at very low proportions rates (0.1-1%).
Throughout this article we will briefly review the changes in the foam sector to fight fires in the last decade, especially in the following fields:
- Testing Standards
- Environmental regulations
- Foam Concentrate
- Fire-fighting Systems
1. Testing Standards
Until 2001, when the European Standard EN-1568 unified the criteria for approving and evaluating the foam concentrates, each country used its own standards, what made very difficult to compare the quality of foam concentrates manufactured in different countries.
Since 2001, the reference standard in Europe for testing and qualification of foam is the standard EN-1568, which consists of four parts:
- EN-1568-1: Fire extinguishing media. Foam concentrates. Specification for medium expansion foam concentrates for surface application to water-non miscible liquids.
- EN-1568-2: Fire extinguishing media. Foam concentrates. Specification for high expansion foam concentrates for surface application to water-non miscible liquids.
- EN-1568-3: Fire extinguishing media. Foam concentrates. Specification for low expansion foam concentrates for surface application to water-no miscible liquids.
- EN-1568-4: Fire extinguishing media. Foam concentrates. Specification for low expansion foam concentrates for surface application to water-miscible liquids.
In 2008, a new version replaced the original edition from 2001. The most significant changes between the two versions are:
- Definition of the material for the testing pans (Stainless Steel).
- Clarification of the requirements for a product to be classified as IA according to EN-1568-3, especially in the French version of the standard.
- Introduction of a new fuel on the fire tests of Part 4 (Isopropyl Alcohol).
The standards EN-1568-1: 2008 and EN-1568-2: 2008 do not establish classifications for products, only the fulfilment or not of the standards themselves. However parts 3 and 4 (EN 1568-3: 2008 and EN 1568-4: 2008) establish a classification of products according to their performance on the fire, both in extinguishment and in re ignition. For this reason, it is not enough to establish as requirement the compliance with these standards, but it should be indicated the minimum classification required for each individual part of the standard applicable (3-4).
Below we make a summary of the possible classifications for foams according to these standards:
EN 1568-3: 2008
- Extinction capacity by forceful application to hydrocarbons.
- Extinction capacity by forceful application to hydrocarbons when the application of the foam is interrupted (slow extinction).
- Extinction capacity with hydrocarbons by gentle application.
Once the extinction test has been carried out, it is performed a burn back test to measure the level of protection that the foam is able to provide after extinguishment. There are four classifications (A, B, C and D); A indicates the highest level of resistance and D the lowest.
A product that meets the standard EN-1568-3 can be classified between class IA (maximum) and class IIID (minimum), it can be also classified in the intermediate range of classes between class IA and class IIID.
EN 1568-4: 2008
On polar solvents, tests are performed only with gentle application and the classifications are as follows:
- if extinction time is below 3 minutes.
- if extinction time is longer than 3 minutes.
In this case, it is also carried out a burn back test to determine the resistance of the foam, being the class A for those foams with longer burn back times and the class D for the shortest.
The new version of 2008, in addition to the acetone test, has incorporated a test with isopropyl alcohol (IPA). Some foams with good behaviour on acetone are very poor in other polar solvents such as IPA. For this reason it was decided to keep both fuels in the standard in order to have a more realistic range of behaviours of the foam. It must be pointed out that the rankings may be different for both fuels, e.g. the same foam can be rated as IA with acetone and IIB with IPA.
****Those users who want to have premium quality products, which are capable of dealing with any hazard of liquid fires with guarantees, should demand products rated IA or IB according to EN-1568-3 / 4:2008.
Along 2016 is expected to be published a third version of EN-1568, which will include new classifications, reference to Fluorine Free Foams and some ecotoxicological data.
Until the appearance of standard EN 13565-2 (“Fixed firefighting systems. Foam systems, design, construction and maintenance”) in May 2009, the different classifications according to the test standard EN-1568 had no impact in the design of firefighting systems. EN 13565-2, depending on the classification of the foam according to the standard EN-1568 i.e. depending on the quality of the foam, settles the application rates to be used, “rewarding” those products with a higher performance at lower application rates. It also takes into account what type of system to use (foam cameras, monitors, spears manuals, etc.) in the design of operating conditions.
UL listing based on the standard UL-162 (Foam Equipment and Liquid Concentrates) is a worldwide recognized standard for testing firefighting foam concentrates. The laboratory which manages this certification, follow-ups, etc. is Underwriter Laboratories Inc. (UL).
The main difference with other standard for foams is that UL-162 not only describe a fire testing method for foam concentrate but also a “compatibility” confirmation between all the components that are present in the “chain” from the manufacturing process to the final use of the product; compatibility with drums, proportioning tests, foam quality tests, marking, etc. are subjected to the standard. Additionally, a follow up is required in a quarterly base; samples of concentrates and containers are taken and sent to UL laboratories for verification.
The listing or certification process for UL-162 is more complex than for other standards as EN-1568, ICAO, LASTFIRE, etc. with which only physic-chemical properties and fire tests are analyzed in fixed conditions. UL-162 requires to conduct foam quality tests with commercial equipment (UL listed) in order to verify foam quality previously to fire testing.
For the above, the customers who require UL listed concentrates are not only demanding a fire performance (which is covered by other standards) but also for a product with a performance of the foam when it is used with a specific type of equipment and which is subjected to periodically controls by an external body, assuring homogeneity along the time with not formulation or packing changes out of control.
According to UL-162 there are 3 different applications that a foam concentrate can be listed with:
- Sprinklers and Spray Nozzle (point 9)
- Topside Discharge Devices (point 10)
- Subsurface Injection (point 11)
Each type of application has a different testing method.
The most common and the normal requirement is the Topside Discharge defined as “A method of foam discharge wherein the foam is applied onto the top of burning fuel surface”. This type of discharge includes monitors, hand nozzles, foam chambers, etc.
Full-scale equipment (“field installed components, such as proportioners and foam makers that are intended to extinguish fires”) should be selected for the listing process with the concentrate. Both proportioner and foam maker should be UL listed for the operation conditions that will be used in the tests.
The fire tests have to be conducted with a nozzle which gives approximate same expansion and 25% drainage time of the full-scale equipment (tolerances are detailed in the standard). Depending on the equipment selected, the foam quality generated will have different properties so fire performance can be also difference; non-aspirating monitors, which have an excellent reach, produce pourer foam quality than aspirating hand nozzles; with non-aspirating devices the foam concentrate quality should be high quality to pass the UL-162 tests.
Fire Tests Topside discharge
The UL-162 establishes two different topside application discharge outlets:
- Type III: For portable or fixed devices that delivers foam directly onto the fuel surface causing general agitation (monitor, hose stream nozzles, etc.).
- Type II: Fixed devices that deliver foam in a “gentle” manner (foam chambers, foam makers, etc…)
The hydrocarbons fire tests are conducted using heptane. The discharge type and application rate depends on the type of product (Proteinic, Fluoroproteinic, Synthetic, AFFF, FFFP) according to table 3.
In case of polar solvents, there is a reference fuel for each type of chemical structure (see table 4). Only Type II application can be listed for polar solvents and the application is selected by the manufacturer and should be indicated in the listing certificate. Note that MTBE requires a specific tests to be considered listed with this fuel.
Each foam concentrate only can be delivered with the container which is listed with. It is not allowed to mark with UL logo packing not approved or those that not meets UL-162 requirement for example totes or IBC.
For the oil industry, the greater risk of fire comes from the large hydrocarbon storage tanks, where are stored large tonnages of liquid fuel products. The LASTFIRE test protocol simulates the difficult conditions that occur during a fire in a storage tank, such as the longer time of pre-combustion, metal sheets with great thickness at high temperature, etc. as well as various types of foam application that can be used to extinguish the fire, from the use of aspirated or non-aspirated monitors to the fixed systems. The protocol sets three types of tests:
- Semi-aspirated: Simulates foam application with non-aspirated monitors.
- Aspirated: Simulates foam application with aspirated monitors.
- System: Simulates foam application with foam chambers.
According to this protocol and for each test, the foams obtain different scores depending on fire control time, extinguishing time, vapour suppression and burn back resistance. Then as a result of the obtained score, the products are classified as “Good”, “Acceptable”, “Reduced” and “Poor” Fire Performance. The compliance for the petrochemical industry to LASTFIRE protocol should be acceptable or good rating in all three types of application.
Airports, through the International Civil Aviation Organization (ICAO), has also been active in updating their testing procedures; These changes have been approved in 2013. So far, two levels of foam quality were established: Level A and Level B. Every airport, according to its category and its firefighting equipment must use foam of one of those two levels. Since every time planes seem to get bigger, therefore the risk is also increasing, a new level in the certification for foams has been created, level C, which makes possible to extinguish fires with larger surfaces using the same equipment.
Apart from the introduction of the new level C, the protocol has changed slightly and will not allow the movement of the nozzle throughout the test, which makes extinction more difficult. By contrast, the standard will allow longer time for extinguishment (From 1min to 2 min.)
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