Firefighting foam

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Fire foam is the foam used for fire suppression. Its role is to cool the fire and coat the fuel, preventing its contact with oxygen, resulting in burning. Fire foam was invented by Russian engineer and chemist Aleksandr Loran in 1902.

The surfactant used should produce a foam in concentration less than 1%. Other components of fireproof foam are organic solvents (eg, trimethyl-trimethylene glycol and hexylene glycol), foam stabilizers (eg, lauryl alcohol), and corrosion inhibitors.

Video Firefighting foam

Overview

Low expansion foams such as AFFF, have an expansion rate of less than 20 times as low as viscosity, cellular, and can quickly cover large areas.
Medium expansion foam has an expansion ratio of 20-100.
High expansion foams have an expansion ratio of over 200-1000 and are suitable for enclosed spaces such as hangars, where fast charging is required.
The alcohol-resistant foam contains a polymer that forms a protective layer between the burning surface and the foam, preventing foam damage by the alcohol in the burning fuel. The alcohol-resistant foam is used in the fight against oxygenate-containing fuel fires, eg. MTBE, or liquid fire based on or containing polar solvents.

Maps Firefighting foam

Class A foam

Class A foam was developed in the mid-1980s for fighting forest fires. Class A foam lowers the surface tension of the water, which helps in wetting and saturation of Class A fuels with water. It helps fire suppression and can prevent reignition. A favorable experience causes its acceptance against other types of class A fires, including structural fires.

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Class B Foam

Class B foam is designed for class B fires - flammable liquids. The use of Class A foam on class B fire may produce unexpected results, since Class A foams are not designed to contain explosive vapors produced by flammable liquids. Class B foam has two main subtypes.

Synthetic foam

Synthetic foams are based on synthetic surfactants. They provide better flow and spread over the surface of hydrocarbon-based liquids, to speed up the flames. They have limited post-fire security and are toxic ground water contaminants.

The aqueous film-forming foam (AFFF) is water-based and often contains hydrocarbon-based surfactants such as sodium alkyl sulphate, and fluorosurfactants, such as fluorotelomers, perfluorooctanoic acid (PFOA), or perfluorooctanesulfonic acid (PFOS).
An aqueous film-forming foam (AR-AFFF) is an alcohol-resistant foam and may form a protective film.

Protein foams

Foam protein contains natural protein as a foaming agent. Unlike synthetic foams, protein foams can be biologically degraded. They flow and spread more slowly, but provide a foam blanket that is more heat resistant and more durable.

Foam proteins include common protein foams (P), fluoroprotein (FP) foams, film-forming fluoroproteins (FFFP), alcohol-resistant fluoroprotein (AR-FP) foams, and alcohol-forming film fluoroproteins (AR-FFFP).

Foam protein from non-animal sources is preferred, because of the possible threat of biological contaminants such as prions.

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Apps

Each type of foam has its application. High expansion foams are used when enclosed spaces, such as dungeons or hangars, must be quickly filled. Low expansion foam is used to burn spills. AFFF is best for jet fuel spills, FFFP is better for cases where burning fuel can form deeper pools, and AR-AFFF is suitable for burning alcohol. The highest flexibility is achieved by AR-AFFF or AR-FFFP. AR-AFFF should be used in areas where gasoline is mixed with oxygenate, since alcohol prevents the formation of film between FFFP and gasoline foams, breaking foams, making FFFP foams almost useless.

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History of fire fighting foam

Water has long been a universal agent for suppressing fires, but is not the best in all cases. For example, water is usually ineffective in oil fires, and can be dangerous. Foam firefighting is a development to extinguish oil fires.

In 1902, a combustible liquid fire extinguishing method by enveloping them with foam was introduced by Russian engineer and chemist Aleksandr Loran. Loran was a teacher at a school in Baku, the center of the Russian oil industry at the time. Impressed by the huge and difficult to destroy oil fires he had seen there, Loran sought to find a liquid that could handle them effectively. He created the fire-fighting foam, which was successfully tested in experiments in 1902 and 1903. In 1904 Loran patented his invention, and developed the first foam extinguisher in the same year.

The original foam is a mixture of two powders and water produced in a foam generator. It's called chemical foam because of the chemical action to make it. In general, the powder used is sodium bicarbonate and aluminum sulfate, with a small amount of saponin or sweet root added to stabilize the bubbles. Hand foam extinguishers use two of the same chemicals in solution. To move the extinguishers, the seal is damaged and the unit is reversed, allowing the liquid to mix and react. Chemical foam is a stable solution of small bubbles containing carbon dioxide with a lower density than oil or water, and shows perseverance to cover flat surfaces. Because it is lighter than a burning liquid, it flows freely above the liquid surface and extinguishes the fire with a stifling action (oxygen removal/prevention). Chemical foams are considered obsolete today because many powder containers are needed, even for small fires.

In the 1940s, Percy Lavon Julian developed a type of foam called Aerofoam. Using mechanical action, the liquid protein-based concentrate, made from soy protein, is mixed with either proportional water or aeration nozzles to form air bubbles with free flowing action. Expansion ratio and ease of handling make it popular. Foam proteins are easily contaminated by some flammable liquids, so treatments should be used so that the foam is applied only above the burning liquid. The protein foam has a slow knockdown characteristic, but is economical for post-fire safety.

In the early 1950s, high expansion foam was conceived by Herbert Eisner in England in Safety in Mines Research Establishment (now Health & Safety Laboratory) to fight coal fires. Will B. Jamison, a Pennsylvania Mining Engineer, read about the proposed foam in 1952, asking for more information about the idea. He started working with the US Mining Bureau on the idea, testing 400 formulas until a suitable compound was discovered. In 1964 Walter Kidde & amp; The company (now Kidde) buys patents for high expansion foams.

In 1960, National Foam, Inc. developing fluoroprotein foam. The active agent is a fluorinated surfactant which provides oil removal properties to prevent contamination. In general, it's better than protein foam because longer life blankets provide better security when entries are needed for rescue. Fluoroprotein foam has a rapid knockdown characteristic and can also be used in conjunction with dry chemicals that destroy protein foams.

In the mid-1960s, the US Navy developed aqueous film-forming foam (AFFF). This synthetic foam has low viscosity and spreads rapidly on the surface of most hydrocarbon fuels. Water film formed under the foam, which cools the liquid fuel, stops the formation of flammable vapors. It provides dramatic fire fighting, an important factor in fire suppression fire suppression.

In the early 1970s, National Foam, Inc. creating AFFF Resistant Alcohol technology. AR-AFFF is a synthetic foam developed for hydrocarbon and polar-solvent materials. Polar solvents are flammable liquids that destroy conventional firefighting foams. These solvents extract the water contained in the foam, breaking the foam blanket. Therefore, this fuel requires a foam that is resistant to alcohol or polar-solvent. The alcohol-resistant foam should bounce off the surface and be allowed to flow down and over the liquid to form its membrane, compared to standard AFFFs that can be sprayed directly onto the flame.

In 1993, Baums Castorine of Rome, New York, developed a wetting agent with superior effective cooling properties in Class A, Class B, Class D as well as three-dimensional and pressurized fires involving carbon-based hydro fuel and polar solvents such as alcohols and ethanol. This wetting agent, UL is classified as a fire-fighting foam, first marketed under the name Pyrocool. The patented formula was awarded the 1998 Green Chemistry Award as a bio-degradable alternative to AFFF and AR-AFFF and other foams and wetting. Now marketed under the name Novacool UEF (Universal Extinguishing Foam). Novacool UEF is applied to 0.4% for Class A fires and 0.5% for Class B and Class D fires. Novacool UEF can be biologically degraded.

In 2010, Orchidee International of France developed the first FFHPF, the highest performance fluorine-free foam. Foam has achieved a 97% degradability rating and is currently marketed by Orchidee International under the brand name "BluFoam". The foam is used in 3% both in hydrocarbon fires and polar solvents.

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Environmental and health issues

Studies have shown that PFOS is a persistent, bioaccumulative, and toxic pollutant. It was added to Annex B of the Stockholm Convention on Persistent Organic Pollutants in May 2009. Rules in the United States, Canada, the European Union, Australia and Japan have banned the production of new PFOS-based products, including fire-fighting foams. 3M gradually released PFOS production in 2002 due to toxicity problems.

One study, published in 2015, found that firefighters were more likely to have fluorinated surfactants in their bloodstream. By 2016, the United States Air Force pays $ 4.3 million for water treatment systems for residents downstream of Peterson Air Force Base in Colorado.

In the United States, the release of AFFF to surface water is regulated by the US Environmental Protection Agency (EPA) and the Department of Defense, in accordance with the Clean Water Act.

In Australia, in 2015 public safety announcements are issued by the New South Wales Environmental Protection Authority after contamination of water sources near Williamstown RAAF Base. Surface water, groundwater and fish are reported to contain chemicals from foam fires that have been released by Australia's Australian Air Force Base before the change of training protocols in 2008. The residents of the area are advised not to consume drill water, in eggs and seafood from the fauna exposure to contaminated water. This discovery led to the prohibition of all forms of fishing in the waters of Fullerton Cove until early October 2016.

In 2017 the Department of Defense dealt with two class action lawsuits brought by those affected by contamination in Williamtown and at the Oakey Army Aviation Center. Along with many airports and fire services, the Department of Defense is investigating possible contamination at 18 military sites across Australia. In Williamtown, it also conducts studies on uptake and residual contamination in plants, chickens and eggs.

In December 2017, the New Zealand Ministry of the Environment announced that higher than acceptable levels of PFOS and PFOA were found in groundwater at two New Zealand Royal Air Force bases, allegedly derived from the ancient use of firefighting foam containing the substance. Residents living near the air base are advised to drink bottled water until wider testing is possible.

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References

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Firefighting foam

Minggu, 17 Juni 2018