High Expansion Foam System Descritption

A detailed analysis of cases of fires in recent years shows that not always the traditional fire-fighting systems, which mainly use water or low or medium expansion foam ensure the effectiveness of any intervention.
The main cause of this failure is due to the inability for that solution to reach quickly the fire source, in some cases, the presence of explosive dust or chemical gas during combustion makes the standard protection systems not valid.

High-expansion foam systems operate in a combined action on fire, creating a layer of foam that carries water at the point where the heat is developed and the congestion in the area of risk smothers the fire, removing toxic vapors and particles developed during combustion.

Compared to other fire suppression, high-expansion foam systems limit the damage machinery or products stored in the risk area significantly. By definition, high-expansion foam is the one that generated the expansion ratio exceeds 200 to 1. Normally, the values obtained by SABO Española generating foam system produce an expansion ratio higher than 600 to 1, therefore the amount of water contained in the bubble is extremely small. The small amount of water limits the cooling effect on solid surfaces, which are the main cause of early destruction of the foam. To remedy this inappropriateness the design legislation provide that the foam discharge add the replacement of the destroyed part of the foam layer (up to 4)

The high-expansion foam is particularly suitable for extinguishing fires of solid fuels as well as paper or wood fires. A depth fire can be suppressed over a long period and the foam wet action penetrates deeper than the normal action of the water. The foam in a fire, creates a protective barrier for exposed materials and the structure is not directly involved in the fire.

High-expansion foam systems are recommended to be used when we have to protect indoor places where may contain the volume of foam generated by the system. It is not recommended to use this kind of protection in open places because the presence of wind may move easily and the slightly foam expanded away from the protection zone.

A special attention to the sizing of the installation allows the protection of LPG gas installations. For this particular application the American NFPA 11 Standards and European Standard EN 13565-2 provide all necessary information. In this particular situation, the high-expansion foam is not used to extinct a fire but is used to reduce the intensity of fire to block the reaction of radiation and to eliminate toxic and flammable vapors.

Another limiting case considers the use of high-expansion foam for the content of inert gas inside the tanks during the welding process.

Operation Description

The solution consists of high-expansion foam and water mixed in proper proportion by fixed or portable proportioners. The foam solution is driven by the pumping system to the foam generators.

SABO Española generators are static, this means that they do not require any external power source (for example, electricity or other energy for its operation. They consist in a carbon steel or stainless steal body, depending on the model and the costumer requests. The injector uses the line pressure to vaporize the foam solution. During the process is created a venturi effect that sucks the circumferential air directing, with the liquid, into the generator body where the two elements are mixed through the perforated mesh creating bubbles of foam. The foam created has a lightweight appearance, with stable and large bubbles.

High expansion foam systems do not include “pelton” turbine easily to obstruct due to the lime of water and which need a major maintenance.

The volume of foam produced varies depending on the model used, with values ranging from 51 m3 / min for the smallest model of the generator SE-GAE-100 to 336 m3 / min for the SE-GAE-400. This large mass of high-expansion foam fills quickly large areas and effectively smothering the fire.

Applications

SABO Española high expansion foam generator is useful to extinguish Class A amd Class B fires, solid and liquid fuels, in enclosures where foam can be contained.

Common application
• Logistics warehouse
• Tire storage
• Warehouses in general
• Cinemas
• Aircraft hangers
• Engines chambers
• Generators with gas turbines
• Garbage dump
• Excavations
• Cables tunnel
• Transforms room
• Boats on cars deposit
• Storage of hazardous materials
• Coal dust abatement
• Storage of flammable liquid drums • Engine test chambers
• Download zone

Advantages

The amount of water required to extinguish a fire is minimal, this feature is very important in those facilities where the provision of water is limited or where the elimination of fire fighting water is a problem.

The main difference between this and other foam system is in this case that the most important value to consider is the volume of foam generated.

The high-expansion foam cause minimal damage to structures and their contents.

Due to the high value of expansion ratio, a small amount of water is needed to produce a large amount of expanded foam.

High-expansion foam contains very little water in its interior and it may be used in many applications with voltage presence.

When it is produced in an appropriate volume, you can cut the flow of air which is necessary to continue burning.

When it is to contact with the fire / temperature, the water contained in the foam it is converted in vapour reducing the concentration of oxygen below the necessary level to sustain the combustion. During this process a demolition of the temperature is also gotten below the point of combustion or the temperature of auto injection for liquid of Class A and Class B.

The redoubt superficial tension of the foam solution, which drains from the expanded foam, penetrates in the materials of Class A extinguishing braziers in depth.

The insulating properties and thermo reflecting of the foam mantle, creates a shield of protection to the material not involved in the combustion.

The high expansion foam generators of Sabo Española, are of easy installation, their lower weight and their particular geometry allow the assemblage of it both in vertical (plate perforated revolt downward) that in horizontal.

Requeriments of installation

The expansion of the high-expansion foam generator depends on many factors such as the feed pressure, the type of foam used and the quality of air used to generate the foam.

Sabo Española, recommend that the generator works in a pressure range of 4 to 6 bar, however, because it is a static type of equipment, the range of operation may be larger, but it should be noted that there won’t be good results. Our experience leads us to recommend the use of clean air from the outside or the use of specific foam type “Hot Foam”. This is because the air in this space could contain dust or chemical products which could affect the quality of the bubbles or in the case of a delayed detection of the fire, the temperature within the room may be very high increasing the bubbles evaporation.

Air feed

It is recommended to feed generators with clean air from outside, unless you can prove that the air inside the room to be protected can be used, obviously considering the gas produced by burning any material stored.
It is suggested to consult the foam supplier to know the characteristics of the product, if it is used in presence of smoke.
As a support to the discharge calculations, the designer can support theoretical data with a functional test in presence of fire in real conditions of use (temperature, stored materials, etc…).
The test should be done according to NFPA 11.

The most important results should be flow rate, expansion ratio, drainage time and the saturation time.
The designer may consider a greater destruction of the foam increasing, if it is necessary, the discharge in the installation to compensate a lower expansion ratio obtained.

Air recirculation

We recommend the presence of vents in order to expel any gas eventually produced by combustion, helping to maintain the temperature not too high.

Accessibility for inspection operations and maintenance

The high-expansion generators should be arranged that the inspections, checks and other maintenance activities can be easily done, minimizing the time that the plant should be out of service.

Pipes

The pipes should be in constant contact with the concentrate foam and should be constructed with corrosion resistant materials and compatible with the foam used. The galvanized is not compatible with some types of foam; also consider the galvanic corrosion effect.
A filter with maximum passage of durst inferior to 4 mm must be considered to avoid possible incrustation and stoppages of the discharge nozzles, and to discretion of the technician to consider the presence of a single filter in the line of distribution or the presence of more unitary, each devoted to a single generator. The filter must be checked and cleaned after every use or test.
If considered necessary, in case of installation in places with dusts suspended in air (boxes of painting etc.) the use of nylon bonnets can be considered in protection of the nozzles, these bonnets are to put on and to fix through in very provisional way through elastic, allowing in case of operation the expulsion of the protection by the same pressure of feeding.
Attention: precaution to be considered only in extreme cases, since the possible conk out of the protection and therefore not expulsion puts out of use in partial or total way the generator of foam.

The high expansion foam systems must be projected and installed in accordance to the actual norms and in particular way in accord to the American norm NFPA 11 or to the EN-13565-2.

When the generators are fitted on in fixed position, it must be operated with maximum care not to damage the geometry of the generator, using for the support all the necessary precautions.

Maintenance

The NFPA rules request for an annual maintenance for the high expansion system, while the Italian norms reduce this time to 6 months.
The test must be performed from specialized personal, the test must underline every found defect both of planning and of installation and must restore the conditions of applications operation, at least up to the following inspection.

The technical operator can pretend a test of discharge if considered necessary and must compile in presence of the client a report of inspection bringing all the found defects.

Types of foam concentrate

Normally in the high expansion systems shall be used synthetic foam type to realize high expansion ratios and an elevated quality of the foam.

All types of foam used, it has to satisfy the applications of the norm EN 1568-2.
If it is thought to use the air inside of the space that must be protect, it is suggested to use of specific foam type normally called “Hot Foam” type.

Disposition of the generators.
The high expansion foam generators must be installed keeping in mind of the dimensions and the characteristics of the zone to protect. The foam “falls” from the body of the generator and it is distributed uniformly flowing from all the sides. A suitable distance between a generator and the other one will assure the total coverage of the volume to protect. If necessary the foam can be distributed through of the canalizations to realize the desired distribution.

Personal safety

The high expansion foam is not harmful for the personal safety.
Even if it is possible to breathe when you are submerged by the high expansion foam produced with fresh air (not the air full of smokes and due toxic substances to the spillage of vapours of combustion), we dissuaded to remain inside the place during the operation of the high expansion foam system. The enormous volume of foam produced can bring some states of anxiety and disorientation slowing down the evacuation of the personnel. We recommend therefore signalling in advance the starts of the fireproof plant giving the possibility to the whole personnel to evacuate the zone at the right moment. All the electric apparatuses must be shut off unless is not held necessary from an evaluation performed by a competent organ.

Where possible, the location of the points of unloading of the foam they must have prepared considering the exits present in the place and facilitating the more possible the evacuation of the same.
To enter a place full of high expansion foam, different systems can be used for demolishing the foam, creating herself a passage through of it. The simplest system asks for the use of a dust extinguisher. The weight of the dust will effectively demolish the mantle of foam. In alternative you can be used some throws of water exploiting the fire nozzles. The systems above described must be uses only in case of emergency, preferring the personal safety and not the protection of the place, for this the Sabo Española warmly dissuades the entry the place. If instead the re-entry were essential, it recommends him to use some independent systems of personal respiration.

Availability and service

The Sabo Española high expansion foam system is available through a network of domestic and international distributors.
(To find a distributor near you contact Sabo Española Corporation).

Guarantees

For details of warranty, refer to Sabo Española’s current list price schedule or contact Sabo Española directly.