Low-expansion foam

expansion ratio <20

Characteristics
Low-expansion foam consisting of small bubbles with a relatively high weight and small volume. It has good flowability, is resistant to flames and thermal radiation, is gastight and prevents burn-back. Depending on the foam concentrate and induction rate, low-expansion foam has good adhesive properties to vertical objects. The extinguishing performance relies mainly on the separation and cooling effect. In addition, the separation effect of AFFF/-AR and FFFP/-AR is increased by the formation of an aqueous or polymer film.

Low-expansion foam is generated in low-expansion foam branch pipes, foam monitors or in fixed/mobile foam installations. Optionally fitted sieves, meshes, or baffles, e.g. goose necks, have the effect of expanding the foam solution even more effectively with the inducted air, creating a more rigid foam consisting of finer bubbles.

Application
Low-expansion foam is used for extinguishing both liquid and solid fires, due to its exceptionally good flowability. The foam rapidly spreads over the entire fire surface, creating a gastight seal. Its adhesive properties are particularly advantageous when fighting solid fuel fires. Special foam-generating methods, e.g.
CAFS, encourage this effect. If used as a preventative measure, low-expansion foam suppresses emission of flammable gas. Flammable materials remain covered by a gastight, insulating and cooling foam blanket for a longer period of time. As a result of its relatively high weight, a long projection range is achievable with low-expansion foam, allowing for firefighting operations from a safe distance.

Aqueous film-forming foam concentrates, e.g. STHAMEX®-AFFF, MOUSSOL®-APS, FOAMOUSSE®-FFFP, may be used as both expanded foam, or non-aspirated aqueous solution, e.g. at airports, fuel depots, in plastic and recycling industries, aboard ships, as well as in on- and off-shore sectors. These foam concentrates are also suitable for use with sprinkler and deluge systems. The foam’s relatively short water drainage time enhances
aqueous film formation and thereby improves flowability. Then foam solution’s low surface tension increases the wetting effect, when extinguishing solid material fires.