HIGH EXPANSION FOAM

MARINESHELF publishes articles contributed by seafarers and other marine related sites solely for the benefit of seafarers .All copyright materials are owned by its respective authors or publishers.

Expansion Ratio maximum of 1000 to 1

        

This is the maximum expansion ratio allowable under SOLAS. It compares with ratios of 12:1 for traditional low expansion foams and 20:1 for AFFF.

High Expansion foams are produced from synthetic detergents such as Ammonium Lauryl Esther Sulphate. Air is blown through a net fabric which is wetted by water which has picked up foam compound by entrainment.

Foam production may be adversely affected by smoke in the air steam. Some manufacturers say their products are not affected.

The foam is persistent, insulates well and absorbs radiant heat. Some of the foam expands to steam at the fire, with an expansion ratio of 1700 to 1, which gives an oxygen content of below 8% by volume and so smothers the fire. The latent heat required is removed from the fire, producing a cooling effect.

The foam generating equipment must be readily accessible and separate from the protected space.

The rate of application must ensure the foam level in the engine room rises at least 1 metre per minute.

The quantity of foam forming liquid must be able to supply five times the volume of the protected space.

          Foam generating equipment and controls must be outside the protected space, readily accessible and simple to operate. Ducting material must be at least 5mm thick. Ducts must be fitted with automatically operated dampers installed in the openings of the boundary bulkheads
  In the ‘HotFoam’ system the foam generator has no fan/blower. The air is drawn in with a jet of the foam/water solution in a similar manner to a standard mixer nozzle.

The foam produced uses the air and combustion gases within the protected space – hence the name HotFoam. [Unitor].