3.6 Expansion ratio
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC/Circular.798 – Guidelines for Performance and Testing Criteria and Surveys of Medium-Expansion Concentrates for Fire-Extinguishing Systems – (Adopted on 9 June 1997) - Annex - Guidelines for Performance and Testing Criteria and Surveys of Medium-Expansion Foam Concentrates for Fire-Extinguishing Systems - 3 Tests for Type Approval of Foam Concentrates - 3.6 Expansion ratio

3.6 Expansion ratio

  3.6.1 The test should be carried out in accordance with 3.6.2 with seawater at about 20°C. Simulated seawater with the characteristics stated under 3.6.3 may be used. The expansion ratio obtained with the foam generators used on board should be consistent with the expansion ratio obtained with the foam generators during the fire test.

  3.6.2 Determination of the expansion ratio:

  • .1 Apparatus:

    • .1 plastic collecting vessel of volume (V), approximately 200l, and accurately known to ± 2 l;

      (An example of suitable vessel is given in ISO 7203-2)

    • .2 medium-expansion foam-making equipment which when tested with water has a flow rate not less than 3 ± 0.1 l/min at a nozzle pressure of 5 ± 0.1 bar.

      (An example of suitable apparatus is given in ISO 7203-2).

  • .2 Procedure:

    • .1 wet the vessel internally and weight it (W1). Set up the foam equipment and adjust the nozzle pressure of 5 ± 0.1 bar. With the discharge facility closed, collect the foam in the vessel. As soon as the vessel is full, stop collecting foam and strike the foam surface level with the rim. Weight the vessel (W2). During the filling operation, keep the discharge facility in the bottom of the vessel closed until the total weight of the foam is determined;

    • .2 calculate the expansion E from the equation:

      where it is assumed that the density of the foam solution is 1.0 kg/l;

      V = is the vessel volume, in m l;
      W1 = is the mass of the empty vessel, in grammes; and
      W2 = is the mass of the full vessel, in grammes.

    • .3 open the drainage facility and measure the 50% drainage time (see 3.7.1 below).

      Determine the drainage either by having the vessel on a scale and recording the weight loss, or by collecting the drained foam solution in a measuring cylinder.

  3.6.3 Simulated seawater may be made up by dissolving:

  • 25 g Sodium chloride (NaCl),
  • 11 g Magnesium chloride (MgCl2 6H2O),
  • 1.6 g Calcium chloride (CaCl2 2H2O),
  • 4 g Sodium sulphate (Na2SO4).
Parent topic: 3 Tests for Type Approval of Foam Concentrates
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