3.6 Expansion ratio
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC/Circular.670 – Guidelines for The Performance and Testing Criteria and Surveys of High-Expansion Foam Concentrates for Fixed Fire-Extinguishing Systems – (Adopted on 5th January 1995) - Annex - Guidelines for The Performance and Testing Criteria and Surveys of High-Expansion Foam Concentrates for Fixed 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 according to paragraph 3.6.2, with sea water at about 20°C. Simulated sea water 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

  • (a) Apparatus:

    • plastic collecting vessel of volume V, approximately 500 L and accurately known to ± 5 L;
    • high expansion foam-making equipment which when tested with water has a flow rate of 6.1 ± 0.1 L/min at a nozzle pressure of (5.0 ± 0.1) bar.

    An example for a suitable apparatus is given in document ISO 7203-2.

  • (b) Procedure:

    • (b.1) Wet the vessel internally and weigh it (W 1). Set up the foam equipment and adjust the nozzle pressure to give a flow rate of 6.1 L/min. With the discharge facility closed, collect foam in the vessel. As soon as the vessel is full, stop collecting foam and strike the foam surface level with the rim. Weigh the vessel (W 2). During the filling operation, keep the discharge facility in the bottom of the vessel closed until the total weight of the foam is determined.

    • (b.2) Calculate the expansion E from the equation:

      in which it is assumed that the density of the foam solution is 1.0 kg/L and where:

      V = is the vessel volume, in mL;
      W 1 = is the mass of the empty vessel, in grammes;
      W 2 = is the mass of the full vessel, in grammes.

      Assume that the density of the foam solution is 1.0 kg/L.

    • (b.3) Open the drainage facility and measure the 50% drainage time (see paragraph 3.7.1 hereinafter).

      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.

      Care should be taken to ensure that there are no voids in the foam collected in the vessel.

  3.6.3 Simulated sea water may be made up by dissolving

25.0 g Sodium chloride (NaCl)
11.0 g Magnesium chloride (MgCl26H2O)
1.6 g Calcium chloride (CaCl22H2O)
4.0 g Sodium sulphate (Na2SO4)

 in each litre of potable water.

Parent topic: 3 Tests for Type Approval of Foam Concentrates
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