3.7 Expansion ratio
3.7.1 - The test should be carried out according to
para 3. 7 .2 , wi th sea water at about 20°C. Simulated sea
water having the characteristics stated under 3.7.3 may be
used.
The expansion ratio obtained with nozzles used on board
chould be consistent with the expansion ratio obtained
with the nozzles durimg the fire test .
3.7.2 - Determination of
the expansion ratio
(a) Apparatus:
- plastic collecting vessel of volume V, known to 16 mL
as shown in figure 2, equipped with a bottom discharge
facility;
- foam collector as shown in figure 3 ;
- foam making equipment with nozzle as shown in figure 4
which when tested with water has a flow rate of 11,4
L/min at a nozzle pressure of (6.3 0.3) bar.
(b)
Procedure:
(b
.1) Check that the pipework and hose from the
foam solution tank to the nozzle is completely full of
solution .Set up the nozzle horizontally directly in
front of the foam collector .with the front of the
nozzle (3+0.3) m from the top edge of the
collector. 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 L/min.
Discharge the foam and adjust the height of the nozzle
so that the discharge strikes the collector centrally.
Keep the nozzle horizontal. Stop the foam discharge and
rinse all foam from the collector. Check that the foam
solution tank is full. Start discharging the foam and
after ( 30 +5) s to allow the discharge to
stabilize, place the collecting vessel, with the
discharge outlet closed, on the collector . As soon as
the vessel is full, remove it from the collector ,
strike the foam surface level with the rim and start the
clock. Weigh the vessel (W
2).
(b. 2)
Calculate the expansion E from the equation:

in which it is assumed that the
density of the foam solution is 1.0 and where:
V is the vessel
volume (mL)
W
1 is the mass
of the empty vessel (g)
W
2
is the mass of the full vessel (g).
(b .3) Open the drainage
facility and collect the foam solution in the measuring
cylinder to measure the 25% drainage time (see paragraph
3.8.1 hereinafter).
3.7.3 - Simulated sea water may be made up by
dissolving
25,0 g Sodium chloride ( NaCl )
11,0 g Magnesium chloride (MgCI
2
6H
2O)
1,6 g Calcium chloride (CaC1
2 2H
2
O)
4,0 g Sodium sulphate (Na
2 SO
4) in
each litre of potable water.