should consider the fluid's propensity to foam and the fluid's
viscosity. Refer to Appendix A, Figures A-17 and A-18 for the
AFFF viscosity characteristics curves.
d) Carbon steel cannot be used with the AFFF
surrogate because the chemical picks up iron molecules. Tanks,
pumps, piping, and appurtenances should not be carbon steel,
irrespective of the solution concentration of the chemical.
Copper piping or 316L stainless steel is an acceptable piping
e) From the solution tank the foam concentrate should
be pumped in underground pipes to the hose station day tank.
The flow rate should allow the day tank(s) to be filled in
approximately 15 minutes. The concentrate distribution pump
should be controlled by start-stop push-button stations at each
hose station. The solution tank should include provisions for
filling 19 L cans to be used with the portable foam
f) The device sensors can distinguish between
3 percent AFFF and pure water. However, instructors feel that a
6 percent solution is more realistic in appearance. The
proportioner is field adjustable. A 6 percent solution should
be used for design purposes unless indicated otherwise. The
19F4 trainer uses 3 percent solution.
g) The 21C12A trainer requires a AFFF mixed solution
for extinguishers of 59 ml. of 40 percent concentrate in 9 L of
Portable AFFF Fire Extinguishers. Portable AFFF fire
extinguishers are only required on submarines, therefore, only
used in the 21C12 and 21C12A trainers. These extinguishers are
stainless steel cylinders that store 9 L of a premixed solution
of AFFF concentrate and water. Cylinders are pressurized with
air to 689 kPa at 21 degrees C. The AFFF is discharged from the
bottom of the cylinder through the siphon tube, extinguisher
valve, and discharge hose to the nozzle. The AFFF fire
extinguisher weighs approximately 12 kg when fully charged and
has a 55- to 65-second continuous discharge time. The AFFF