AFFF concentration: MMC(SS) Fannin.
AFFF concentrate for submarines is both class and equipment specific. An improper mixture will produce foam that is too lean or too rich and degrades fire fighting performance. Sailors are under the impression that 6% AFFF concentrate is more concentrated than 3% or 1%. The reality is the exact opposite, 1% is the highest and 6% is the lowest concentration. The AFFF concentration determines the mixing ratio required to obtain the fire fighting performance. For example, in a 100 gallon system, 1% solution is designed to be mixed with 1 gallon of AFFF to 99 gallons of water. Using the same 100 gallon system and 3% solution the mixing ratio is 3 gallons of AFFF to 97 gallons of water. That said, systems will not work properly if the wrong AFFF concentrate is used. The more-concentrated 1% agent is not "better" than 3%. An excess concentration of AFFF is just as bad as one that is too dilute.
NSC is working with NAVSEA and SUBMEPP to correct the following PMS discrepancies:
-MIP 6641/009, MRC A-22R, Portable AFFF Injection Units (PAIU), provides a SPMIG for 1% AFFF concentrate but does not provide a stock number.
-MIP 5551/039, AFFF/SW Fire Extinguishing System does not provide a SPMIG or stock number for 3% AFFF concentrate.
-MIP 6641/009, MRC R-48 for Portable AFFF Extinguishers provides a SPMIG with only one stock number which is for the 6% AFFF concentrate. Currently there is no SPMIG or stock number provided for the 1% or 3% AFFF concentrate.
Note: PAIU's must only use "ANSULITE" 1% AFFF concentrate. It is recommended that 688 and TRIDENT boats without PAIU's only use Type 6 mil spec MIL-F-24385 AFFF per current allowances.
MIP 6641/009, MRC R-48 provides a table with the specific amount of AFFF concentrate that is to be added to each 2-1/2 gallon portable fire extinguisher. The table considers the AFFF concentration available to each class of submarine and ensures fire fighting performance is maintained when mixed at the proper ratio.
AFFF Concentrate Stock Numbers 1% AFFF Concentrate 4210-01-573-8005 Type 3 - 3% AFFF Concentrate 4210-01-139-4972 Type 6 - 6% AFFF Concentrate 4210-01-056-8343 Table 1 Type of AFFF Concentrate Amount of AFFF required Ship Classes Type 1 - 1% 1 cup (8 ounces) SSN-774 Class Type 3 - 3% 1 pint (16 ounces) SSN-21 Class