46 CFR §170.245

1. (a)Installation of foam must be approved by the OCMI.
2. (b)If foam is used to comply with § 171.070(d), § 171.095(c), or § 173.063(e) of this subchapter, the following applies:
   1. (1)Foam may be installed only in void spaces that are free of ignition sources.
   2. (2)The foam must comply with NPFC MIL-P-21929B (incorporated by reference; see 46 CFR 170.015), including the requirements for fire resistance.
   3. (3)A submergence test must be conducted for a period of at least 7 days to demonstrate whether the foam has adequate strength to withstand a hydrostatic head equivalent to that which would be imposed if the vessel were submerged to its margin line.
   4. (4)The effective buoyancy at the end of the submergence test must be used as the buoyancy credit; however, in no case will a credit greater than 55 lbs per cubic foot (881 kilograms per cubic meter) be allowed.
   5. (5)The structure enclosing the foam must be strong enough to accommodate the buoyancy of the foam.
   6. (6)Piping and cables must not pass through foamed spaces unless they are within piping and cable trunks accessible from both ends.
   7. (7)Sample specimens must be prepared during installation and the density of the installed foam must be determined.
   8. (8)Foam may be installed adjacent to fuel tanks if the boundary between the tank and space has double continuous fillet welds.
   9. (9)MIL-P-21929B is incorporated by reference into this part.
   10. (10)The results of all tests and calculations must be submitted to the OCMI.
   11. (11)Blocked foam must—
       1. (i)Be used in each area that may be exposed to water; and
       2. (ii)Have a protective cover approved by the OCMI.