46 CFR §182.422

1. (a)A keel cooler installation used for engine cooling must be designed to prevent flooding.
2. (b)Except as provided in paragraph (e), a shutoff valve must be located where the cooler piping penetrates the shell, as near the shell as practicable, except where the penetration is forward of the collision bulkhead.
3. (c)The thickness of the inlet and discharge connections, outboard of the shutoff valves required by paragraph (b) of this section, must be at least Schedule 80.
4. (d)Short lengths of approved nonmetallic flexible hose, fixed by two hose clamps at each end of the hose, may be used at machinery connections for a keel cooler installation.
5. (e)Shutoff valves are not required for integral keel coolers. A keel cooler is considered integral to the hull if the following conditions are satisfied:
   1. (1)The cooler structure is fabricated from material of the same thickness and quality as the hull;
   2. (2)The flexible connections are located well above the deepest subdivision draft;
   3. (3)The end of the structure is faired to the hull with a slope no greater than 4 to 1; and
   4. (4)Full penetration welds are employed in the fabrication of the structure and its attachment to the hull.