46 CFR § 150.130 - Loading a cargo on vessels carrying cargoes with which it is incompatible.
(a) The containment system must separate the hazardous material or its residue from any cargo in table I with which it is incompatible by two barriers such as formed by a:
(2) Empty tank;
(3) Void space;
(4) Cargo handling space;
(5) Tank containing a compatible cargo; or
(6) Piping tunnel.
(b) In this subpart, isolation across a cruciform joint is equivalent to isolation by two barriers.
(c) The containment system for the hazardous material must not have a piping or venting system that connects to a containment system carrying a cargo with which the hazardous material is incompatible. Any such piping or venting system must have been separated from the containment system carrying the incompatible cargo by:
(1) Removing a valve or spool piece and blanking off the exposed pipe ends, or
(2) Installing two spectacle flanges in series with a means of detecting leakage into the pipe between the spectacle flanges.