USCG cargo compatibility chart, 46 CFR part 150

46 CFR part 150, Compatibility of Cargoes, is the United States Coast Guard regulation carrying the cargo compatibility chart that the chemical tanker trade uses worldwide. It matters out of proportion to its jurisdiction for a simple reason: the IMO publishes no equivalent chart, so a US regulatory artefact has become the global reference.

The structure is two sets of groups. Groups 1 to 22 are reactive groups, running from non-oxidizing mineral acids, sulfuric acid and nitric acid through organic acids, caustics, ammonia and the amine families to isocyanates, vinyl acetate, acrylates, alkylene oxides, epichlorohydrin, ketones, aldehydes, alcohols and glycols, phenols and cresols, and caprolactam solution. Groups 30 to 43 are cargo groups, which appear only on the left axis and do not react hazardously with one another. Groups 23 to 29 are unassigned and reserved.

Reading the two group numbers from Table I and finding the intersection on Figure 1 gives an X where the pair is incompatible. The underlying criterion, in appendix II, is that a binary mixture is treated as hazardous where the temperature rise exceeds 25 degrees C or a gas is evolved under the test conditions. Appendix I lists tested combinations found not dangerously reactive, which are the exceptions permitted in adjacent tanks, and appendix III gives the test method. The full article will set out the groups, the reading method and the legal distinction between compliance in United States waters and convention everywhere else.