Chemical Tankers / Day 2 / Day 2 Topic 2 Cargo Compatibility

Reactivity ,Solubility,Compatibility

Background to the incident:

Ship had a cargo of Caustic Soda stowed adjacent to inhibited Acrylonitrile – this was permitted at the time by the current compatibility chart.

Due to engine problems the voyage to Japan was very long.

Reactivity ,Solubility,Compatibility

The ship had a history of tank cracks and had reported recent suspected tank bulkhead cracks.

It is believed that caustic soda leaked into the A.N. tank and neutralized the inhibitor, A.N. became reactive/polymerized, resulting in a severe explosion.

Reactivity ,Solubility,Compatibility

CONCLUSION:

As a result of this incident the compatibility chart was amended. The stowage of caustic adjacent acrylonitrile is now prohibited under section (b) of the exceptions list although the compatibility chart would at first indicate it is permitted.

For this reason it is essential to always use the latest Compatibility Chart as published in CFR46-150.

It is also essential to check the ‘exceptions list’ to the chart.

Reactivity ,Solubility,Compatibility

Polymerization - A chemical reaction, commonly the result of exposure to heat, which results in solidification (or chemical bonding)

Monomers, such as Styrene, are particularly susceptible to this reaction and the solidification of Isocyanates from moisture is a similar reaction

Reactivity , Solubility, Compatibility

Reactivity:

Cargoes

Slops

Cleaning Chemicals

Tank Coatings

Heat

Water

Air

Reactivity ,Solubility,Compatibility

Cargoes

The risk is in the potential breakdown of the “common barrier” - the bulkhead.

To eliminate this risk, we implement the USCG Compatibility Chart data as was discussed.

Reactivity ,Solubility,Compatibility

Slops

Unlike “pure” chemicals, there is no firm data available, because there are too many variables (concentration, temperature, etc) but the USCG Compatibility Chart may be used as a guideline and the Marpol regulations must be followed.

Reactivity , Solubility, Compatibility

We must also consider commercial requirements. In order to reprocess slops, it is usually necessary to avoid, or minimize, the use of

chemical additives if slops have any value for reprocessing.

Reactivity , Solubility, Compatibility

We need to be practical on board and separate different categories of slops (Annex 1 oil slops / Annex 2 chemical slops / Veg Oil slops) Mixing them all together produces a thick, glutinous stew!

In any case it is prohibited to mix Annex-1 oil residues with other slops.

Reactivity , Solubility, Compatibility

Cleaning Chemicals

Used to induce a reaction, eg: degreaser, de-emulsifier, detergent, oxidizer, de-odorizer, solvent, etc