6.2 Product contamination by other cargoes
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6.2 Product contamination by other cargoes

 Contamination of a product may affect its odour, acidity or flashpoint specifications, and may occur in several ways; those relevant to ships with an inert gas main (or other gas line) interconnecting all cargo tanks are:

  • .1 Liquid contamination due to overfilling a tank.

  • .2 Vapour contamination through the inert gas main. This is largely a problem of preventing vapour from low flashpoint cargoes, typically gasolines, contaminating the various high flashpoint cargoes listed in 6.1.1, plus aviation gasolines and most hydrocarbon solvents. This problem can be overcome by:

    • .2.1 removing vapours of low flashpoint cargoes prior to loading; and

    • .2.2 preventing ingress of vapours of low flashpoint cargoes during loading and during the loaded voyage.

When carrying hydrocarbon solvents where quality specifications are stringent and where it is necessary to keep individual tanks positively isolated from the inert gas main after a cargo has been loaded, pressure sensors should be fitted so that the pressure in each such tank can be monitored. When it is necessary to top up the relevant tanks, the inert gas main should first be purged of cargo vapour.

Parent topic: 6 Product Carriers
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