Cold flow properties of marine fuel

The cold flow properties of a marine distillate are the three measured temperatures that describe how it behaves as it cools and paraffin wax begins to crystallise: cloud point, at which wax first becomes visible; cold filter plugging point, at which the crystals are large enough to block a test filter; and pour point, at which the fuel ceases to flow under its own weight. Only one of the three is a limit in ISO 8217:2024 for most distillate grades.

The full article will set out what the standard actually requires. DMX carries a maximum cloud point of minus 16 degrees C. DMA, DFA, DMZ and DFZ carry a report requirement for cloud point and cold filter plugging point and a pour point limit of minus 6 degrees C in winter and 0 degrees C in summer. DMB and DFB carry neither cloud point nor CFPP. The 2024 edition removed the winter and summer distinction for cloud point and CFPP while retaining it for pour point, and added an informative annex on cold flow characteristics.

The article will cover the operational consequence, which the standard itself acknowledges: a pour point limit does not guarantee operability for all ships in all climates, and the buyer has to confirm that all three properties suit the ship design and the intended voyage. It will address winter Baltic and Arctic purchase specifications, cold flow improvers and pour point depressants, and the test methods EN 116 and EN 16329 that replaced IP 309 and IP 612 in the 2024 edition. It links to marine gas oil and the Polar Code .

For residual fuels the standard takes a different route entirely: Annex F states that the paraffinic and waxy nature of residual VLSFO precludes the use of cloud point and cold filter plugging point, and that cold flow behaviour is best characterised by pour point, with storage at least 10 degrees C above it. See heavy fuel oil .