Whilst hot filtration stability tests (TSP/TSA/TSE) indicate how much sediment may precipitate from a marine fuel sample, the measurement of the fuel samples “stability reserve” highlights the likelihood of asphaltenic precipitation, irrespective of how much sediment is present.

For this determination, VPS use ASTM D7061 to measure the Separability Number, (Reserve Stability Number (RSN)), of residual and low-sulphur blended fuels.

So, Separability Number (SN), indicates the resistance of a fuel to form sludge.

SN is an excellent accompaniment to the routine hot filtration methods. It can identify potentially troublesome fuels (unstable) even when the HFT method is indicating a low sediment content.

Conversely, it may indicate that a high sediment fuel is in fact quite stable and unlikely to form sludge.

This information in combination, is extremely useful from an operational perspective, as it will indicate in advance if and what mitigation steps are appropriate.