Fuel lubricity and the HFRR test
Why deep desulphurisation removes a distillate natural lubricity, how ISO 12156-1 measures wear scar diameter, and the 520 micrometre limit in ISO 8217.
Fuel lubricity is a distillate fuel capacity to form a protective film in the sliding contacts of a fuel injection pump, which relies on the fuel itself rather than on lubricating oil. Hydrodesulphurisation removes the polar sulphur and nitrogen compounds that provide most of that film, so a deeply desulphurised distillate can be within specification on every other parameter and still wear a fuel pump.
The full article will cover the high frequency reciprocating rig test under ISO 12156-1, which measures a corrected wear scar diameter at 60 degrees C, and the 520 micrometre maximum that ISO 8217 imposes. The limit is conditional in a way that is frequently overlooked: it applies to fuels with a sulphur content below 500 mg/kg, that is 0.050 percent by mass, and it cannot be shown at all on a DMB sample that is not clear and bright. The current test edition made digital camera measurement of the wear scar mandatory.
The article will also record the field position, which is less alarming than the specification implies. MAN Energy Solutions states in its low-sulphur operating guidance that it does not regard fuel lubricity as a major issue, has not experienced a failure attributed to it, and has been unable to provoke one in test. It links to marine gas oil and marine engine fuel injection systems .