“CAMOUFLAGING PROBLEM” CAUSING PROPERTIES OF BUNKER FUEL
Over the last few weeks, very interesting analysis results have been identified in bunker fuels from South East Asia. The sediment values (ISO 10307‐1 method) are 0.03% to 0.06%. The stability (ASTM D4740 method) of these fuels is number 1. However, the Reserve Stability Number (RSN) (ASTM D7061) is between 14.7 and 16 (one exception at 9.2) and the Xylene Equivalent Number (XE) (modified BP 230) from 38 to 45 (Normal Average). RSN in normal fuels is below 5 and XE is below 30. The ASTM D7061 method says “if the separability number is above 10, the stability reserve of the oil is very low and asphaltenes will easily flocculate, or have already started to flocculate”. According to Diesel United‐Sulzer engine Makers technical document, if the Xylene Equivalent result is high, there is a real risk of fuel pump problems.
As per the Class NK document “Guidance for Measures to Cope with Degraded Marine Heavy Fuels Version II”, “When the xylene equivalent becomes greater than 30, problems are likely to occur.” When very high values for RSN and XE are observed, the fuel should also normally show higher sediment values and poor stability values (3, 4,5). In these cases however, only marginally increased sediment content is noted and the stability is 1.
We feel certain that an additive or a blend component is added to the bunker fuel which suppresses the organic sediment value and bring it within spec. In this process the stability test value is also brought to number 1. It may be argued that when the sediment value is within limits and stability is 1, why worry about this fuel.
As a matter of fact, these fuels have caused problems in the engines. They have also shown presence of contaminants in the GCMS analysis including high levels of styrene (300 to 600 ppm), indene (500 to 700 ppm) phenols (150 to 1050 ppm). In addition a few other contaminants are noted in the fuel. The type of problems experienced were piston ring breakage in multiple units and purifier choking.
So how do we protect against such camouflaging?
We recommend carrying out a XE and RSN test when the sediment content is greater than 0.03%/0.04% to make sure they are not at levels likely to cause problems.
Did you subscribe for our daily newsletter?
It’s Free! Click here to Subscribe!