Bunker problems are quite common nowadays due to the use of new fuel blends. However, not all fuel issues are solely caused by the bunkers themselves; a thorough investigation is required to accurately identify the root cause. That’s where GeoStem, our bunker procurement and planning solution, steps in to ensure high-quality, compliant, and cost-effective bunker solutions.
Back in the first week of June 2025, a Handymax tanker vessel received 470 MT of VLSFO bunkers at the port of Venice. The vessel lifted the bunkers on June 2nd, but the fuel was only put into use at the end of August, shortly after which, the vessel experienced minor issues, including sludging in the purifiers. By the first week of September, the vessel reported to GeoServe that the bunker fuel was causing problems and could not be consumed. Initially, the vessel owners even demanded a complete de-bunkering of the batch.
At GeoServe, our first step is always to identify the real problem.
If the issues stem directly from the bunkers with no scope of mitigation for smooth consumption, we represent our customers and request the supplier to de-bunker the batch. However, if the problem can be resolved through additives or operational measures, we guide our clients accordingly to avoid unnecessary delays and the complexities involved in de-bunkering.
In this case, we requested the vessel to provide:
The vessel provided pictures showing purifier sludging, but the fuel filters were not clogged and there was no mechanical power loss in the units.
Our analysis concluded the vessel faced initial fuel stability issues, which could be resolved by using sludge dispersant additives.
The GeoStem team recommended appropriate sludge dispersant additives with dosage ratios and guidance on operational procedures for the crew. The vessel promptly followed our instructions, leveraging existing additives in stock, to experience significant drop in issues by mid-September. Bunkers could now be consumed without any hassles.
Towards the end of September, the scavenge port inspections during flushing revealed abrasive wear marks on the liner surface and scoring marks on the ring surface. The vessel suspected the bunker batch for these problems.
The GeoStem team discovered that the root cause was improper lubrication, based on the vessel’s scavenge port inspection reports from the past three months, along with scavenge drain (under-piston space cylinder oil) sample test results.
The vessel decided to proceed with replica analysis to confirm the findings. The analysis revealed partly closed graphite lamellae structures, confirming that the problems were caused by incorrect lube oil dosage and that the bunkers were not responsible for the machinery issues.
Subsequently, we guided the vessel on maintaining the feed rate appropriately.
At GeoServe, we have strong expertise not only in bunker procurement but also in adding value by guiding clients when issues arise.
With GeoStem, our bunker procurement and planning solution, we ensure that every bunker delivers its full value, safeguarding our clients from unnecessary costs, delays, and uncertainty.
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