Loss of propulsion incident: a cautionary tale for maritime decarbonisation

The case study examines an incident in February 2025 in which a prominent shipowner bunkered one of its vessels with 405 metric tonnes (mt) of VLSFO in New York. While laboratory testing undertaken by VPS showed the fuel met ISO8217 specifications, they also indicated via CGMS-Headspace Screening, the presence of volatile organic compounds (VOCs) in the form of Indene and 4-Methylphenol. This led the fuel testing firm to undertake a more detailed forensic GCMS-Vacuum Distillation analysis, which identified the presence of several chemical compounds not typically associated with marine fuels. As a result, VPS provided cautionary notes on its findings within this GCMS-VD report on 27 February. The notes said alkene and styrene compounds “were collectively present in substantial concentration and are known to cause sticking and seizure of fuel pumps, plunger and barrel.” Additionally, the report said phenolic compounds were present in “a disproportionately high concentration of 8782 ppm (0.88%). These compounds are known to cause sludge formation in fuel filters/separators and fuel injection issues.”

But despite VPS test results and advisory comments, the authors report that the vessel had no other choice but to begin to use this fuel from 28 February and subsequently struggled to consume the bunker. With frequent calls at ECA-based ports, the ship was required to make frequent fuel changeovers. “However, with this specific VLSFO bunker, the vessel experienced excessive sludge formation in filters and purifiers, which forced the vessel to slow down or stop and perform several cycles of filter and purifier cleaning until the changeover in the system was complete,” said the authors.

According to the study, on 3 May, the tank containing the above grade was stripped to allow for the next grade of VLSFO to be used. Within a few hours, while the last of the contaminated bunkers were being used, all main engine plunger barrels seized, the purifiers clogged, and the filters were choked. It was noticed that an unusual and excessive plastic-like, hardened sludge, had formed and this inundated the settling/service tanks and sludge tanks.

“It drifted from outside ECA waters, close to fixed oil rig structures”

This resulted in the vessel losing propulsion for more than three days. “It drifted from outside ECA waters close to fixed oil rig structures within the US Gulf region, as it tried to recover from the precarious situation. This posed a significant safety risk to the vessel and crew,” according to the authors.

This resulted in a major emergency alert due to the loss of propulsion, necessitating the involvement of Qualified Individual (QI), USCG and tug assistance to be on standby as a contingency measure for mobilisation, if necessary. It necessitated several days of cleaning and clearing of filters, purifiers, pipelines and tanks. Additionally, the rest hours of the crew were severely disrupted and significant overtime incurred.

Furthermore, the owners incurred significant costs and added reporting requirements because of the incident. They engaged various shore workshops to clean sludge and tanks onboard while conducting full manual tank cleaning. And there was also considerable time and effort in reporting to authorities, followed by flag state and USCG inspections.

The authors of the case study concluded that considerable shipboard damage and work stress can be caused by contaminated bunkers. “It is also worth noting, following the final stripping of the fuel, the situation became even worse, indicating the contamination may well have settled in the lower part of the fuel. However, the far greater risk posed was one of the safety of the crew and vessel, when the vessel became immobilised at sea due to such a bunker condition. On reflection, the consequences of this could quite easily have been even more disastrous and immeasurable, than they were,” noted the authors.