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VPS: Why do VLSFOs still require quality considerations?

VLSFO play an important role, comprising 55% of marine fuel samples; while no official ISO8217 specs exist, VLFSOs demand careful management due to unique properties.

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Steve Bee, Group Commercial & Business Development Director of marine fuels testing company VPS, on Thursday (18 August) shared that in the pursuit of greener shipping, the shipping industry should not overlook the importance of quality fuel management for traditional fossil fuels. 

Very Low Sulphur Fuels (VLSFO) play an important role, comprising 55% of marine fuel samples. While no official ISO8217 specs exist, VLFSOs demand careful management due to unique properties:

As the world of shipping quite rightly focuses on reducing its carbon footprint and endeavours to comply with a host of decarbonisation legislation, it may be easy to forget that traditional fossil fuels are still the main energy source for the majority of the global fleet. As such, the fuel management of fossil fuels and their quality, continues to be an important factor in protecting vessels, their crew and the environment.

As the most widely used fossil fuel, Very Low Sulphur Fuels (VLSFOs) require more focus than others, in terms of their fuel management. VLSFOs currently account for 55% of all marine fuel samples received by VPS for fuel quality testing. There are still no official standard specifications within ISO8217 for VLSFOs.

As such, most VLSFOs are tested against the RMG380 specifications, knowing that the viscosities of VLSFOs in particular, are very much lower than 380cSt. Currently, 68% of all VLSFOs tested have a viscosity between 20cSt-180cSt. This can have a significant impact on the transfer and injection temperatures onboard a vessel, requiring much less heating of the fuel to achieve the optimum injection viscosity. It would be beneficial to see the introduction of a minimum viscosity specification limit for VLSFOs, as well as a current maximum viscosity limit within ISO8217?

Currently 3.8% of all VLSFOs tested have at least one off-specification parameter. This compares favourably with the off-specification rates for HSFO fuels at 11.4% and MGO fuels at 16.9%. However, the VLSFO off-specifications are potentially more concerning than some of those associated with HSFO and MGO. Sulphur, water, cold-flow properties and cat-fines are the most frequent of VLSFO off-specification parameters.

Screenshot 2023 08 21 at 1.47.56 PM

Sulphur off-specification is the most common of all VLSFO off-specifications, with over 30% of all off-specifications being attributed to this one parameter. However, recent test results have shown that sulphur off-specification is certainly better today than it was back in 2021, with only 1.6% of VLSFOs tested being >0.50% Sulphur compared to 2.4% >0.50% in 2021.

Also, it would appear that so far this year, suppliers are producing more fuel in the 0.41%-0.46% Sulphur range, than the 0.47%-0.50% range, than over the past two years, which means that there is less chance of the VLSFOs falling outside of the 95%-confidence interval, or being off-specification.

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Due to the higher level of paraffinic content of VLSFOs over HSFO fuels, it is more likely to see wax precipitation occur with VLSFOs, when subjected to colder temperatures.

The formation of wax crystals during storage and consumption is a potential major source of operational problems with VLSFOs. Therefore, it is vitally important to test for wax appearance (WAT) and wax disappearance temperatures (WDT), as the pour point of the fuel is not a reliable indicator of potential cold-flow issues.

During 2019, VPS developed a proprietary test to be able to measure both WAT and WDT in VLSFOs, which many of our customers have become reliant upon to safeguard their vessels from wax precipitation and it’s potentially damaging consequences.

Current global averages show VLSFO Pour Point is 16°C, whilst the average WAT is 38°C, and the average WDT is 48°C. These figures illustrate why using +10°C above the pour point as an indicator of the cold-flow properties of VLSFO blends is simply insufficient, as well as inappropriate as a risk mitigation measure.

When WAT and WDT results are high, vessels need to consider raising the temperatures of their onboard separators, as well as the temperatures within storage, settling and service tanks.

However, VLSFOs with a short shelf life and high WAT may not be suitable for storing, as heating such fuel accelerates the ageing process and increases the likelihood of fuel sludging.

VLSFOs with low viscosity but high WAT & WDT, need to be heated to ensure a stable flow and to prevent wax formation. Such fuels will likely need to be cooled before entering the main engine, due to their low viscosity. This could present operational issues such as wax formation when the fuel temperature drops below the WAT.

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Stability issues relating to VLSFOs have been a concern since their introduction in 2019. To this day we still witness spikes in Total Sediment Potential (TSP) across the world.

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Some VLSFO blends appear stable on bunkering but become unstable over time (within a week or two). Heating the fuel in the tanks (to maintain suitable storage and transfer) and purifiers (to achieve efficient purification) deteriorates the fuel’s stability and fastens the ageing process. 

VLSFOs that are incompatible can cause separator sludging and clogging of filters. As such, numerous vessels have witnessed incompatibility issues when the vessels change from MGO to VLSFO or (vice versa). 

VLSFOs with high WAT/WDT and high cat-fines create a need to operate separators at higher temperatures, at shorter discharge intervals. When this is practice is undertaken, wax starts to form, affecting purifier operation as well as clogging the fuel system’s filters. 

Finally, regarding stability, VLSFOs with high WAT/WDT, that also have chemical contamination, followed by low viscosity, will unlikely to be handled on-board of vessels. In such cases, the only solution is to de-bunker the fuel. 

Between Feb-July 2023, VPS detected contamination in VLSFO fuels in Houston. This contamination saw the presence of two specific isomers of Dicyclopentadiene (DCPD) at concentrations between 1,000ppm-40,000ppm. 

The specific isomers were: 

  • Di-hydro dicyclopentadiene Chemical CAS Number: 4488-57-7 
  • Tetra-hydro dicyclopentadiene Chemical CAS Number: 6004-38-2 

DCPD’s are unsaturated chemical compounds which can polymerise and oxidise under certain conditions. When DCPD polymerises, the fuel begins to exhibit a level of stickiness and becomes more viscous, making it difficult for moving components, eg fuel pump plungers & fuel injector spindles to move freely. These effects cause damage to the fuel injection system. Over a period of time excessive sludge formation is likely to be experienced. 

This specific case saw 12 vessels which bunkered the fuel in Houston suffer major operational issues and damages to auxiliary engines & fuel delivery systems, from fuel supplied by 4 suppliers. The type of problems witnessed were fuel leakage in the ICU (Injection Control Unit) units and fuel pumps not being able to develop the required fuel pressure.

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In order to mitigate the risks associated with chemical contamination of VLSFOs, VPS recommend their GCMS-HS Chemical Screening service with each VLSFO bunkering. This service is a pre-burn, rapid, low-cost test, which can identify the presence of volatile chemicals within VLSFOs such as styrene, DCPD and chlorinated hydrocarbons, to name but a few and provide an elevated level of protection to the vessel. 

To summarise, VLSFOs as the most widely used marine fuel powering today’s global fleet, can potentially create numerous operational and compliance issues, due to their varying quality. In order to mitigate the potential risks caused by, poor cold-flow parameters, fuel stability, chemical contamination, low viscosity and sulphur non-compliance, effective fuel management and testing can certainly help reduce and even eliminate such risks.

Related: VPS identifies new bunker fuel contamination at Houston
Related: FOBAS: Possible bunker fuel contamination in Houston and US Gulf area
Related: Viswa Group gives update on bunker fuel issues in Houston
Related: FuelTrust analysis finds fuel content discrepancies in 39% of global bunker deliveries
Related: VPS: Houston contaminated VLSFO bunker fuel was also supplied in Singapore
Related: BREAKING: Vessels supplied in Singapore yet to report engine issues due to contaminated bunkers, following Houston VLSFO case

 

Photo credit: VPS
Published: 21 August, 2023

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Port & Regulatory

ISWG-GHG 22: IMO working group aims to present NZF text at MEPC 85

The Chair expressed his observation of a genuine willingness within the Group to make concrete further progress at the next ISWG-GHG meeting and work towards presenting text to MEPC 85.

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The Intersessional Working Group on Reduction of Greenhouse Gas (GHG) Emissions from Ships (ISWG-GHG 22) met for its 22nd meeting from 1 to 4 September 2026, chaired by Mr. Sveinung Oftedal (Norway), according to the International Maritime Organization on Friday (4 September). 

According to a meeting summary by IMO, the meeting had a high level of participation, with nearly 1200 registered participants, in person and online.

During the meeting participants considered the following agenda items:

Consideration of proposals, including documents submitted to MEPC 84 and 85, previous sessions of ISWG-GHG, as well as documents submitted to ISWG-GHG 22, on how to address concerns with the draft amendments to MARPOL Annex VI on the Net-Zero Framework, in line with the 2023 IMO GHG Strategy

Following constructive discussions, the Chair expressed his observation of a genuine willingness within the Group to make concrete further progress at the next ISWG-GHG meeting and work towards presenting text to MEPC 85 that adequately addresses the noted progress made in the consideration of proposals on how to address concerns raised regarding the draft amendments to MARPOL Annex VI on the mid-term measure.

The Group invited interested delegations to continue to consult intersessionally to address remaining concerns with the draft amendments to MARPOL Annex VI, in line with the 2023 IMO GHG Strategy, taking into account views expressed at the Group’s session, with a view to submitting concrete proposals reflecting enhanced convergence allowing timely adoption and effective implementation.

Further consideration of the draft guidelines supporting the uniform and effective implementation of IMO’s mid-term measures.

The Group held a preliminary exchange of views on this agenda item, although time became a limiting factor and the Group and agreed to defer the consideration of all documents submitted to this session under this agenda item to ISWG-GHG 23 (23-27 November 2026).

Further consideration of the development of the IMO Life Cycle GHG Assessment (LCA) framework.

Due to time constraints, the Group was not able to consider the agenda item related to the IMO Life Cycle GHG Assessment (LCA) framework. The Group deferred the consideration of those documents to ISWG-GHG 23, in conjunction with the report of the fourth meeting of the GESAMP-LCA Working Group expected to be submitted to MEPC 85.

Next steps

The next meeting of the Intersessional Working Group on Reduction of Greenhouse Gas (GHG) Emissions from Ships (ISWG-GHG 23) is scheduled for 23 to 27 November 2026, ahead of MEPC 85 (30 November to 3 December).

The second extraordinary session of MEPC (adjourned last October) is scheduled to resume on 4 December, subject to discussions at MEPC 85.

 

Photo credit: International Maritime Organization
Published: 7 September, 2026

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Port & Regulatory

UCL on ISWG-GHG 22: Majority back GHG pricing, centralised fund in IMO NZF talks

A significant majority of IMO member states backed a centralised system for collecting revenues to reward early adopters and support a just transition, according to UCL.

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UCL Shipping and Oceans Research Group on Friday (4 September) said the IMO’s 22nd Intersessional Working Group on GHG emissions has concluded with significant majority of member states supporting a centralised system for collecting revenues, operationalised through a GHG price (RU price), and disbursing it for rewards for early adopters and supporting a just and equitable transition. 

The group of member states focused on a technical-only solution and abandonment of GHG pricing, remained small and consistently composed of strongly fossil fuel aligned governments.

Just as at MEPC 84, the political dynamics observed at MEPC.ES2 did not occur in this meeting. 

The discussions were more representative of the ISWG-GHG 19 and MEPC 83 negotiating dynamics, but this does not rule out the potential for the dynamics that occurred at MEPC.ES2 returning in future meetings. That said, there was reassuring evidence from the week that reduces that risk, including in the contrast between strong public (press) positions taken against the IMO’s NZF, and the substance of how delegations negotiated in the meeting.

Dr Tristan Smith, Professor of Energy and Transport at UCL Shipping and Oceans Research Group, said: “Whilst there are many positives to take away – there is clear potential for a return to a strong policy solution and decision making this December, there remains high uncertainty in the extent that both industry’s transition and low-income countries’ transitions will be supported. 

“There remains high risk that in the effort to find a creative way forwards, the equilibrium between these two aspects, that enabled the NZF in the first place, is lost to the detriment of the outcome overall.”

In addition to the discussion on centralised system for revenue collection and disbursement, the meeting discussed a number of other items as guided by the chair, discussed in detail with member state positions in the readout. Some of these included:

  • GFI (Global Fuel Intensity) reduction pathway: GFI is likely to be softened initially (around 2030), but then steeper in the period to 2040. 
  • ZNZ rewards: ZNZ reward still broadly supported and a priority to many member states, but the broad support for a multiplier, despite it being taken off the table at the last meeting, could yet lead this to be incorporated to provide incentivisation. 
  • Compliance approaches
  • Most interventions confirmed support for the compliance mechanisms as setup in NZF ‘as is’. The strongest support was for the two least controversial options common to all proposals: reducing GHG intensity and pooling/transfer of SU. 
  • Direct contributions: Japan’s proposal to replace GHG pricing with shipowner-directed contributions was robustly rejected, particularly by the member states that would need to ‘swing’ to support it for this to start to build momentum. 
  • SU (Surplus Units) trading: Majority of member states opposed the inclusion of energy efficiency SU credits and the concept of printing SU’s to manage an SU price shock, citing various reasons, primarily a concern that this would destabilise the SU market and undermine investment predictability. 
  • Netting: China’s proposal to balance of RU and reward payments that could be netted to form a single transaction received broad support. However, the details of the concept will now need to be set out in guidelines and there remain a number of issues regarding this approach, as raised by several delegations.

Note: The full article can be read here

 

Photo credit: UCL Shipping and Oceans Research Group
Published: 7 September, 2026

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LNG Bunkering

LR awards AiP to CSSC Huangpu Wenchong for 12,500 m³ LNG bunker vessel design

Vessel design incorporates Type C LNG cargo tanks and has been evaluated against a range of class notations covering gas operations, automation, environmental performance and cyber resilience.

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Classification society Lloyd’s Register (LR) on Thursday (3 September) said it has awarded Approval in Principle (AiP) to CSSC Huangpu Wenchong Shipbuilding Co., Ltd. for a new 12,500 m³ LNG bunkering vessel design.

The AiP was signed at SMM 2026 in Hamburg and confirms that the vessel concept has successfully completed an independent design assessment against LR’s latest classification requirements.

The new 12,500 m³ vessel design incorporates Type C LNG cargo tanks and has been evaluated against a comprehensive range of class notations covering gas operations, automation, environmental performance and cyber resilience.

LR’s assessment was carried out in accordance with its Rules and Regulations for the Classification of Ships and Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquefied Gas in Bulk.

Constantinos Chaelis, LR’s Global Gas Segment Director, said: “This project demonstrates the continued market confidence in LNG and the importance of building the supporting infrastructure that enables owners to make practical emissions reductions today, while maintaining flexibility for the future. Through early engagement between shipyard and class, we can accelerate the delivery of robust designs that meet both operational and regulatory requirements.”

A Huangpu Wenchong spokesperson, said: “This Approval in Principle from Lloyd’s Register validates the technical approach and provides a strong foundation for future development. We believe vessels of this type will play an increasingly important role in supporting the energy transition by helping ensure LNG is available where shipowners need it most.”

 

Photo credit: Lloyd’s Register
Published: 7 September, 2026

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