How Fuel System Check Monitoring Will Reduce Risks, Save Time & Money

By Steve Bee – VPS Group Marketing & Strategic Projects Director

Statistically, data indicates that a vessel will suffer between one and two incidences of main engine damage over the course of its operational lifetime. The average damage costs have been estimated at around $650,000 per incident, with even more damaging incidents costing up to $1.2 million per claim. Therefore, it is important to identify the main causes of this damage and understand how it can be prevented.

Prevention of damage is, of course, preferable to cure. Fuel quality and handling issues remain a leading contributor to critical main engine failures. VPS frequently observe that such issues could have been prevented through the implementation of a robust and well-structured fuel management programme onboard vessels.

A common misconception is that a fuel meeting the international marine fuel quality standard, ISO 8217, means it is “fit for purpose”. But this is definitely not the case as even fuels that are “on specification”, at the point of delivery to the vessel, can cause major engine damage if not properly managed post-delivery. ISO 8217 specifies the requirements for petroleum fuels for use in marine diesel engines and boilers, prior to appropriate treatment before use, which means that fuels should then be treated onboard between delivery and being burnt.

Catalysts used in petroleum refining are made of Aluminium Silicates, which over time breakdown. The resulting, coarse, dense fragments composing of aluminium and silicon, eventually reside in the residual portion of the refining stream. Known as “Cat-Fines”, these particles are highly abrasive and can cause severe damage to vessel engine parts.

Major marine engine manufacturers recommend a fuel should contain less than 10-15 mg/kg Aluminium plus Silicon (Al+Si) at the engine inlet. However, assuming a delivered fuel meets the stringent ISO8217:2024 limits of 40-60 mg/kg Al+Si, dependent upon the fuel grade, the fuel treatment plant would have to operate at an efficiency level capable of removing 75%-83% of these highly abrasive particles in order to meet the engine manufacturers’ requirements.

Furthermore, the International Council on Combustion Engines' (CIMAC’s) recommendation regarding fuel quality states “Fuel analysis is the only way to monitor the quality of fuel as delivered at the time and place of custody transfer, before and after the fuel cleaning onboard and at the engine inlet. Regular monitoring of the fuel cleaning plant will provide information, which will help to make decisions about the maintenance cycles of the equipment as well as potential engine problems resulting from malfunctioning or inadequate operation.”

Yet one of the most important, but often overlooked processes, is that of regular Fuel System Checks (FSCs) in order to assess the level of aluminium and silicon catalytic fines within fuel. The presence of “cat-fines” within fuel can be extremely damaging, causing rapid engine-part wear. Monitoring cat-fine levels before they can enter vessel engines, can prevent such damage. Therefore, sending samples for analysis which are taken Before & After purification processes, on a quarterly basis is the most effective way to monitor cat-fine levels. FSCs will also help comply to the engine manufacturers general recommendation of a maximum of 10-15 mg/Kg level of cat-fines in the fuel, entering the engines and assess purifier efficiency.

There are numerous reasons why regular fuel system checks are critical:

• Help identify potential risks & operational issues before major damage occurs.
• Confirm that the system’s flow rate, temperatures, discharge cycles are properly adjusted to handle the specific fuel that is being treated
• Verify that the fuel treatment system is properly maintained
• Reduce operating cost and increase lifecycles of critical components
• Identify presence of unusual components that can enter fuel post- delivery.

Periodic sampling from the fuel treatment system will also identify problems such as water ingress from ballast systems, leaking heating coils and cargo contamination. The last thing anyone wants to see is a purifier working as a pump!

A prime example and case study is highlighted below:

An LPG Tanker bunkered HSFO in Fujairah where its fuel met ISO 8217 specifications. However, after using the bunkered fuel, the Chief Engineer reported the main engine expansion tank low level alarm, with the main engine exhaust gas temperature high on cylinder unit 2 & 4. The vessel commenced a gradual slowdown of the main engine. The Chief Engineer reported the vessel was unable to run the engine due to suspected leaks on the main engine cylinders. The vessel drifted for about 10 hours before dropping anchor off the coast of India.

Upon dismantling the engine, the following findings were made:

The VPS Technical Advisor recommended the vessel submit fuel system samples and upon checking, the results from the system, these indicated that the purifier was in fact only working like a pump.

The screening size of Al+Si on the before engine sample further confirmed why the vessel was having problems, as the physical size of Al+Si particles ranged: 5-45 µm.

The ideal particle size range of cat-fines that can be effectively removed by a marine vessel's purifier system typically falls between 5 to 15 µm. Purifiers are designed to target these smaller particles, as they are the most common size found in heavy fuel oil and can cause significant wear and damage to engine components

If the particle size of catalytic fines is greater than 15 µm, it can pose significant risks to marine engines. Larger particles are more abrasive and can cause severe wear and damage to critical engine components such as cylinder liners, piston rings, and fuel injectors.
 

Potential Issues:

• Increased Wear: Larger cat-fines can embed themselves in softer metal surfaces, leading to accelerated wear and tear
• Engine Efficiency: The presence of larger cat-fines can reduce engine efficiency and increase fuel consumption.
• Maintenance Costs: More frequent and costly maintenance may be required to address the damage caused by these particles.

Mitigation Strategies:

• Enhanced Filtration: Using advanced filtration systems to capture larger particles before they enter the engine
• Regular Monitoring: Continuously monitoring fuel quality and performing regular maintenance to detect and address cat-fines early.
• Fuel Treatment: Employing fuel treatment systems to reduce the concentration of cat-fines in the fuel.

This VPS fact finding was highly appreciated by the vessel Chief Engineer and the ship owner, following their realisation of what was the cause of the problem. They subsequently put in place routine sampling of fuel system check (FSC) samples to prevent the same incident from reoccurring.

As part of the VPS FSC service, each vessel has a monitoring chart checking the cat-fine level upon receipt of the fuel, then the before-purifier level and the after-purifier level. Should any submitted FQT (Manifold) sample show >40mg/Kg Cat-fines, then the vessel will be advised to send an additional sample for Fuel System Check. The before-purifier sample should always have a lower cat-fine level than the manifold sample. Then the after-purifier should always be below 15mg/kg cat-fines, if the purifier is working efficiently.
 

Currently 52% of all samples received by VPS for testing are VLSFOs, with a further 32% being HSFOs. As the two leading fuel grades used in global shipping, they are the two which will and often contain varying levels of cat-fines.

For VLSFOs across Q1-2025, 17% of all samples tested had cat-fine levels between 41-60 mg/Kg, which was slightly lower level than Q4-2024 and full year 2024, at 18%. These levels are high enough to cause concern and would trigger the request for additional FSC samples to be sent for analysis. 

Across 2024 and Q1-25, less than 2% of samples tested exceed the ISO8217 specification limit of 60 mg/Kg.

So, around 19% of VLSFOs delivered in Q1-2025 had cat-fine levels >40mg/Kg. Should the recipient vessels not have effective, efficient, purification of their fuel, then they run the risk that 1 in 5 fuel deliveries could cause engine damage.

For HSFOs across Q1-2025, 12.5% of all samples tested had cat-fine levels between 41-60 mg/Kg, which was lower level than Q4-2024 and full year 2024, at 19% and 20% respectively. These levels are also high enough to cause concern and would trigger the request for additional FSC samples to be sent for analysis.

Again, like VLSFOs, HSFOs across 2024 and Q1-25, showed less than 2% of samples tested exceed the ISO8217 specification limit of 60 mg/Kg.

So, around 13% of HSFOs delivered in Q1-2025 had cat-fine levels >40mg/Kg. Should the recipient vessels not have effective, efficient, purification of their fuel, then they run the risk that 1 in 7 fuel deliveries could cause engine damage.

In summary, Cat-fines found in the residual component of VLSFO and HSFO fuels, are highly corrosive materials, which can cause considerable and costly damages to vessels. Regular monitoring of onboard purifier performance efficiency, as part of a routine preventive maintenance programme, should be a key tool in mitigating such risks.

It is therefore, recommended that a vessel submits “before and after purifier” samples, for each onboard purifier, four times per year. This way the efficiency of the purifiers can be checked and advice provided to ensure optimum efficiency is being achieved and the engine is being protected to the highest level possible.

For further information on how Fuel System Checks (FSCs) can help you protect your vessels from costly breakdowns, damages and repairs, please contact marketing@vpsveritas.com

By Steve Bee – VPS Group Marketing & Strategic Projects Director & Emilian Buksak – VPS Decarbonisation Advisor

On Friday 11th April 2025, the International Maritime Organization (IMO) achieved another important step towards establishing a legally binding framework to reduce greenhouse gas (GHG) emissions from ships globally, aiming for net-zero emissions by or around 2050.

The IMO Net-zero Framework is the first in the world to combine mandatory emissions limits and GHG pricing across an entire industry sector.   Approved by the Marine Environment Protection Committee during its 83rd session (MEPC 83), the measures include a new fuel standard for ships and a global pricing mechanism for emissions.

These measures, set to be formally adopted in October 2025 before entry into force in 2027, will become mandatory for large ocean-going ships over 5,000 gross tonnage, which emit 85% of the total CO2 emissions from international shipping.  This Net-Zero Framework will be included in a new Chapter 5 of MARPOL Annex VI.

With an estimated 900 renewable-fuel-ready vessels expected to be sailing the seas by 2030, it is felt necessary to implement global regulation to deliver renewable fuels at a commercially viable price, as current pricing for “green fuels” is 3-4 times the price of fossil fuels. Such regulations will make it possible for ships to operate on green fuels and also incentivise fuel and energy providers to invest in new production capacity.

Under the draft regulations, ships will be required to comply with: 

1.    Global fuel standard: Ships must reduce, over time, their annual greenhouse gas fuel intensity (GFI) – that is, how much GHG is emitted for each unit of energy used. This is calculated using a well-to-wake basis, meaning total emissions are measured from fuel production through to its use on board.  

2.    Global economic measure: Ships operating above GFI thresholds will need to acquire remedial units to balance their excess emissions, while those using zero or near-zero GHG  fuels or technologies will be eligible for financial rewards for their lower emissions profile.

3.    Two-tier Compliance Targets: Each ship will have to meet both a Base Target and a Direct Compliance Target for its annual GFI. Vessels that stay under the stricter Direct Compliance Target are eligible to earn surplus units, whereas those over the thresholds face a compliance deficit that must be remedied.

4.    Data Collection & Reporting: Operators must calculate and report their attained annual GFI each calendar year, verifying it against their target annual GFI. This includes rigorous recordkeeping and submission to the IMO GFI Registry, which tracks each vessel’s emissions performance and any remedial or surplus units.

5.    IMO Net-Zero Fund Contributions: Ships that exceed their GFI limits are required to make GHG emissions pricing contributions to the new IMO Net-Zero Fund. Collected revenues will be used to reward ships using zero/near-zero fuels, support research and technological innovation in cleaner shipping, and help ensure a just and equitable transition for the maritime sector.

Net-Zero Framework Implementation and Green Balance Mechanism
From 2028 to 2030, ships will be subject to a tiered levy linked to their well-to-wake (WtW) carbon intensity. Based on a 2008 baseline of 93.3 gCO₂eq/MJ (the industry average in 2008), operators will face no charge for fuel emissions at or below approximately 77.44 gCO₂eq/MJ, a moderate levy of $100/mtCO₂eq for emissions between 77.44 and 89.57 gCO₂eq/MJ, and a higher rate of $380/mtCO₂eq for emissions exceeding 89.57 gCO₂eq/MJ. These thresholds and levies align with the overarching goal of driving down overall carbon intensity by a minimum of 4% by 2028 and 17%for direct compliance targets—with further, more stringent reductions taking effect in subsequent years.

Surplus Units and Over-Compliance
A ship’s carbon intensity below the lower threshold (77.44 gCO₂eq/MJ) constitutes “over-compliance,” generating surplus units that can be banked or traded. Conversely, exceeding thresholds will require the purchase of remedial units to cover the compliance deficit.

Sustainable Fuel Certification Scheme (SFCS) and Fuel Lifecycle Label (FLL)
Under the new framework, all fuels must carry a Fuel Lifecycle Label (FLL), which documents their GHG intensity and other sustainability attributes on a well-to-wake basis. These values must be certified by a recognized Sustainable Fuel Certification Scheme (SFCS), ensuring accurate, transparent calculations and preventing any misrepresentation of environmental impact.

Zero or Near-Zero GHG Technologies, Fuels, and Energy Sources
Recognising the importance of incentivising advanced solutions, the regulation sets specific lifecycle emission thresholds for what qualifies as a zero or near-zero GHG (ZNZ) fuel or technology: Initial threshold (valid until 31 December 2034): ZNZ fuels must not exceed 19.0 g CO₂eq/MJ on a well-to-wake basis. Post-2035 Threshold: Starting 1 January 2035, the permissible GHG intensity tightens to no more than 14.0 g CO₂eq/MJ.

Ships adopting fuels and technologies below these thresholds can earn financial rewards through the IMO Net-Zero Fund, effectively offsetting some of the initial costs of transitioning away from conventional fossil fuels. By gradually lowering the allowable GHG intensity, the regulation encourages ongoing innovation, investment, and broader adoption of advanced, low-emission solutions across the global fleet.

Green Balance Mechanism
Central to this approach is the Green Balance Mechanism, which integrates closely with the GFI. In essence, it applies a fee on higher-intensity fossil fuels and allocates those proceeds to green fuels, balancing costs across a diverse energy mix. The greater the well-to-wake emission reductions a fuel delivers, the larger the financial allocation it receives—effectively levelling the playing field and stimulating a shift to sustainable alternatives.

Disbursement of Revenues
All revenues from levies and remedial unit purchases will be directed to the IMO Net-Zero Fund, which will then distribute the funds to:

• Reward low-emission ships
• Support innovation, research, infrastructure, and just-transition initiatives (particularly in developing countries)
• Fund training, technology transfer, and capacity-building aligned with the IMO GHG Strategy
• Mitigate impacts on vulnerable States, such as Small Island Developing States (SIDS) and Least Developed Countries (LDCs)
• By steadily lowering the permissible carbon intensity and introducing financial incentives for clean fuels, the new framework aims not only to reduce overall emissions but also to accelerate the maritime sector’s transition to sustainable energy solutions.

How VPS Can Help
Staying ahead of new regulatory demands isn’t just a matter of compliance—it’s a strategic move that protects both profitability and operational excellence. With industry-leading expertise in low-to-zero carbon fuel testing, advanced emissions measurement technology, and comprehensive decarbonisation software and advisory services, VPS empowers it’s customers to meet and exceed environmental targets, being uniquely positioned to guide customers through every step, ensuring accurate reporting, cost control and ongoing improvement.

1.    Bunker Delivery Note (BDN) Validation & Fuel Testing
Fuel Quality & Lifecycle Analysis: VPS lead the way in marine fuel testing, developing new methodologies to provide key data on all fuel types. The past 4 years have seen major innovations and developments for biofuels and methanol testing and advisory services.

VPS validate the greenhouse gas intensity of customers fuels whether they are fossil or low-to-zero carbon fuels, based on well-to-wake standards. By analysing lifecycle GHG emissions, customers can gain confidence in their compliance numbers and avoid under- or over-reporting.

Accurate Renewable Content Measurement: Through state-of-the-art lab testing and Fuel Lifecycle Label (FLL) verification, VPS confirm the genuine renewable portion of biofuels—helping you pay the correct level of carbon taxation or remedial contributions.

Early Issue Detection: By validating BDNs and testing delivered fuel, VPS services can help prevent engine damage, unplanned downtime, and costly disputes over fuel quality.

2.    Direct Emissions Measurement & Reporting
Advanced Monitoring Systems (e.g., Emsys and ShoreLink): These systems provide real-time emissions data, allowing customers to track their vessel’s GHG Fuel Intensity (GFI) and compliance status in one seamless workflow.

Data Accuracy & Transparency: Automatic digital data transfer ensures vessel emissions records are consistent, easily auditable, and ready for both internal use and external verification.

Timely Remedial Actions: With up-to-the-minute reporting, operators can make course or speed adjustments to keep emissions in check, reducing the likelihood of expensive remedial unit purchases.

3.    Operational Efficiency & Advisory
Fuel Selection & Hybrid Solutions: VPS experts help match the right fuel to each vessel’s operational profile, whether that’s low-carbon or near-zero carbon fuels, blends, or hybrid setups combining LNG and batteries to reduce methane slip. This tailored approach ensures maximum efficiency and a smaller overall GHG footprint.

Power Generation & Predictive Maintenance: VPS advisors optimize power distribution to cut fuel usage and enhance system reliability. By conducting in-depth fuel performance analysis, its possible to detect early engine abnormalities, enabling proactive maintenance that prevents costly repairs and downtime.

SEEMP Updates & Crew Training: VPS provide step-by-step guidance in incorporating new regulations into Ship Energy Efficiency Management Plan (SEEMP). Additionally, we train vessels’ crew on best practices that build a culture of efficiency, helping our customers reduce emissions and comply with evolving GHG limits.

4.    Net-Zero Fund & Market Mechanisms
Remedial & Surplus Units: Understand how to acquire remedial units (if GFI thresholds are exceeded) and capitalise on surplus units or zero-/near-zero fuels to earn financial rewards.

Cost-Benefit Analysis: VPS Advisory team helps the evaluation process when purchasing or trading units is beneficial versus investing in cleaner technologies or optimising operations.

Strategic Positioning: Tap into VPS insights on emerging market mechanisms to stay ahead of future pricing changes and incentives that could shift the competitive landscape.

5.    Long-Term Decarbonisation Roadmaps
Holistic Compliance Planning: Whether preparing for EEXI, CII, or the IMO’s Net-Zero Framework, VPS design future-proof strategies that keep the fleet competitive for the long haul.

Integrated Training & Engagement: From onboard crew training to management briefings, VPS ensures everyone understands the regulations, the rationale behind them, and how to maintain best practices.

Continuous Improvement: VPS advisory goes beyond periodic check-ins; by partnering with our customers regarding ongoing performance reviews, data benchmarking, and the identification of new efficiency measures.

Next Steps
Formal adoption of the IMO Net-Zero Framework is scheduled for October 2025, with entry into force by 2027. However, preparation must start now to avoid last-minute risks, manage costs effectively, and stay ahead of competitors.

If you’d like to assess your vessel’s readiness or explore how to optimize your operations under the new rules, please get in touch with our decarbonisation advisory team at: Emilian.buksak@vpsveritas.com

We’re here to help you convert regulatory pressure into practical advantages—keeping you compliant, cost-effective, and resilient for the future.

Steve Bee – VPS, Group Marketing & Strategic Projects Director

Cashew Nut Shell Liquid - Background

As demand grows from all modes of transportation for low-to-zero carbon fuels, to support efforts in complying and achieving numerous environmental legislation leading to global decarbonisation, many alternative fuel sources are being considered. One of the most common and in demand sources of such fuels, is Fatty Acid Methyl Esters (FAME), as either a 100% fuel-source, or as part of a bio-fossil blend. But with road transportation, aviation and shipping, all seeking to use FAME in their respective biofuels, demand is outweighing supply. Therefore, other bio-materials are being considered as alternatives to FAME.

One such material is Cashew Nut Shell Liquid (CNSL), which is the oil extracted from the shells of the cashew nut. This by-product of the cashew industry is a naturally occurring substituted phenol, which is abundantly available and a waste product, with a lower demand than FAME. The composition, properties and quality of CNSL depend upon the specific manufacturing production process used to extract the oil from the shell. These vary from, mechanical pressing to solvent extraction, vacuum pyrolysis, vacuum distillation or solvent extraction.

The industrial applications where CNSL is a key component are wide ranging and include, the production of polymers, plastics, resins, adhesives, surface coatings, insecticides, fungicides, anti-termite products and even pharmaceutical products.

There are three main components of CNSL, these are Cardanol, (also known as Ginkgol), Cardol and Anacardic Acid:

These substituted phenols tend to exhibit high acid number values (>3mgKOH/g). They also show high iodine values (>300gI2/100g), indicating an elevated level of unsaturation and hence increased degrees of reactivity and instability. Then also, high potassium levels leading to potential post-combustion deposits and corrosion of turbocharger nozzle rings.

As monomers, these chemicals are also prone to polymerisation at temperatures, >200ºC. As a consequence CNSL is potentially a highly reactive, very corrosive material.

However, the levels of acidity and reactivity can be reduced during the production and refining process by converting Cardol and Anacardic Acid to Cardanol. If the CNSL is >98% Cardanol, then the reactivity is significantly reduced.

VPS Testing of CNSL as a Biofuel

Over the past 3 years VPS have tested various CNSL compounds and fuel-blends to assess the potential of CNSL to be a viable biofuel.

Firstly, the use of CNSL blends can significantly reduce HC, CO/CO2 and smoke emissions, although they can raise NOx emissions slightly. However, VPS would advise never to use 100% CNSL as a fuel, as its far too reactive and corrosive. Further advice is to always check with the OEM regarding the compatibility of CNSL-based biodiesel blended products, with their machinery. Traditional marine fuels when blended with CNSL, may reduce the high acid number, reactivity and potassium levels of 100% CNSL, but also increase the energy content, sulphur content, cold-flow and sediment potential issues.

Fuel Combustion Analysis (FCA) of CNSL/Fossil Fuel Blends

In the recent past, VPS have tested CNSL products, blended with marine gas oil (MGO), very low sulphur fuel oils (VLSFO) and high sulphur fuel oils (HSFO). When undertaking fuel combustion analysis (FCA) of CNSL blended at varying percentages with MGO, VLSFO and HSFO, a wide range of results were produced in relation to, estimated cetane number, ignition delay and rate of heat release (ROHR), examples are given in the table below:

The CNSL blends with HSFO which undertook FCA, were particularly poor, with low Estimated Cetane Number (ECN), long Ignition Delay and low ROHR. CNSL blended with VLSFO gave better results, with acceptable ECN, shorter ignition delay and improved ROHR. Blending CNSL with MGO, gave better results than those obtained by HSFO/CNSL and VLSFO/CNSL blends.

Whether the blends were 80/20, 70/30 or 50/50 Fossil/CNSL, the blends using HSFO consistently gave the poorest FCA results. This may be due to a negative interaction between the asphaltenic content of the HSFO and the acidic nature of the CNSL.

Each of the CNSL blends gave poorer FCA results, when compared with the 100% fossil fuels, HSFO, VLSFO, MGO and 100% FAME.

Please note, to VPS knowledge, the above highlighted CNSL blends were not burnt onboard a vessel.

Burning CNSL/Fossil Blends

CNSL-blended fuels with MGO, VLSFO, or HSFO, have shown mixed reactions to vessel operations, where some CNSL-blends have been stored and burnt without issue, whilst, other CNSL-blends have given rise to operational problems such as:

• Fuel sludging
• Fuel injector failure
• Corrosion of engine parts
• Filter clogging
• Fuel system deposits
• Corrosion of turbocharger nozzle rings
• Damage to Selective Catalytic Reactor (SCR) units.

The quality of the CNSL, through its production and refining processes, will of course be significantly influential in relation to the quality of the fuel, but also the quality of the fossil fuel with which it is blended, will also have an influence.

A B100 Case Study

In early 2024, two vessels bunkered a B100 fuel in Flushing. The B100, was assumed to be 100% FAME, however, the first vessel began burning the fuel and experienced significant difficulties with blocked filters, delayed ignition and abnormal exhaust temperatures. Prior to burning the fuel, the second vessel sent samples to VPS for testing and via proprietary GCMS methodology. The fuel was found to consist of 40% FAME, 10% FAME Bottoms and 50% CNSL. So theoretically the fuel was a B100, it just wasn’t the 100% FAME, which had been ordered. This case highlights the need to know your fuel, its components and for biofuels, the need to know if the bio-source is truly sustainable? Having the fuel certified by an independent body such as ISCC, accompanied by independent testing from VPS, will provide the necessary confidence regarding the biofuel.

Potential Contaminating Properties of CNSL

In the final quarter of 2024, a VPS customer experienced numerous operational issues with its vessels when burning VLSFO fuels. These issues included blocked filters, delayed ignition and abnormal exhaust temperatures. On testing the fuel, GCMS analysis detected and identified the presence of 10,000-15,000ppm of CNSL within these fuels.

Up to the end of 2024, CNSL, which is a non-volatile chemical species, could only be detected using high-end, GCMS methodology. As CNSL is now more common within the fuel supply chain, it brings an elevated risk of potential contamination to fossil fuel supplies.

Therefore, VPS has developed a pre-burn, rapid screening technique, which detects and identifies the presence CNSL and other non-volatile organic chemicals. Whereas previously, only volatile organic chemicals could be detected by GCMS-Headspace Screening, this new and unique development of a qualitative GCMS-Headspace chemical screening method makes it possible, within a single analysis, to detect volatile (VOC), semi-volatile (SVOC) and non-volatile (NVOC) components within HSFO and VLSFO fuels. 

Over the upcoming weeks, VPS will be releasing a technical white paper covering the development of this new GCMS-HS Advanced Screening Method, which is now available from every VPS laboratory.

CNSL Summary – Friend or Foe?

CNSL has certainly divided opinion of its applicability to be considered as a bio-component within marine biofuels. Its natural high level of acidity and reactivity, along with its potential to polymerise, certainly raises negative questions. Data would indicate using 100% CNSL as a fuel should be avoided, along with blending CNSL with HSFO fuels. Vessel operational issues, due to the presence of high levels of CNSL have caused fuel system, engine and exhaust damages.

For the purposes of ISO 8217:2024 and all preceding versions, CNSL is not recognised as a standard fuel component. Accordingly, its presence in a marine fuel may be considered a contaminant and potentially classified as off-specification when assessed against the ISO 8217 standard.

However, in instances where CNSL is intentionally used as a blending component and does not fully conform to any of the defined categories within ISO 8217, the fuel may still be deemed acceptable—provided that its characteristics and specification limits are mutually agreed upon by the buyer and seller. In such cases, the fuel shall be classified under an appropriate category defined in ISO 8217, accompanied by any necessary deviations or additional parameters required to adequately characterise the fuel's properties.

It is also worth noting that CNSL production and refining techniques are improving in order to produce a higher quality product. As stated, when the CNSL has a Cardanol content of >98%, with a significant reduction in the presence of Cardol and Anacardic Acid, then the product is a far less reactive component. Therefore, from a fuel purchasers perspective, it will be the choice of the CNSL supplier and the production processes they employ, which will be a significant factor in what is received and the CNSL properties, behaviour and overall quality of the product.

CNSL does require a much higher level of fuel management than other fossil fuel, or biofuel blends. So, whether it is in the development of a fit-for-purpose marine fuel blend, or in damage prevention detection of CNSL as a contaminant within fuels, VPS can provide high level, in-depth, expertise and experience in relation to CNSL-based fuels.

For further information on how VPS can assist and support you regarding CNSL-based marine fuels, please contact marketing@vpsveritas.com

As global market leader in marine fuel testing and bunker quantity surveys, VPS has tested the most marine fuel samples in the market to-date and has witnessed first-hand what new fuels have to offer, and what the expected issues and risks in managing these fuels will be. Based on this data, VPS has launched Marine Fuel Insights.

Marine Fuel Insights is a quarterly subscription-based service, where VPS’ technical expertise is combined with its proprietary database of fuel oil and distillate samples, to derive special insights for its users. Subscribers receive insights on: availability of VLSFO, quality of tested fuels, potential operational issues, fuel performance, operational characteristics, compliance levels.

Stay ahead in the marine fuel industry with Marine Fuel Insights.

By Steve Bee – VPS Group Marketing & Strategic Projects Director

Introduction to Distillate Fuels 29th May 2025 With the recent implementation on 1st May 2025, of a new Emission Control Area (ECA) in the Mediterranean Sea, the question arises, will we see an increase in demand for marine gas oils/distillates? If so, will a higher demand result in a lower quality product? This article looks to address current marine distillate quality and the test parameters which can be employed to assist in determining fuel quality and the relevant fuel management considerations, required to mitigate any associated risks through the following:

1. Density
2. Viscosity
3. Flash Point
4. Cold-Flow Properties
5. Lubricity
6. FAME
7. Microbial Activity
8. Incompatibility  

For decades global shipping has thought of distillate fuels, as problem-free fuels. Yet whilst High Sulphur Residual Fuels and Very Low Sulphur Fuels, offer certain fuel management challenges, marine distillate fuels, are not exempt, they simply have different considerations and challenges. 

Within the ISO8217:2024 marine fuel standard, there are four grades of fossil marine distillates, DMA, DMB, DMX, DMZ, plus three Fatty Acid Methyl Esters (FAME) containing distillates, DFA, DFB and DFZ, to support decarbonization compliance.

Today, DMA is the most commonly used marine distillate. Suitable for most marine engines, DMA is known for its cleaner combustion, consistent performance, and ability to reduce emissions when compared to heavier, residual marine fuels. This type of fuel is also commonly referred to as, Low-Sulphur Marine Gas Oil (LSMGO).  

DMA: This is the LSMGO Highlighted above. As per its classification, it’s a standard marine distillate suitable for various marine engines.

DMB: The heaviest fuel among the distillates and is typically used in medium-speed marine engines.

DMX: Often referred to as a special light distillate, DMX is used primarily for emergency engines and equipment, plus some high-speed engines that require fuels with lower viscosity and density.

DMZ: This is a clean distillate intended for use with more sensitive engines.

Ultra Low Sulphur Fuel Oil (ULSFO) is another similar fuel type. Marine fuels like DMA are often integrated with specific additive blends, these are designed to address and counter challenges typical of marine environments, for instance, microbial growth in storage tanks. DMA’s cetane number, which indicates the ignition quality of the fuel, usually surpasses 45, whilst ULSFO’s cetane number floats between 40 to 45. While there are premium diesel variants with a higher cetane number, the main objective of ULSFOs is to lower sulphur emissions.

The higher cost of DMA is another differentiating factor and can be swayed by marine-specific rules, the demand it witnesses in ports, and the overarching dynamics of the global marine fuel market. For ULSFO, its pricing hinges mainly on elements like crude oil prices, the capacity of refineries, transportation overheads, and the demand from the road transportation sector.

Marine Distillates (MGO) and ULSFOs account for 14.2% and 1.2% respectively, of all fuel samples sent to VPs for testing: 
 

Whilst distillate deliveries remained stable in Q1-2025 at around 800,000mt, ULSFO deliveries have risen 15% quarter-over-quarter.

Fuel Management Concerns relating to Marine Distillates 
Minimising Financial Risks: Density Short-lifting - Fuel is delivered by volume but paid for by weight. Overstated density stated in a Bunker Delivery Note (BDN) results in operators paying for fuel that was not actually supplied. VPS data and vast experience indicates that short lifting of distillates significantly exceeds that of HSFO and VLSFO. This fact, together with the premium price of distillates can be a substantial drain on the operating budget of a company. 

Currently 39% of MGO samples tested by VPS, fall below 850Kg/m3, where the ISO8217:2024 specification limit is 890Kg/m3. The BDN values are predominantly higher, indicating such overstatements, result in lost fuel for the vessel.

Mitigating Operational Risks: Low Viscosity -  Marine fuel delivery systems and engines are generally designed for operating on higher viscosity HSFO and VLSFO. The low viscosity of distillate fuels may result in insufficient injection pressure which could challenge engine start-up, manoeuvring, or low load operation.

Even without heating the fuel, a warm engine room can easily heat the fuel to e.g. 50°C. A fuel bunkered as 2cSt at 40°C, will have a viscosity of 1.7cSt at 50°C, below the required minimum 2cSt that is recommended by major engine, boiler and pump manufacturers.

Currently 99.1% of all MGO samples tested by VPS in Q1-2025, have a viscosity >2.0 CSt and less than 6.00 CSt.

Ensuring Compliance with Statutory Regulations: Low Flash Point -  Flash point is the temperature at which the vapours of a fuel ignite when a test flame is applied. It is considered to be a useful indicator of the fire hazard associated with the storage of marine fuels. The Safety of Life at Sea (SOLAS) convention and ship classification society rules, require all fuels to have a flash point of more than 60°C, with the exception of Emergency Equipment (eg lifeboat engines). Yet, the Flash Point of marine distillates is an on-going issue. In 2024, the Flash Point cases relating to MGO fuels, accounted for 22% of the Bunker Alerts issued by VPS.

Poor Cold-Flow Properties: Poor cold flow properties, indicated through pour point (PP), cold filter plugging point (CFPP) and cloud point (CP), can lead paraffinic wax precipitation from the fuel. This wax can then lead to clogged filters and pipe lines and in the worst case, complete solidification of the fuels in vessel tanks if not heated sufficiently. 

In Q1-2025 the average Pour Point of MGO dropped to -7°C: 

Insufficient Fuel Lubricity: Marine engine fuel pumps are self-lubricated. If the lubricity of the distillate is poor, high wear may be caused usually within a short period of time. The risk of encountering poor lubricity is higher when sulphur is below 0.05% (500ppm). Therefore, in such cases testing the fuel for its lubricity level is a key requirement. This is undertaken via laboratory test method ISO12156-1, with a specification limit of 526µm Corrected Wear Scar Diameter.

Many people believe it is sulphur which actually provides the distillate with its natural lubricity. This is incorrect. The process to remove sulphur from fuel is termed, “hydrodesulphurization” and it is this process to remove sulphur which also removes polyaromatics present, which do provide the natural lubricity to fuels. Fatty Acid Methyl Esters (FAME): It now seems ironic that prior to ISO8217:2010, FAME was seen as a contaminant if found within marine fuels.

Then the 2010 revision, allowed “de-minimus” levels of FAME to be present in marine fuels. The ISO8217:2017 went a step further by including three new distillate grades, DFA, DFB and DFZ, with a FAME limit of 7% in each. Now the ISO8217:2024 allows up to 100% FAME in relation to marine biofuel blends. 

Although FAME has good ignition, combustion and lubricity properties, as well as providing a reduction in GHG emissions, it can reduce oxidation stability and increase the risk of microbial growth. The risks increase if the fuel is to be stored for a prolonged period of time, e.g. more than 3 months.

Microbial Contamination: Bacteria, yeast and fungi can live and thrive in distillate fuel tanks in the presence of water and elevated temperatures. Such conditions provide an ideal environment for microbial growth. Such microbes, if allowed to grow can lead to operational issues such as clogged filters/nozzles and corrosion in fuel tanks and pipework. This situation can be further complicated by the presence of Fatty Acid Methyl Esters (FAME), which can provide a further source of nutrients for bugs to feed upon. To monitor this microbial activity it is recommended to carryout BYF-testing. Good onboard house-keeping, ensuring a water-free environment will reduce the risks of bug-growth. However, should the situation deteriorate, then biocides can be used to kill the microbes. 

Incompatibility Issues: Loss of propulsion and/or fuel incompatibility during fuel change-over from HSFO or VLSFO to a distillate fuel when entering an emission control area (ECA) is another problem that ship operators should be aware of. Changing between residual-based fuels and distillate fuels can inevitably result in mixing in the fuel system. The result may be incompatible mixtures and in the worst case, a loss of propulsion.

MGO Off-Specifications: In Q1-2025, 7.3% of MGO samples tested were off-specification for at least one test parameter. The Top 4 off-specification parameters were Pour Point (39%), FAME (23%), Flash Point (14%) and Lubricity (7%). In terms of Offspecification Distillates by region, 22% of samples tested from Singapore were off-specification, with 7.3% of those from Europe, 7% off-specification samples from North America and 4.7% of samples from Asia Pacific. 

VPS Additional Protection Service (APS): For a number of years VPS have recognized some of the short-comings of various revisions of ISO8217, in not providing sufficient protection to vessels, crew and the environment. For this reason VPS introduced the Additional Protection Service (APS) which offer ISO8217 testing plus some key additional tests, to support greater protection and provide more information about the fuel ship owners and operators are purchasing. This service includes a test slate for marine distillates: 
 

VPS also provide APS-Bio packages, which cover biofuels, including MGO/FAME blends.

Summary

It is fair to say, despite some opposing opinions, that marine distillates can exhibit challenging fuel management issues. Like all fuels, distillates have their pro’s and their con’s, but if the con’s are known and understood, then the associated risks can be minimized. Testing of distillates is a major part of this fuel management process in reducing the potential risks associated with poor quality distillate fuels.

As the drive to decarbonize shipping continues, the reduction of GHG along with sulphur oxides (SOx), nitrogen oxides, (NOx) and particulate matter (PM) will continue. So, just as the Mediterranean Sea have now implemented a new ECA, other regional ECAs will come into force.  

Going forward at this time, the sulphur limit to enter and operate within an ECA will continue to be 0.10%, This will inevitably lead to an increase in demand for MGO fuels and ULSFOs for vessels sailing within these waters. We may also see an increase in demand for FAME/MGO biofuel blends in order not only achieve the sulphur requirements, but also to simultaneously reduce the CO2 and GHG emissions within the ECAs.

On average, the world fleet spends an estimated 6% of time at sea within the Mediterranean ECA, based on 2024 data, with cruise and passenger vessels among the most exposed vessel types, each spending around 20% of time at sea within the ECA boundaries.  

Already within the Mediterranean Sea, we have seen an increase in marine distillate bunkerings. May-25 is already showing an increase in distillate tonnage deliveries of +35% over May-24 and a comparison between January-25 and May-25 suggests distillate tonnage to increase by 2.5 times. The off-specification of distillates is currently running at 3.1% within the Mediterranean Sea.

With developments and advances in marine fuels progressing at an ever increasing rate, it is more important than ever for vessel owners and operators to work closely with a Fuel Management partner, such as VPS, to ensure protection and compliance in this fast-changing world.

For further information and support regarding your marine distillates fuel management, please contact: steve.bee@vpsveritas.com

2pm Friday 20th June 2025

Riviera Maritime Media Webinar

Presenter: VPS Commercial Director-Europe, John MacKenzie

Register: Lubricants for conventional and emerging marine fuels

By Stanley George – Group Science & Technical Manager 

Engines running on Bio-blends containing Fatty Acid Methyl Esters (FAME), especially pure FAME, e.g. 100% FAME can experience decreased engine oil viscosity over time.

Fuel oil contamination in engine lubricants is a known phenomenon, and most marine-grade engine oils are formulated to tolerate certain levels of such contamination while maintaining operational performance.

The impact of FAME contamination is more pronounced in four-stroke trunk piston engines due to their design and operational characteristics. These engines use a common oil sump for both crankcase and cylinder lubrication, making them more vulnerable to fuel ingress through injector leaks or blow-by gases. Unlike two-stroke crosshead engines, which have separate lubrication systems that limit fuel-oil interaction, four-stroke engines continuously recirculate the same oil, allowing FAME (which has a high boiling point and low volatility), to accumulate over time. This leads to a more significant reduction in oil viscosity and faster degradation of lubricating properties.

A typical SAE (Society of Automotive Engineers) 30 grade engine oil has a viscosity of about 90 to 110 cSt at 40°C and a B100 (100% FAME) or its fossil counterpart such as DMA (distillate fuel) has a viscosity in the range of 4 cSt at 40°C. Any contamination of the fuel (distillate or Bio distillate blends contain FAME)  into the used engine oil can therefore significantly reduce the viscosity of the used engine oil.

Most OEMs specify both minimum and maximum viscosity limits for engine oils, beyond which the engine must not be operated to avoid wear or lubrication failure. For example, a common condemning limit is a 25% reduction in viscosity at 40°C from the fresh oil value. In the case of an SAE 30 grade oil (with a typical fresh viscosity of around 90 cSt at 40°C), this corresponds to a minimum allowable limit of approximately 67 cSt.

When comparing the viscosities of distillate fuel and B100, there is no significant difference (both typically range between 3 to 5 cSt at 40°C). However, a noticeable drop in engine oil viscosity is not usually observed when engines operate on conventional distillate fuel. This is likely due to the higher volatility and lighter fractions present in fossil fuels, which tend to evaporate over time. Additionally, the routine top-up of fresh oil during engine operation, needed to compensate for losses from evaporation and leakage, helps maintain a more stable overall oil viscosity. As a result, the dilution effect is minimised, and the lubricating oil retains its properties for a longer duration compared to operation on B100. 

Distillation Behaviour Analysis of FAME

ISO 3405 is an international standard that outlines a laboratory method for determining the distillation characteristics of petroleum and related products at atmospheric pressure. This tests helps us to understand the composition and behaviour of fuel during storage and use including the tendency to form vapours.

Typically in this method, the sample is distilled under controlled conditions. Throughout the distillation, the temperature at which specific volumes of the sample evaporate is recorded. Key measurements include, Initial Boiling Point (IBP) -Temperature at which the first drop of condensate is collected, Final Boiling Point (FBP) -Temperature at which the last drop of liquid evaporates and temperature at Specific Recovery Percentages, temperatures corresponding to 10%, 50%, and 90% volume recovery, among others. The collected data is used to construct a distillation curve, which illustrates the boiling behaviour of the sample.

In order to understand this phenomenon we compared the distillation characteristic of a 100% FAME (B100), 30% FAME (B30) and pure straight run distillate fuel using the ISO 3405 method. Below is a graph illustrating the differences in the distillation characteristics.

Initial Boiling Point 
From the above figure we can see that a B100 has a very high IBP as compared to a B30 and Distillate fuel.  

B100: ~272°C | High — FAME starts evaporating late, indicating low volatility.

B30+DMA70: ~175°C  | Blend behaviour — initial light fractions (from DMA) start boiling early.

100% DMA: ~172°C Volatile — begins boiling almost immediately.

Impact – Higher IBP in B100 means relatively poor cold start and atomisation; DMA ignites easily

Shape of curve and implication

B100 | Flat and elevated | Narrow boiling range, all components are heavy.

B30  | Gradual and intermediate | Balanced volatility — mix of light and heavy fractions.

DMA | Steep rise from early stage | Broad volatility, good combustion over temperature range.

Impact: B100 may cause issues in engines designed for distillates due to poor vaporisation.  Due to the heavy components in the B100 any fuel oil that is leaked into the sump, remains in the sump oil and does not easily evaporate where as in the case of DMA or (B30) the lighter fractions evaporate. This means the vessel may witness a reduction in the topping-up of fresh oil when a B100 is used, as the sump oil may tend to rise due to the FAME contamination.  

B30 offers a compromise, cleaner burn than B100, whilst DMA gives optimal performance in terms of ignition and combustion. 

Case study 
VPS examined a few vessels operating on B100 for extended periods of time, in order to monitor the reduction of viscosity and relationship with FAME contamination. The study includes tests that were carried out on four-stroke auxiliary engine oils (SAE 40) over a period of two years’ operating on B100. 

The below graph shows a comparison of change in viscosity over the given time period.  
 

Due to the above stated impact of FAME on engine oil, measuring the FAME  in used engine oil when operating on Bio blends with FAME becomes very critical. 

FAME Detection in Lubricating Oil

FAME content is routinely measured in distillate fuels using techniques such as Nuclear Magnetic Resonance (NMR) , chromatography and FTIR (Fourier Transform Infrared Spectroscopy).

FTIR detects FAME by its characteristic absorption band at around 1745 cm⁻¹, which is due to the ester carbonyl bond.

This bond is absent in hydrocarbon distillate fuels and the same principle can be applied to petroleum-based lubricants.

The FAME content of a petroleum based lubricating oil can be found by measuring the carbonyl bond around 1745 cm-1.  

Since there are typically no overlapping bonds with the lubricating oil, the percentage FAME content can be calculated from a typical Lambert-Beer law calibration curve.  

FTIR offers high speed, repeatable determinations requiring very little sample preparation. 

VPS recommends that vessel operators using Bio blends containing FAME routinely monitor the FAME content in the engine oil and take appropriate measures to maintain the lubricating oil  quality. 

Mitigation and Preventive Measures:

To mitigate the effects of FAME contamination in engine oils, operators should implement routine monitoring of oil viscosity, oxidation, and FAME content using FTIR analysis. This allows early detection of degradation and helps adjust oil change intervals based on actual condition rather than fixed hours. Maintaining fuel injector integrity is essential to reduce fuel ingress, and operators should review OEM viscosity limits in light of operational experience with biofuels. Together, these steps help preserve lubricant performance and protect engine components when running on high-FAME or pure biofuel blends.

Key Takeaways 

Engines operating on B100 biofuels are more susceptible to rapid oil viscosity degradation due to FAME dilution. Unlike conventional fuels, FAME does not evaporate easily, leading to cumulative effects. Proactive monitoring, using FTIR-based FAME quantification, and adjusting maintenance schedules accordingly, are essential to mitigate the operational risks associated with biofuel use in four-stroke marine engines.

For further information and support regarding the use and effect management of lubricating oils when using FAME-based biofuels and your general oil condition monitoring requirements, please contact: marketing@vpsveritas.com

Join Senior VPS Management and fellow Expert Panelists at the next Free VPS Seminar, covering key decarbonization topics, including low-to-zero carbon fuel management issues. Registration link: https://forms.gle/dvsfJMaMJsGZgcxn8

A Stack of Reasons for Continuous Emissions Monitors in Shipping – Why understanding the challenges faced by Ship Owners/Operators is so important.

By Chris Briggs – VP Commercial, VPS Emsys.

Driven by tightening global regulations, emissions monitoring systems are emerging as a critical investment for shipowners and charterers, but operating in this changing landscape is not easy. This is precisely why futureproof, flexible and modular solutions are critical characteristics in today’s advanced emissions monitoring technologies which can extend beyond  compliance to help enhance operational efficiency of entire fleets.  

However, as the maritime industry now faces a step change and potentially profound transformation over the coming years, the VPS Emsys approach has never been more important: VPS Emsys is not a traditional Continuous Emissions Monitoring System (CEMS) manufacturer. Since conception, the vision and mission has always been “Emissions Monitoring for Ships”. This direction is at the core of the growth and development of the Emsys product portfolio. To date numerous ship owners and operators have already benefited from Emsys systems onboard their vessels, in supporting their navigation towards decarbonisation and sustainability.  

Regulations will certainly become more stringent and therefore, low-to-zero carbon fuel adoption will continue to evolve as advances in, technology, safety, availability and commercialization become realised. With all this, the composition and volumes of Green House Gases (GHG) emitted will fall increasingly under the spotlight. 

This evolution will always present uncertainty for shipowners, but the implications of not managing these transitions can be mitigated with investment in scalable emissions monitoring systems, that use technologies which can adapt with upgrades and further integration.  

Retrofitting and upgrading of new technology on ships are a constant, but still a challenge. Vendor selection and decision making for installing new technology needs to be built on trust, which is gained through accuracy, reliability and support. For ships in particular, a vendor with the ability to provide service globally with a team of dedicated “marine” service technicians is key.  

When considering emissions measurement technology in terms of accuracy and reliability, laser technology offers superior performance. This technology, coupled with gas extraction via “Hot-Wet” capabilities, meaning there is no need for cooling and dilution of the extracted exhaust sample, offers so many benefits.  

Firstly, removing the need for additional gas conditioning equipment, makes the system easier to install and maintain during operation. Then, using solid state laser technology which does not require cooling to operate reliably, means that its calibration does not drift in service. This is particularly relevant for a global trading vessel that can experience large changes in ambient temperatures. The advantage being that this removes the need for regular system calibration and investment in expensive calibration gases.

Single analyser laser technology, configurable for multiple gas measurement without the need for instrument air, gas conditioning units, or large amounts of space, make them ideal for retrofit projects, or complex new-build applications, where space is at a premium. 

With shipowners and operators in mind, employing technology such as this, enables vendors to offer low through life operation cost, due to low maintenance and minimal consumables, thereby significantly reducing OPEX.  

Simplicity through reduced complexity, alleviates major failure points, increasing reliability and the demand for in service maintenance by ship staff or specialist technicians.  

An assured trust in accuracy is vital for shipowners to ensure a sound commercial investment. Whilst the technology used and how it is deployed contributes to this, third party verification through classification society “type approval” to the necessary regulation, such as the NOX technical code, provides further confidence and peace of mind shipowners need to make the right choice of emissions measurement system.  

A common question arising from conversations in the industry is “I have data, but what can I do with it?”.  It’s a very valid question and something advanced CEMS systems are increasingly capable of helping to answer.  

The best solutions offer data in real time, enabling vessels to assess the amount of emissions produced during a particular operating condition at a particular point in time. Armed with this knowledge, vessels are able to make informed decisions to alter their operating circumstances in a way that achieves lower emissions outputs. 

Emissions data collection is multifaceted, reporting being the obvious main feature. However, historical and retrospective data is incredibly valuable for analysis, learning and improvements too, especially when combined with off-ship data technology for shore-based analysis.  

Taking this further, by linking on-board emissions hardware & software to decarbonisation cloud based  platforms, enables automatic processing through verifiers to submit regulatory reports on behalf of shipowners. Thereby reducing the administrative burden of managing and processing the data collected, with the confidence of ensuring compliance.  

Each vessel has its own operational nuances, meaning that every optimisation process is slightly different. With that in mind, solutions that are easy to use, both onboard and ashore, which give crews and shore-based teams greater insights, will ensure that precise measurements and continuous improvements are realistic, scalable goals for any vessel.  

Keeping up with evolving regulations is probably the biggest challenge faced by shipowners today. Therefore, it is also the challenge for technology companies, system suppliers and integrators to provide the solutions to successfully overcome these challenges.

In the opinion of VPS Emsys, the best way to achieve this is to intimately understand our customers challenges and needs. Transparent collaboration between shipowners and vendors is a key way to make that happen.  

With this approach, aligned in a common goal, together we can help to ensure the shipping industry meets the ambitious targets set out by the IMO and decarbonise our industry in an efficient and sustainable way.  

For further information and support regarding continuous emissions monitoring, please contact: chris.briggs@vpsveritas.com

VPS, the world’s leading marine fuel testing company, updates their recent findings regarding contaminated marine fuel delivered to vessels in the Port of Singapore.

Following its bunker alerts issued on the 11th and 31st March 2022, VPS can confirm it has now identified 60 vessels that have received High Sulphur Fuel Oil (HSFO) deliveries containing chlorinated hydrocarbons bunkered in the port of Singapore. Each of these deliveries were made from two suppliers and 12 delivery barges, between mid-February to mid-March 2022 and contained chlorinated hydrocarbon contaminants of up to 2,000ppm.

VPS also confirms, no new reports have been received from vessels experiencing, seriously damaging effects due to these bunker fuel contaminations, other than the 14 originally reported in our press release of 31st March.

VPS CEO Malcolm Cooper stated “We have now identified a significant quantity of bunker fuel, 140,170 metric tonnes to be precise, that has been contaminated with chlorinated hydrocarbons. This equates to $120 million at current market value. We would advise our customers to be very aware that this contaminated fuel remains in the supply chain and could potentially be reused or re-blended for use as a bunker fuel. The best mitigating measure to prevent the risk of receiving and using this fuel, is to test at the point of bunkering. However, as shown in this case, standard ISO8217 test methods are not sufficient to detect these contamination events. VPS therefore strongly recommend GCMS screening as the most effective method of detecting chemical contaminants in bunker fuel including chlorinated hydrocarbons.”

By Steve Bee – VPS Group Marketing & Strategic Projects Director.

Today’s ships can carry a number of different marine fuel types, from High Sulphur Fuel Oils (HSFOs), to Very Low Sulphur Fuel Oils (VLSFOs), Marine Gas Oils (MGOs), Ultra Low Sulphur Fuel Oils (ULSFOs), Biofuels, LNG and Methanol. Each of these fuels have varying degrees of stability, or instability, which can be triggered by numerous causes and effects.  

However, to mitigate the risks of de-stabilzation, a range of fuel management approaches can be applied to marine fuels. This paper aims to cover the more common fuels, their associated stability issues and how to monitor and potentially overcome them.

High Sulphur Fuel Oil (HSFO) & Very Low Sulphur Fuel Oil (VLSFO) 
Today, residual fuel is often referred to as HSFO, whereas VLSFO is a blended fuel of mainly distillates and residual fuels, which results in a usually less stable fuel than HSFO. Yet VLSFOs are still prone to certain similar stability concerns as its 100% residual counterpart and hence the associated test parameters.

Residual fuel, is comprised of process residues where the fractions did not boil during refining. These fuels contain asphaltenes, usually between 3-10%, which are the organic part of the crude oil, or residual oil, that is not soluble in straight chain solvents, eg pentane, heptane.  

Asphaltenes exist as a colloidal suspension stabilized by resin molecules (aromatic ring systems) in the oil. The stability of asphaltic dispersions depends on the ratio of resin to asphaltene molecules. 

The determination of the quantity of resin is important in estimating the potential damage created by asphaltenes. Asphaltene precipitates as a result of pressure drop, temperature, acids, mixing of incompatible oils, chemical contaminants, or other conditions and/or materials that break the stability of the asphaltic dispersion. This is the sludge witnessed when marine fuels de-stabilize.  

The ability to retain asphaltenes within the fuel solution is known as the “Stability Reserve” of the fuel.

Bulk residual fuel stored for long periods can become unstable, where the asphaltene content can precipitate out of solution causing the formation of sludge. This has the potential to block filters and pipes, leaving tanks with an unpumpable residue.

The ‘fuel break up’ is dependent on the nature of the liquid hydrocarbons in which the asphaltenes are suspended. If the medium is aromatic then they will remain in suspension. If it’s paraffinic, the asphaltenes may have a propensity to coalesce into sludge. Once a fuel has chemically broken down there is no way to satisfactorily reverse the process. Precipitated asphaltene cannot be redissolved.

Industry best practice is to avoid mixing fuels. Arbitrary comingling can lead to incompatibility problems and a loss of stability in the resultant blend. For example, when a heavy fuel oil with a high asphaltene content is mixed with a low-gravity distillate with a predominance of paraffinic aliphatic hydrocarbons, the stability reserve can be depleted and asphaltenes can flocculate and precipitate as sludge.  

Compatibility problems must be treated as a critical concern, as they can lead to fuel starvation in diesel generators, potentially resulting in power loss. Incompatibility may cause fuel system paralysis  and the subsequent clean-up is often both complex and time-consuming. There is a very simple, indicative test which can be carried out to highlight a fuels compatibility, the ASTM D4740 “spot test”. Here a blend composed of representative volumes of the sample fuel and the blend stock is heated and homogenized. A drop of the blend is put on a test paper and heated to 100°C. After 1 hour, the test paper is removed from the oven and the resultant spot is examined for evidence of precipitation and rated for compatibility against D4740 reference spots. 

To provide valued information regarding a residual fuel’s stability there are a series of laboratory tests to further assess stability:

Total Sediment Potential (TSP) 
The measurement of sediment involves filtering the oil through a filtration medium under vacuum. The mass of sediment is reported as a percentage by mass. The test provides an indication of the stability of the fuel as asphaltenes precipitate out forming sludge, blocking filters and choking purifiers. For residual fuels, TSP involves ageing the oil at 100ºC for 24 hours. So far in 2025, 1% of all HSFO off-specifications are related to TSP, whilst 3% of all VSLFO off-specifications are related to the same parameter.

Total Sediment Accelerated (TSA): (Chemical Aging): A sample of the fuel is heated to achieve a viscosity of approximately 50Cst. After 10 minutes, a measured amount of hexadecane is added and the sample is placed in an ageing bath at 100ºC  for one hour. The sample is shaken vigorously prior to passing through a filter paper. The result of the test is reported to the nearest 0.01% m/m and is expressed as Total Sediment Accelerated (TSA).

The agreed limit for both TSP and TSA is 0.10% m/m. A fuel that falls below this limit should be viewed as thermally stable and able to homogenously maintain asphaltenic phase suspension.

Total Sediment Existent (TSE): A fuel sample is heated to 100ºC and passed through a filter paper. The amount of dry sludge retained on the filter paper correlates with the amount of sludge that is likely to be separated by an on-board centrifuge.

Separability Number, or Reserve Stability Number (RSN): is a complimentary test to the hot filtration stability methods of TSP, TSA, TSE. Using this method, the fuel is mixed with toluene which is aromatic and keeps the asphaltenes in solution. If the sample has poor stability reserve, then asphaltenes will precipitate when Heptane is added- which is naphthenic.  As asphaltenes fall out of solution the transmittance through the sample increases resulting in a measure of the separability number.

Separability Number is an excellent accompaniment to the routine hot filtration methods.  It can identify potentially troublesome fuels (unstable) even when the HFT method is indicating a low sediment content.   Conversely, it may indicate that a high sediment fuel is in fact quite stable and unlikely to form sludge.  This information in combination, is extremely useful from an operational perspective, as it will indicate in advance if and what mitigation steps are appropriate. 

It is estimated that the average storage life of a HSFO is around 6 months, whilst the more paraffinic to residual-blended VLSFOs have a storage life of approximately 3 months and tend to be far less stable.  

One fact to note regarding residuals, is the fuel can stratify over time, meaning the fuel components separate into distinct layers due to differences in density, temperature or composition. In storage tanks the heavier components settle at the bottom, with the lighter components at the top. Water and sludge may accumulate leading to microbial growth and corrosion. Stratified fuel can cause inconsistent combustion and damage to fuel systems.

Within a combustion chamber thermal stratification can lead to uneven air-fuel mixtures affecting ignition timing and combustion stability.

To prevent stratification within tanks, maintain homogeneous mixing, control temperatures and pressure and if necessary fuel stabilizers can be used. Whilst in a combustion system, optimized injection timing must be adhered to and the use of splitinjection techniques can be employed.

In terms of HSFO stability, 2025 year to date, shows global TSP data is relatively stable, with only 7.1% of all HSFO samples tested exhibiting a TSP of 0.06-0.10% and only 0.1% of samples tested exceeding the specification of 0.10%.

Whilst, 3.5% of all VLSFO samples tested showed a TSP of 0.06-0.1% and only 0.3% exceeding the specification 0.10%. 

However, the same HSFO samples when tested for RSN, show 44% exhibit poor stability reserve, 36% show intermediate stability reserve and only 20% showing a stable level of reserve. This data indicates that whilst the HSFO may have a low volume of potential sediment, the likelihood is that 44% of the fuel will precipitate asphaltenic sludge.

However, VLSFOs tested for RSN this year have shown only 3% of samples with a RSN>10 and only 5% with an RSN of between 5-10. 

A further cause of destabilization of fuel is the presence of chemical contaminants. Chemical contamination can arise from various sources. With increased levels of fuel blending, various blending agents and cutter stocks can contain potential contamination. The complex fuel supply chain is also a potential entry point for crossproduct contamination, along with possible adulteration of fuel with waste materials.

Contaminants such as volatile chemicals, styrene, dicyclopentadiene, indene, chlorinated hydrocarbons, phenols, have a proven history of destabilizing fuel, initiate sludging, as well as causing operational issues such as, injector failures, fuel pump damage, exhaust problems, to name but a few.  

To mitigate the risks associated with the presence of chemical contaminants, pre-burn screening of the fuel using Gas Chromatography Mass Spectrometry (GCMS), is a highly  effective means of identifying potentially dangerous chemicals within the fuel. Last year, 8.2% of samples which undertook GCMS-Headspace Screening, gave rise to a “Caution” result, indicating the presence of at least one volatile chemical contaminant, highlighting the benefit and value if undertaking fuel screening before even burning the fuel. 

Marine Distillates 
As marine distillates are relatively highly refined fuels compared with residual fuels, they contain no asphaltenes and consequently are more stable than residual fuels. A typical distillate may be stable for 12 months.

They main concerns with distillates relate to their cold-flow properties, lubricity, microbial contamination, oxidation stability and concerns relating to the presence of Fatty Acid Methyl Esters. For further marine distillate information, please refer to the VPS article:  Distillate Fuels: The "Trouble-Free" Marine Fuel? | VPS

Biofuels 
Fatty Acid Methyl Ester (FAME) based biofuels, are the most common biofuel used for marine applications. However, this fuel-type is far less stable than marine fossil fuels due to a high degree of unsaturation and propensity to oxidise. Exposure to light, increased temperatures and length of storage time, will all contribute to the destabilization of the fuel. As FAME-based biofuels oxidize, their colour becomes darker, plus their viscosity and acidity increases. All this can lead to sludging, blocked filters and pipes and possibly lead to fuel-starvation to the engine.

There are specific tests which can be carried out to monitor and determine the stability of FAME-based biofuels:

Oxidation Stability (EN 15751) – The Rancimat method is an accelerated-aging test, where the results are given a traffic-light coding: Green >8hr; Amber 5-8hr; Red <5hr. 

Iodine Value (EN 14111) is used to determine the total unsaturation of fatty acids. Iodine Value is reported as the number of iodine grams necessary to react completely with 100g of samples and its limit is set by the EN 14214 regulation.

VPS results show a good inverse correlation between Oxidation Stability & Iodine Value as expected.

Linoleic Acid & Linolenic Acid – FAME stability is strongly affected by the presence of polyunsaturated fatty acids (PUFAs) in the feedstock, and the 2 most common PUFAs are linoleic acid and linolenic acid and can be measured in 100% FAME only by using this GC method. 

Summary 
In terms of precautionary actions relating to fuel stability, irrespective of fuel type, the following should be undertaken:

• Avoid mixing bunker fuels from different sources wherever possible  
• Store fuels separately until compatibility testing has been carried out  
• Do not mix straight-run fuel oil (the product of atmospheric or vacuum distillation) with a cracked (additionally processed) one. If this is not possible, keep the ratio to a minimum.  
• Steer clear of mixing fuels with greatly dissimilar densities  
• Where possible choose fuels with similar viscosities and densities  
• Where operationally possible, do not mix a fuel oil with a marine gas oil, or biofuel.

All marine fuels exhibit numerous and different stability issues depending upon their type and grade. Each fuel requires specific fuel management considerations and testing requirements to determine and monitor their stability.

For further information regarding marine fuel stability, please contact: steve.bee@vpsveritas.com

By Peter van den Boomgaard: VPS BQS Business Development Manager & Steve Bee: VPS Group Marketing Director.

Marine bunker fuel purchases are mostly made between a vessel operator and a fuel supplier, whilst the vessel is in a port hundreds, or thousands, of miles away from its company offices. Whilst each bunker delivery has an average cost of $1million, the purchaser is not present when the fuel is delivered to the ship. For this reason, the best mitigation strategy is the employment of an independent Bunker Quantity Surveyor, to ensure the correct amount of fuel is delivered to the vessel, in line with the contractual supply agreement.

As the pioneers of the Bunker Quantity Survey (BQS) service back in 1987, VPS have performed almost 200,000 surveys across the world’s ports, using knowledgeable, impartial, independent Surveyors, who carry out their work according to the detailed VPS Code of Practice.  

A recent investigation covering 10,000 surveys, showed by using a VPS surveyor, a single vessel can now potentially save up to $145K per year, by checking density shortages, measurements, temperatures, draining bunker lines and remaining onboard fuel (zero soundings) when the bunker tanker supposed to be empty. By using a VPS Surveyor, a customer can mitigate risk and delivery tricks, ultimately receiving the correct quantity and quality of fuel and avoid lengthy claims processes. 

The Bunker Quantity shortage risk potential for any bunker fuel delivery can occur for various reasons which may be categorized as follows:

1. The Ordered Quantity & the Bunker Delivery Note quantity was different. 
2. The Bunker Tanker delivered quantity & Bunker Delivery Note quantity was different. 
3. The Bunker Tanker delivered quantity & the Vessel’s received quantity was different. 
4. The Bunker Tanker delivered quantity fuel density was different from the Vessel’s received fuel density. 
5. The ROB quantity on the vessel as measured by the Bunker Surveyor was different from that declared by the vessel’s staff.

Since bunkers are sold by weight but delivered in volume, the presence of a professional bunker Surveyor is needed to ensure that the correct quantity is delivered. A thorough and experienced Surveyor prevents fraudulent behaviours and the employment of “tricks of the trade”, which can result in short deliveries of fuel. Plus an inclusive investigation to determine the remainingon-board fuel levels, supports finding hidden bunkers as well as the investigation of shortages or alleged “cappuccino” practices, during bunkering operations. The Surveyor will also offer a helping hand with inconsistency, or errors on the BDN and advise the vessel’s staff accordingly assisting in quantity dispute resolution. 

VPS Surveyors are all equipped with professional, calibrated measuring tools and are often seen by the Chief Engineer as a valued support. The Surveyor will advise the Chief Engineer with any safety checklist, custom papers and papers provided by the supplier, such as a bunker requisition and sample labels and special requirements from the customer.

It is the Surveyor who supervises the whole bunker operation, making sure the bunker hoses are in a good condition and whether they are well supported in accordance with relevant international standards. The Surveyor will also assist in effective communication between the bunker tanker and the vessel, to enable immediate shutdown if this should be necessary.

Another responsibility undertaken by a Surveyor is the taking of representative samples by drip method. This is done preferably at the vessel’s manifold (point of custody transfer). This sample has to be collected and witnessed during the entire bunker operation and the content should be properly mixed and poured into the bottles when the bunker operation is finished. The bottles have to be labelled, sealed and distributed between all parties concerned. The presence of the VPS Bunker Surveyor, throughout the entire fuel delivery, can therefore ensure that the sampling process is closely monitored, and internationally accepted survey & sampling standards are followed, in line with SS 600:2022 Code of practice for bunkering, SS 648:2024 Code of practice for bunker mass flow metering, ISO 13739:Petroleum Products‐ Procedures for the transfer of bunker to vessels(Second Edition 2020‐02) & the VPS Bunker Quantity Survey Code of Practice 2019.

This will correct any incorrect bunkering practice & ensure that a truly representative sample at custody transfer is taken & documented to give the highest likelihood of successful claims handling. 

Case Study 

A recent Case Study showed a vessel from a large Container Fleet, bunkering in ARA in early July, was taking delivery of 400mt MGO and 4,000mt VLSFO. The bunker supplier attempted to short deliver on both fuel grades:

MGO: 
Nominated quantity: 400.000 MT 
Barge (BDN) figures: 385.687 MT 
Vessel figures: 383.342 MT

Bunker Tanker delivered 14.313 MT short from nominated quantity. Price of MGO $720 x 14.313 = $10,305.  

VLSFO: 
Nominated quantity: 4000.000 MT 
Barge (BDN) figures: 3937.761 MT 
Vessel figures: 3937.251 MT

Bunker Tanker delivered 62.239 MT short from nominated quantity. Price of VLSFO $520 x 62.239 = $32,364.

Due to correct measurement, temperatures, draining bunker lines and ROB on the bunker tanker, the Surveyor was able to calculate the correct quantity delivered.

The presence and work of this VPS Surveyor saved the vessel $42,669. 

Since January 2017, the use of Mass Flow Meters (MFM) for bunker fuel delivery in Singapore has been mandatory. In addition to Singapore we will see similar mandatory MFM deliveries in the ports of Rotterdam, Antwerp and Bruges as of 1st of January 2026. This will significantly impact the working processes of our Surveyors. Although the MFM system will show how much fuel has been delivered, it is definitely not a plug and play system, requiring numerous checks, carried out by trained bunker Surveyors in order to make sure the correct quantity has been delivered:

• Check MFM approval for ‘use in trade’. 
• Check meter calibration record. 
• Check meter zero verification report. 
• Check bunker tanker’s meter totalizer log. 
• Check all system seals. 
• Witness setting of meter reading to zero. 
• Monitor whether stripping is done. 
• Witness meter reading at the end of the bunkering. 
• Obtain copy of Metering Ticket. 
• Ascertain vessel’s received quantity. 
• Ensure proper sampling is done by all parties concerned and check seal numbers.

Overall VPS data has shown the following: 
An average loss of ‐6.6 M/tons for HFO/VLSFO and ‐3.7 M/tons for MDO/MGO can be expected for a bunker delivery. This translates to an approximate total loss of $6,008 per bunkering or $60,084 per year per vessel.  

There is a 4.6% chance of a bunker quantity shortage of an average ‐20.2 M/tons during a bunker delivery where a Note of Protest is issued for a claim. This translates to an annual loss of $10,504 per vessel. 

ROB Quantity on vessels requires consistent monitoring to avoid excess bunker expense. Any undeclared bunkers constitute cost savings. The average excess ROB found onboard was 15 M/tons. This translates to a loss $7,800 per bunkering or $78,000 per year per vessel.

Improper sampling can compromise a quantity dispute related to density. This translates to a loss of $1,420 per bunkering or $14,200 per year per vessel.

Overall, VPS data has shown that bunkering activity needs to be methodically controlled with the constant presence of a knowledgeable & professional VPS Bunker Surveyor to avoid a quantity shortage situation. Failure to do this will result in a potential total bunker quantity loss in the order of over $160,000 per vessel per year. VPS is able to generate these savings through our high‐quality surveying service, underpinned by a detailed BQS Code of Practice and a rigorous training and refresher programme for all Surveyors. The engagement of a VPS Bunker Surveyor at approximately 10% of this cost will not only save money, but significantly reduce management stress, time & reputation. 

Globally, VPS Surveyors’ work is regularly checked via a quality audit programme ensuring all surveyors follow strict procedures, use the right equipment and to check their performance on board. This sets out the best practise regarding documentation, equipment requirements and verification of procedures during a bunker operation. VPS Surveyors are specialists in the performance of their work, ethical, independent and working with the highest degree of integrity.

For further information and support regarding VPS Bunker Quantity Surveys, please contact: petervandenboomgaard@vpsveritas.com