Bunker Fuel Quality

VPS: How elevated catfines can damage marine engines

VPS’ latest article highlights the dangers catfines can cause within vessel engines and how to avoid damages by using its fuel system check service.

Published

2 months ago

May 7, 2026

Admin

Marine fuels testing company VPS on Wednesday (6 May) released an article highlighting the dangers catfines can cause within vessel engines and how to avoid damages by using the VPS fuel system check service:

A common concern of maritime chief engineers, regarding vessel engine damages, is the presence of highly abrasive “catfines” within marine fuel. To fully understand the seriousness of this issue, we first need to understand the source of the problem.

Oil refineries use catalysts in their Fluid Catalytic Cracking Units (FCCU) or “Cat Plants” to process crude oils in the production of numerous products from the source crude. These catalysts are high in aluminium silicate (Al+Si) content and over time and repeated use, can breakdown and fragment into smaller particles, or catalytic fines. These catalytic fines, known throughout the industry as “Catfines” can eventually find their way into the heavier refining streams and consequently the HSFO and VLSFO fuels being burnt onboard vessels. Higher levels of catfines within the fuel can be extremely abrasive and damaging to ships engines.

It is critical to note the ISO8217 specification limit for Al+Si for residual fuels delivered to the ship, is 60 mg/Kg for all revisions post-2005. This level is significantly greater than the OEM engine inlet limit of 15mg/Kg and therefore the fuel requires efficient onboard purification, monitored via a frequent fuel-system-check, process in order to avoid potentially catastrophic engine damages.

From a recent review of more than 3,000 Fuel System Check samples taken before-purifier and after-purifier, VPS found 16% of the fuels after-purifier catfine concentrations were above the 15mg/Kg OEM limit. This indicates that some 480 vessels had purifiers failing to operate to their optimum efficiency in order to protect the engine.

At this time of the Middle East military conflict, one might suspect that refinery output around the wider region to have been impacted by crude availability, thus reducing the ultimate throughput of any refinery. However, under certain refinery operating conditions, reduced throughput may lead to higher relative concentrations of catfines in heavier streams. Thus these catfines can potentially end up in marine fuel supply chains.

In 2-stroke crosshead engines, ineffective removal of catfines can result in their entry into the combustion chamber, where they cause abrasive wear between piston rings and cylinder liners. Conversely, medium speed engines tend to be generally more tolerant, due to continuous oil circulation and filtration, but still vulnerable if catfine levels are excessive.

Another consideration within this equation is that cylinder oil (used exclusively in 2 stroke engines) is “single use” and exhausted after first use. Thus it’s overuse, in any attempt to combat catfines and minimise wear can be commercially punitive, unnecessary and in some cases contribute to damages, exacerbating the “grinding paste” effect occurring within the cylinder liners.

Cylinder lubricants are primarily a base oil, plus an additive “pack” (a combination of carefully selected compounds focused on providing various qualities e.g. Base Number (BN) to combat fuel sulphur and detergency to clean etc). However, inappropriate cylinder oil selection, or excessive feed rates may contribute to deposit formation on piston crowns and ring zones.

Over-lubrication is not an effective mitigation strategy as it may increase deposit formation and will certainly increase operating costs.

A first step to prevention of catfine damage would be in the selection of a reputable supplier, known for delivering low-catfine fuel. Data in relation to this is highlighted in the VPS PortStats application. However, its recognized on numerous occasions, the owner/operator of the ship dealing with sub-standard fuel is not the entity who purchased the fuel. Therefore, further practical considerations should also be made including, appropriate tank cleaning, circulation and movement to avoid catfine settling and concentration at much higher levels than the original test results obtained from the vessel manifold sample.

In the case of managing catfine levels above OEM engine entry limits, effective purification remains key. Statistically, a vessel will suffer one to two instances of main engine damage over the course of her operational lifetime. These costs can reach millions of dollars, far more than the average main engine damage costs of $650K highlighted in the Swedish Club paper “Engine Damage”. https://www.swedishclub.com/uploads/2023/12/TSC-Engine-Damage-WEB2023.pdf

Monitoring and Quality Control – Fuel System Checks (FSC)

It is essential that fuel samples are taken both before and after purifier. This should be carried out at regular intervals (on a quarterly basis), with increased frequency when high catfine levels are identified. In addition, whenever VPS see a vessel manifold sample with a catfine level >40kg/Kg, an alert is automatically sent to the vessel, with the instruction to take additional before and after purifier samples, as a cautionary procedure.

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.

Core Operating Conditions

In addition to the FSC programme it is key to undertake the following practices:

Maintain the correct inlet temperatures as purifiers rely on centrifugal separation, enhanced by density differences. The fuel must be heated to the manufacturer-specified temperature for optimal separation and reduced carry-over.

Ensure the separator is correctly configured and operated (e.g. gravity disc selection in conventional units or proper control settings in automated systems) to avoid reduced separation efficiency, which could allow water or catfines to pass through to the engine.

Keep the feed-rate of fuel slow and steady. Running purifiers in parallel at minimum feed-rate improves separation and reduces carryover.

Match settings to oil density. Density changes with fuel grade, so adjusting settings ensures proper bowl separation.

Maintenance Practices that Directly Improve Efficiency

Clean filters and heaters regularly. Blocked filters or fouled heaters reduce flow and temperature stability, lowering purification quality.

Clean fuel tanks at scheduled intervals. This prevents high sediment and catfine concentrations from overwhelming the purifier.

Avoid by-passing any fuel-treatment equipment. By-passing risks engine damage and eliminates the purifier’s protective function.

Ensure adequate spare parts are onboard. Worn seals, gaskets, or disc stacks, reduce bowl pressure and separation efficiency.

Follow the vessel’s preventative maintenance schedule and manufacturer’s intervals. Planned maintenance ensures consistent cleaning, inspection and overhaul cycles.

Summary

So, with the recent survey by VPS finding 16% of fuels after-purifier catfine concentrations were above 15ppm, this highlights the fact, these purifiers are failing to operate to their optimum efficiency and their primary function to protect the engine.

All the above, monitoring, quality control and operational steps, are key to ensure a vessel’s engine is protected from the abrasive wear catfines can cause. Plus, by following this advice, the vessel will see an improvement in combustion efficiency due to burning cleaner fuel. This will all result in reduced downtime and repair costs, avoiding purifier failures which can lead to major engine issues.

Photo credit: VPS
Published: 7 May, 2026

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Bunker Fuel Quality

Fuel quality issues drive 50% rise in bunker claims, says Gard

Gard says bunker-related claims increased significantly in between January and May 2026, with over 70 cases recorded – a 50% rise compared to 2025 and notes that most claims involve fuel quality.

Published

20 hours ago

June 22, 2026

Admin

Maritime protection and indemnity (P&I) club Gard on Friday (19 June) released a report on practical observations from recent cases of bunker-related claims, highlighting recurring challenges and essential considerations for managing fuel quality issues effectively:

Key findings

Sharp rise in bunker claims and geopolitics: Bunker-related claims increased significantly in early 2026, with over 70 cases recorded – a 50% rise compared to 2025. Most claims involved fuel quality, with a noticeable uptick following the escalation of the Middle East conflict.
Global risk profile with concentration driven by supply volumes: Bunker quality incidents were recorded worldwide, reflecting a broadly dispersed and global risk environment rather than a localized issue. Higher numbers of claims at major hubs such as Singapore, Houston, and ARA mainly reflect their large bunkering volumes
VLSFO remains the primary source of claims: Very Low Sulphur Fuel Oil (VLSFO) accounts for the vast majority of bunker quality claims. Its complex blended nature increases the likelihood of variability and contamination, making it more prone to quality issues. This reinforces that VLSFO continues to be the key technical risk area in marine fuel usage.
ISO 8217 compliance does not guarantee fuel suitability: A significant proportion of cases involved fuels that met ISO 8217 Table 2 parameters but still caused operational issues and damage to machinery. This underscores the growing importance of Clause 5, which focuses on whether fuel is fit for use and free from harmful substances. Standard testing alone is often insufficient, requiring more advanced analysis to identify problematic contaminants.
Claims are driven by both technical and contractual challenges: Bunker disputes are often complex due to misaligned contractual relationships between owners, charterers, and suppliers. Issues related to binding sample, parameter(s) to be tested, time bars and evidentiary requirements frequently complicate claims resolution.
Operational impact is often underestimated compared to headline casualties: While no major casualties were directly linked to poor fuel in this dataset, several vessels were disabled or required towage. These incidents can create high exposure when occurring in congested or coastal waters. The absence of catastrophic outcomes should not obscure the underlying operational risk.

This report draws on Gard’s claims data from the first five months of 2026, with additional data contributions from VPS.

Note: The full report titled ‘Beyond Specification: Bunker claims insights in early 2026’ can be found here.

Photo credit: Shaah Shahidh on Unsplash
Published: 22 June, 2026

Bunker Fuel Quality

Bunker flash: High concentrations of catalytic fines, elevated acid numbers found in Singapore

Maritec-Naias issued an alert regarding high levels of catalytic fines and elevated acid numbers present in multiple VLSFO bunker samples from deliveries in the Singapore port.

Published

1 week ago

June 15, 2026

Admin

Bunker fuel testing and marine surveying business Maritec-Naias on Friday (12 June) issued an alert regarding high levels of catalytic fines and elevated acid numbers present in multiple VLSFO bunker samples from deliveries in the Singapore port:

During the period of 20 May 2026 and 02 June 2026, Maritec Pte. Ltd. (hereafter referred to as Maritec-Naias) conducted testing on five samples representing Very Low Sulphur Fuel Oil (VLSFO) deliveries from two suppliers in the Singapore port. The analyses revealed Aluminium and Silicon (Al+Si) concentrations ranging from 61 mg/kg to 68 mg/kg.

It is important to note; these values exceed the ISO 8217:2010/2017 specification limit of 60 ppm but remain within the permissible tolerance limit of 72 ppm under ISO 4259 for a single test result. In this regard, Catalytic Fines content, (Aluminium+Silicon), above 60 ppm is regarded as high. Of the five samples, three originated from one supplier, while the remaining two were from another.

Aluminium and Silicon constitute the principal classes of abrasive solids in fuels. Elevated concentrations of such particles at the engine inlet can precipitate abnormal wear and tear of fuel system components, piston rings, and cylinder liners. To safeguard against this, many engine manufacturers stipulate a maximum threshold of 15 mg/kg Al+Si at the engine inlet.

The primary method of mitigating Catfines is through an efficiently operating fuel purification system. Monitoring Aluminium and Silicon levels both before and after centrifugation provides a reliable measure of the system’s effectiveness in removing these contaminants.

During a similar period, Maritec-Naias also tested fifteen bunker fuel samples representing VLSFO that exhibited elevated Acid Numbers, ranging from 2.0 mg KOH/g to 2.5 mg KOH/g. While these values remain within specification limits, they are nonetheless considered at higher side. Elevated Acid Numbers may stem from contamination with acidic compounds such as Phenolic compounds and Alkyl Resorcinols, often associated with Estonian Shale Oil. Such contaminants can lead to operational complications including sludge formation, fuel pump seizures, and compromised injection equipment cleanliness.

Maritec-Naias Recommendations

High Catfines monitoring: Maritec-Naias advises collecting samples at critical points within the fuel system — including the fuel oil tank transfer pump, before and after centrifuge, service tank, and after fine-filter — to evaluate the efficiency of fuel cleaning.
Elevated Acid Numbers: For fuels with elevated Acid Numbers, Maritec-Naias recommends conducting Gas Chromatography-Mass Spectrometry (GC-MS) using the Solid Phase Extraction (SPE) method to identify the specific acidic compounds present or upgrading your marine fuel testing package to MFTP Plus, which enables pre-emptive monitoring to detect major harmful substances prevalent in the market, such as Cashew Nut Shell Liquid (CNSL), Phenolic compounds and Alkyl Resorcinols that cause damage to equipment.

Maritec-Naias states, while all data and findings presented in this document are true, it does not reflect on the overall quality of fuel being supplied in Singapore region. If you intend to bunker at this region, please request for a Certificate of Quality (CoQ) prior to loading.

Photo credit: Hans Reniers on Unsplash
Published: 15 June, 2026

Bunker Fuel Quality

VPS highlights fuel quality management for vessels idled in Arabian Gulf, Gulf of Oman

Captain Rahul Choudhuri, President of Strategic Partnerships at marine fuels testing company VPS offers insight and advice on how to manage fuel quality onboard idle vessels in the Gulf region.

Published

2 weeks ago

June 9, 2026

Admin

Captain Rahul Choudhuri, President of Strategic Partnerships at marine fuels testing company VPS, on Monday (8 June) offered insight and advice on how to manage fuel quality onboard idle vessels in the Gulf region:

The Current Situation

Since the closure of the Strait of Hormuz to most commercial shipping in late February 2026, an estimated 1,550 vessels, carrying approximately 20,000 seafarers, have been unable to transit, or have chosen to remain at anchor in the Arabian Gulf, Gulf of Oman, and approaches. Traffic through the Strait, which normally averages around 138 vessels per day, has fallen to near-zero on most days. The conflict began on 28 February 2026, resulting in vessels being idle for approximately 90 days. Many are expected to remain idle until a navigable resolution to the situation emerges, which cannot be predicted at this time.

For vessel owners and operators responsible for such vessels, there is a need to focus on the technical consequences of extended idle upon fuel quality and what needs to be done in order to protect the vessel, crew and the environment.

Fuel Quality Deterioration During Extended Idle

Fuel deterioration in idle vessels is caused by a combination of time, temperature, water ingress, and inactivity. Each mechanism reinforces the others. The Arabian Gulf summer (June–September) is one of the most demanding storage environments in global shipping, with bunker tank temperatures on unshaded anchored vessels regularly reaching 50–55°C.

Biofuel Blends

The UAE, principally Fujairah and Jebel Ali, has begun supplying ISCC-certified marine biofuel blends, primarily FAME (UCOME) blended into VLSFO, at concentrations typically ranging from B10 to B30 (10–30% FAME by volume). Vessels that bunkered Biofuel blends before going idle face additional degradation risks that do not apply to conventional fuel:

FAME (UCOME) blends, may exhibit reduced storage stability. Although storage life varies, a typical shelf life is often considered to be around 3 to 4 months, after which the risk of oxidation, acid formation and microbial contamination may increase, particularly under elevated ambient temperatures.

FAME is hygroscopic and absorbs water from tank atmospheres, promoting microbial growth at rates significantly higher than conventional VLSFO. Here, the free-water monitoring frequency should be doubled for any tank containing a biofuel blend.

FAME can cause filter blockage. Depending on feedstock composition, may be susceptible to crystallisation at lower temperatures. Therefore, Wax Appearance Temperature testing should be performed before re-activation for any vessel sailing to cooler latitudes post-Gulf.