Connect with us

Analysis

Infineum: Ensuring on board operability of VLSFO bunker fuels

Some conventional fuel quality tests have struggled to provide sufficient guidance to ship operators since the introduction of VLSFOs, shares Infineum experts.

Admin

Published

on

marine fuels table 2

Rob Ashton, Infineum Marine Fuel Additive Market Manager and Dr Robert Rae, Infineum Fuel Technologist, in January published an article explaining how a simple-to-use spin test, which relates more closely to the stress factors fuels may experience on board a vessel, can give a better picture of whether VLSFOs provided into the marine marketplace are suitable for use.

There are currently two tests that are frequently used in the assessment of marine fuel stability – the Total Sediments test referenced in the ISO8217 standard and the Separability Number test (ASTM D7061). However, in a previous article (click here to read), Insight highlighted the shortcomings of these tests and showed how the Alfa Laval spin test can be used as a tool to assist mariners to determine if fuels are suitable for reliable on board operations from a stability and compatibility standpoint. The test is particularly attractive as it is a simple laboratory test using the fuel in question (with no addition of extra reagents/chemicals) and subjecting it to a short centrifugation step, which can then be correlated to actual on board operation of the ships fuel purifier systems.

In our view, the Alfa Laval spin test provides valuable support to the existing Total Sediments tests.

In the same article, we also referenced the Separability Number test (ASTM D7061), which responds to a very wide range of dispersant additives at very low treat rates and questioned whether this amount of additive offered any real benefit. In recent work we have been scoping out the potential of the spin test, including a study using a new fuel purification rig (a smaller scale version of what is used on board ship). This work suggests that a low treat rate of Infineum additive technology is effective at providing both excellent reserve stability number (RSN) response and significant on board operability benefits.

In order to understand the mechanisms at work here it is important to first explore the three test methods: Total Sediments, spin and Separability Number, in more detail.

Total Sediments test (TSP/TSA)

This test features in the ISO 8217 standard. Each test is a two-stage process featuring an aging step, (TSP is thermal aging and TSA is chemical aging) followed by a hot filtration step (TSE) through a 1.6 micron filter where a result of <0.1 mass % sediment is an acceptable result.

marine fuels table 2

The TSP is believed to be a better indicator of a fuel’s relative stability under storage whereas the TSA is thought to better represent fuels’ inter-compatibility. The Total Sediments test has served the industry well for many years. However, following the introduction of low sulphur residual fuel, the test has struggled to provide adequate protection or guidance for ship operators in assessing whether a fuel is suitable for use. For example, fuels having an acceptably low TSP/TSA (<0.1 mass % sediment) can exhibit on board issues with regard to excessive sludging, and conversely fuels having a high TSP/TSA (>0.1 mass % sediment) can operate effectively without on board issues. The 1.6 micron filter used in the hot filtration step may be contributing to the discrepancy as this does not directly equate to the filter mesh that is employed on board.

Infineum asphaltene management additives are capable of reducing TSP and TSA test results. However, high treat rates of additive are required to reduce or to break/disperse the asphaltene agglomerates into a size that is small enough to pass through the total sedimentation filter (see images below).

jan 22 spin test 1 1

Infineum additive effect in the TSP test

It is increasingly apparent that a supporting or bridging test is required, one that relates more closely to the stress factors that a fuel can experience in the supply system on board the vessel. Infineum has invested in the assessment of various tests and has determined that the Alfa Laval spin test method could help to provide confidence in operability protection to ship operators.

The Alfa Laval spin test

The Alfa Laval spin test is performed by heating the fuel in question to a defined temperature. The recommended temperature to be employed in the spin-test (and for on-board separation) is dictated by the viscosity of the fuel, as recommended by Alfa Laval. However, the temperature actually used on board may vary for other reasons and so the spin-test can be conducted at any temperature, and which reflects the intended/actual operational environment. The fuel is then placed into a temperature-controlled centrifuge where it is subjected to centrifugal force via a fixed rpm for a fixed period. Once the test is complete, the centrifuge tubes are removed and inverted so that the fuel oil drains out leaving the compacted sediment in the base of the tube. The fuel oil operability is evaluated by determining the quantity of sediment that has come out of solution from the fuel sample and settled at the bottom of the centrifuge tube. The rating system is shown below:

vlfso table

During the course of our test evaluation, we discovered that significantly lower treat rates of Infineum asphaltene management additives (relative to those required for TSP/TSA test reduction) were effective. This was the case for either maintaining fuel in optimum condition for processing through a purifier, or improving a fuel which exhibits excessive sludging without additive, as can be seen in the case below. The test VLSFO represents a severe case, which experienced on board operational issues, having a base TSP of 0.28% mass sediment i.e. well above the ISO8217 specification. In addition to this, additive treatment was ineffective at significantly improving the TSP. However, in the spin test, a low treat rate of Infineum additive has recovered this apparently unusable fuel into one that would not present issues in on board operation.

jan 22 spin test 2 v2

Low volumes of Infineum additive are effective at improving fuel that exhibits excessive sludging without additive

This spin test mimics the forces the fuel experiences as it passes through the ships purifier system and these results clearly show the disparity between the Total Sedimentation test methodology versus a test designed to assess on board operability. To further our understanding of the applicability of this test, Infineum has developed a rig using a ship’s fuel purification system and the results that obtained from the rig align closely with the spin test, showing demonstrably decreased levels of sediment in the purifier bowl.

jan 22 spin test 3 1

Additive effect in Ship Purifier Rig

Separability Number test (ASTM D7061)

The Separability Number test measures the reserve stability number (RSN) by adding a fixed volume of heptane to a toluene-diluted fuel oil sample. The measurement is obtained by scanning the sample with a near infra-red source to determine the destabilisation of the solvent-diluted fuel oil sample over a 15-minute period and then the test sample is rated.

marine fuels table

Our apprehension about adopting this test methodology has previously been reported

In our view the test can give overly optimistic results with regards to a fuel’s suitability for use.

For example, a fuel which is inherently unstable and has an excessive sludging issue, where the fuel has already flocculated, can show as a stable fuel in this test or a stable fuel (such as a high sulphur fuel oil) can show as an unstable fuel.

We have also expressed our concern that this test is extremely responsive to low treat rates of additive and could give misleading information to a ship operator as to the efficacy of an additive solution. However, recent work in scoping out the potential of the spin test, suggests that low treat rates of Infineum additive technology is indeed effective at providing operability benefits.

We have further investigated the application of the Separability Number test and the additive effect in relation to spin test results. In another problematic fuel sourced from the market, where the base TSP was high at 0.27 mass % sediment, we were able to demonstrate similar spin test findings to those above. That is to say, low treat rate of Infineum additive is effective at reducing the spin test result from unfit for use to, in this case, borderline acceptable.

jan 22 spin test 4 1

However, this problematic base fuel yielded an excellent low reserve stability number of <1 thus indicating high stability reserve in both the unadditised and additised cases which is clearly not the case.

These results, along with other testing, confirm that the Separability Number test remains unsuitable as a screener test for determining the suitability of VLSFOs.

Conclusion

Infineum has investigated the mode of action of various test methods used to determine if VLSFOs are suitable for use. These studies have established that:

  • The Total Sedimentation Test requires a supporting test to give a more accurate assessment of whether a fuel is suitable for use on board. High additive treat rates of Infineum asphaltene management additives are required to influence the test due to the small filter mesh used in the test.
  • The Alfa Laval spin test correlates well with a ship’s purifier system and can be positively influenced by low treat rates of some additives to maintain or improve fuel performance in the ships fuel purification system. It is an excellent contender as a complimentary test for the sedimentation tests above.
  • The Stability Number Test remains unsuitable to reliably distinguish between useable and unusable fuels and can be misleading with regard to effectiveness of additive solutions.

Our investigations support the view that a combination of sedimentation and spin tests along with low treat rates of Infineum additives are the best option to ensure protection for ships and peace of mind for ship operators.

Related: Infineum: Proving marine additive performance
Related: Infineum additives contributing towards sustainable shipping activities
Related: Infineum: Spin test shows promise of identifying stable VLSFOs and bunker fuels
Related: Current testing methods for VLSFO stability and compatibility may require supporting tests, says Infineum
Related: Infineum clarifies indicators from certain testing protocols about VLSFO stability
Related: Infineum publishes first Sustainability Report in conjunction with Earth Day
Related: Infineum: IMO approves emissions cuts

 

Photo credit: Infineum
Published: 10 February, 2022

 

 

Continue Reading

Bunker Fuel

Alkagesta highlights key insights on European choke point pressures in August

Update covers dual supply crisis currently shaping global bunker markets — a stalled Strait of Hormuz peace process and Rhine water levels at a 140-year record low — and the implications for Singapore.

Admin

Published

on

By

Alkagesta

Malta-based global commodity trading house Alkagesta recently shared latest market insight examining the dual supply crisis gripping global energy markets as diplomatic efforts to reopen the Strait of Hormuz stall and Rhine water levels fall to record lows, creating what the company describes as a “state of emergency” for European inland fuel distribution.

In an article published on Alkagesta Market Insights on 11 August, the company’s trading and market intelligence teams outlined how the convergence of two simultaneous logistical crises is tightening prompt fuel availability across Singapore, Northwest Europe, and the Mediterranean:

Strait of Hormuz transits fell to a near-one-month low of 13 ships on August 9 following an attack on an ADNOC-linked tanker, as both the US and Iran demand war reparations before any reopening agreement can be reached. Simultaneously, Rhine water levels at the Kaub chokepoint fell to 16 cm on August 10 — the lowest since records began in 1880 — with forecasts pointing to a further drop to just 4 cm by August 14, effectively halting barge traffic and trapping fuel oil stocks at the ARA hub.

The supply picture across both key hubs has deteriorated sharply. In Singapore, Middle Eastern fuel oil imports nearly tripled week-over-week to 328,878 mt by July 29 — the highest volume since March — providing some relief as onshore commercial heavy distillate stocks rose to a five-week high of 19.58 million barrels by August 5. However, July bunker fuel sales are estimated to have fallen 3.7% month-over-month to 4.44 million mt, with elevated premiums redirecting prompt demand toward alternative ports including Zhoushan and Port Klang.

In Europe, the VLSFO market remains acutely undersupplied as refiners continue to prioritize high-margin diesel over low-sulfur blending components, while the Rhine crisis has forced barges to operate at just 15–20% of normal capacity — with freight rates from Rotterdam to Karlsruhe rising more than 400% in two months.

Alkagesta’s strategic outlook points to a potential total breakdown in Rhine-linked inland distribution by mid-August, a VLSFO Hi-5 spread likely to remain above $200/mt through Q3, and a global crude market that analysts warn requires an additional 2.1 million b/d for 18 months to rebuild depleted inventories.

Note: The full article can be read here.

 

Photo credit: Alkagesta
Published: 17 August, 2026

Continue Reading

Bunker Fuel

Integr8 Fuels: Why bunker markets could be lower than we thought

Marine fuel prices could prove lower than previously anticipated as easing refinery margins and improving bunker market fundamentals outweigh a still-uncertain crude oil outlook, says Integr8 Fuels.

Admin

Published

on

By

6 5

By Steve Christy, Expert Contributor, Integr8 Fuels

29 July 2026

We have just seen one false dawn, is there another to come? 

Last month, we wrote about how close we were to the expected lows in Brent and Rotterdam bunker prices, but not yet Singapore. Given what has happened since, a month is not only a long time in politics, but also a very long time in the bunker market. 

There was a resumption of attacks in the Arabian Gulf region on 13 July, followed by targeted Houthi attacks on Saudi Arabia’s Red Sea oil infrastructure and shipping in the Bab el-Mandeb region, the gateway between the Red Sea and the Gulf of Aden. As a result, Brent futures fell to lows of around $70/bbl in late June and early July before surging to a high of $100/bbl on 23 July. Over the same period, Singapore VLSFO fell to $635/mt before climbing to $865/mt, a swing of $230/mt in just 16 days. 

Jul 2026 Graph 01 1024x613 1

Prices at the start of this week fell sharply after a halt in Arabian Gulf attacks over the weekend, with front month Brent was down to intra-day lows of $84/bbl, and Singapore VLSFO $750/mt.  However, at the time of writing there has been a ‘surprise’ attack by Iran, and retaliatory action by the US, with prices rising again.  It looks like we could be at another false dawn. 

The obvious questions are: will there be a return to peace negotiations, and are we close to the end of the war and free-flowing traffic through the strait of Hormuz (and also the Bab el-Mandeb)? The obvious answer is, we don’t know; there are only a few people that are likely to know the answer to this. All we can do is plan for every eventuality. 

Low stocks, higher bunker prices, and a strong Singapore VLSFO premium: it’s a challenge 

For those of us in the bunker market, the point we made last month about Singapore VLSFO trading at a strong premium to crude still holds, albeit slightly less pronounced. The loss of supplies through the Strait of Hormuz, together with the added uncertainty surrounding Saudi product exports from the Jizan and Rabigh refineries on the Red Sea, has sustained this premium. 

These developments are likely to keep the Singapore VLSFO premium to crude at elevated levels until there is greater confidence that Middle East crude and product supplies are returning to more normal trading patterns. Amid all the price volatility, this Singapore VLSFO premium remains a key indicator to watch. 

Backwardation in Brent futures illustrates market psychology 

One month ago, backwardation in Brent futures (front month minus second month) had fallen from $7/bbl to virtually nothing, reflecting the market’s belief that an end to the war was little more than a negotiating step away. It wasn’t. The resumption of attacks, coupled with Houthi involvement in the Red Sea, sent prices sharply higher again, with backwardation in the Brent futures market returning to almost $6/bbl. 

Jul 2026 Graph 02 1024x572 1

The halt in attacks over the past weekend has taken steam out of the market, with prices and backwardation falling sharply. Where we go from here depends if there is again a belief peace is on the horizon, or if this is another false dawn. The past month highlights how impossible it is to predict an ending to the war, and how fragile any expectations of peace can be. 

We cannot ignore the price, but still must look to the future

It is impossible to write a report and not highlight the turmoil of the current market and what is happening. However, we still must look beyond this, to see where we could end up. 

In an earlier report, we suggested the run-up to the US mid-term elections in November may be a backstop to the war. However, even this is not guaranteed. There are many dynamic elements to the economy and voter intentions, but one feature that will always crop up in the US is the gasoline price. This has risen from $3/gallon before the war to over $4/gallon for the past four months. 

Jul 2026 Graph 03 1024x570 1

If it comes to it, will Republican voters want to see a resolution to the war and a return to $3 gasoline prices ahead of the elections? 

We have a change of heart on how low bunker prices can go

We don’t know exact timings, but in any planning, we must look at what happens when the war does finally end and prices fall, whenever that may be. In past reports we have highlighted the view that Brent crude prices are unlikely to fall back to pre-war levels in the $60s, and Singapore VLSFO unlikely to go back in to the $400s. This may be the point at which these views change.

Previous thinking was based on a relatively short war, where there would be a large loss of oil supply and a massive stock-draw. In this case, tighter stock levels would be sufficient to keep prices higher than their pre-war levels once we returned to ‘normality’. This would mean Brent futures in the $70s (and not in the $60s), and Singapore VLSFO in the $500s, and not the $400s.

A number of mainstream analysts also held this view, although there were some that were lower and some higher.

Given the war has already gone on for much longer than almost everyone expected, this thinking must change. Yes, global stocks have been drawn down at a rapid rate, but this is slowing. Higher pricing and inflationary blows have had a major impact on global oil demand, with current indications that total oil demand in the second quarter of this year was some 4 million b/d lower than year earlier levels.

The graph below shows this sharp drop in demand and even if the war comes to an end relatively soon, and demand gets back towards some normality, a structural loss of more than 1 million b/d in global oil demand is still expected to have taken place because of the extended period of conflict.

If the war goes on for even longer, structural losses in global oil demand are likely to be even greater.

Jul 2026 Graph 04 1024x579 1

Source: US EIA

It’s a hard road, but we can get there

This means that once the war does end, market psychology will be looking at a rapid increase in oil supplies going into a global market which is much lower in demand.  This opens the way for prices to easily return to their pre-war levels of Brent in the $60s and Singapore VLSFO in the $400s. 

Now we just need those at the centre of negotiations to get us there.

 

Photo credit and source: Integr8 Fuels
Published: 30 July, 2026

Continue Reading

Bunker Fuel Quality

FOBAS report warns of growing operational risks from ISO-compliant bunker fuels

LR’s latest FOBAS Fuel Quality Report reveals that the biggest fuel quality risks are no longer confined to off-specification fuels, with some compliant fuels creating operational challenges.

Admin

Published

on

By

New FOBAS report warns growing operational risks from ISO-compliant bunker fuels

Classification society Lloyd’s Register (LR) on Tuesday (14 July) warned that ship operators are facing a growing risk from fuels that appear compliant under routine ISO 8217 testing but still present operational risks once onboard.

According to LR’s latest Fuel Oil Bunker Analysis and Advisory Service (FOBAS) Fuel Quality Report, covering the first half of 2026, off-specification fuels remain a persistent challenge. 

However, some of the most disruptive cases now involve fuels that pass routine compliance testing but show poor stability or compatibility, or contain non-conventional blend components that are only identified through more detailed investigative analysis.

Several incidents investigated highlighted this trend. In March and April, a number of vessels reported operational difficulties after bunkering fuel in a major bunkering hub. Further forensic analysis found that many of the fuels contained elevated concentrations of Estonian shale oil, in some cases estimated to be around 10-15%.

While shale oil is recognised within ISO 8217 as an acceptable blend component, FOBAS investigations found that higher concentrations can be associated with fuel instability and operational issues affecting filters, separators and fuel pumps.

The report also shows that fuel quality variability remains stubbornly high. Off-specification cases remained elevated throughout the first six months of 2026, suggesting that quality issues are no longer isolated events but a more persistent feature of today’s marine fuel supply chain.

The most common recurring issues included sulphur exceedances, excessive water content, sediment and stability problems, elevated catalytic fines, sodium contamination and low flash point distillate fuels.

At the same time, biofuels (especially FAME blends) are continuing to grow without being a primary source of quality issues. Where issues occurred in blended fuels, they were generally associated with the conventional VLSFO component rather than the FAME fraction.

The report concluded that operators will need to adopt a more proactive approach to fuel management as marine fuels become more diverse and fuel quality risks become harder to identify through routine compliance testing alone.

Greater emphasis on fuel stability, compatibility and understanding fuel composition will be critical to reducing operational disruption and maintaining vessel performance.

Murray Kirkwood, Fuel Specialist Consultant, Lloyd’s Register, said: “The findings from our latest report show that fuel quality risk is evolving. The challenge is no longer simply identifying fuels that fail specification. Increasingly, operators are encountering fuels that meet the required limits but still create operational difficulties once they are stored, handled and used onboard.

“As fuel blending becomes more complex, the distinction that matters is increasingly not between on-spec and off-spec fuel, but between fuels that are operationally resilient and fuels that are operationally fragile. Understanding that difference is becoming essential for shipowners and operators.”

The latest findings reinforced FOBAS’ long-standing view that effective fuel management increasingly depends on understanding fuel behaviour rather than relying solely on pass-or-fail specification testing.

By combining routine fuel quality monitoring with forensic investigation of operational incidents, FOBAS provides shipowners with a clearer understanding of emerging fuel quality risks as the industry continues its transition to a more diverse and complex fuel landscape.

Note: The FOBAS Fuel Insight: Fuel Quality Report H1 2026 is available at FOBAS Fuel Insight: Fuel quality reports | LR

 

Photo credit: Lloyd’s Register
Published: 15 July, 2026

Continue Reading
Advertisement

OUR INDUSTRY PARTNERS



Trending