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VPS publishes 2023 annual review of its findings on bunker fuels

Findings in VPS’ review include 58% of its 2023 Bunker Alerts were for VLSFO fuels, followed by 24% for MGO fuels and 14% for HSFO; most common problematic parameter was Flash Point.

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Marine fuels testing company VPS on Tuesday (16 January) published an article titled ‘2023 Marine Bunker Fuels Review’ by Steve Bee, VPS Group Commercial Director, giving insightful annual review of VPS findings on both global and regional maritime fuel matters, focusing on marine fuels. 

Introduction

2023 saw the continuing evolution and the widening of available maritime fuel types and grades, as the global shipping industry gathered decarbonisation momentum to reduce its emissions and achieve current and future legislation targets. Existing CII and EEXI requirements, the incoming EU ETS legislation, plus the slightly longer-term IMO legislation, saw increasing demand for additional testing, lower-carbon fuels, data and digitalisation solutions across the shipping sectors.

As the leading maritime decarbonisation testing and advisory services provider, VPS continued to be at the forefront of marine fuels and lubricants analysis, utilising our experience, expertise and innovative approach, to support this drive for a more sustainable shipping fleet.  

Throughout the year, VPS witnessed further fuel quality issues with VLSFOs in terms of cold-flow property issues, sulphur compliance and cat-fines. HSFO and VLSFO suffered numerous degrees of chemical contamination, whilst MGO suffered from cold-flow, flash point and FAME off-specifications.

Biofuels usage certainly gathered momentum and the increased demand from the market led to increasing queries regarding their fuel management and their “fit-for-purpose” as a drop-in marine fuel, which in turn called upon VPS to provide answers and solutions to customers, utilising our extensive knowledge and understanding of biofuels and their associated test parameters. 

The Marine Fuel Mix

Across 2023, the fuel mix with respect to samples received for testing in VPS laboratories, equated to 62.7 million MT, which is over 5 million MT of marine fuels per month. VLSFO was the most popular marine fuel with 54.3% of the fuels used, followed by 29.5% HSFO (a growth of 15.4% over 2022), 14.2% MGO, 1.2% ULSFO and 0.8% Biofuels. Regarding biofuels usage, the samples tested by VPS equated to an increase from 231,000 MT in 2022 to 558,000 MT in 2023.

VPS 2023 MARINE BUNKER FUELS REVIEW

VPS Bunker Alerts

Bunker Alerts highlight short term fuel quality issues identified by VPS, for a specific test parameter of a specific fuel grade/type in a specific port. The service provides valuable information to customers, to assist in avoiding potentially problematic fuel types in a highlighted port or region, to further protect the customer’s asset and crew.

In 2023 VPS issued 28 Bunker Alerts, eight fewer than in 2022. The 2023 Bunker Alerts included all major fuel grades, i.e. VLSFO, HSFO, MGO and ULSFO, ten different test parameters, 12 ports and 9 countries.

58% of the 2023 Bunker Alerts were for VLSFO fuels, followed by 24% for MGO fuels and 14% for HSFO. The most common problematic parameter was Flash Point, accounting for 28% of the Bunker Alerts, followed by Sodium at 24%, with Sulphur and TSP at 10% each.

Singapore (32%) and ARA (21%) were the regions/ports most frequently requiring a Bunker Alert to be issued. But as these are the two busiest bunkering regions, it is not too surprising.

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Screenshot 2024 01 29 104316 1

VLSFO Fuel Quality

As the most used marine fuel type, VLSFO accounts for more than half of the fuels tested by VPS. In terms of quality, Europe provided the highest level of off-specification VLSFOs in both 2023 (7.8%) and 2022 (7.9%). Africa provided the next highest level of off-specification fuels with 6.7% in 2023 and 7.0% in 2022, with North America third with 4.4% of fuels tested exhibiting at least one off-specification parameter in 2023 and 4.3% in 2022.

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Sulphur is the most common off-specification parameter of VLSFOs, accounting for 26.6% of VLSFO off-specs in 2023 and 31.5% in 2022. 0.7% of VLSFOs tested in 2023 had a sulphur level of 0.50%-0.53%, with 0.5% of samples tested having a sulphur level greater than 0.53%.

Pour Point was also a common off-specification parameter for VLSFOs with 13.6% of VLSFOs off-specs relating to this parameter in 2023 an increase over the 11.4% level witnessed in 2022. 

The importance of the additional cold-flow test of Wax Appearance Temperature (WAT) and Wax Disappearance Temperature (WDT), was highlighted in 2023 with 63% of VLSFOs exhibiting WAT of 31-40ºC and 14% having WAT between 41-50ºC. 55.7% of VLSFO samples had a WDT of 41-50ºC, with 28.1% having a WDT of >50ºC. VLSFOs cold-flow properties are a definite concern with wax precipitating from the fuel at temperatures way in excess of 10ºC above the pour point, potentially causing numerous operational problems such as filter and pipework blockages.

Sulphur is the most common off-specification parameter of VLSFOs, accounting for 26.6% of VLSFO off-specs in 2023 and 31.5% in 2022. 0.7% of VLSFOs tested in 2023 had a sulphur level of 0.50%-0.53%, with 0.5% of samples tested having a sulphur level greater than 0.53%.

Pour Point was also a common off-specification parameter for VLSFOs with 13.6% of VLSFOs off-specs relating to this parameter in 2023 an increase over the 11.4% level witnessed in 2022. 

The importance of the additional cold-flow test of Wax Appearance Temperature (WAT) and Wax Disappearance Temperature (WDT), was highlighted in 2023 with 63% of VLSFOs exhibiting WAT of 31-40ºC and 14% having WAT between 41-50ºC. 55.7% of VLSFO samples had a WDT of 41-50ºC, with 28.1% having a WDT of >50ºC. VLSFOs cold-flow properties are a definite concern with wax precipitating from the fuel at temperatures way in excess of 10ºC above the pour point, potentially causing numerous operational problems such as filter and pipework blockages.

2023 also saw a significant increase in cat-fine levels in VLSFOs, with 12.7% of all off-specifications relating to this parameter, compared to 8.5% in 2022. 16.2% of all VLSFOs showed a cat-fine level greater than 40ppm. Frequent checking of purifier efficiency via VPS’ Fuel System Checks (FSC) service is a highly recommended proactive safeguard in respect to increased cat-fines within VLSFOs.

VLSFO viscosities vary enormously depending upon to blend components used. In 2023 VLSFO viscosities ranged from <20Cst to >380Cst. 16% of all VLSFO off-specifications were due to viscosity. Only 0.5% of VLSFOs had a viscosity of >380Cst. 68% of all VLSFO viscosities were less than 180Cst. Viscosity is such a key operational parameter, determining the transfer and injection temperatures of fuel onboard ships and therefore determining the exact viscosity of VLSFOs is crucial to ensure optimal efficiency.

Biofuels

As global shipping looks towards low-to-zero carbon fuels to answer many emissions reduction challenges, biofuels offer an immediate “drop-in” solution. As such VPS tested the equivalent of over 500,000 MT of biofuels in 2023 compared to ca. 230,000 MT in 2022.

Europe, (mainly ARA-region) provided the highest volume of biofuels at almost 400K MT (ca. 74%) and Singapore second (ca. 21%), providing just over 100K MT.

The most common biofuel blend was B30 (10-30% bio), which accounted for 34.3% of biofuel samples tested by VPS. Yet, B100 (>90% bio) was not far behind with 30.1%.

The majority of biofuels contained Fatty Acid Methyl Esters (FAME) as the bio-component, although VPS did test others containing HVO, HEFA, Cashew Nut Shell Liquid (CNSL) and Tyre Pyrolysis Oil (TPO).

Where FAME is the bio-component within marine biofuels, the key considerations are:

  • Energy Content, Renewable Content
  • Fuel Stability, Cold-Flow Properties
  • Corrosivity, Microbial Growth

Of the biofuels tested by VPS in 2023, 9% of those tested for oxidation stability gave the concerning result of <5 hours, highlighting a high degree of instability, whilst 6.7% gave a result of 5-8 hours which is still a cause for concern.

In terms of corrosivity, 11.9% of those biofuels tested provided an amber/caution result, whilst 8.5% of those tested provide a red warning, indicating potential high levels of corrosivity.

It is fully expected that the growth in biofuels usage for marine applications will continue to increase across 2024 and the VPS Additional Protection Service (APS) when using biofuels, will only increase in importance as the industry looks for more information regarding the fuel management of biofuels.

Summary

2023 once again highlighted the importance of bunker fuel quality testing, as a proactive means to protect vessels, their crew and the environment. With additional tests, currently not included within ISO8217, providing further  vital information in achieving heightened levels of protection.

Whilst we can expect a new revision of ISO8217 in early 2024, additional tests will still hold an important role in fuel management.

Biofuels usage will continue to increase in demand and importance, as ship owners and operators look to achieve improvements through CII and EEXI, as well as looking to counter the financial impact of the EU ETS scheme.

Methanol demand and usage will also grow, following the recent success of Maersk’s Laura Maersk and the rapidly growing order book for methanol-powered vessels.

So 2024, suggests another year of widening marine fuel types and grades coming to market, coupled with their growing fuel management considerations.

Note: The full article titled ‘2023 Marine Bunker Fuels Review’ with related graphs and charts can be found here

Related: World’s first methanol-fuelled boxship christened and named “Laura Maersk”

 

Photo credit: VPS
Published: 30 January, 2024

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Bunker Fuel Quality

VPS: Key steps in avoiding risk of receiving bad bunker fuels

Steve Bee, Dr Malcolm Cooper and Stanley George explain how to safeguard vessel operations against the impact of bad bunkers and share on the key steps that should be taken to avoid the risk of receiving bad bunkers.

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Steve Bee, VPS Group Commercial Director, Dr Malcolm Cooper, VPS CEO and Stanley George, VPS Group Science & Technical Manager explained in an article on how to safeguard vessel operations against the impact of bad bunker fuels and shared on the key steps that should be taken to avoid the risk of receiving bad bunkers:

Bad bunkers can significantly impact vessel operations, necessitating intervention from the crew and in some cases result in operational failure - varying from operational damage through to loss of power and subsequently loss of propulsion. Mitigating the impact of bad bunkers can help to prevent damage to vessel’s equipment and protect the safety of those on board and the environment. Bad bunkers can lead to fuel stability problems, chemical contamination and poor cold-flow properties. This paper describes the key steps that should be taken to avoid the risk of receiving bad bunkers.

Bad Bunkers

Bad bunkers refer to fuel of substandard quality, which can lead to operational disruptions and challenges in fuel management. Common fuel quality concerns include poor stability, chemical contamination, corrosive tendencies, poor combustion and poor cold flow characteristics. Thorough testing of bunkered fuel prior to putting it in operation is highly advantageous as it reveals potential issues inherent in the fuel. This data often enables proactive measures to mitigate the risk of operational complications stemming from such fuel.

Whilst the general quality of bunker fuel has been consistent over recent years, it is important to note that off-specification fuel statistics are typically based on the criteria outlined in Table 1 and 2 of ISO 8217 standard. There have been numerous occasions when bunker fuel meeting these criteria has proven to be unsuitable for onboard use due to its poor quality and on a number of occasions has caused catastrophic failures (e.g. ARA contamination case - August 2022 and March 2024, Houston contamination case April 2023 and Singapore contamination case August 2022). This necessitates additional testing methodologies such as GCMS, WAT/WDT, and Reserve Stability Number to accurately assess fuel quality.

The increase in reported operational issues stemming from contaminated fuels, which often elude detection through routine ISO 8217 testing, has experienced a notable uptick in recent years. This trend can be attributed, at least in part, to the drive towards decarbonization, notably spurred by initiatives such as IMO 2020. Consequently, fuel suppliers are increasingly experimenting with a diverse range of feedstocks to serve as blend components in conventional fossil fuels.

As the world’s largest marine fuel quality testing company covering 50% of all fuel testing, VPS can offer valuable insights and advice in relation to poor quality and/or contaminated fuel. Proactive, pre-burn, fuel testing on a regular basis, is definitely a highly recommended approach to mitigating risks to vessel operations, crew safety and environmental impact. The typical off-specification parameters associated with engine failure are usually Pour Point, Total Sediment Potential, Cat-fines and/or Water content. Whilst the International Marine Fuel Quality standard, ISO8217, includes these test parameters, it’s certainly a more diligent and wiser approach, to consider a fuel’s overall stability, cold-flow properties, chemical contamination and potential corrosivity.

At VPS, we possess the proficiency and extensive experience necessary to conduct specialised tests specifically designed to detect these issues. Our tailored testing protocols enable us to identify potential fuel-related challenges and offer operational guidance to minimise associated risks effectively.

Fuel Stability

Both High Sulphur Fuel Oils (HSFOs) and Very Low Sulphur Fuel Oils (VLSFOs), can suffer with varying degrees of instability due to thermal-aging and over-heating, high sediment content, or chemical contamination, to name but a few potential causes. Instability usually manifests itself through sediment formation, which can in turn, block onboard filters, pipework, potentially then starving an engine of fuel.

ISO8217 includes the Total Sediment Potential (TSP) test, which is a good indicator of the amount of sediment which may be potentially produced in relation to a fuel’s stability. However, additional tests such as Total Sediment Accelerated (TSA), a deliberate fuel-aging test, Total Sediment Existent (TSE), a measure of fuel cleanliness and the determination of a fuel’s stability reserve, via Separability Testing, to measure the fuel’s capacity to hold long chain asphaltenes within the fuel solution, can provide much more information regarding fuel stability determinations.

In particular, Separability Number is an excellent accompaniment to the routine hot filtration methods. It can identify potentially troublesome unstable fuels even when the Hot Filtration Test methods indicate 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.

VPS: Key steps in avoiding risk of receiving bad bunker fuels

Chemical Contamination

Over the years chemical contamination of marine fuels has resulted in many onboard operational issues, with numerous chemicals and chemical groups being identified as the cause. Major widespread contamination events, include Houston (2018), with over 200 vessels damaged due to a potential phenolic contamination, to Singapore (2022) where 80 vessels were affected by chlorinated hydrocarbons within the fuel and then more recently ARA (2023) where around 20 vessels suffered issues due to a cocktail of styrenes and dienes within the fuel. In between such times, many smaller cases of chemical contamination have been identified by VPS. Thankfully, many at a pre-burn stage, thus avoiding any operational issues or damage cases.

Over time, all of the following chemicals have been found by VPS in marine fuels. The effects of these are highlighted below:

VPS: Key steps in avoiding risk of receiving bad bunker fuels

Risks from chemical contamination of fuel can be significantly mitigated through pre-burn screening of fuels using VPS Chemical Screening Service. This low-cost test, utilising Gas Chromatography Mass Spectrometry (GCMS) analysis, will warn of the presence of over 70% of all volatile chemicals within fuel. With both VLSFO and HSFO we continued to see cases of vessel damages due to chemical contamination during 2023. Focusing specifically on the VPS GCMS-Head Space Chemical Screening service, as a damage prevention service, 19.9% of applicable marine fuel samples received by VPS since 2018, have undertaken this rapid, pre-burn protection service, with an average 8% of samples tested, giving rise to a “Caution” result, indicating the presence of at least one chemical contaminant and thus the notified vessel has avoided any damages.

In April 2023, a Singaporean-owned chemical and product tanker bunkered 415 m/tons of VLSFO in Houston. The vessel began to burn the fuel in May and quickly began to experience numerous issues with the auxiliary and main engines, such as exhaust gas deviating temperatures and the wearing of fuel pumps and plunger barrels. In addition, problems such as start-failure due to insufficient fuel injection, pressure build up, as well as worn out and leaking fuel pumps.

Of greater concern was the complete engine stoppage enroute to the next US port, when the main engine failed. Multiple attempts were made to start the engine, all without success.

Subsequent VPS forensic laboratory testing, utilising a proprietary Gas Chromatography Mass Spectrometry (GCMS) Acid Extraction methodology, detected the presence of several phenols and fatty acid compounds within the fuel.

The vessel initiated the necessary repairs to both auxiliary and main engine fuel pumps, at a total spares cost of $200,000. In hindsight the vessel owner stated pre-burn screening would have helped significantly in avoiding such damages and costs.

Cold-Flow Properties

VPS: Key steps in avoiding risk of receiving bad bunker fuels

The cold-flow properties of fuels are also important to monitor closely, especially when sailing in colder temperature regions. The Pour Point of HSFOs, VLSFOs and MGO fuels, should always be monitored when colder climates are encountered. Pour Point was the most common MGO off-specification parameter in 2023, with 36.6% of MGO off-specs attributed to Pour Point. However, prior to reaching the pout point of MGO fuel, its cloud point and cold-filter plugging point behaviour offer earlier warning-signs of potential cold-flow issues, relating to wax precipitation from the fuel. It is key fuel management practice to measure these two cold-flow parameters within MGO distillates.

VLSFO fuels have a higher paraffinic content than HSFO and as a consequence, have a greater potential to precipitate wax, which can cause filter and pipework blockages, which can ultimately starve an engine of fuel. As VLSFOs are dark fuels, the cloud point cannot be seen, as it can with a distillate fuel. Therefore in 2019, VPS developed a proprietary test method to measure the Wax Appearance (WAT) and Wax Disappearance Temperatures (WDT) of VLSFOs.

Generally, it is recommended that the fuel temperature is kept approximately 10oC above the PP to avoid risk of solidification. However, in the majority of the global bunker ports in 2022-23 the average WAT was often higher than 30oC, and WDT higher than 40oC. This may also mean heating the fuel to avoid solidification during transfer. However, this should not necessarily mean an increase in storage temperature. Fuel oil transfer pumps on board are generally positive displacement pumps and can handle certain amount of wax that are present in the fuel.

If the fuel has a high WAT/WDT, VPS recommend heating the fuel just before the transfer operation.

VPS: Key steps in avoiding risk of receiving bad bunker fuels

Therefore, additional fuel tests, such as, Total Sediment Existent (TSE), Separability Number (Reserve Stability Number, RSN), Wax Appearance/Wax Disappearance Temperature Testing, Cloud Point, Cold Filter Plugging Point and Chemical Screening, can provide significantly greater and more valuable protective information, when assessing fuel quality than ISO8217 alone. This is why VPS offer our Additional Protection Service (APS) “bundles”. The APS includes the standard ISO8217 parameters but also fuel-relevant additional tests, in order to support our customers to greater levels with respect to, asset, crew and environmental protection.

Over the years, VPS Off-specification fuel data has proactively highlighted the potential risks associated with certain parameters. The importance of regular and wider-ranging marine fuel testing, through the Additional Protection Service, will definitely support mitigation strategies to prevent disruptions in vessel power supply due to fuel-related issues. Even a minor fuel quality issue can prove costly. A 2018 report by the Swedish Club highlighted the average cost per incident of fuel-related damage on vessels is $344K.

 

Photo credit: VPS
Published: 9 April 2024

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Bunker Fuel Quality

Singapore: CTI-Maritec publishes whitepaper on upcoming mandatory enhanced bunker fuel tests

CTI-Maritec shared its insights and recommendations related to testing of COCs, TAN and SAN for all bunker supply in Singapore following mandatory enhanced checks at Singapore port effective 1 June.

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Bunker fuel testing and marine surveying business Maritec Pte Ltd (CTI-Maritec) on Monday (1 April) published its latest whitepaper related to the Maritime and Port Authority of Singapore’s (MPA) move to introduce enhanced testing parameters for marine fuel batches intended to be delivered as bunkers in the port of Singapore from 1 June. 

In accordance with the MPA’s Port Marine Circular No 3 of 2024, from 1 June 2024 onwards, bunker suppliers in the Port of Singapore must ensure that:

  • Residual & bio-residual bunker fuel do not contain Chlorinated Organic Compounds (COC) above 50mg/kg and are free from inorganic acids.
  • COC must be tested using the EN 14077 accredited test method and shall be reported in the “Certificate of Quality” (COQ) provided to receiving vessels.
  • Inorganic acids must use the ASTM D664 accredited test method as prescribed in ISO 8217 and the Strong Acid Number (SAN) (in addition to the Total Acid Number (TAN) shall be reported in the COQ (i.e. SAN = 0) provided to receiving vessels. For distillate / bio-distillate bunker marine fuel batches, SAN must be tested as per ASTM D664 test method and reported in the COQ.
  • Residual marine fuels are free from polystyrene, polypropylene & polymethacrylate. These can be tested by filtration, microscopic examination, & Fourier-Transform Infrared spectroscopy analysis. 

In view of the above, CTI-Maritec shared its insights and recommendations in the paper, titled Insights & Recommendations on Singapore MPA’s Enhanced Testing Parameters for Marine Fuel Batches, related to the testing of COCs, TAN and SAN for all bunker supply in Singapore, and its recommendations for testing Polymers for reported problem cases.

In the conclusion of the whitepaper, CTI-Maritec said the issue of chemical contamination has plagued the bunker industry for years, and the risk of receiving contaminated bunker fuels is likely to persist.

“This is mostly due to complex bunker supply chains, which consists of a network of different stakeholders including refineries, traders, and physical suppliers operating their own barges, with some performing their own fuel blending operation,” it said.

“However, with the imminent enforcement of MPA’s Port Marine Circular No 3 of 2024, the stage is set to raise the bar of the bunkering fuel quality in the Port of Singapore and further support stronger vessel health.”

CTI-Maritec added the new requirements in Singapore could also pave the way for other international Port Authorities to implement the same requirements for their bunker suppliers.

“Furthermore, a key learning from the 2022 incidents is the critical need for bunkering buyers / ship owners / vessels to adopt, as a standard practice, an enhanced fuel testing approach as a pre-emptive measure in securing their vessel’s health,” it added, referring to the bunker contamination incident in Singapore in February 2022, where about 200 ships were supplied with High Sulfur Fuel Oil (HSFO) containing high levels of Chlorinated Organic Compounds (COC) in the Port of Singapore. 

The firm encouraged bunker buyers to consult the bunker suppliers in advance and have proper contractual agreement for the quality of fuel bunkered.

Manifold Times previously reported the move by MPA for enhanced checks for marine fuel delivered at Singapore port receiving largely positive feedback from several local bunker fuel testing agencies including VPS and Intertek.

Related: Singapore: Marine fuel quality testing agencies applaud move for mandatory enhanced bunker fuel tests
Related: Singapore: MPA tightens testing parameters to reduce contaminated bunker fuels
Related: MPA: Glencore and PetroChina supplied contaminated bunkers to about 200 ships in the Port of Singapore

Note: The full copy of CTI-Maritec whitepaper titled ‘Insights & Recommendations on Singapore MPA’s Enhanced Testing Parameters for Marine Fuel Batches’ can be viewed here

 

Photo credit: Louis Reed from Unsplash
Published: 2 April 2024

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Bunker Fuel

VPS discusses mitigating risks in sustainable vessel operations with its APS

Harun Rashid, Senior Technical Manager of VPS explains how to safeguard vessels against bunker fuel instability with VPS Additional Protection Service.

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VPS discusses mitigating risks in sustainable vessel operations with its APS

Harun Rashid, Senior Technical Manager of marine fuels testing company VPS on Tuesday (19 March) published an article on how to safeguard vessels against marine fuel instability with VPS Additional Protection Service (APS):

Stability has long been a highly unpredictable character of marine fuels, which is extremely sensitive to a fuel’s formulation and its storage and handling conditions. For these reasons, fuel buyers have no direct control on fuel stability, unlike other physical parameters, other than relying upon a supplier’s due diligence regarding the fuel formulation and the ship’s engineer’s professionalism in managing the fuel on board.

Asphaltenes within residual-based fuels can precipitate as sediment/sludge whenever a fuel’s available solvency to retain asphaltenes in suspension drops below the fuel’s stability reserve. The ISO 8217:2012/17 standard has a sediment limit of a maximum 0.10% m/m to protect buyers’ interest where an elevated sediment value can be indicative of an unstable fuel. Today’s fuels are no longer produced from straight run refining processes, but undergo a series of complex processes, for example, vacuum distillation, vis-breaking, catalytic cracking, in order to extract the lighter end components as much as possible, leaving the bottom end components with reduced reserve stability. The solvency can further diminish with unregulated blending in order to meet the Sulphur compliance levels within MARPOL Annex VI & statutory regulations.

During 2023, VPS handled numerous sludge formation cases which led to severe filter & separator blockages. The majority of these cases involved VLSFO fuels and for a sizeable number, the sediment content at the ship’s manifold was actually below the 0.10%m/m specification limit. In one case, a ship received a VLSFO in an Asian port with sediment content 0.07%m/m and reported severe sludge formation soon after the fuel was put into use, with sludge formation continuing throughout the use of the fuel.

The sludge formation was so severe that the engineers had to clean the purifier bowl assembly every 4 hours, compared to a usual cleaning interval of 250 hours. At one point, the engineers discontinued using the fuel, as the vessel ran out of spare parts. Analysis of system samples later confirmed that the sludge formation was indeed due to unstable fuel and not from on-board mixing.

While the number of sludge formation cases clearly singles out VLSFO as more unstable and challenging to manage on-board, compared to HSFOs, another challenge is to prevent wax formation without exposing fuel to excessive heat and accelerated fuel ageing. With VLSFOs being  more parafinnic in nature, a good number may require heating beyond their pour point to prevent wax formation.

VPS discusses mitigating risks in sustainable vessel operations with its APS

VPS 2023 data shows, at least 15.8% of VLSFO samples had a wax appearance temp (WAT) above 40C, including 1.6% above 50C. These samples will precipitate wax if storage temps are not kept above the WAT, compared to the lower storage temperature requirements based on their tested pour points.

Wax formation is a reversible process, so theoretically, it should not cause any operational issue as long as fuel remains stable, but unfortunately, fuel stability is not guaranteed. Moreover, if wax is allowed to form, wax and aspheltenes (sludge) can co-mingle together as a result, the wax disappearance temperature may increase significantly and in the worst case, the wax may no longer disappear.

Taking a middle approach and striking a balance could be one option where the fuel is not severely overheated, nor the wax allowed to form freely during storage and only increase temperatures during transfer if needed. VLSFO with such high WAT/WDT will need close attention and care during storage, transfer, treatment and use. Prolonged storage should also be avoided for such fuels.  

Sludge formation on the other hand is an irreversible process, meaning it is not possible to convert the precipitated sludge back into the fuel. As there is no quick fix, efficient handling of fuel treatment plants becomes so critical otherwise, severe clogging of filters and separators can lead to fuel starvation to the engine and a loss of propulsion placing greater risk to the safety of the crew, ship, and the environment.

Avoiding a catastrophic situation requires visiting the entire fuel management chain and adhering to best practices. It starts with buying fuel from trusted suppliers, followed by verifying the fuel quality in one of the VPS, ISO17025 accredited laboratories.

VPS offers  an Additional Protection Service (APS) package which includes a stability assessment of the fuel.

VPS discusses mitigating risks in sustainable vessel operations with its APS

VPS additional protection service (APS) package

Parameters such as Separability Number (Reserve Stability Number) and Total Sediment Existent (TSE) together with Total Sediment Potential (TSP) results provides an excellent indication of fuel stability while GC/MS screening and follow up testing ensures the fuel is not contaminated with harmful chemical species at levels considered “unfit for use”. Testing Wax appearance & disappearance temperatures assist in maintaining optimal heating to prevent wax formation whilst also avoiding overheating and fuel ageing.

If a vessel uses stability additives, then its performance evaluation should not only be in assessing the improvement of the reserve stability number, but to conduct a broader assessment across fleet including assessing sediment reduction. Crew training is key, as poor handling of fuel by incompetent crew can also trigger a sludge formation situation.

A deeper understanding of the fuel’s quality can be achieved, coupled with a further reduction of any associated risk, by going beyond ISO 8217 and using the APS test scope. This service will ultimately save time, money and company reputation.

 

Photo credit: VPS
Published: 20 March 2024

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