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Bunker Fuel Quality

VPS: Bunker fuel quality in emergency equipment

Wolf Rehder, VPS Area Manager Germany, focuses on the critical importance of maintaining high bunker fuel quality standards for emergency equipment onboard vessels, which is often overlooked.





Marine fuels testing company VPS on Tuesday (13 February) published an article by Wolf Rehder, VPS Area Manager Germany, emphasising the critical importance of maintaining high bunker fuel quality standards for emergency equipment onboard vessels, which is often overlooked:

Prevent emergency equipment from failing during an emergency

The lifeboats, emergency generators, and emergency fire pumps onboard are among the vital critical equipment essential for efficient, dependable, and prompt operation during onboard emergencies and across diverse climatic conditions.

Most companies and vessels have procedures in place to monitor their fuel quality. Close attention is paid to the management of fuels to be used in main and auxiliary engines, regardless of fuel-grade, as this has a direct impact on safety, health and the environment as well as on the economic operation of the vessel.

Most companies and vessels also have routines in place to regularly test emergency equipment. Nonetheless, it seems that in numerous instances, there is insufficient focus on the quality of fuel utilised in emergency equipment.

Fuel grade DMX within the ISO8217 specification is specifically intended for use within emergency equipment. However, since this is not a mandatory requirement, marine gas oil (MGO grade DMA) used for other purposes on board, is often used to fill up emergency equipment tanks. This could lead to hazardous outcomes as the DMA grade fuel might not be suitable for its intended use. The quality of the fuel in the emergency equipment tanks may also deteriorate during storage. Hence it is essential to test and ensure that the quality of the fuel being taken into the tanks is ’fit for purpose’ and monitored at regular intervals.

Impact of various parameters on the operation of the emergency equipment

Cold Flow Properties (Cloud Point and Pour Point)

Distillate fuels are predominantly paraffinic in nature and under colder temperature conditions, the paraffins can precipitate from the fuel in the form of wax. As a consequence, this wax can lead to blocked pipework and filters, leading to numerous operational issues including potentially starving the vessel engine of fuel.

Cloud Point (CP) of a distillate fuel is the temperature at which the paraffinic wax begins to separate from petroleum oil and form a cloudy appearance. This is the first indicator of cold-flow issues with a fuel.

Pour Point is the lowest temperature at which the fuel will flow, i.e., the fuel becomes solid.

Whilst the Pour Point of a distillate can be lowered using additives, the Cloud Point is not affected by such additives. This means that even when a distillate has a very low Pour Point, it’s Cloud Point could be very much higher. As the fuel temperature drops to, or below the Cloud Point, wax crystals will start to form, at which point, filter clogging could begin to take place, resulting in fuel starvation and engine stoppage. Satisfactory storage, transfer and filtration needs a fuel temperature about 3-5°C above the Cloud Point. The Cloud Point of fuels used for emergency equipment should be below the ambient temperatures at which the equipment it is operating, or likely to operate.

One real case example saw a fuel in a lifeboat engine storage tank which had a Pour Point of -33°C whilst the Cloud Point was +17°C. This fuel could only be safely used at ambient temperatures above 20°C.

The additives used can also potentially cause operational problems as some of their chemicals can be absorbed by filter materials, causing them to appear blocked. This problem is exacerbated for emergency equipment which are typically fitted with very fine filters.

Filter blockage due to high Cloud Point

Filter blockage due to high Cloud Point

Fatty Acid Methyl Esters (FAME)

Due to the practice of blending FAME into automotive diesel and heating oil, it is now more common and indeed inevitable, that some distillates supplied in the marine market contain FAME. FAME can lead to complications with respect to storage and handling in a marine environment, due to its increased level of oxidation tendency, long-term storage issues or shorter shelf life, it’s affinity to water and risk of microbial growth. Additional issues regarding FAME’s degraded low-temperature flow properties and FAME material deposition on exposed surfaces, including filter elements, also add to the fuel management concerns. Therefore, testing for the presence and levels of FAME within marine distillates, is a highly recommended practice.

Visual Appearance

Fuels grades DMA/DMZ/DMX should be bright and clear. If the fuel is hazy, it could indicate the presence of water or a high Cloud Point. Haziness could also indicate poor oxidation stability.

Sulphur Content

Vessels (including emergency equipment) required for securing the safety of a ship, or saving life at sea are exempted from the MARPOL Annex VI Regulation 3.1.1 Sulphur requirement. However, for the testing of emergency equipment in an Emissions Control Area (ECA), compliant fuel with sulphur content less than 0.10 % m/m should be used.

Fuel contamination, a potential hazard

Since fuels in the emergency equipment storage tanks remain unused for long periods of time, quality of such fuels may deteriorate due to the following:

Water can originate from contaminated fuel or condensation, and engines may not run because of water in the fuel lines. The presence of water can promote growth of microorganisms such as bacteria, yeast and fungi, and can also lead to blockage of fuel lines and filters due to icing when ambient temperature drops below 0°C.

Microorganisms (bacteria, yeast, fungi) – Given the correct conditions in fuel storage systems, micro-organisms can grow and multiply. Bacteria, fungi and yeast are living organisms which may be present in fuel storage tanks and in particular where water is allowed to build up. Distillate fuels are more prone to bacterial infection. Microbial infection can lead to slimy deposits in tank bottoms, plugging of filters, pitting corrosion on fuel tank bottoms or at oil water interface and injector fouling.

Corrosion caused by bacteria

Corrosion caused by bacteria

Gas Oil Stability – Many different chemical reactions can cause a gas oil to be unstable. Instability can lead to sedimentation and eventually to the formation of gums. Instability is usually indicated by a colour change over a period of time.

Mitigate your emergency equipment risks

It is thus obvious from the above reasons that engines, which should be the most reliable of all, may fail to operate when they are most needed.

Testing of the fuel’s cold-flow parameters, FAME content, sulphur levels, water content and microbiological activity, is highly recommended. These tests will provide vital information and knowledge of a fuel’s quality and the management requirements that go beyond adherence to imperfect specifications. These are necessary to help ship operators deal with fuels which may meet the specification numbers but give serious operational problems. 


Photo credit: VPS
Published: 14 February, 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.






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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Alternative Fuels

VPS updates Chinese shipping sector on bunker fuel quality, new fuels, and decarbonisation challenges

Representatives from China Shipowners’ Association, China Maritime Safety Administration, VPS and DNV informed the audience on latest developments from the marine fuel and shipping sectors.





Zhang Ai Guo, Secretary General, China Shipowners’ Association

Marine fuels testing and decarbonisation services company VPS on Thursday (28 March) held its Fuel Quality, New Fuels & Decarbonisation Challenges seminar at Jin Mao Tower in Shanghai, China.

The event was attended by about 100 local shipping executives and graced by Zhang Ai Guo, Secretary General, China Shipowners’ Association (CSA) and Zhang Wei, Director, China Maritime Safety Administration (MSA) Shanghai who both delivered opening speeches.

CSA – Green maritime developments part of national plan

“President Xi Jinping has encouraged green development and the transition to alternative fuels for the maritime sector is an important means towards lower carbon and pollution emissions especially in highly populated areas,” said Mr Zhang of CSA.

“By 2030, we are going to reduce traditional fuel consumption by 20 to 40 million tonnes. The Chinese Ministry of Transport has launched some options for green shipping.

“We going to establish our own standards for green shipping technology. By 2030, green power such as LNG and methanol, as well as other low carbon energy will be used to propel Chinese vessels plying not only inland rivers but also international waters.”

Zhang Wei, Director, China Maritime Safety Administration (MSA) Shanghai

Zhang Wei, Director, China Maritime Safety Administration (MSA) Shanghai

MSA, Shanghai – Establishment of Maritime Energy Efficiency Centre

Mr Zhang of China MSA Shanghai branch updated the audience about the recent establishment of its Maritime Energy Efficiency Centre as part of operations to support International Maritime Organization (IMO) activities.

“The Maritime Energy Efficiency Centre was opened about a week ago and work is driven by the IMO Data Collection System (DCS),” he explained.

“IMO has asked related flag States to record and report fuel oil consumption data of their ships, which will be later used to calculate the vessel’s operational Carbon Intensity Indicator (CII).

“This centre is established to fulfil the requests of IMO and we are going to responsibly provide data of the Chinese fleet to ensure compliance when operating on international waters.”

Captain Rahul Choudhuri, President Strategic Partnerships, VPS

Captain Rahul Choudhuri, President Strategic Partnerships, VPS

VPS – Proposes ‘joint effort’ to enhance biofuel bunker quality standards

Captain Rahul Choudhuri, President Strategic Partnerships, VPS began his presentation by highlighting the ‘Two Mountains’ theory of President Xi which noted clear waters and lush mountains to be invaluable assets when compared to resources of gold and silver.

He further mentioned: “As earlier pointed out by Mr Zhang of China MSA, decarbonisation is a joint effort required by all stakeholders.”

Noting the inadequacy of current ISO 8217 fuel quality standards for biofuels as a marine fuel, Captain Choudhuri said Singapore has developed its own provisional national standard on specifications of marine biofuel (WA 2:2022) and will be happy to work with China to enhance its biofuel bunker quality standards.

“I am pretty sure China will be a big biofuel producer in the future. We should find common waters to develop a strong biofuel standard for local and global use by China’s shipping industry,” he suggested.

Li Ting, Decarbonisation Advisor, VPS

Li Ting, Decarbonisation Advisor, VPS

VPS – Showcases suite of maritime decarbonisation advisory services

Li Ting, Decarbonisation Advisor, VPS meanwhile gave delegates an introduction to the firm’s suite of maritime decarbonisation advisory services including Maress, Portstats and Emsys which leverages upon VPS’ operational, fuel and emissions databases.

Ms Ting shared Maress is a digital management system for fleet data-driven decarbonisation. The subscription-based system, currently used by about 500 vessels, has reduced more than 200,000 metric tonnes of carbon dioxide emissions within the last three years.

“Maress has helped companies such as Tidewater decrease fuel consumption and related GHG emissions by 5% per active vessel in the North Sea fleet, while increasing efficiency by as much as 13% in some vessels,” she said.

“A partnership with SIEM Offshore has shown Maress increasing its overall FO-efficiency for its fleet of 22 vessels by 2.3% higher than the expected consumption baseline.”


Photo credit: VPS
Published: 8 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.





Louis Reed from Unsplash

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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