Connect with us

Fuel Testing

VPS: Cold flow characteristics of biodiesel blended petroleum distillates

Dr. Sunil Kumar highlights how environmentally friendly biodiesel bunker blends can be negatively impacted by cold weather environments and how VPS testing methods could help ship operators ensure safe navigation through low temperatures.

Admin

Published

on

RESIZED VPS logo

Dr. Sunil Kumar of marine fuels testing company VPS on Tuesday (12 March) discussed how environmentally friendly biodiesel blends can be negatively impacted by cold weather environments. 

The article also highlighted VPS offering various test methods in place to evaluate the cold flow property of the biodiesel blended fuels, which can help the ship operators to make the right decision how to handle the fuel at low temperatures: 

Environmentally friendly fuels like biodiesel blended with petroleum distillates can have an impact on the cold flow property. Currently biodiesel is one of the choices which is renewable, biodegradable, and less toxic compared to fossil fuels. Biodiesel significantly reduces carbon dioxide, carbon monoxide, sulfur oxides, volatile organic compounds, particulate matter, and unburned hydrocarbons when compared to petroleum distillates like Marine Gas oils (MGO), very low sulfur fuel oil (VLSFO) and Heavy fuel oil (HFO).

Cold flow prediction of biodiesel blended petroleum distillates is very important when a ship is sailing through cold weather regions. The cold flow characteristics of a blended fuel can be different from the individual fuels used for blending. MGO, VLSFO and HFO basically originate from fossil fuels whereas biodiesel is from a renewable source. Both are essentially hydrocarbons but contains compounds with different structural characteristics and properties. So, the structural difference of the compounds responsible for the cold flow property shall be considered since it is a physical phenomenon. This will have an impact on the cold flow property of the fuel since the blend is from two different origins and can sometimes lead to unpredictable paraffin agglomeration.

Veritas Petroleum Services (VPS) has various test methods in place to evaluate the cold flow property of the biodiesel blended fuels. The Laboratory determined test results can help the ship operators to make the right decision how to handle the fuel at low temperatures. 

Cold Flow Property of Biodiesel, MGO, VLSFO and HFOBiodiesel, MGO, VLSFO, and HFO share a common characteristic: the presence of polymethylene groups influencing cold flow properties. The severity of low-temperature flow centers on the amount of heavier paraffins present, with longer polymethylene chains exacerbating the impact. Biodiesel, while advantageous in many respects, falls short in cold flow performance, prone to wax crystallization in colder climates, leading to potential filter blockage and potential engine damage. The composition of these fuels, particularly the presence of saturated and unsaturated paraffins, significantly affects their cold flow properties. Different feedstocks for biodiesel production yield varying performance in low temperatures; for instance, palm oil-based biodiesel fares worse than soybean-based biodiesel due to differing paraffin characteristics. Origin, whether plant or animal-based, profoundly influences cold flow properties, necessitating meticulous evaluation, especially in blends with MGO, VLSFO, and HFO. Proper assessment of low-temperature behavior is critical for blended fuels with diverse sources and characteristics.

VPS Laboratory Scale Evaluation

There are several test methods used to determine the cold flow characteristics in fuels like MGO, VLSFO, HFO, biodiesel, and their blends. VPS utilises four main methods: Cloud Point (CP), Pour Point (PP), Cold Filter Plugging Point (CFPP), Wax Appearance Temperature (WAT), and Wax Disappearance Temperature (WDT). CP indicates the onset of paraffin crystallization, serving as an estimate for operational limits. PP signifies near-complete paraffin crystallization and guides the lowest usable temperature. CFPP indicates filter clogging due to paraffin crystallization, impeding fuel flow.

Each test offers insight into how a fuel behaves in cold conditions. However, methods ISO3015 (visual method) and ASTM D5773 (optical light source) can only be used to measure cloud point when the “petroleum products are transparent in layers 40mm in thickness”. For this reason, VPS researched and developed an “Automatic Test Method for Wax Appearance Temperature of VLSFOs” and published a White Paper on this in 2019.  

VPS Innovative (WAT/WDT) method for Non-Transparent Fuels

The ASTM D5773 method is used to determine the cloud point of clear petroleum products and biodiesels. VPS’s innovation extends this to dark fuels like VLSFO, HFO, and biodiesel blends.

The VPS developed method WAT/WDT test offers a comprehensive view of wax appearance and crystallization temperatures in blended biodiesel with MGO, VLSFO, and HFO. This provides an extensive insight into low-temperature behavior, complementing conventional tests. There’s a correlation between cloud point and WAT, both marking the onset of wax appearance.

Appendix 1 and 2 details some test results of various fuel types identifying the variance in the cold flow properties that are identified by tests in addition to the conventional ISO 8217 tests.

VPS Innovative Gas Chromatography (GC) method for the Biodiesel Impurities in the Fuel Blend

Impurities in biodiesel with FAME, arising from incomplete transesterification of feedstocks, can impact cold flow properties. Elevated total glycerol due to incomplete conversion and glycerol residue can cause issues like injector deposits and clogged systems. These impurities can affect cold weather performance when blended into fuels. Compounds like saturated monoglycerides (SMG) can precipitate above the blend’s cloud point, potentially causing filter plugging. EN 14105 assesses free glycerol and residual glycerides in B100. VPS’s innovative GC method determines mono-, di-, triglycerides, and free glycerol in biodiesel blends with MGO.

Conclusion

The diverse paraffin compositions in biodiesel blends pose challenges in establishing a general cold flow property relationship. These paraffins, from both biofuel and fossil fuel origins, add complexity to the crystallization process. The structural differences between biodiesel and diesel fuel compounds leads to an inconsistent flow behaviour of the blended fuel.

Given the unpredictable nature of low-temperature flow characteristics in blended biodiesel, comprehensive laboratory tests are crucial. Conducting CP, PP, CFPP, WAT/WDT, and GC analysis aids in understanding SMG in MGO blended biodiesel is recommended. Such thorough testing provides valuable insights into the cold flow properties of biodiesel blends.

Note: The full article by VPS accompanied with Appendix 1 and 2 can be found here.

 

Photo credit: Manifold Times
Published: 13 March 2024

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

Bunker Fuel Quality

VPS on lifeboat fuel quality: A safety of life at sea critical risk

Neil Chapman and Steve Bee said regular fuel testing, correct fuel selection, and proactive fuel management are essential to ensure lifeboats are ready when they’re needed most.

Admin

Published

on

By

RESIZED VPS logo

Neil Chapman, Managing Director of Americas, and Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Monday (13 July) said regular fuel testing, correct fuel selection, and proactive fuel management are essential to ensure lifeboats are ready when they’re needed most: 

Performance when its most critical

In an emergency, a lifeboat engine is not simply a mechanical asset, it is a life-saving system. If the fuel in that system is of poor quality due to degradation, contamination, or simply unsuitable for the operating environment, then the result may be failure to launch, manoeuvre, or sustain operation, when human lives depend on it. Fuel failures in lifeboats onboard Cruise Liners are high-consequence life-safety risk as the engine may be the only power source available during an emergency. It is a key SOLAS (Safety of Life at Sea) requirement that lifeboats should hold sufficient fuel to enable them to run at 6 knots for no less than 25 hours.

The primary consequence of a lifeboat failure is not the commercial  loss, but the potential failure of a safety-critical system during an abandon-ship scenario. Financial, legal and reputational consequences will undoubtedly follow but the immediate risk is to life.

Now with the inclusion of Biofuels and FAME in the marine fuel mix and assuming the same fuel used in the main engines may be used in the emergency systems, how do you verify the operability of the lifeboats in times of crisis?

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 lifeboat fuel tanks. This could lead to hazardous outcomes as the DMA grade fuel might not be suitable for its intended use. DMA fuel whilst acceptable for general machinery use, will unlikely provide the same assurance of low-temperature operability, ignition quality, storage reliability, or starting reliability required for emergency craft. The quality of the fuel in the lifeboat 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. DMX fuel should be chosen due to its ability to operate at a lower temperature, superior ignition quality and  improved starting capabilities. However, this fuel only accounts for approximately 1-2% of the global supply, compared to the regular DMA grade.

Failure Modes in Emergency Operations

SOLAS compliance should not be viewed only in terms of carrying the required quality of fuel. The fuel must also remain fit-for-purpose regarding stability, cleanliness and be capable of supporting reliable engine operation throughout the vessel’s operation. Lifeboat failures are rarely a singular dramatic event, rather a chain of events. These are typically caused by degraded fuel, filter blockages or storage issues.  Incorrect handling and storage can result in the ingress of water, which with modern fuels, can promote the growth of filter blocking bacteria rendering the engine inoperable.  So rather than the issue being no fuel, it is more likely to be an issue of fuel that is of poor quality. As lifeboat engines may sit idle for long periods it potentially allows the fuel to degrade, if the correct due care and attention is not paid to this key piece of emergency equipment.

The handling and storage of fuel, coupled with the observance of quality operating procedures can lessen the risk of these failures, but are unlikely to eliminate them completely. However, the failure to follow established procedures can result in issues that are likely to cause catastrophic financial and reputational damage to the cruise line operator.

The most common failure modes in emergency lifeboats can be categorised as follows:

  • Fuel Starvation
  • Contamination
  • Degraded Fuel
  • Blocked Filter/Injectors

Contamination in the engine due to the presence of water, as previously mentioned, can be catastrophic as this can induce corrosion and oxidation, along with promoting microbial growth which results in filter blocking and fuel starvation to the engine.

If an engine fails to start, or runs poorly under load, due to fuel related issues this would likely cause a secondary emergency, compounding the reason the lifeboat was required in the first instance.

The danger with degraded fuel is that the risk is often hidden. A lifeboat may appear available, inspected and compliant, whilst he fuel inside its tank is steadily losing the properties required for reliable emergency operation.

IMO guidelines indicate that inspectors and regulators are increasingly looking at emergency systems for fuel compliance, highlighting its importance in the operation of a vessel.

Seasonal & Regional Fuel Requirements

Often overlooked are the cold flow properties of diesel and biofuels.  While hydrocarbon-based diesel has very good (low temperature) cold flow properties, this is not the case for biofuels, so lifeboats fuelled in the Caribbean for the summer season may be completely inoperable if the vessels are transferred to the Northeast or higher location, for a winter period.

Root Cause Failure Mechanisms

The failure to follow the appropriate standards which result in engine failure can be categorised as follows:

image 45

The Effect of Biofuels on Marine Fuel Quality

In a study recently completed by a major shipping line, blends of biofuels were tested for a wide range of parameters.  The findings were:

Biological growth appeared within the first month, increasing rapidly with exposure to light.

Within 3 months oxidative corrosion started to occur requiring regular monitoring.

46 CFR § 169.837 states:

“(2) The fuel tanks of motor propelled lifeboats have been emptied, and fuel changed once every twelve months.”

Yet the evidence shows fuel stability effectively starts to deteriorate within the first month and can be unusable by month 3.

Prevention Strategy

Fuel testing should be viewed as part of the vessel’s safety assurance programme. It provides evidence that the lifeboat fuel remains fit-for-purpose, not only on the day it was supplied, but throughout storage and across changing operational conditions. A strong housekeeping policy requires a multi-pronged approach to ensure operability in times of crisis; such steps include:

  • Housekeeping – ensuring the fuel system remains closed when not in use to eliminate the ingress of water.
  • Operation – frequently run the engines so that fuel and lubricants are cycled through the units.
  • Testing program – likely to be cheaper and more efficient than changing out the fuel. A well-developed fuel testing program can eliminate the need to change the fuel.
  • Documentation – by recording all the actions taken to protect the emergency systems historic data can be tracked.

Advanced Testing Programs

Due to the importance of these emergency assets several different tests should be considered to ensure the suitability of the fuel.  Testing should include:

  • Cold-Flow properties using Pour Point, Cold Filter plugging Point, Cloud Point
  • Water content for moisture
  • BYF for Microbial testing
  • Acid Number for corrosion tendencies
  • FAME for biofuels content
  • Sulphur for MARPOL Annex VI compliance
  • Visual Appearance
  • Viscosity for flow properties
  • Density
  • Flash Point for SOLAS compliance
  • Cetane Index

Conclusion

It is possible to avoid engine failures, but this can only be achieved with a well-documented and well-followed operating procedure.  Regular fuel sampling and testing along with general good housekeeping techniques will ensure these units are ready go when they are most needed. Once they are seen as an active safety-critical asset rather than a dormant emergency component the value in this process will be realized.

Lifeboat fuel quality is not a housekeeping detail, it is a Safety of Life at Sea issue. Emergency craft must be capable of starting manoeuvring and operating for the required duration whenever called upon. Sub-standard, degraded, contaminated, or unsuitable fuel can compromise that capability and turn an emergency response into a secondary emergency. Regular testing, correct fuel choice, controlled storage and documented fuel management provide the evidence and assurance that lifeboats remain ready when lives depend on them.

 

Photo credit: VPS
Published: 14 July, 2026

Continue Reading

Engine

VPS on precision testing for reliable engine performance: Importance of coolant analysis

Steve Bee of VPS highlighted that coolant analysis can prevent failures through early chemical detection, protect components, maintain performance, plus reduce costs and downtime.

Admin

Published

on

By

RESIZED VPS logo

Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Thursday (9 July) highlighted that coolant analysis can prevent failures through early chemical detection, protect components, maintain performance, plus reduce costs and downtime: 

Engine coolants play a critical role in protecting equipment performance, efficiency, and longevity. As cooling system technologies and coolant formulations continue to evolve, regular laboratory analysis has become an essential part of proactive maintenance.

It is widely known that coolants should be managed with the same discipline as other critical fluids, as chemical changes can develop long before visible failures occur.

However, it must be emphasized that coolant analysis is about reliability, not just fluid condition. Modern engines and cooling systems operate under higher thermal loads and tighter tolerances, so even small changes in coolant chemistry can affect corrosion control, heat transfer, and component life.

An effective coolant analysis service should provide operators with an early warning system, helping to identify contamination, degradation, and inhibitor depletion before they become operational failures. The service can be a practical tool for reducing downtime, preventing avoidable repairs, and extending equipment life.

As stated above, many cooling system issues start at the chemical level, long before anything is visible and without analysis you are effectively blind until a failure starts. Through coolant testing, risks such as corrosion, cavitation and scale formation can be detected long before damage occurs.

image 41

As an example, the above images show the damage that can occur when a coolant does not have sufficient concentration to provide adequate protection. This damage can appear as scale formation, reduced heat-transfer efficiency and lower flow rates, which can ultimately lead to corrosion.

Coolants don’t just control temperature, they also chemically protect engines and coolant systems. They effectively prevent corrosion of metals and components, reduce cavitation damage in liners and pumps and help avoid deposit build-up and blockages in heat exchangers. Its true that cooling system damage, is a major source of engine failure.

Coolants must be chemically stable in order to transfer heat effectively, as poor cooling performance directly impacts engine efficiency, fuel consumption and reliability. As a predictive maintenance tool coolant analysis moves operations from emergency repairs to planned maintenance.

Should coolants exhibit degrees of incompatibility, then further issues can arise. Mixing incompatible coolants can cause sludge formation, which will in turn affect coolant circulation, leading to reduced efficiency. In addition incompatible coolants can form sludge or gels, which negatively impacts circulation and heat transfer creating hotspots. Those hotspots can break down lubrication and cause micro-welding between piston and liner surfaces, leading to piston pick-up.

image 42

Historically, many coolants were relatively simple glycol/water formulations supported by inorganic inhibitors such as silicates, phosphates, or borates. However, modern coolants are more sophisticated, including OAT, HOAT, NOAT, POAT, and other specialized blends designed for longer service life and improved protection. This added sophistication creates a need for verification: when systems are topped up, mixed, contaminated, or serviced.

Organic Acid Technology (OAT) coolants, can be formulated with various organic acids such as Sebacate, which is an ester of sebacic acid. Sebacate exhibits low volatility and excellent flexibility at low temperatures. Also tolytriazole can be a component, which is best known as a thermally stable, metal corrosion inhibitor.

So organic acid technology uses organic acids to provide targeted corrosion protection, especially for aluminum and mixed-metal systems. The advantages are, long service life of up to seven years, reduced abrasive deposits, and protection that is generally gentler on seals and components. However, whilst such coolants offer long service life, OAT coolants are not maintenance-free. Its also possible that coolant protection can be slow to establish and performance can be compromised by incorrect mixing, contamination, or loss of inhibitor balance. This is where routine analysis helps verify that the coolant is still doing its job.

Hybrid Organic Acid Technology (HOAT) coolants are newer generation coolants which combine organic acid technology with selected inorganic additives. They aim to provide both long-life protection and faster initial corrosion control through improved heat transfer and cooling performance. This makes them attractive for demanding engines and systems where heat transfer, compatibility, and corrosion control are all critical. The important point is that HOAT chemistry is more complex than traditional coolant chemistry. That complexity can make correct identification, compatibility, and contamination control more difficult. The downsides to HOAT coolants are they are more expensive than traditional coolants, but more concerning is they can be more susceptible to becoming contaminated, affecting their effectiveness and lifespan. Therefore, routine lab testing helps confirm whether the coolant in service still matches the intended formulation and whether the inhibitor package remains effective.

The shipping fleet has numerous sectors and each have various considerations when it comes to the use of coolants:

image 43However, the underlying need for each shipping sector is similar, in that cooling-system reliability supports uptime, safety, and cost control. Deep-sea shipping, offshore and marine services, harbour and coastal operations, cruise and ferry operators, inland waterway vessels, plus port or terminal operators, all have equipment where coolant condition can affect reliability. The commercial message is that coolant analysis can be positioned alongside existing marine fluid management services, making it a logical extension rather than a separate standalone offering.

A typical coolant analysis test slate includes the following tests highlighting what each test parameter detects, their frequency and benefits:

image 43

To take an analogy from Oil Condition Monitoring, Coolant Analysis is effectively a “blood test” for the cooling system.

So in summary, Coolant Analysis can prevent failures through early chemical detection, protect components, maintain performance, plus reduce costs and downtime.

 

Photo credit: VPS
Published: 10 July, 2026

Continue Reading

Trending