Safeguarding your fuel system
Wilhelmsen insights
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Alex Qiang, Head of Product Management - Energy Solutions
Mastering microbial risk through proactive fuel management
Sofia Michalakidi, Product Manager Energy, and Alex Qiang, Global Head of Product, Wilhelmsen Ship Service (WSS), explain why microbial contamination remains a persistent silent threat onboard – and what you can do about it.
Are you managing fuel proactively – or waiting for problems to strike?
Marine fuel quality has always been critical to vessel performance, but the conditions facing operators today demand a fundamental shift in mindset. Consider the following:
- Do your crew(s) carry out regular, systematic fuel testing – or do they act only when something goes wrong?
- Have you updated you fuel management practices to include biofuel blends and associated challenges regarding compatibility and water contamination?
If you are relying solely on “on spec” reports from a fuel testing lab or intermittent visual checks, your vessel is exposed to hidden risks that can compromise safety, compliance and operational integrity. Microbial contamination is a silent, progressive threat – and it is becoming more prevalent as shipping transitions to cleaner fuels.
Here we present a comprehensive, authoritative framework to address this growing challenge, introducing Prevent, Test, Treat (PTT) – our integrated approach for fuel management that combines proven chemistry, practical tools and technical advisory expertise into a single, closed-loop solution.
An underestimated threat: how fuel degrades in service
While marine fuels may comply with specifications on delivery, their quality is not static. Once bunkered, fuels – especially low-sulphur distillate and bio-based blends – become vulnerable to degradation. The principal enabler of this degradation is water.
Water can enter fuel systems through multiple pathways:
- Condensation within tanks, especially under varying thermal conditions
- Leaks in cooling or pipework systems
- Residual moisture from prior cargoes or cleaning
- Minor ingress during handling, transfer or storage
The presence of water creates the ideal breeding ground for microbial life. These organisms consume fuel as a food source and thrive at typical marine temperatures (up to 30-40°C). Their proliferation leads to:
- Formation of sludge and biofilms (slime) that can potentially clog filters and pipelines.
- Generation of organic acids that can corrode tanks and equipment.
- Production of hydrogen-sulphide gas (H₂S), posing serious safety hazards for crew members during tank entry or maintenance.
Operators face not only operational disruptions and unplanned maintenance, but also the risk of significant financial losses through wasted fuel and downtime.
The fallacy of relying on “on spec” delivery
It is a common but dangerous misconception that fuel delivered “on spec” is inherently safe throughout its operational life. This belief overlooks the reality that contamination occurs after delivery – during storage and use – especially when fuels are stored for extended periods, as is common with dual-fuel operations or vessels using biofuel blends.
Premium distillate fuels, often perceived as cleaner and safer, can in fact be more prone to water retention and microbial attack. Without structured preventive measures and testing, operators risk unknowingly allowing fuel degradation to progress until major damage has occurred.
Why testing is overlooked – and why this has to change
Despite the availability of simple, cost-effective testing solutions, fuel testing is often seen as an optional extra rather than a core operational control. The reasons typically lie in:
- A lack of awareness about the link between water, microbes and fuel degradation
- Overconfidence in initial fuel specifications
- A reactive, rather than proactive, approach to maintenance
Such thinking is costly. A single contaminated tank can render hundreds of tonnes of fuel unusable, require complex and expensive cleaning operations, and jeopardise compliance – particularly when alternative fuels are unavailable in restricted emission zones.
According to a 2018 report from The Swedish Club, the average cost per incident of fuel-related damage on vessels was USD 344,000 – a figure broadly consistent with an earlier study from 2015. Poor fuel management was identified as one of the three most common causes of engine damage across the study period, alongside lubrication failure and incorrect maintenance.
Prevebt Test Treat: an integrated solution
Our PTT methodology is designed to close this gap. It provides a complete, structured approach that spans prevention, monitoring and targeted intervention – delivered through a combination of specialised products, crew-friendly tools and knowledge support.
Where many providers offer isolated solutions – chemicals without testing, or diagnostics without treatments – PTT integrates all elements into a coherent system, backed by global technical advisory capability.
PREVENT – eliminate conditions for microbial growth
Prevention focuses on removing the root cause – water – and stabilising fuel to make it hostile to microbial life. Two principal tools are employed:
Unitor™ DieselPower BioEnhancer – An antioxidant and water-separating additive dosed during or just before bunkering, BioEnhancer limits microbial-friendly conditions from day one. It helps separate water from fuel and inhibits oxidation, which reduces the ‘living environment’ for microbes right from the start.
Unitor™ Snake Water Removal Filter – Installed in the tank or other convenient locations, these filters continuously absorb free water – even outside scheduled maintenance windows. They can be viewed as passive insurance keeping water content negligible.
Together, these measures form the first and most cost-effective line of defence against contamination.
TEST – reveal hidden risks before damage occurs
You can’t manage what you don’t measure. Routine testing ensures that microbial activity or water ingress is detected early. WSS provides a suite of kits designed for ease of use, with no specialist training required:
Unitor™ Bacteria Single Test Kit – detects microbial presence with a simple six-drop visual test.
- Combined Test Kit Plus and EasyShip – test water content, emulsification levels and general fuel condition.
The bacteria test takes 15 minutes and the water test 2-3 minutes, with clear, actionable results. Testing every 2 weeks is recommended, with more frequent checks advisable for vessels using biofuel blends or operating in challenging climates.
TREAT – precise intervention when contamination is confirmed
When contamination is identified, targeted remediation is essential. Unitor™ DieselPower BioControl is a fuel-specific biocide developed to address microbial contamination without harming fuel system components. Unlike generic products, it is formulated for optimal solubility and dispersion in marine fuels, ensuring effective treatment without excessive chemical load.
Importantly, treatment is applied only when necessary, supporting environmentally responsible fuel management practices and avoiding unnecessary chemical usage.
Operational ease, global support
The PTT system is designed for practical adoption. All products are supported by clear, straightforward guidance and port service engineers and technical sales specialists are available globally to provide support. This ensures operators and crews can deploy the system effectively, integrating it into standard operating procedures without disruption.
Compliance, documentation and audit readiness
Though microbial control is not mandated by regulation, proactive fuel management aligns with MARPOL Annex VI principles and demonstrates diligence during inspections, vetting and charter-party reviews. Documented testing and treatment provide a valuable audit trail that can help operators defend against claims and demonstrate robust fuel hygiene practices.
As the industry shifts towards greater accountability in fuel management – driven by both regulation and commercial expectations – operators with structured fuel management strategies will be better positioned to meet stakeholder demands.
Action is imperative in a changing fuel landscape
The shipping industry’s transition to bio-based and blended fuels will continue to increase the risk of water retention and microbial contamination. These fuels’ characteristics demand a more vigilant approach to fuel management. Relying on outdated assumptions or reactive maintenance exposes operators to unacceptable risk.
By contrast, adopting the PTT methodology delivers measurable operational, financial and compliance benefits. A small, proactive investment in prevention and testing safeguards fuel worth hundreds of thousands of dollars, protects critical equipment and prevents unplanned disruptions.
Preparing for fuel management excellence
Microbial contamination is not a hypothetical risk. It is a real and growing threat that calls for structured, proactive management. PTT provides operators with an authoritative, comprehensive solution – backed by WSS’s technical expertise and global support network.
In the context of evolving fuel types, regulatory expectations and operational demands, adopting PTT is no longer optional. It is the standard for responsible, resilient marine fuel management.
Next steps
We invited operators seeking to strengthen their fuel management strategies to reach out to us for technical advice, product guidance and tailored solutions that meet your vessel profiles and operational requirements.