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Too often, attention is turned to fuel quality in critical systems when a failure has occurred. Weather events or utility outages frequently highlight the fragility of the fuel systems on standby generators.

Savings during construction can translate into costs and reduced asset availability for the business thereafter.

A reactive approach of tank cleaning and fuel polishing after detection of contamination means that horse has bolted for reliability and uptime.

A proactive approach, whereby fuel is stored in controlled conditions has many savings: safety, environmental, reputational and financial. By monitoring and controlling the root causes of fuel contamination reliability is assured.

A robust fuel management system has several components:

  • Staff training
    Empower staff to know what the correct operations and procedures are for fuel handling.
  • Fuel quality standards
    Set warning and action limits for the fuel quality: water content, particle count, microbial contamination are critical properties as these can deteriorate in storage.
  • Sampling and analysis
    to measure adherence to standards. The importance of accurate, timely sampling and analysis cannot be understated. Only when quality data is present, a system’s reliability can be verified.
  • Facility, design and operation
    This is a big area where poor system design and execution can mean the difference between an impossible task or an easy check to keep fuel clean.
    Diesel is an organic product and will degrade over time. Moisture, heat and oxygen are catalysts which accelerate the deterioration process.

In-line filter suffering from fuel deterioration, asphaltenes

In-line filter suffering from fuel deterioration, asphaltenes

Used and Dirty Offline Fuel Filter Inserts

Used and dirty offline fuel filter inserts, saturated with absorbed contaminants from the fuel system

The single best tool to defend against fuel deterioration is an offline fuel filtration system or fuel polisher, as it is sometimes called.

All fuel filters are not created equal however. Depth type fuel filter should be used in addition to in-line filters as they offer greater dirt holding capacity and greater efficiency. Removal of particles smaller than 2 microns along with water and soft contaminants is a pre requisite of a diesel polishing filter.

Fuel sample bottles, from the left:
– Clean diesel
– Water removed from
the system
– Dirty diesel

A cellulose based depth fuel filter can adsorb the asphaltene on its fibres which otherwise passes through glass based filter media. Cellulose can also absorb water and retain hard particles such as rust and grit.

A particle count of ISO 4406: 14/13/11 along with clear bright appearance of the fuel should be the target with water less than 90 ppm for reliable engine performance.

One of the by-products of fuel deterioration is a black tarry substance called asphaltene. Asphaltenes are sub-micron particles and are a soft contaminant. An effective polishing filter needs to be capable of removing sub-micron particles to cope with asphaltenes.

This substance is deposited from the fuel when short hydrocarbon molecules combine to form long chain molecules of higher density compounds. Standby fuel tanks are especially prone to asphaltene deposits as the same fuel can be in them for years.

This black tarry substance can block the fuel filters and cause smoky exhaust. The fuel injected into the cylinders does not burn completely and black smoke is often the first tell-tale sign.

CJC Offline Fuel Filter

A CJC™ Offline Fuel Filter

One of the main benefits of long term fuel polishing is complying with the requirement to clean tanks. The health and safety, cost and operational benefits are significant as tank cleaning is a high-risk activity if not managed properly.

For optimum installation of the depth fuel filter, the supply to a fuel polisher must be from the bottom of the diesel tank to ensure water and settled particles can be captured by the fuel filter. The return needs to be as far as possible from the suction to effect proper turnover of the tank contents.

System monitoring of filter blockage and leak detection are also advised, so systems can be monitored remotely. To ensure best fuel quality, it is recommended to take frequent fuel analyses.

Fleury Engineering has installed hundreds of fuel filtration systems using CJC™ Fine filters from C.C.JENSEN on tanks from 50 litres on small generators to 15,000 tonnes on Combined Cycle Gas Turbine Power Plants.

We tailor solutions for applications from arctic climates to desserts with turnkey packages a speciality.


Article co-written by Mr. Mark Fleury, Fleury Engineering and Mr. Jan Foged, C.C.JENSEN Ireland

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