Fuel Oils: Handling, Mis-handling, and Contamination (Part 3)

Steven M. Lindholm, P.E., P.M.P.

Part 3:  Supply Trends and Treatments

Welcome to the last of a three-part presentation on current trends in fuel oils and fuel oil contamination.  EDT hopes you will come away from this series with better knowledge of oil as a fuel, what can contaminate fuel oil, the damages caused by contaminants, and the available means to prevent or identify fuel contamination.  This part of the series will cover trends in fuel oil blending, means to protect your equipment, or discover when your fuel oil has been contaminated. Following this article are some references regarding contamination in fuel oil.

Trends

Contamination in fuel oils has long been a problem.  Lately, some types of contamination have been showing up with greater regularity:

Polymers in feedstock.  In 1998, Det Norke Veritas (DNV), an international accredited registrar and classification society, reported in their class circular 7/98 that isotactic polypropylene had been found in heavy fuel oil of high viscosity (280 centistoke), leading to fuel filter clogging. These are long repeating chains of propylene, which would be invisible in the fuel oil, but separated by mechanical filtering. More recently, the U.S. Coast Guard has issued safety alert 10-18 regarding polymers found in intermediate fuel oil (IFO), which is less viscous (180 centistoke) than heavy fuel oil, causing similar issues in coastal vessels.  Polymers in fuel oil can be difficult to detect and these contaminants are not part of standard fuel specification testing.

Heavier fuel oil.  Not heavier in weight, but more viscous.  With refineries attempting to get the highest possible revenue from each barrel of raw petroleum, further catalyzation of the residual fuel oils is done.  This results in the remaining residuals which become bunker oil being even closer to asphalt.  With the increased refining, the chances of sand (silicon dioxide) showing up in higher percentages increases.

Catalysts.  With increased refining using catalysts to break the longer oil chains into shorter, more volatile chains, the chances of some of the catalysts getting into the residual fuel oil is higher.  Aluminum, silicon, and vanadium have been on the increase, with more reports of fuel oil deliveries which are unusable after independent laboratory test samples.  GARD, the largest marine insurer in the world, has a good article written in 2014 on catalytic fines in fuel oil.

Shale Oil.  Shale oil can be one of two variations – petroleum which has been forced out of oil shale into the sands above by water injection, or oil which has been converted from the petroleum precursors in oil shale.  In either case, this oil is lighter than crude petroleum oil (contains more volatile oils which can be distilled) and contains higher amounts of iron, paraffin, and calcium.  Shale oil requires different catalysts and setpoints during cracking than crude oil – if the refinery hasn’t adjusted for the difference in composition, the resulting fuel oils may be out-of-specification in ways which cannot be discovered in normal fuel oil tests.

Sulfur.  The trends for sulfur in fuel oil are decreasing – a bright spot in an otherwise bleak report.  Though high sulfur raw petroleum is still a cheaper base, regulatory requirements for low sulfur fuel oils have created a market which is demanding lower sulfur level to meet these requirements.  The cost to meet the requirements is higher than accepting the higher sulfur content, but the market is being pushed to inevitably buy low sulfur fuel or switch to even more expensive fuel solutions.

Protect Your Investment

Problems with fuel oil are not readily apparent – contaminated fuel oils look the same as ‘clean’ fuel oil.  They may even be supplied from reputable, long-standing vendors, often unknowingly.  So how does an operator protect his investment from damage resulting from ‘off-spec’ or contaminated fuel oil?  Proactively, the operator should monitor and treat the fuel they receive.

Fuel Oil Testing.  Operators who purchase fuel oil from multiple vendors or from multiple locations should routinely have the fuel oil tested.  There are many third-party fuel testing laboratories such as Veritas Fuel Services who will quickly turnaround fuel oil analyses.  Mostly they test to general standards such as ISO 8217 – but they can also test for other contaminants if requested through the application of ASTM D7845, Standard Test Method for Determination of Chemical Species in Marine Fuel Oil by Multidimensional Gas Chromatography/Mass Spectrometry, if necessary.  Operators using IFO or marine gas oil (MGO) should take care to expand the fuel oil tests to look for polymers, paraffins, and fines.

Fuel Treatment.  Fuel oil can be treated to help emulsify water or settle out fines and inorganic particles.  In this case, it is a chemical treatment of the fuel oil, usually using an inert detergent or alcohol to bind to water or a flocculent to settle inorganics out.

Separators and Centrifuges.  For many types of fuel oil, particulates can be centrifuged out, leaving the fuel oil stripped of contaminants.  Likewise, water can be separated from the oil the taking advantage of the difference in specific gravity (relative density).

Segregation.  For operators with large volumes of fuel oil, requiring multiple tanks for storage, segregation of new fuel oil is a good strategy.  By refraining from blending new stock with existing, proven stock, an operator can ‘buy time’ to have the fuel oil properly tested.  The testing can also determine the degree of fuel treatment – either mechanically with separators or chemically – required to use the new stock.

Even with proactive monitoring of fuel oil, an operator may find contaminated fuel getting into his machinery and causing damage.  While this unfortunate event cannot be undone once it happens, bringing in an expert can assist in containing the damage.  The chosen expert should be well versed in what to look for and the tools needed:

Testing.  Once fuel oil contamination is suspected, the expert should pursue testing of the fuel in question.  Savvy experts are up-to-date on trends in fuel oil contamination, and request specific testing to rule out – or, more likely, confirm – suspected contaminants.  Each case will present different clues, based on what the operator may tell their expert, and the expert should key into the events preceding the incident.

Forensic Analysis.  Your expert should be able to examine the extent of the damage and ask questions about the events prior to the incident.  Was a separator in use?  Was the flow rate reduced out of the separators?  What temperature is the fuel oil flowing?  Has the pressure out of the booster pumps changed recently?  Has the power into the pumps changed recently? How long has this fuel oil been in use?  How long since the last fuel delivery?  From where was the fuel delivered?  Every incident is a story, and your expert should be curious about the prologue when creating their conclusion.

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References

Det Norske Veritas, Casualty Information 7/98, ‘Clogged filters due to contaminated fuel oil,’ Hovik, Norway, 1998

Gard Services A/S, Insight 165/2002, ‘Effects of off-Spec bunkers,’, Arendal, Norway, 2002

Gard Services A/S, Loss Prevention Circular 01-14, ‘Prevention of engine damage due to catalytic fines,’ Arendal, Norway, 2014

International Maritime Organization (IMO), In Focus, ‘Sulphur 2020,’ http://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx, London, England, accessed July 30, 2018

United States Coast Guard, Safety Alert 10-18, ‘We’ve all experienced bad gas, but how about IFO 380? U.S. Gulf Coast Bunker Contamination,’ Washington, D.C., 2018