Following the continued coverage of bunker issues in the US Gulf, the UK P&I Club published a short FAQ in conjunction with Brookes Bell. There have been several bunker quality-related engine problems following the delivery of fuel supplied in the US Gulf region, particularly in Houston, but these also extend to fuels supplied at Panama.
As explained, these claims appear to relate to fuel bunkered late March-May this year, with the problems manifest variously in the form of sticking and seizure of fuel injection system components and blocking of fuel filters.
What appears to be the problem?
Evidence suggests that the cause of the problems is linked to the inclusion of adulterants, or contaminants, in the fuel that are of non-petroleum refining origin. There appear to be at least two different forms of contamination involved, i.e. not all problem fuels share the same burden of contaminants, some showing evidence of chemical waste related to bisphenol manufacturing operations, other showing evidence of bio-derived contaminants including Tall Oil, a bi-product from the timber industry.
But ISO 8217 testing will show that bunkers are off-spec, so why should I be concerned?
The standard ISO 8217 ‘Table 2’ Test Requirements involve the determination of physical and chemical characteristics, and include tests designed to assess the levels of normal manufacturing and handing impurities, such as catalytic fines, water and used lubricating oil, and to highlight the presence of contaminants that may impinge on the flash point of the fuel.
However, it is impractical for specifications to include tests and limits for all possible contaminants that might occasionally finding their way into marine bunker fuels, and there are materials which can adversely affect the fitness of fuel for use in a marine engine, the presence of which will not necessarily be revealed by the basic Table 1 (distillate fuels) or Table 2 (residual marine fuels) Test Requirements.
As with the current rash of problems from the USGC region, the fuel appear to meet the basic ISO 8217 Table 2 Test Requirement, but still appear to cause problems in use and it is increasing more common, and necessary, to call for additional tests and analytical techniques in an effort to investigate why a fuel might be giving rise to problems and to assess whether there might have been a breach of Clauses 5.2 to 5.5 of the International Standard.
Are there additional tests that can be run?
There are more advanced analytical techniques that can assist, such Gas Chromatography combined with Mass Spectrometry (GCMS). Gas Chromatography (G.C.) essentially provides a means of separating the volatile components of complex mixture (generally in order of increasing boiling point).
Separation is achieved effectively by differential rates of adsorption onto and desorption from an active ‘stationary phase’ of a G.C. column (located in a temperature programmable oven) through which a portion of the sample is passed under the influence of an inert carrier gas. The separated components are detected electronically as they elute from end of the G.C. column are displayed in the form of a series of peaks on a time-based chromatogram, with the peak size (area) being roughly proportional to the quantity of component present.
There are different ways in which the GC-MS technique can be applied:
- ‘Head-space’ analysis, which involves injecting only the more volatile (vapour phase) components of a sample into the instrument. This approach is useful for looking for highly volatile contaminants, such as chlorinated solvents, but would not detect the less volatile variety
- Direct injection of the fuel, after precipitation of the asphaltenic contaminants
- Pyrolysis GC-MS, which is particularly useful for analysis less volatile solid samples.
It should be noted that not all contaminants are directly amenable to separation and identification by GC-MS analysis, and, as with the current rash of USGC based problems, it has been found necessary to apply additional preparative steps to isolate and convert certain types of contaminants into forms that are more readily separated and identified by the GC-MS techniques. Those steps have included the isolation of polar species by the solid phase extraction technique and conversion of these, by a derivatisation process, to the trimethyl silyl esters.
At present, there are only a limited number of laboratories worldwide that have the facilities to conduct the appropriate range of analyses that may be required to get to the root of the problem and, as such, scheduling is not easy at present.
Are there any warning signs that the fuel may be off-spec they are being burned?
If an owner is lucky, and dependent on the nature of the contaminant, some blockages of the filters may occur first which could alert the engineers to stop using the fuel. However, in many cases, sticking fuel pumps have been the only indication of a problem.
What should we do if the warning signs arise?
Stop using the fuel and segregate if possible. You should retain fuel samples for laboratory analysis and any damaged/seized components (fuel injection pump barrels/plungers) should be retained for metallurgical examination/analysis. However, do not expect laboratory results promptly at this time – they are all congested.
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