Development of a Bunker Norm for Ships 5. Purchasing BunkersWhen a shipowner is about to order bunkers for a ship, obviously it is not enough to agree on the price, the quantity, and the time and place of delivery. The basis for the order is, first and foremost, to find out what type of fuel oil the engine manufacturer is specifying for the relevant type of engine, and to ensure that the requisite oil treatment facilities onboard are consistent with these. Roughly, machinery can be divided into two groups: those designed for distillates of one grade or the other, and those designed for combustion of residual oil of one class or the other within this range. For reasons of competition the engine manufacturers generally specify the "poorest" type of oil – and thereby also the most inexpensive type – on which the machinery can run. Because the costs of bunker oil represent a very large part of the operating expenses, the price obviously has great influence on the choice of oil type. This does not necessarily imply, however, that the shipowner will then consistently choose the cheaper and poorer type. In addition to price, the type of engine and oil treatment gear, the choice also depends on the operating experience and reliability achieved by the relevant shipping company over the years – as well as the assurance of supply and quality. So that the ship and the shipowner can satisfy themselves that they are actually getting the specific bunker oil they have ordered, it is very common for the ship to draw a representative bunker oil sample from the bunker pipe – a so-called drop test, where the oil drips into a test vial throughout the bunkering process. The sample is then sealed by the ship’s crew in the presence of the bunker supplier, and the oil sample is sent to an independent laboratory for analysis. When the analysis has been performed, the shipping company and the ship will be notified by telex or fax of the result, i.e., the content of co-substances as well as other details about the oil and its treatment for purification as well as any operational difficulties. It is a very common rule not to use the new bunker oil until the result of the analysis is to hand. It is also quite usual to refrain from mixing fuel oils of different origin, as this can lead to unfortunate operational consequences. Of course, sooner or later one may have to mix the oils, but before they are mixed, one must be certain that the oil types are mixable. Despite the fact that diesel oil or heavy fuel oil as per ISO 8217 or with the shipping company’s extra specification requirements is ordered, one cannot be certain that the relevant oil in fact meets the standard or the specification, because – as already mentioned – the quality of bunker oil may vary within the same grade. This is one of the reasons why many shipowners have registered with the fuel oil analysis scheme, at least if they bunker worldwide. This has been known for many years, and it is still a problem with heavy fuel qualities around the world. But it is perhaps even more surprising that the quality of so-called "finer" oil types such as distillates or diesel oils varies considerably within the same grade. An investigation made of the three distillates DMA, DMB and DMC according to the ISO standard shows the following deviations:Marine Diesel Oil samples submitted in the period of 01/01/95 – 30/6/95 Samples breakdown: Total Samples for this period:3212 Table 5.1 For DMA, DMB and DMC the following results can be derived from the above diesel oil analysis: DMA DMB DMC An examination of the sulphur content problems shows that it must be said to comply quite reasonably with the requirements in the standard – as shown by the following extract from the analysis:
A typical bunker specification used for bunker purchases by a major Danish shipping company sailing worldwide may look as follows: Quality – Bunker Specifications
As will appear from the above specification, oil is ordered according to ISO 8217, but with the noted limitations and additions to the specification based on the shipping company’s experience – so as to achieve reliable and safe operations on the relevant type of oil. A typical bunker specification used when purchasing bunkers for a major Danish ferry line sailing in Danish waters looks as follows: Typical specification SMD
Typical specification LMD
If these two types of diesel oil – SMD and LMD – are to be referred to the ISO standard, the nearest group will be DMB. The SMD oil is for summertime use and may have a slight tinge. The LMD oil is clear and for wintertime use. A typical bunker specification used for the purchase of diesel LS classified as gas oil (MGO) for a major Danish ferry line navigating Danish waters looks as follows: Typical specification for diesel LS (MGO)
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