Development of a Bunker Norm for Ships 3. DefinitionsBecause the principal aim of this report is to examine and review fuel oils for ships, it is appropriate to define what is understood by fuel oil and gas oil in the light of the EU Directive. The Directive uses the following definitions: 1. Fuel Oil Any petroleum-based liquid fuel falling under CN codes 2710 00 71 to 2710 00 78 (these are the numbers in the Common Customs Tariff) or which (except for gas oil as defined in 2. below), by reason of its distillation limits, falls within the category of heavy oils intended for use as fuel and of which less than 65% by volume (including losses) distils at 2500C according to the ASTM D86 method. If the distillation cannot be determined by means of the ASTM D86 method, the oil product is classified as fuel oil. 2. Gas Oil Any petroleum-based liquid fuel falling under CN code 2710 00 69 or which, by reason of its distillation limits, falls within the category of middle distillates intended for use as fuel and of which at least 85% by volume (including losses) distils at 3500C according to the ASTM D86 method. Diesel oil as defined in Article 2 (2) of European Parliament and Council Directive on the quality of petrol and diesel oil is not covered by this definition. Definitions of fuel oils within the shipping industry Over the years many different definitions of fuel oil have been used in the shipping industry, and even today there is a number of different standards according to which shipowners order fuel. Some years ago, fuel was ordered by defining it as:
stating the desired viscosity in sec. Redwood I at 1000F and the approximate specific density at 150C. But in consequence of the technical development at the oil refineries, where cracking methods for the crude oil were improved and more products could be extracted, and in line with the enhanced environmental awareness on land – but not on board ships – this development also caused the quality of fuel for ships to deteriorate, because no environmental demands were made on the shipping industry in those days. Engine designers therefore had to start thinking in other terms and designing engines capable of using the poorer fuel oils – a development which is still in progress. At the same time, shipowners were forced to make more stringent demands as to the bunker oil they ordered, and in 1982 the first standard (which also comprised the so-called heavy oils) was introduced. It was designated BS MA 100, and it subdivides fuel oils into twelve groups, each group containing threshold values for the properties of the oil. The main groupings in BS (British Standard) MA 100 are: M1: Marine gas oil It is important to note that the groups refer to the viscosity of the oil. It should also be noted that this standard has several limitations. Thus, it provides no information regarding important heavy-oil properties such as:
This BS MA 100 standard is still used by many shipowners when they order bunkers around the world, but it is probably losing popularity in favour of the ISO 8217 standard, which is likely to be the predominant standard today. CIMAC’s fuel oil recommendations are also used quite a lot. ISO 8217 and CIMAC’s definitions are often seen integrated into the same table or standard. (CIMAC means CONSEIL INTERNATIONAL DES MACHINES A COMBUSTION and safeguards the interests of engine manufacturers and users). The classification of fuel oils according to ISO 8217 and CIMAC standards is listed in the following table: a) Distillate grades
As is evident from the above table of distillate grades, ISO 8217 and CIMAC describe four categories of distillate fuel. Furthermore, the standard indicates the minimum and maximum values for the following:
b) Residual Grades
Remarks as to the above table regarding residual grades – referred to ISO 8217 and CIMAC. The standards are arranged with the viscosity of the oils as starting point. A 10 and B 10 C 10 and up to H 55 K 35, K 45 and K 55 As is evident from the tabular listing concerning residual grades, ISO 8217 and CIMAC describe thirteen categories of residual grades. Furthermore, the standard indicates the minimum and maximum values for the following:
I may seem sad that even the new 1996 version of the ISO 8217 standard fails to include limitations on several of the substances that are patently often present in fuel oils. Among them are:
It is true that the standard indicates maximum values (in mg/kg) for aluminium and silicon, but it does not mention the size, hardness or specific density of the particles. This is quite an important parameter for abrasion of the fuel system and the cylinder liners. The standard should also specify that the fuel oil must not contain chemical waste and spent lubricants. The standard should also make it clear if the oil in question could remain stable, so that the content of asphaltene would not give rise to the formation of sludge. Nor is information included regarding a parameter as important as the CCAI value (CCAI = Calculated Carbon Aromatic Index, an indication of the oil’s combustion and ignition properties). A more recent problem, which emerged in 1997 and remains unsolved, is the fact that analyses of bunker oils have revealed particles of propylene with lengths ranging from 30 m up to 5 mm. These foreign objects were identified in the US Gulf, the eastern coast of the USA, the Baltic states, and Russia. So it is starting to become a global problem. At the present time it is not clear how these particles of propylene have emerged or got into the oil. It should also be noted that ISO 8217 and CIMAC describe only the technical and operational aspects of the maximum and minimum values associated with the extraneous substances. The environmental impact of these substances is not mentioned anywhere in the standards. Newer investigations are in progress to cast light on this problem with various types of engine and at varying loads.
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