The draft of the 4th edition of international marine fuel specification ISO 8217 is currently out for balloting. Additionally, the ISO 8216-1 standard entitled "Petroleum products - Fuels (class F) classification - Part 1: Categories of marine fuels" has also been revised and is similarly out for balloting.

Before considering some of the particular points of the draft 4th edition it is important to understand how the balloting process functions within the overall ISO procedure. ISO - or to give the full title "International Organization for Standardization" (in French "Organisation Internationale de Normalization") - is a worldwide network of the national standards institutes of 162 countries with a Central Secretariat in Geneva, Switzerland, that coordinates the entire system of producing standards.

ISO is a non-governmental organisation, which means that its members are not delegations of national governments. Thus, ISO occupies a very unique position between the public and the private sectors. Membership of ISO is open to national standards institutes, or similar organisations, which undertake standardisation work in their own countries. There is one participating member per country, in the UK, for example, that is the British Standards Institution (BSI).

Each ISO standard is produced through a balloting process, which consists of a number of different stages. The balloting procedure is designed to ensure that the final result is accepted by not less than a two-thirds majority of the Permanent (P) Members votes and that no more than one-quarter of the total number of votes cast are negative. The ISO ballot process is an important part of a democratic system of standards development.

The 4th edition of ISO 8217 is currently at the enquiry stage of balloting system and so the Draft International Standard (DIS) version is available from the ISO website (www.ISO.org) for public comments. The balloting period is 5 months which means that the ballot will close in December 2009. After resolution of the comments received, the Final Draft International Standard (FDIS) version will be prepared with further 2 months of balloting for editorial/ non-technical changes. It is expected that by June 2010 the whole balloting process will be closed and the standard will be ready for publishing.

A particular driver behind the development of this 4th edition was a specific request by IMO to have it ready by the implementation date of the revised MARPOL Annex VI, 1 July 2010. In order to meet this deadline the ISO TC/28/SC 4/Working Group 6 (WG6) committee met almost every month since March 2008 through to June 2009 representing a substantial commitment by each and every member.

The Working Group comprises 33 expert members from 14 countries, covering the following aspects of the marine industry: marine fuel manufacturers, major oil companies, marine engine manufacturers, shipowners, shipbuilders, marine fuel oil purchasers, marine fuel oils suppliers and distributors, classification societies, technical universities, engineering research and development centres, energy management services, marine engineers and marine fuel oil testing services.

The ISO WG6 committee represents a well understood mechanism for considering the wide range of factors which influence marine fuel quality, which has evolved as a result of many years of international standardisation work. In order to facilitate progress the Working Group was sub-divided into smaller sub-groups to cope with the numerous issues needing resolution. Each sub-group worked tirelessly to achieve approval by majority of the WG6 members.

There were a number of lengthy debates within the Working Group covering, amongst other topics, three key issues:

1. Biodiesel
The current marine standard ISO 8217:2005 specifically refers to petroleum derived products only, thereby excluding any bio-derived products. During its deliberations the Working Group became aware that, due to the practice of blending first generation biodiesel into automotive diesel, it is almost inevitable, under current supply processes, that some marine distillates, and even perhaps marine residual fuels, could contain a limited proportion of this biodiesel as a result of cross contamination within the distribution system.

In marine industry today there is no known generalised experience in respect of the storage, handling, treatment and service performance of biodiesel, or biodiesel blends, within the broad spectrum of the marine environment. Furthermore, there are the issues as to the potential adverse effects on the existing range of marine engines and other ancillary equipment together with related systems such as the bilge oily water separators and overboard discharge monitors currently in service.

On this basis the Working Group's recommendation, at the current stage of specification development, is that only a de minimis level, defined as an amount of minimum importance, resulting from carry over or cross contamination through the supply chain - would be tolerated. The Working Group is seeking to develop a suitable test method, or methods, to measure biodiesel concentrations in marine distillate and residual fuels in order to be able to quantify this issue. In view of this stance, ISO asked IMO to consider the status of biodiesel fuels, and blends of the same with petroleum based fuels, with regard to the MARPOL Convention and other Instruments.

It is, however, recognised that, under controlled conditions, there may be interest in using such fuels, or blends of same with petroleum based fuels, under trial conditions but that where that is to go ahead it is to be in the full knowledge of all parties as to the particular composition of the fuels being used.

2. Hydrogen sulfide - H2S
The Working Group acknowledges that whilst H2S should not be present in marine fuels, the current test methodology and the requirements for setting the specification limits cannot guarantee that H2S gas will not be released from some fuels during the course of onboard storage and handling. It has therefore recommended 2 mg/kg in the liquid phase as the maximum limit for both residual and distillate fuels. The limit is based on two separate items: 1- the test method reproducibility value R and 2- the 2 x R rule for setting the specification limit in accordance to ISO 4259 in clause 8.2.

The most important reason and benefit of measuring H2S in liquid phase is that it deals with the key issue, which is to measure the potential that a fuel could have to release H2S over a period of time under suitable conditions when that fuel is transferred, heated or agitated by the rolling action of the ship, rather than the measurement of the variable equilibrium dynamics of the vapour phase.

Measurement of H2S, using Draeger tube in vapour phase, as per the standard test method (ASTM D5705) is needed and totally appropriate as an occupational health protection measure. However, due to its limitations it cannot be considered as a marine fuel specification test method. The head space gas distribution in the test method's container is uniform in composition, in contrast to the gas distribution within the head space of a ship's tank or, for example, in the vicinity of an air pipe head which in all cases will typically be highly variable and dependent on numerous external factors.

Furthermore, the vapour phase measurements in ship's tank head space are strongly influenced not only by the amount of H2S in the liquid phase but also by factors such as: fuel oil chemistry, fuel temperature, volume of the headspace, degree of agitation of the fuel, configuration of tank venting arrangements and duration of storage.

The ASTM test method is a simple field test method for the rapid determination of H2S in the vapour phase of residual fuel oils and while it is a repeatable, consistent, test (since the results are obtained under the equilibrium conditions) cannot predict the outcome of actual in service fuel oil handling situations. Therefore the measurement of H2S in vapour phase of the test method's container as a fuel quality parameter could provide a false expectation for safe use, often providing lower than expected results. Such results must be interpreted with due diligence and care as they are not related to the total H2S entrained in the fuel (or indeed cargo when the test method is used in such applications).

ISO has invited IMO to consider possible operational and technical measures to mitigate the risk of any incident resulting from H2S gas evolving from marine fuels in service. At the IMO MEPC 59 meeting in July 2009 the comments received were to either remove H2S measurement from the specification or to reduce the limit. The latter is not possible as there are not as yet sufficiently sensitive enough sensors. Knowing that in today's market H2S levels can exceed 2 mg/kg, the industry ought to answer the following question - do we value safety and thus do we want to know the true H2S level in the bunkers supplied or would we rather not know it? By removing this parameter from the specification there will be no warning and no further developments to improve on the test methods available. The balloting comments will provide the answer to this question.

3. Ignition quality
From the specification writer's point of view it is hard to describe the enormity of the task at hand when considering this aspect, not least because the ignition quality of a fuel is only one of a number of factors which affect the actual in service performance (engine design and load together with performance and ambient conditions can be equally critical). The chemistry of residual fuels is probably the most complex of the oil barrel and some of the components of the final blend are, it must be accepted, resultants rather than controlled fractions. Furthermore, as the various specification grades of, residual fuels are not blended at the refineries the particular chemistry of the vast variety of possible cutter stocks available to the supply chain also needs to be added to the total unknown. With this in mind the complexity of the ignition/combustion properties of marine fuels must be fully appreciated and carefully researched.

The WG6 concluded that:

• CCAI is a well tested simple and readily accessible tool which despite its limitations has proven to be useful over the years in predicting a fuel's ignition characteristic. In this it is of course accepted that it can neither fully assess the complex chemistry of a particular fuel nor address the various outside factors which ultimately affect actual ignition performance under specific conditions.
  
• The test results obtained by the FCA method (IP541/06) have a good repeatability and reproducibility. The challenge is to relate these results to the impact on in service engine operation.  What would be a low quality fuel with regard to ignition properties for one engine under a particular load and operating condition it might not necessarily give any operational problems for a different engine design or under different conditions. Hence including this test as a standard parameter would at this time be premature.
• Consequently, the CCAI limit included in the marine fuels standard should be considered as the one, but by no means all inclusive, controlling limit against the supply to a ship of a too highly aromatic fuel.

The work of maintaining and developing of marine fuels quality standards will always require some degree of compromise with the industry's various stakeholders demanding from each other the best engine performance, the best fuel quality and the best price together with widespread availability. The Working Group in total believes that the proposed 4th edition of the ISO 8217 standard represents a significant advance on previous editions and fairly reflects the realities of the current petroleum and marine worlds.
Article - ISO 8217:2010