fuel specifications

Marine Fuel Specifications and Recommendations

Historically fuel for the marine market, with the exception of distillates, has been dictated by viscosity. While viscosity is an important characteristic, it does not give an indication of any other characteristics of the fuel. With viscosity as the sole criterion when ordering marine fuels, shipowners remain unaware of the other fuel characteristics. Likewise, designers of machinery and fuel systems are not always informed of the fuel characteristics to which they should be designing.

In 1978 the General Council of British Shipping initiated the setting up of a Working Group to consider the development of a standardised specification for marine fuels. In 1980, the British Standards Institution made a formal proposal to the relevant technical committee within the International Organisation of Standardisation (ISO), stating that an international standard for marine fuel should be prepared. This proposal was accepted and an international working group was then formed to address this problem and the needs of those involved.

Ideally the shipowner wants the maximum quality control at the minimum price, two diametrically opposed requirements. Also shipowners who trade worldwide need to have reasonably assured access to fuel oil of some defined quality. In concurring with any specifications, shipowners should be mindful of their existing installations as well as those they will order in the future.

The real priority of the engine builder is to match the requirement of the customer, namely the shipowner, while realising their engines must burn residual fuels in order to compete in the marine market. Usually this is synonymous with fuel that varies widely in quality and is broadly similar to the product used for steam raising plant.

The major oil suppliers recognise the use of residual fuels in marine diesel engines, therefore, there is an obligation for them to regulate the quality of the fuel so it can be used economically and safely. In theory this might not sound difficult to achieve, however, in practice there is a wide divergence in the design of on board fuel handling systems. The inevitable question, therefore, is whether the ship should be designed for the fuel, or the fuel for the ship. Usually the answer lies somewhere between the two extremes.

Aspects of a Specification

The development of a series of marine industry specifications for different grades of marine fuel oil define the maximum or minimum permissible values of the fuel quality criteria. In practice, the fuels supplied will frequently have many quality points below the maximum and above the minimum.

It is essential for a specification to be reasonable, useful and economic. For example, it would not be reasonable to include requirements with no technical importance, or which demand closer precision than is normally possible during commercial testing. The specification of a particular parameter must serve some obvious purpose and contribute to the usefulness of a complete specification. One would not expect the colour of a residual marine fuel oil to be specified as it would not serve any useful purpose. Likewise, in being economical, the specification must not be needlessly restrictive. The determination of any particular parameter must be made with due regard to any effect on manufacturing, which if overly restrictive, could result in limited availability or an uneconomical price for the user.

The first national standard for marine fuel oil was published in 1982 by the British Standards Institution (BSI), entitled BS MA 100: 1982 (Petroleum fuels for marine oil engines and boilers). In the foreword it was noted that ‘Because there is an urgent need in the UK for this standard, and reaching international agreement can by its nature be slow, this British Standard has been published as an interim measure. It is expected that an early revision will be arranged to implement the International Standard when published’.

As the British Standard Group were developing BS MA 100:1982, the engine builders in the form of a CIMAC (International Council on Combustion Engines) Working Group were developing their own recommendations. These were published in the technical presses in early 1982 and included additional grades of light intermediate fuels which, although limited in availability, were still needed for older type diesel engines. CIMAC published their second edition of fuel recommendations in 1985, and their third edition in 1990.

The International Standard

In 1982 the Working Group responsible for the development of the international standard issued a draft proposal which became ISO 8217 Petroleum products — Fuels (Class F) — Specifications of marine fuels. Another draft proposal was issued at the same time which became ISO 8216 Petroleum:products — Fuels (Class F) — Classification Part 1 — Marine Fuels. In 1987 the first edition of the international standard was published followed by the publication of BS MA 100 in 1989, which was identical to the International