The ISO 8217 Final Draft International Standard (FDIS) on marine fuel specification is out now and expected to be available for sale at www.iso.org.
The process of revising the existing ISO 8217:2005 standard has involved representatives from all parts of the bunker industry, with DNV Petroleum Services (DNVPS) participating in the Technical Expert working group in cooperation with National Standardisation Bodies around the world.
Since the completion of the balloting for the ISO 8217 Draft International Standard (DIS) in December last year, two follow-up meetings, in Dubai and London respectively, have contributed to the development of the FDIS. This document is now subjected to a two-month balloting period where further technical changes are not expected.
According to the schedule, the FDIS will graduate into the official ISO 8217 standard by July 1, 2010.
The final ISO 8217 revised specification will be an improvement over the current (2005) edition. The following changes are especially important.
Aluminium and silicon (Al+Si)
Compared with ISO 8217: 2005, the level of aluminium and silicon in the FDIS has been reduced and the new maximum limits range from 25mg/kg for the lowest residual grades to 60mg/kg for the highest grades. This revision should reduce the risk of too-high levels of abrasive particles reaching the engine's inlet.
Ash, vanadium and sodium
Similarly, the Vanadium and Ash limits specified in the FDIS for most residual grades are now reduced. Maximum levels for sodium are also added as a new parameter. Traditionally, sodium is associated with sea water contamination, but this element may also originate from the pre-treatment of crude oils at the refineries. Experience has shown sodium from this source may not be removed from the fuels by onboard treatment and could contribute to post-combustion deposits.
Calculated carbon aromaticity index (CCAI)
CCAI is now included in the specification for all residual grades. The revised limit is 870, but according to DNVPS statistics, as little as 0.02 percemt of IFO 380 delivered to ships globally exceeded a CCAI level of 870. The ISO 8217 Working Group has therefore also included more details in the standard's Informational Appendix (Annex F) on alternative ignition and combustion quality test methods. One such alternative method is IP 541 utilising the fuel combustion analyser. Clause 6.3 of the FDIS points out that "where the ignition quality is known to be particularly critical, Annex F provides a basis for suppliers and purchasers of residual fuels to agree on tighter ignition quality characteristics".
2 cSt minimum viscosity limit for gas oils at engine inlet
The FDIS introduces DMZ, a new distillate grade with a 3 cSt at 40° minimum limit. Catering to engines that require a higher minimum viscosity limit for distillates, DMZ is essentially DMA with a higher minimum viscosity limit. A too-low injection viscosity is a safety issue because marine diesel engines – especially the larger ones – may not be able to pick up full load and in the worst cases, propulsion engines may fail to start during maneuvering in congested waters and port areas.
Removal of DMC grade
The DMC grade has been removed and this blended distillate is now in the table for residual fuels as RMA10.
Amendment to Clause 5 of ISO 8217
The general requirements in Clause 5 have been expanded to include more reference to materials that render marine fuels unacceptable for use in diesel engines. Both ISO and CIMAC have initiated research on the analysis and interpretation of the chemical composition of waste materials, as well as the levels at which these materials may start to cause engine problems.
FAME and oxidation stability test for marine distillates
Marine distillates should be free from bio-derived materials other than "de minimis levels" of FAME (fatty acid methyl ester). The definition of "de minimis levels" has been moved to Annex A of the FDIS.
The presence of FAME in clear and bright distillates is mentioned in the FDIS due to increasing marine use of biodiesel as a fuel product or blend component. In addition, there are concerns about greater cross-contamination risks in the delivery chain. FAME in marine distillates could cause problems with oxidation stability, particularly during long-term storage. If, however, FAME is not present in marine distillates, DNVPS noted that oxidation stability testing may not be relevant or required. More research will be carried out to ascertain that this recommendation does not impact ships' safe operation; given that distillate products may be stored onboard for longer periods before use.
Lubricity test
Lubricity testing is required only for marine fuels with sulphur levels lower than 0.050 percent mass (500 mg/kg). If the fuel lubricity is too low, fuel pumps in diesel engines may particularly experience wear from prolonged operation on such fuel.
Strong Acid Number (SAN).
SAN, originally included in the ISO 8217 DIS as a test parameter, has been removed from Tables 1 and 2 in the ISO 8217 FDIS. In general, ISO 8217 stipulates that marine fuels shall be free from inorganic acids.
ISO 4259
Compared with the ISO 8217 DIS, Annex L of the ISO 8217 FDIS on interpretation of results now contains a more thorough and balanced reference to ISO 4259 procedures and its applications.
Hydrogen Sulphide
While DNVPS' recommendation was to exclude the 2ppm (in liquid) limit for the time being and to focus on a vapour limit, the former remains but will only be effective from July 2012. In the meantime, the 2ppm (in liquid) limit should be taken as a guideline to increase the awareness of H2S as a potentially fatal and flammable gas. DNVPS will be among the industry players conducting further research and development to understand and refine the limits and test methods for H2S such that the eventual specification for this parameter can be embraced with confidence in 2012.
As it stands now, the 2ppm (in liquid) limit for H2S is still being questioned for possibly giving a false sense of security, since 2ppm H2S in liquid can result in a vapour level exceeding the 10ppm limit commonly used a safety limit on board a ship. Training and safety routines concerning H2S should therefore continue to be important for shipboard personnel.
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