01 NOV 2006
By Olav Tveit, DNV Petroleum Services
EU Directive 2005/33/EC deals with issues similar to those in MARPOL Annex VI, although its dates for implementation do not coincide with those of Annex VI. It also provides for a maximum sulphur content in marine gas oils of 0.2 per cent from 11th August 2006. Further, there will be a reduction of sulphur content of marine fuels for vessels at berth in EU ports, the entry into force date being 2010, with the maximum sulphur content from that date being 0.1 per cent. Other implementation dates are as follows:
On 19th May 2006 the Baltic Sea SECA under IMO came into force. On 11th August 2006 the Baltic Sea SECA became enforceable by EU member states. On 11th August 2007 the North Sea SECA will become enforceable by EU member states. On 21st November 2007 the North Sea SECA enters into force under IMO.
Needless to say, the pressure on charterers and operators to provide ships with LSFO will increase. As a result, bunker management will be more complex. It is also vital that owners/charterers and bunker purchasers ensure that MARPOL Annex VI clauses (Regulations 14 and18) are included in their charterparties and bunker purchase confirmations. INTERTANKO has developed contract clauses that may be suitable in this respect.1
– Use inherently low sulphur crude stocks.
The blending option seems to be the preferred future method. Regrettably, it appears that this option is also the one which could impact the bunker quality in a negative way as explained below.
Increased stability and compatibility problems
Sulphur content deviations
Some samples tested also exceed the 1.5 per cent limit, although in most cases only marginally. The IMO has not yet provided guidance as to whether an allowance can be made, like for instance whether 1.54 per cent can be acceptable as 1.5 per cent. Currently this is left to the discretion of the individual port and flag states.
Some suppliers and certain testing companies introduce a default standard margin of error (reproducibility). It is argued that deviations above 4.5 per cent or 1.5 per cent would be caused by a default margin of error during testing. The problem is that the concept of margins of error has not been discussed at IMO so one can not say whether authorities will accept any result above 1.5 per cent in a subsequent flag or port state control. Hence, until further notice it is recommended that any indication of sulphur levels above 4.5 per cent or 1.5 per cent respectively should be accompanied by a notification to the flag administration, bunker port administration and supplier according to the requirements of the IMO Port State Control Guidelines for MARPOL Annex VI.2
Following the ISO 4259 standard, for a supplier to be 95 per cent confident that the fuel delivered will have a sulphur level of 1.50 per cent, the suppliers’ target should not be higher than 1.42 per cent.
Considering the possible margin of error, as well as the aspect of fuel oil change-over, owners should consider whether a limit of 1.5 per cent in orders is sufficient or whether they should specify a lower sulphur limit.
Increased levels of catfines (Al/Si)
Increased ignition and combustion problems
As a minimum, the crew must verify the sulphur content in the bunker delivery notes and that the official MARPOL sample is representative of the bunker supplied. In accordance with the IMO Port State Control Guidelines for MARPOL Annex VI, any non-compliance must be reported through a notification to the flag state and the bunker port authorities.
High sulphur fuels
In the event a fuel testing company detects a sulphur level which exceeds the MARPOL limits and is above that specified in the bunker delivery note, the following course of action should be taken:
– A notification should be sent to the flag state and the bunker port authorities, highlighting the indicated sulphur level deviating from the bunker delivery note level.
With a high sulphur limit of 4 per cent and a LSFO level of 1.49 per cent, reaching the required 1.5 per cent limit will take time, if it can be done at all.
Although not yet specifically required, realistic and proven change-over procedures should be developed for each ship or group of ships with similar fuel tank configuration and system set-up.
The pre-requisite for change-over is the exact sulphur level of existing fuel and LSFO, i.e., a bunker delivery note sulphur level set as “less than 4.5 per cent” and “less than 1.5 per cent” should not be accepted as it creates uncertainty regarding change-over time (in addition to uncertainty regarding the selected base number (TBN) of the cylinder lube oil used on board).
Some owners have converted their ships by dedicating a bunker tank to LSFO with separate bunker line, as well as introducing separate LSFO service and settling tank with piping ensuring split separator operation. This option means that the change-over can be carried out quickly.
However, the majority of ships have conventional fuel oil systems with a limited number of bunker tanks and only one service and settling tank. For these ships the main contributors to change-over time are the following:
– Total consumption (main engine + auxiliary engines + boilers).
Cylinder lube oil
Some shipowners have flagged their intention to continue operating with TBN 70 cylinder lube oil at LSFO down to 1 per cent, by feed-rate regulation, provided not already on the limit. This alternative also appears to be supported by engine manufacturers, provided the operation on LSFO is limited to approximately 1-2 weeks.
There are, however, examples of shipowners who have operated with reduced feed rate on South American LSFO for instance down to 0.5 per cent over approximately a month without experiencing any excessive deposits or wear.
However, some owners have decided to make modifications on board and install redundant service tanks: one for TBN 70 and one for TBN 40/50 with a three-way switch-over valve in-between.
Regardless of alternative chosen, it is recommended that the crew perform periodical checks of cylinder condition (including ring-pack) shortly after change-over. As always, the quality of the cylinder lube oil regarding thermal stability, detergency and dispersion is also essential.
Abatement technology (exhaust gas cleaning)
One additional challenge is future requirements (particularly EU and US requirements) for handling of waste water from such units before discharge to sea.
Although the investment is high, exhaust gas cleaning systems have the advantage of eliminating the LSFO premiums as well as bunker management complexity. Further, they will reduce the particulate matter in the exhaust, for which new legislation is coming soon.