Multi-Mapping — the Good and the Bad
Following a paper presented by Norway to MEPC 69 in April 2016, there has been an ongoing debate at the IMO and elsewhere as to how best to deal with the flexibility that electronic control confers on modern marine diesel engines. With so much attention being paid to reducing shipping’s output of CO2, a proposal to make better use of the flexibility of electronic control should have been welcomed but instead appears to have become something of a controversial subject at MEPC and in the PPR sub-committee which has been tasked with reviewing it.
With older engines, the camshaft mechanically-controlled the timing of the engine and the injection of fuel. Without the potential to significantly alter the parameters without major work and component changes being made, the engines were configured for the intended operating profile of the vessel at the time of construction. This meant that for most vessel types a significant amount of time was spent with engines operating under less than ideal conditions.
For example, a single engined bulker or tanker might spend as much time in ballast as fully loaded and while mostly it would be at sea, some time would also be spent manoeuvring in port. Liner vessels are less affected because they operate mostly in loaded condition although if practicing slow steaming, the engine is operating under a lower design load and although there is some fuel saving it is not maximised as it would be if the design speed was reduced when the engine originally configured.
In an electronically controlled engine there is no camshaft and the timing of the valves opening and injection taking place is managed by software which controls the hydraulics of the valves and the injection pumps. The paper presented by Norway was intended to demonstrate how the operating profile or ‘map’ of an electronically controlled engine could be adjusted to reduce fuel consumption and thus emissions of CO2.
It made the point that although the majority of electronically-controlled main engines are delivered with a single map programmed into the controls simulating the mechanical controls of older engines, individual engines destined for different ships could be programmed with different maps. As an electronically-controlled engine has the possibility to have several maps prepared by the engine manufacturer there is no physical reason why an engine could not be supplied with two or more maps integrated into the controls. Different maps could then be available to the operator allowing the engine to be optimised to the load and thereby reducing fuel consumption.
The Norwegian paper also identified the main flaw in the idea – at least as far as current IMO emission regulations are formulated – and that is there is a trade-off between NOx emissions and SFOC, which means that an engine optimised for SFOC will increase its NOx emissions and vice versa. This is not a new discovery as it is well known that all of the in-engine methods of controlling NOx will increase fuel consumption and is one reason why Miller timing alone cannot be used to meet the NOx Code Tier III requirements.
Falling foul of MARPOL
After demonstrating potential scenarios in which the benefits of switching between maps could be achieved, the paper went on to say ‘that unrestricted changes in maps could be regarded as an irrational emission control strategy as defined in regulation 2.13 of MARPOL Annex VI and is not permitted according to regulation 13.9 of the Annex. Furthermore, if a system was in place that switched automatically dependent on load that would be regarded as a defeat device as defined in regulation 2.6 of MARPOL Annex VI.
An ‘Irrational emission control strategy’ is defined as ‘any strategy or measure that, when the ship is operated under normal conditions of use, reduces the effectiveness of an emission control system to a level below that expected on the applicable emission test procedures’.
A defeat device is a means which ‘measures, senses, or responds to operating variables (engine speed, temperature, intake pressure or any other parameter) for the purpose of activating, modulating, delaying or deactivating the operation of any component or the function of the emission control system such that the effectiveness of the emission control system is reduced under conditions encountered during normal operation, unless the use of such a device is substantially included in the applied emission certification test procedures’.
The paper closed by saying it would be beneficial to discuss the acceptability to use more than one map and to develop guidance on how often and under which conditions a map can be changed. This will provide every stakeholder with the same possibilities, requirements and restrictions when it comes to the use of maps.
MEPC 69 referred the proposal to the Sub-Committee on Pollution Prevention and Response (PPR) for its consideration and advice at PPR 4. Since then there have been comments on the paper at PPR and again at MEPC 71 and the discussion has now focussed much more on the potential for the NOx Code to be undermined than on the fuel saving measures that multi-mapping could help to deliver.
For example, the US presented a response paper to MEPC 71 a large part of which detailed reasons why multi-mapping should not be permitted and indeed were not necessary. Commenting on the proposal in the Norwegian paper, the US response said ‘This type of Map switching is currently not allowed and should not be allowed as it defeats the purpose of the MARPOL Annex VI NOX limits.
On another point, involving engines equipped with post-combustion treatment devices, such as selective catalytic reduction (SCR): where there may be one engine map when the unit is engaged and one when it is not, the US argued this is not a valid example of a situation where two maps would be needed. It said under the NOx Technical Code such an engine is dual certified to two sets of standards (Tier III with the unit engaged, Tier II without the unit engaged), and has two EIAPP Certificates. The reasoning is similar for pre-combustion systems such as fuel conditioning systems, such as fuel emulsification. If the engine is certified to only a single emission standard (Tier II for example), it must certify in the highest NOX emitting configuration, which would be without emulsified fuel. When emulsified fuel is used, the NOX emissions would be reduced, so this is a non-issue.
A third example where the US argued against multi-mapping involved an engine that operates on different fuels: distillate inside and ECA and HFO outside an ECA. The US position is that fuel characteristics were one of the reasons behind the engine group concept –the need to adjust some engine parameters for varying fuel quality. If it is not possible to operate the engine without a map change over the range of fuels the engine will encounter in use, the map change to accommodate different types of fuel (distillate v HFO) is something that needs to be approved by the flag state at certification and must be documented in the engine’s Technical File.
The US paper argued against several more scenarios and concluded that in addition to defining the range of acceptable adjustments and restrictions on their use, any discussion of revisions of the current programme to allow the use of multiple engine maps in restricted conditions and associated guidelines to define those restrictions must also consider the impacts of such an approach on the integrity of the engine certification process and the MARPOL Annex VI NOX compliance programme.
Specifically, the procedures contained in the NTC must be reviewed with a view to addressing how engine manufacturers would certify engines with multiple engine maps, including but not limited to: limits on the nature of those maps (limits on what they may be designed to do), the number that may be applied to any one engine (two? four? unlimited?), how they will operate (automatic? operator selected?), identification of worst case NOX at each speed and load point, and how continued compliance with the regulation 13 NOX limits will be demonstrated to ensure that the engine as produced will not exceed those NOX limits across the entire operating range of an engine equipped with such maps (continuous emission monitoring?).
Finally, MARPOL Annex VI will need to be revised to include anti-tampering provisions to ensure the ship operator does not take the engine out of its certified configuration through unauthorised interference with the electronic or other controls that govern the use of the maps or any other engine feature that may affect those maps.
IACS sees both sides
In an article in its latest annual report, IACS commented that the low cost and ease of making changes to maps makes it attractive when there is a positive effect, such as better performance and lower fuel consumption., However, map-changing also influences emissions, opening up scenarios where a ship’s engine might not comply with the mandatory requirements set out in international regulations. However, there are good reasons for changing a map in an engine while it is in use, for example, to make available extra power for limited periods, adapt to different fuels, adapt to different environmental regulations in force in different areas (Selective Catalytic Reduction (SCR) in operation v. SCR shut-down) or privilege reactivity over stability during manoeuvres.
IACS is of the view that the regulations concerning marine engine emissions, namely MARPOL Annex VI and the NOx Technical Code, are not fully clear in allowing or preventing the use of multi-mapping and it therefore deems it important to clarify the matter. In fact, it is IACS’ opinion that multi-mapping should not be ruled out without discussion but should be carefully evaluated by regulatory bodies in view of allowing its use while preventing abuses that could infringe environmental regulations.
There are good points made by both sides and if anything, the debate is just the latest in the series over how the IMO has made the matter of regulating far more difficult by treating each component of the engine exhausts separately rather than adopting a more balanced approach.