Ship Engines – 5 important rules to comply with

Considering that the power and propulsion systems of a ship are arguably the most important aspects beyond even navigation and communication systems, there is very little ship engines regulation. What is included in the SOLAS and MARPOL conventions is more concerned with their availability in times of emergency and the composition of the engine exhaust emissions.

Regulation of ships’ power and propulsion systems is a comparatively recent thing except of course for fire and safety aspects of engine rooms and machinery spaces and a requirement for emergency steering. The power source itself is effectively only regulated by MARPOL Annex VI and the EEDI regulations and there is little if any direct regulation of ship engines or propulsors beyond that set down in classification society rules. The question of lubricant choices for propeller shafts and rudders can be a matter of regulation if the lubricant is not considered environmentally acceptable.

Shipowners drive change

Despite the growing list of regulations aimed at the emissions aspect of power generation on board, modern ships’ systems have advanced significantly primarily because of owners’ demands for more reliable, more efficient and less thirsty vessels. Almost all designers and manufacturers involved have reacted to those demands with innovative measures and evolved technology that has involved massive R&D expenditure only sometimes aided by grant funded research such as the HERCULES engine research project.

In SOLAS the regulations covering propulsion machinery are scattered throughout the whole document and cover aspects such as having sufficient means of a number of starting attempts for the main ship engines, ensuring availability of essential services, fire and explosion prevention and means of control. For some ship types, redundancy of systems is a requirement but the choice of power and propulsion machinery is not regulated meaning that operators are free to choose their own combination of the increasing number on offer.

Much of the safety regulations have come about as reaction to incidents and accidents – many tragic – rather than being proactive. Examples of this are the requirement for double walled fuel lines and for some ship engines to be fitted with crankcase oil mist detectors or engine bearing temperature monitors. Another example is that since 2010 passenger vessels have been required to have redundant engine systems.

Most recently in 2015 the MSC adopted the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code), along with amendments to make the Code mandatory under SOLAS with effect from 1 January 2017.

The use of gas as fuel firstly LNG and later ethane has increased in recent years due to lower sulphur and particulate emissions than fuel oil or marine diesel oil. Because gas and other low-flashpoint fuels pose their own set of safety challenges and prior to the IGF Code regulation was only possible by individual flag states meaning that there was no universal standard. The IGF Code addresses this and will likely lead to more gas and dual-fuel ships being built.

The IGF Code

The amendments to SOLAS chapter II-1 as a result of the IGF Code include amendments to Part F Alternative design and arrangements, to provide a methodology for alternative design and arrangements for machinery, electrical installations and low-flashpoint fuel storage and distribution systems; and a new Part G Ships using low-flashpoint fuels, to add new regulations to require ships constructed after 1 January 2017 to comply with the requirements of the Code, together with related amendments to chapter II-2 and Appendix (Certificates).  The Code contains mandatory provisions for the arrangement, installation, control and monitoring of machinery, equipment and systems using low-flashpoint fuels, focusing initially on LNG with the intention to expand the provisions as new alternative fuels gain acceptance.

The Code addresses all areas that need special consideration for the usage of low-flashpoint fuels, taking a goal-based approach, with goals and functional requirements specified for each section forming the basis for the design, construction and operation of ships using this type of fuel. The MSC also adopted related amendments to the STCW Code, to include new mandatory minimum requirements for the training and qualifications of masters, officers, ratings and other personnel on ships subject to the IGF Code. These amendments also have an entry into force date of 1 January 2017, in line with the SOLAS amendments related to the IGF Code.

From an operator’s point of view, ship engines, propulsion and steering arrangements regardless of type are all considered essential systems and therefore will feature in just about all approved ISM Code safety systems adding another layer to any regulatory requirement for operation and maintenance.

To fully articulate all of the regulation in SOLAS that affects power and propulsion systems with regard to safety would take a volume somewhat larger than this article. Furthermore much of what is included has its origins in classification society rules and recommendations that have arisen following official investigations into accidents. As a consequence the regulations or rules will frequently vary with flag state and class society. In some instances P&I and Insurance surveyors will also have some input as might Port State Control inspectors especially as to factors affecting general safety such as general cleanliness and unsafe repairs and practices.

Ship Engines – The Energy Efficiency Design Index (EEDI)

Throughout history shipowners have selected ships that are best suited to the employment for them that they have in mind. This has led to a diverse range of vessel capabilities even in similar sized ships in the same sector. In times past speed was one of the main essentials as is evidenced by the frequent races by clipper ships against each other some of which such as the Great Tea Race of 1866 grabbed the public attention. Similarly passenger vessels vied with each other to win the Blue Riband for the fastest Atlantic crossing. S

peed was a major consideration in container vessels especially right up to the 2008 crash when slow steaming to reduce fuel costs and reduce overall fleet capacity became the norm.

With the advent of the IMO’s energy efficiency measures contained in the Energy Efficiency Design Index (EEDI) rules made mandatory at MEPC 62 in 2011, new vessels ordered and built since 2013 must for the first time take measures to match ship engine power output with cargo capacity.

The EEDI is a non-prescriptive, performance-based mechanism that leaves the choice of technologies to use in a specific ship design to the owner and as long as the required energy efficiency level is attained, ship designers and builders are free to use the most cost-efficient solutions for the ship to comply with the regulations. The EEDI provides a specific figure for an individual ship design, expressed in grammes of CO2 per ship’s capacity-mile and is calculated by a formula based on the technical design parameters for a given ship.

Although there is no prescriptive limit on power output of the ship engines on any ship subject to EEDI, the fact that the formulae under which ships’ EEDI ratings are calculated does include figures for engine power output means that the total power is one of the variables that must be considered by designers at the earliest stages of ship construction.

The effect of the EEDI in reducing CO2 output is designed to become more stringent over time. From an initial Phase 0 (2013-2015) aimed at setting benchmarks, there follow three five year periods in which the allowed CO2 levels are reduced by 10% each time. It is considered highly unlikely that the reductions can be met using engine efficiency measures alone but other improvements to the propulsion system will help and the rest will need to be achieved by way of weight saving and hull design improvements as well as energy recovery.

Most experts believe that the effect of EEDI will be to reduce the choices open to shipowners and could preclude any attempt to revive ideas of rapid sea transport at speeds of up to 40kt which were being contemplated earlier this century.

Unlike most other equipment on board vessels, there are no performance standards or guidelines for the power and propulsion systems beyond vague references to the flag states requirements and a reference in the regulation that calls for interim and special surveys to ensuring the main machinery should be in a satisfactory condition and fit for purpose.

Regulation also comes at a national level under port state rules. Where national regulation is concerned, there are developments such as the Norwegian NOx Levy and Fund, EU regulations or the California Air Resource Board’s (CARB) attempts to limit and measure emissions above and beyond that required under IMO rules. In addition, so long as a ship is registered with a classification society there are the rules and requirements of the class society in question that need to be considered.

Preventing pollution with MARPOL

While SOLAS is relatively quiet on ship engine performance, the same is not true of MARPOL where the whole of Annex VI is devoted to emissions to air from ship engines and boilers. Currently the controlled emissions are limited to SOx and NOx although EEDI is designed to limit overall CO2 production it does not actually restrict the output of any individual ship engine per se.

Future MARPOL regulation is expected on particulate matter and black carbon but nothing concrete has yet been proposed beyond the definition of what constitutes black carbon adopted by the IMO at MEPC68 in May 2015. Black carbon is intended to be regulated as part of the IMO Polar Code but it was also noted at the same meeting that at this stage measures to reduce the impact on the Arctic of emissions of black carbon from international shipping are not possible.

The IMO has laid down rolling reduction programmes for both SOx and NOx but only the latter can be controlled from within the engine. SOx emissions depend entirely upon the sulphur content of the fuel (which can be zero in case of LNG and other alternative fuels) and can only be further reduced using scrubbing technology or replacing the ship engines – both quite expensive undertakings. Fuels which contain the maximum permitted levels of sulphur for the operational region can be used without any treatment process. A more detailed explanation of the SOx regulations and treatment systems can be found in the ShipInsight Environmental Technology Guide.

As far as regulation of NOx is concerned, all of the facts are contained in the IMO NOx Technical Code. This was first produced in 1997 and amended in 2008. It is currently available as part of the IMO publication MARPOL ANNEX VI AND NTC 2008 WITH GUIDELINES FOR IMPLEMENTATION (2013 Edition). The Code limits allowable NOx emissions based on ship engine speed and power output.

The 1997 version of the NOx Code laid down many of the technical requirements but set limits which have since become known as the Tier I standard which was to apply to all but the smallest ship engines and generators from 1 Jan 2000. This ruling came into force in May 2005, with the NOx standard being applied retrospectively to ship engines fitted after the 1 Jan 2000 date. The 2008, amendments introduced new standards now referred to as Tier II and III with the first coming into force for new engines with effect from 1 Jan 2011 and from 1 Jan 2016 for Tier III .

The amendments also set out condition under which the Tier I NOx requirements could be applied to existing pre-2000 engines. This would only happen if ship engine makers were able to make available means of modifying the engines. MARPOL Annex VI also permits the setting up of emission control areas. An Emission Control Area can be designated for SOx and PM, or NOx, or all three types of emissions from ships, subject to a proposal from a Party to Annex VI.

Presently the only four ECAs in operation are The Baltic Sea (2005), The North Sea (2006) the North American ECA, including most of US and Canadian coast (2012) and the US Caribbean ECA including Puerto Rico and the US Virgin Islands (2014). The first two cover SOx only and the third and fourth both NOx and SOx. The Tier III standards only apply to ships operating in ECAs the number of which look to expand with proposals in place at the IMO for the two European SECAs to be redesignated as full ECAs. China has in 2016 declared some areas of its coastline as ECAs but while the regulations must be complied with they are not yet adopted by the IMO.

Complying with the NOx Code

The NOx Code limits allowed emissions in accordance with the above graph but leaves the method by which this is achieved to the discretion of ship engine manufacturers and operators. Under the Code, all vessels built since 2000 must have a Technical File which identifies the engine’s components, settings or operating values which influence exhaust emissions.

The file is prepared by the engine maker and approved by the flag state. It must be retained onboard for the whole life of the engine and will be used to ensure compliance. The engine to which the Technical File refers is to be installed in accordance with the rating (kW and speed) and duty cycle as approved together with any limitation imposed by the Technical File.

The Technical File must, at a minimum, contain the following information:

  • Identification of components, settings and operating values of the engine which influence its NOx emissions
  • Identification of the full range of allowable adjustments or alternatives for the components of the engine
  • A full record of the engine’s performance, including its rated speed and rated power
  • A system of onboard NOx verification procedures to verify compliance with the NOx emission limits during onboard verification surveys
  • A copy of the test report for an engine tested for pre-certification or a test report for an engine installed onboard ship without pre-certification
  • If applicable, the designation and restrictions for an engine which is a member of an engine group or engine family
  • Specifications of those spare parts and components which, when used in the engine, according to those specifications, will result in continued compliance of the engine with the NOx emission limits
  • The Engine International Air Pollution Prevention Certificate (EIAPP)

Compliance with the code can be achieved using one of three options alone or a combination. The first option is to run the engine always within the parameters as laid down in the technical file and to use only OEM spare parts when any component identified in the technical file requires replacement.

The second is to install a continuous monitoring system of the type offered by manufacturers such as Kittiwake, Martek Marine, Green Instruments or Norsk Analyse, among others. Some of these systems can measure other exhaust gases and might be able to provide evidence of compliance with other regulations such as SOx emissions limits in SECAs or in ports where low-sulphur fuel is mandated. The third option requires the engine to be tested at regular intervals by approved service providers.

Both of the last two options give the operator a degree of freedom to source cheaper non-OEM spare parts or to run the engine outside of the parameters recommended by the engine maker.

Meeting both the Tier I and Tier II limits was not particularly onerous and although Tier III compliant ship engines are also available, ensuring compliance has had detrimental effects in other areas including slightly reduced power and increased CO2 emissions as well as increased capital costs for reduction systems.

Some of the means of meeting Tier III include;

  • Adoption of a gas-burning engine. This will typically result in 90% lower NOx emissions than in a comparable diesel engine running on liquid fuel.
  • Selective Catalytic Reduction (SCR) uses an aqueous urea-water mix and a catalyst to cut NOx emissions from both two-stroke and four-stroke ship engines by up to 90%. Since SCR works more efficiently when the fuel sulphur content is below 1.5%, the technology is well suited to Tier III applications as the sulphur in fuel limit in ECAs has been just 0.1% since the beginning of 2016.
  • Common-rail technology provides flexibility in engine settings, achieving both reduced emissions and smokeless operation at all engine speeds and loads
  • Exhaust gas recirculation (EGR). Part of the exhaust stream is diverted and mixed back into the intake air. The resulting lower combustion temperatures have the potential to reduce NOx by up to 60%. In large ship engines, the recirculated gas must be cleaned due to the high sulphur and ash content of marine fuels
  • Miller valve timing, plus single- or two-stage turbocharging and combustion chamber design optimisation. Combining these technologies offers scope for cutting NOx by up to 50% without penalising fuel consumption
  • Introducing water into the combustion chamber either as a fuel/water emulsion, direct water injection or humid air.

Comfortable ship engines

Ship engines and associated systems and machinery are major sources of both noise and vibration and for a long time these related issues were not regulated. Under the Maritime Labour Convention (MLC) which became effective in August 2013 noise and vibration are now issues that all affected ships must take measures to control both in accommodation and working areas.

In July 2014 new SOLAS rules came into effect. The SOLAS changes follow on from MSC91 when the IMO adopted a new SOLAS regulation II-1/3-12 to require new ships to be constructed to reduce on-board noise and to protect personnel from noise. The new limits are in accordance with the revised Code on Noise Levels Onboard Ships, which sets out mandatory maximum noise level limits for machinery spaces, control rooms, workshops, accommodation and other spaces. The Code supersedes the previous non-mandatory Code, adopted in 1981 by resolution A.468(XII).

It will apply to all vessels of 1,600gt or more which: 

  • are built under a contract signed after 1 July 2014
  • with the keel laid after 1 January 2015
  • have a delivery date on or after 1 July 2018

Meeting the requirements of the new rules will involve a number of measures of which very few are under the control of engine makers. Most measures will be structural or design and involve machinery fixings and dampening materials in the engine rooms and machinery spaces. Shipbuilders and class societies will have a role to play in this regard and any shortcomings dealt with by way of suitable PPE. Some of the measures adopted might be suitable for retrofit by owners with high concerns for crew welfare. Retrofit and other abatement measures may also be required if flag states apply the rules to existing vessels as some have indicated an intention of doing.