The Chief Engineer stands at the control console of a 2011-built Aframax tanker anchored off Mundra Port. In his hand is the latest circular from the technical superintendent in Singapore. The vessel, once the pride of the fleet, is now struggling to meet the stringent MARPOL Annex VI requirements. The Energy Efficiency Existing Ship Index (EEXI) attained value is currently sitting just above the required limit, and the threat of being commercially non-viable looms. For the engine room team, this isn't just about paperwork; it is about the physical limitations now being placed on the main engine to satisfy global decarbonization targets.
As a junior officer or engineer, you need to understand that EEXI is a "one-time" technical certification. Unlike the Carbon Intensity Indicator (CII), which measures how you operate the ship year-on-year, EEXI measures how the ship is built and equipped. For older tonnage—the backbone of many Indian manning companies like Synergy Marine or Fleet Management—optimizing this rating is the difference between a ship staying in service or being sold for scrap.
Implementing Power Limitation: EPL vs. SHaPoLi
The most direct and cost-effective way to bring an older vessel into EEXI compliance is by limiting the engine's power. Since EEXI is calculated based on the installed power, reducing that power improves the rating. There are two primary methods: Engine Power Limitation (EPL) and Shaft Power Limitation (SHaPoLi).
Engine Power Limitation (EPL) is the most common choice for older mechanical engines. It involves a simple mechanical stopper on the fuel rack or a software-based limit in electronically controlled engines (like MAN B&W ME-C series). It prevents the engine from reaching its original Maximum Continuous Rating (MCR).
Shaft Power Limitation (SHaPoLi), on the other hand, uses sensors on the intermediate shaft to measure torque and RPM. This system is more complex but often preferred by owners who want more flexibility. The system monitors the actual power being delivered to the propeller and triggers an alarm if the limit is exceeded.
For the ship's staff, the critical task is maintaining the EEXI Technical File. If you are forced to override the power limit—for example, to avoid a collision or in extreme weather—you must record the duration and reason in the logbook and report it to the Directorate General of Shipping (DGS) or the relevant flag state. This "unlimiting" feature is for safety only; using it for commercial gain is a major non-compliance.
Retrofitting Energy Saving Devices (ESDs)
If power limitation alone doesn't bring the vessel within the required EEXI limits—or if the resulting speed is too slow for the charterer—the next step is hardware. Energy Saving Devices (ESDs) are designed to improve the hydrodynamic efficiency of the hull and propeller.
On older vessels, we frequently see the installation of Mewis Ducts or Pre-swirl Stators. These devices are fitted forward of the propeller to straighten the flow of water, reducing turbulence and increasing thrust. Another common retrofit is the Propeller Boss Cap Fin (PBCF), which breaks up the hub vortex, providing a 2-5% gain in ship efficiency.
During your next drydock at Cochin Shipyard or an international yard, you will likely see these being welded onto the stern frame. As an engineer, your role is to ensure the hull remains clean. Even the most advanced ESD cannot compensate for a fouled hull. Regular underwater inspections and hull cleaning are vital to ensure the EEXI calculations, which assume a clean hull, match real-world performance.
Engine Tuning and Fuel System Optimization
Optimizing the combustion process is another technical lever. For older ships, this often means "Low-Load Tuning." Most older engines were designed to be most efficient at 70-85% MCR. However, with EEXI-mandated power limits, the ship might now be forced to operate at 40-50% MCR.
Operating an engine at low loads for extended periods leads to cold corrosion and increased soot deposits. To optimize the EEXI rating and engine health, companies may opt for:
* Slide Fuel Valves: Replacing older conventional valves with slide-type valves improves atomization at low loads, reducing fuel consumption and emissions.
* Turbocharger Cut-out: In twin-turbocharger setups, one can be "cut out" during low-load operation to maintain higher scavenge air pressure for the remaining unit.
* Variable Geometry Turbochargers (VGT): Though expensive, these allow the engine to maintain high efficiency across a wider range of power outputs.
When you are monitoring the Specific Fuel Consumption (SFC), remember that every gram of fuel saved directly lowers the carbon factor in the EEXI formula. Accurate record-keeping of fuel flow meter readings is not just a daily chore; it is the data that proves the ship's efficiency.
Navigating the Regulatory Framework and MMD Inspections
The final step in EEXI optimization is the verification process. Every Indian seafarer must be familiar with the role of the Recognized Organization (RO)—usually classification societies like IRS, LR, or DNV—and the Mercantile Marine Department (MMD).
Once the technical modifications (like an EPL) are made, the EEXI Technical File is submitted for approval. Following this, an initial survey is conducted to issue the new International Energy Efficiency Certificate (IEEC). If you are serving on a vessel calling at an Indian port, be prepared for an MMD Mumbai or MMD Chennai surveyor to verify the power limitation seal.
As a junior officer, you must ensure that the seal on the fuel rack is intact and that the Onboard Management Manual (OMM) for the EPL is available on the bridge and in the engine room. If a surveyor finds the seal broken without a corresponding entry in the logbook explaining an emergency override, the vessel can be detained. This is a critical point in the decarbonization transition; documentation is just as important as the hardware itself.
Your Next Step
Optimizing an older vessel for EEXI is a complex blend of mechanical engineering and strict regulatory compliance. To stay ahead in your career and master these technical nuances, you need the right tools at your fingertips.
Download the Sailrnetwork app to access our CII Calculator and see how technical EEXI changes impact operational ratings. If you are preparing for your MMD orals, our exam prep module covers the latest MARPOL Annex VI amendments in detail. For quick technical queries on the go, use SailrAI, our specialized maritime assistant, or join the discussion in SailrQ to see how other Chief Engineers are handling EPL overrides and ESD maintenance on similar ship types. Stay sharp, stay compliant.