Verifavia Shipping’s First sea-trial analysis report approved & MEPC 78 Updates
MEPC 78 has cleared clouds hovering over the EEXI and CII regulations which had become a topic of confusion for the ship operators and managers. Some of the major takeaways from the meeting about EEXI are:- Ships that have PTO and need EPL for compliance will have their post-EPL Main engine power for calculation as 75% limited MCR instead of the current 83% limited MCR.
- CFD for estimation of benefits from Energy Saving Devices has been approved and estimated Speed power curves from Sea trial calibrated curves generated from CFD towing tank tests and other numerical calculation methods have been accepted.
- Speed power curves of sister ships are acceptable for pre-EEDI ships.
- Turbocharger Cutoff is now one of the approved methods of Overridable and Permanent Engine power limitation.
- Guidelines by IACS on LNG Carrier’s EEXI calculations.
After the advent of EEXI requirements, most hull paint companies are claiming improvement in the reference speed by application of Low Friction Paint. In-Service Sea Trial is the only acceptable way to determine the increase in efficiency and reference speed post hull cleaning and paint application.
It should be conducted just after the vessel has had its hull cleaned and repainted (either Low friction or normal hull paint) in a drydock. If the sea trial is conducted without doing so, the results will not be as favourable as the resistance due to marine growth will give the reference speed of the ship (Vref).
Few administrative and technical measures to consider before conducting an in-service sea trial are as follows:
- Common international standards (ISO 15016-2015) should be referred to understand the requirements like weather conditions, the number of trial runs, etc. to conduct the sea trial.
- A meeting should be arranged between all stakeholders involved in the process.
- The plan for the period of the in-service performance measurements should be agreed upon and expectations regarding the delivery of the analysis and its format should be aligned.
- All the data recording instruments should be calibrated to avoid any errors during the data collection process.
- The in-service performance measurements should be performed at the EEXI draught condition, and if data exists for a reference condition, then a set of in-service performance measurements may also be performed at this condition to better calibrate the speed-power relation.
- In case the exact EEXI draught condition cannot be met, the Admiralty Coefficient formula may be accepted to adjust the speed-power relation, only for displacement variations of up to 2%, or to the satisfaction of the verifier.
Depending on the ship type and its engine arrangements one can expect an improvement in speed estimation in the range of 1 to 2 Knots and EPL terms a reduction of 5 to 10% EPL requirement.
Another important method that is approved to calculate the reference speed is CFD (Computational Fluid Dynamics). It can be conducted to determine an optimal ESD based on the ship type or to check the change in efficiency post any ESD has been installed on the ship or if any structural changes have been made to the ship. A Model Tank test report or Sea trial report of the vessel or a sister vessel, stability documents, structural plans, and/or lines plans should be available for calibration of the CFD results.
Verifavia Shipping with a team of naval architects and marine engineers is fully equipped and capable of carrying out EEXI calculations, CFD analysis, and in-service sea trials, thus providing an end-to-end solution to the ship operators. We have prepared EEXI technical files for 350+ vessels for more than 50 clients, and Sea Trial reports (Post In-Service Sea Trial) approved by major classification societies like DNV, LR, NK, etc.
- Shubham Jain, EU MRV / IMO DCS Manager
- P. B. Shashi Bhushan, Naval Architect, Technical Expert Back to all Verifavia Shipping News
