Abstract
The International Maritime Organization (IMO) Guidelines for Determining Minimum Propulsion Power to Maintain the Maneuverability in Adverse Conditions is the sole regulation imposed on the routine design and approval of all new-built ships as a part of EEDI requirements. This study reviews the development of the guidelines and summarizes the recent amendments of MEPC76(2021). The present assessment is conducted for a new VLCC design following the new guidelines aiming at investigating the influence of alternative wave added resistance evaluation methods and the propeller design features on the assessment results. It is found that the most simple empirical formula method proposed by MEPC76 is not conservative enough, as could have been expected. On the other hand, spectral analysis methods based on empirically obtained and properly validated wave added resistance responses can produce consistent results. Moreover, discussions are made from the perspective of propeller design to meet the regulatory requirements. It is pointed out that the light running margin is a key design parameter, and propellers with larger light running margins are more advantageous for satisfying the minimum propulsion power regulation, thus ensuring the navigation safety in adverse conditions. These obtained insights and know-how can support the engineers in obtaining optimal design solutions.
Highlights
In the course of development of International Maritime Organization (IMO)’s framework for the Energy Efficiency Design Index (EEDI) regulations to reduce GHG emissions from shipping, serious concerns were expressed by the maritime industry that when the EEDI regulations came into force, the safety of ships when operating in adverse conditions may be compromised, namely, designers and shipowners may opt for a reduction of ship’s design speed to achieve the required EEDI, which in turn would result in a reduced installed power
The most extensive study should be credited to projects SHOPERA and JASNAOE [9], which led to the draft revisions for the 2013 interim guidelines [10,11]
MEPC 76 (2021) approved these amendments to the guidelines for determining minimum propulsion power to maintain the maneuverability of ships in adverse conditions [15]
Summary
In the course of development of IMO’s framework for the Energy Efficiency Design Index (EEDI) regulations to reduce GHG emissions from shipping, serious concerns were expressed by the maritime industry that when the EEDI regulations came into force, the safety of ships when operating in adverse conditions may be compromised, namely, designers and shipowners may opt for a reduction of ship’s design speed to achieve the required EEDI, which in turn would result in a reduced installed power. The International Association of Classification Societies (IACS) proposed that a ship should be able to maintain a minimum speed (and have a minimum power) to maintain the maneuverability for safe navigation in adverse conditions as a necessary safeguard [1,2] This concept was further developed, and, several practical methods were recommended to form the 2013 Interim Guidelines as IMO’s important instrument to ensure the navigational safety of newly designed EEDI-compliant ships [3]. MEPC 76 (2021) approved these amendments to the guidelines for determining minimum propulsion power to maintain the maneuverability of ships in adverse conditions [15] At this stage, as the guidelines are being finalized, case studies based on proven engineering designs can be conducted following the newly amended guidelines, to provide timely feedback to the regulators to further validate the regulations and revise them if necessary. The insights gained from the assessment results are presented and discussed
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