Introduction

This document concerns the procedure of analysing the results obtained from ship speed-power trials.

The primary purpose of speed and power trials is to determine a ship’s performance in terms of its speed, power and propeller shaft speed under the ship's prescribed conditions, and thereby verify the satisfactory attainment of a ship speed stipulated by the Energy Efficiency Design Index (EEDI) regulations and the shipbuilding contract. To determine the contracted ship speed and the ship speed for EEDI, the same procedure is followed. The EEDI forms an integral part of the sea trial conduct and analysis.

The contracted ship speed and the ship speed for EEDI are determined at specific draughts (either contract draught or EEDI draught, or both). For EEDI, the environmental conditions are: no wind, no waves, no current and deep water of 15 °C.

Normally, such stipulated conditions are unlikely to be experienced in part or in full during the actual trials. In practice, certain corrections for the environmental conditions such as water depth, surface wind, waves, current ^[¹^][²^] and deviating ship draught, should be considered. For this reason, during the speed and power trials, not only shaft power and ship speed are measured, but also relevant ship data and environmental conditions.

The purpose of this document is to define the basic requirements for the performance of speed trials and to provide methods for the evaluation and correction of speed trial data, covering all influences which can be relevant to the individual trial runs based on sound scientific grounds, thereby enabling owners and others to have confidence in the validity of the final results.

This document is intended to help the interested parties to achieve the desired target accuracy of within 2 % in shaft power and 0,1 knot¹ in speed.^[¹^]

The procedure specified in this document has been developed largely based on published data on speed trials and on ship’s performance, including the International Towing Tank Conference (ITTC) documents listed in Clause 2.

The basic development of sea trial procedures using the Direct Power Method has been initiated by the STA-Group and later by ITTC. This document takes into account the work of the STA-Group^[³^] and the guidelines of ITTC which are approved by the Maritime Environmental Protection Committee (MEPC) MEPC 65 for EEDI.^[¹^]

In 2002, the first edition of this document was published. ISO 15016:2002 was based on the evaluation of resistance increase and propeller characteristics.

The second edition (ISO 15016:2015) enabled this document to be used for EEDI regulations as well as for the shipbuilding contract. This new procedure was based on the direct power method. The "mean of means" and the "iterative" method were selected for the correction of current effects. For wave correction, several methods were offered as options in combination with observed wave conditions.

This third edition takes into account methods for the correction of wind, waves and shallow water which have been recently developed and validated. The application of these methods has been made consistent and ambiguities are avoided. This document includes modern accurate measurement methods of wind and waves. It has been updated to achieve the specified target accuracy of speed and power.

This document generally applies to ships for which survey and certification of EEDI and Energy Efficiency Existing Ship Index (EEXI) is required under the International Maritime Organization Resolutions.^[⁴^][⁷^][⁸^]For other ships, to which the above International Maritime Organization (IMO) resolutions are not applicable, the terms or phrases of this document are deemed to be replaced as necessary (e.g. “agreement between the shipbuilder, the owner and the verifier” can be read as “agreement between the shipbuilder and the owner” etc.)

In this document, the unit used to express the amount of an angle is “rad” (radian) and the unit of speed is “m/s” (metres per second). Nevertheless, “degree” as a unit for an angle and “knots” as a unit for speed are used wherever indicated. Moreover, for the convenience of the users of this document, numerical values using the units of degree and knots are stated together, where appropriate.