On December 19th 2013, the former Vessel General Permit (VGP) has been replaced by its second edition from the US Environmental Protection Agency (EPA). The 2013 VGP requires the use of environmentally acceptable lubricants (EALs) in any oil-to-sea interface, unless stated as technically infeasible. Due to these requirements, shipyards recently introduced EALs in stern tube lubrication upon requests of ship owners for US waters. Following this, numerous stern tube failure cases have been reported during sea-trials in ship newbuilding projects. Since many years, the classification society DNV-GL has been involved in the development of sound rule requirements for shaft alignment calculations and installations, hereby making combined use of practical experiences and theoretical investigations. Based on this knowledge the Authors of this paper look upon fundamental experience in consulting of several stern tube bearing failure cases, hereby trying to ensure a robust design for all kinds of operation. After investigation of the damages, a root cause analysis is possible. In particular, the investigations focus on review of the design of the shaft alignment and the correct performance of the actual installation. Specific properties of EALs are also taken into consideration, therefore trying to unravel the EAL-Mystery. The experiences from the fact findings from stern-tube failure cases in recent ship new building projects are presented and intend to give guidance for the design and best-practices for the installation procedure of shaft alignment from the perspective of a classification society. In particular the application of new rule requirements is examined in order to ensure a classification societies purpose to strive to safeguard life, property and the environment.

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