Latest DNV Rule Requirements on Thrusters for Designers

抄録

The revision of DNV rules for thrusters (Pt.4 Ch.5 Sec.3^[1]) which became effective in Jan. 2021 cover DNV's core challenges of balancing both safety and business risk. Several examples of this exist within Quality Task Force (QTF) cases and were strictly followed up by DNV’s Key Account Managers (KAM). This together with active support and follow-ups using Root Cause Analysis (RCA) has led to good relationships with owners, and as a classification society further respect by thruster manufacturers.

As to propulsion thrusters with steering capabilities, it is necessary to cover main functions of vessel (Pt.1 Ch.1 Sec.1^[5]) propulsion and steering. Traditional steering gear (SG) operating a rudder is given in Pt.4 Ch.10^[3] and in the Convention for the Safety of Life at Sea (SOLAS). In Pt.4 Ch.5, all links to Pt.4 Ch.10^[3] were deleted and then all requirements related to SG for thrusters are given.

System redundancy based on risk evaluation is required. Exceptions from general redundancy described in Pt.4 Ch.1 Sec.3 [2.3.5]^[1] are not valid for thrusters serving both propulsion and steering. Requirements from IACS unified interpretation (IACS UI) SC242 Rev.2 Jan 2020^[4] is implemented.

Requirements for electric SG is added motivated by serious damage events and need to be specially focused on. Documentation requirements have been totally revised with increased focus on system performance and availability.