Guide for Optimized Shaft Alignment issued by RINA

Classification Society RINA has released the Guide for Optimized Shaft Alignment.

The document was published and became effective on 15 February 2024.

The purpose of the Guide for Optimized Shaft Alignment is to provide guidance on achieving optimal shaft alignment to minimize the risk of damage to propulsion plant components and increase the operating lifespan of ships.

The OSA or OSA-PR notation is assigned to new ships that comply with the requirements of the guide.

The guide outlines definitions for terms such as shaft alignment, shaft alignment optimization, offsets, elastic shaft alignment, FEA, FSI, and CFD, global reference line, MCR, Q, Campbell diagram, misalignment angle, mean shaft misalignment angle, mon-shaft, and very light ballast condition.

Design requirements for the OSA or OSA-PR notation include compliance with the guide's calculation requirements, documentation submission, and procedures for shaft alignment and bearing run-in.

Calculation requirements include shaft alignment calculations, hull deflection calculations, and lateral vibration (whirling) calculations.

The alignment procedure for the OSA-PR notation includes steps such as sighting through, engine bedplate pre-sagging, reactions measurements, bearing-shaft misalignment evaluation, shaft eccentricity verification, intermediate shaft bearing offset readjustment, crankshaft deflection measurements, engine bedplate deflections measurement, gear contact evaluation, and gear-shaft bearings reaction measurements.

Sea trials for the OSA-PR notation include test procedures, bearing run-in procedures, shaft alignment verification during sea trials, and jack-up tests in hot static condition.

Maintenance of the OSA and OSA-PR notations requires prompt reporting of incidents or modifications that could affect shaft alignment and compliance with the survey requirements outlined in RINA Rules for the classification of Ships.

Initial surveys and surveys after construction are required to maintain the OSA-PR notation.

For more information, please see the document below (available only to subscribers):