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Bureau Veritas introduces ESA notation

LNG Industry,

Bureau Veritas has introduced a new set of requirements for shaft alignment on high powered ships. The elastic shaft alignment (ESA) notation will help ensure the integrity of the structure and shaft bearings on very large vessels such as the next generation of LNG carriers and ultra-large container ships.

The ESA notation will apply to vessels with shafts in excess of 750 mm dia., or smaller shafts handling over 20 MW of power, propellers over 30 t or using synthetic bearings. It will require full analysis of the criteria covering hull flexibility with respect to loading conditions, bearing material stiffness, shaft speed and oil film behaviour.

Jean-Francois Segretain, Deputy Technical Director, Bureau Veritas, said: “As ships grow in size and we seek more fuel economies we are now seeing vessels with shafts handling over 20 MW of power driving large diameter propellers of over 30 t weight. Critical attention has to be paid at the design stage to analysing the elastic shaft alignment and ensuring that the bearings and structure match the shaft response, especially when the vessel is turning. If this is not done, huge forces will either lead to bearing failure or excessive vibration […] This new ESA notation sets out standards of how the shaft must be analysed and the criteria the whole shaft, bearings, and aft structure must meet to avoid such problems.”

Edited from press release by Callum O’Reilly

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