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Fatigue Analysis

SRS Failure Position

A fatigue failure of Transocean's Split Reel Spooler (SRS) shaft occurred at the corners of the welded square hollow section used to house a swivel outlet. In order to understand the failure mechanism and establish a solution for a redesign of the shaft, EKES carried out a stress and Low Cycle Fatigue (LCF) life assessment.

Example S-N Fatigue Curve

Example of S-N Fatigue Curve

In the absence of reliable LCF data, empirical zero-mean LCF curves were constructed for the shaft material.

Proposed design changes to the hole shape result in a predicted service life well in excess of the welded design standard.

As a result of the stress/lifing assessment carried out by EKES, the recommendation to monitor the accumulated cycles and the condition of the shafts at defined service intervals, was adopted by Transocean.

FE Model of Original Geometry FE Model of Updated Geometry
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