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Failure of casting: Foundation brackets for steering gear

What happened?

Damage was reported to the steering gear hydraulic ram foundation brackets connecting the ram to the structure of the vessel. The foundation bracket casting failed.

What went wrong? Investigation and findings

  • The failed brackets were of a cast bronze design and by nature of the material were unable to withstand shock loads;
  • It can be seen in the above photograph that the casting had a design flaw whereby there is no radius where the main body meets the flat mounting plate. The clearly shown sharp corner results in a stress raiser where the crack has occurred;
  • Subsequent inspections across the fleet revealed several vessels with damaged brackets.

What lessons were learnt? And what were the actions?

  • Thorough inspection of steering gear ram foundation brackets for cracks is recommended;
  • Appropriate modification of vessel planned maintenance system to include this visual inspection;
  • Our member noted that later vessels have brackets fabricated using welded steel plate.

Failure of welding (search “weld failed” on the IMCA website) yields a number of incidents, but failure of an actual casting is less commonplace.

Safety Event

Published: 9 June 2017
Download: IMCA SF 14/17

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