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Lifting chains parted – hydrogen embrittlement

What happened

Three of four lifting chains on a load parted while the load was being lifted. The incident occurred in the last lift of sections of grillage from a vessel involved in project demobilisation. At the time of the incident, the grillage was suspended, above the deck, by approximately 4m. Following a discussion between the Deck Foreman and the Crane Operator, the grillage was slowly lowered down to the deck. There were no injuries.

What went right?

  • All the work was conducted in line with established risk assessments and with company lifting procedures;
  • All the crew involved had the correct competencies;
  • The rigging was only three months in use from purchase;
  • The load was well below the SWL (Safe Working Load) of the chain;
  • The chain was never deployed subsea and was stored in a rigging locker.

What was the cause?

Analysis by an independent third party, and the chain manufacturer, concluded that hydrogen embrittlement, causing pitting, exacerbated by the tensile load on the internal radius of the links caused surface corrosion cracking,  leading to internal branch cracking and failure.

Actions taken

The rigging was changed from a four-way bridle arrangement to slings and shackles, and the lift was completed safely.

Lessons and further information

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