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Failure of welding on hyperbaric rescue chamber medical lock door assembly

A member has reported that a weld failed on the medical lock door assembly of a hyperbaric rescue chamber. The incident occurred during a pressure test of the system and an employee sustained serious injuries after being struck by the displaced medical lock door.

A report commissioned by the company, conducted by an independent metallurgical laboratory, identified that the welds in the bracket could have failed at any time due to there being less than 1 mm of weld remaining. This was partly due to corrosion of the metal and partly due to poor welding.

It was calculated that a downward force of 10-20 kg would have been sufficient to cause the weld to fail. The full penetration weld within the bracket was only 0.8-1.0 mm thick at best and the supporting fillet weld had no fusion along one of its lengths.

These pictures show the hyperbaric rescue chamber medical lock door assembly and the positioning of the C clamp retaining bracket, the second picture clearly indicating a weld feature that failed whilst in operation.

Medical lock door assembly
Medical lock door assembly
C clamp retaining bracket (after failure)
C clamp retaining bracket (after failure)

The company’s findings were as follows:

  • The C clamp retaining bracket was never regarded as being a load bearing or critical component and as such was never included in ‘routine’ checking or inspection of the assembly.
  • At the time of installation of the assembly the engineering, certification or inspection regimes were not as stringent as they are now.
  • It is recommended that all load bearing components within a dive spread are thoroughly inspected for signs of corrosion or damage.

Safety Event

Published: 24 August 2007
Download: IMCA SF 08/07

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