Hot water fitting failure results in 3m loss of depth in diving bell

What happened?

Whilst the diving bell was on the surface, pre-dive bell checks were being completed by the Bellman, when it was observed by the Dive Supervisor and Bellman that the bell was losing pressure.

The Dive Supervisor began to blowdown the bell to compensate for the loss of pressure.  The Bellman lowered the bell door to isolate the diving bell from the chamber complex.  The Bellman then proceeded to close all emergency valves in the bell and the Deck Diver closed all corresponding external bell valves.  The pressure loss was stopped, and it was determined that a fitting had failed on the hot water distribution system.  The Bellman made the bell safe and returned to the system; the bell was then surfaced for repairs.  

Upon further investigation, it was established that the D2 hot water fitting (see picture below) which connects the isolation valve was cracked.  This opened a leak path via the crack to atmosphere.

The actions taken by the Dive Team clearly demonstrated the effectiveness of conducting training and drills.

What went wrong?  What were the causes?

  • The failure of the fitting is believed to have been caused by the impact sustained from a diver’s bail out bottle making contact with the unprotected fittings at the manifold;
  • The bell was completely refurbished during a dry docking in 2011;
  • There were no records of the fittings being replaced in the company planned maintenance system (PMS);
  • The age of the damaged fittings could not be determined. It was not known if the fittings were replaced after the 2011 dry dock.

What actions were taken?  What lessons were learned?