It was lucky that no one was injured in this crankcase explosion which  lifted and buckled the engine room floor plating,  blew the spare gear store door (which was 2 decks above the crankcase) through the frame , blew the oil mist detector off the engine, and caused extensive damage to lighting, vent trunking, paintwork and of course the crankcase relief valves and doors. The workshop door was buckled and de-laminated The control room door wire reinforced glass was blown through into the control room where shards of glass became embedded in adjacent woodwork.

On investigation the cause of the explosion was found to have been a hole in number 1 cylinder piston crown. Hot combustion gases had then been able to pass down the piston oil cooling return to the crankcase, forming and then igniting the oil mist.

The photograph shows the oil puddle on top of the piston, with a pen lying next to the crack for scaling.

Burn away was excessive on the piston crowns, with numbers 1 and 6 out of tolerance. (number 6 piston crown was also cracked)

The hole in number one piston crown had been caused by erosion due to poor fuel injection. All pistons were examined, and erosion damage and cracking found on all of them. The "burning" of the piston crowns giving them the telltale "elephant skin" surface. The underside of the piston crowns had 3mm build up of carbon deposits which would have compromised the cooling of the piston.