The following happened on a 14 cylinder MAN B&W 48/60 Vee engine. Part of a diesel electric installation, a high oil mist alarm shut the engine down. As the engine came to a rest, a primary explosion lifted the crankcase relief valves and filled the machinery space with a white oil mist.
On investigation, it was found that the piston pin (gudgeon pin) had sheared in two. The piston cracked and a piece broke off around the circlip groove. The liner was badly scored and the piston pin bearing badly damaged.
The cause was established to be faulty stock material used in the manufacture of the piston pins. All pins manufactured from that stock were renewed.
The damaged piston pin bearing