Horror Stories

Piston Pin Failure


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.

This is the sheared piston pin. It looks as if it has been cut in two with a grinder!!

Scoring in the liner. This is the bit that got hot- you can see where it has turned blue!


Close up of the cracked piston and the fractures




The damaged piston pin bearing



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