This happened on a 270 bore medium speed engine (built under licence in China) driving an alternator which had only done a thousand hours from new. A knocking noise severe vibration from the turbocharger, and a high oil mist alarm caused the engine to shut down.

On opening up for inspection the badly damaged piston with a hole punched through it and the remains of two valve heads were found.

The turbocharger nozzle ring and blading were also badly damaged by the debris which passed through the turbocharger.

Inspection of other units showed that all the piston crowns had been damaged where they were hitting the valves. When the rockers were stripped down some of the tappets were found to be smashed.