DAMAGE TO AE PISTON


9th May 05

This machinery failure occurred during my tenure as a Third Engineer on board a bulk carrier.

The generator engine was a B & W with underslung crank shaft, 4 stroke, running on D.O.

While I was walking around in the E/R there was a sudden loud noise from the engine and a large quantity of smoke started coming out of the lifting Crankcase relief doors. The fitter was near the engine, I immediately signaled to stop it. There was a blackout, and power restored with the other engine.

On investigation we found that there were no particular hot spots in the Crankcase or any overheating of components. There was some sign of blowby from one of the units, which was opened up and the piston pulled. The piston crown was found damaged and holed.

The piston in the engine had a conical insert bolted to the inside of the body above the gudgeon pin that served to maintain a certain level of LO in the piston through a small hole on the top of the connecting rod. This oil went into the top of the piston accumulated at the conical insert and overflowed into the Crankcase. The insert had slackened, come off and started knocking around freely in the space between the connecting rod and piston crown, eventually breaking the crown from inside.

Fortunately the damage was restricted to the piston as we were able to stop the engine immediately.