24th Aug 2006

In 1995 I joined a timber carrier. It was fitted with 3 DAIHATSU Aux. engines. The no.1 Aux engine was 6 cylinders 230kw which vibrated excessively.

Due to the excessive vibration on the driving gears and associated pipe lines were breaking very frequently. The vibration was more on the free end of the engine.

The governor was replaced with an overhauled one, but no improvement noticed. Crank shaft counter weights checked, found all in order. Then records of the receipt of spares were checked. The part no. of pistons supplied on board were different from the ones in the engine manual.

Engine crank case was opened up, and all the pistons were checked with magnet. No.1 piston was not attracted to magnet. No. 1 & 2 pistons were pulled out, No.1 piston was aluminum alloy and remaining were cast iron and the weight difference was 10Kg. An old cast iron piston was boxed back in the No. 1 and the engine was started and found running without undue vibrations. Lessons Learned

The Makers changed the material of the piston without sending any information to customers. Both cast iron and aluminum alloy pistons were similar in shape; only upon weighing them the difference could be made out.

Do compare the spare part no. with the manual list while receiving new spares and take corrective actions accordingly. While changing to new spares, always compare with the old ones for shape and weight if possible.
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