Situation:

Daihatsu 8DK28 generator in a container vessel sustained severe damages due to the wrong assembling of exhaust valves and inlet valves when overhauling cylinder head. At sea, when D/G running parallel to Shaft generator, a blackout occurred and the generator major parts of cylinder head, exhaust and inlet valves, push rods, piston, liner damaged beyond repairs. The turbocharger also suffered damages with carried broken parts.

Causes and investigation:

The trouble was caused by one of the exhaust valve seized in valve guide and broken in the combustion chamber and spread the damage. Initially the trouble analyzed as occurred due to material failure and when maker’s service engineer, Daihatsu was involved in analyzing the failure.

Service Engineer’s Observation:

The service engineer identified that the valve spindle damaged in the exhaust port is found to be with clear stamping “S637T” which is referred as Inlet valve spindle. The exhaust valve spindle marked with ‘HNP” was fitted in inlet ports. Makers clearly identified the material configuration of the exhaust valve and inlet valve spindles.

Apparently, at last overhaul the valve spindles were interchanged even after maker’s manual clearly posted the precautionary warning for any possible miss-assembly.

Countermeasures:

There is clear identification mark to discriminate between the intake and exhaust valve as follow:

alt text

When the intake valve and exhaust valve are reassembled, be sure to check stamps on them so as to prevent miss-assembly.

Ensure that these spares are properly tagged and the necessary personnel advised regarding the difference in these spares to prevent any failure.

Whenever an overhaul for cylinder heads in progress, mark the Inlet and exhaust ports correctly, as a benefit of doubt, the spindle selection may be correct due to manufacturer’s precautions, but, inadvertently fitted into wrong ports.

posted 15 Jun '17, 23:27

June 15, 2017, 11:27 p.m.
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