This concerns exhaust valve failures (valve head separating from the valve spindle) on a CAT 3516 generator engine on an offshore jack-up drilling rig. The drilling rig went into service approx 8 months ago and therefore the engine has low running hours and has not yet reached the top overhaul interval.

I am interested to know if any other members have experienced this problem and if they were able to identify the reason for the failure.

I have seen, on the internet, other references to similar CAT 3516 failures but very little information as to the source of the problem.  I have plenty of CAT 399 experience but have not personally worked on the 3500 series engines.

The engine is on a rig offshore West Africa and this is the second failure in the last 6 months. I have not been able to get on the rig and see the failure, so I'm relying on information sent to me.

do the seats have any evidence of severe blow by?
>maintenance trouble (to less a valve clearance)
what does caterpillar say?
>batch problem (manufacturer trouble)
did you check timing of camshafts?
>initial assembling problem.

In agreement with dicer the most likely cause is that the valves(Needle Valves) are pattern made parts although the fact that they are relatively new suggest not.

If the stem is sheared at the valve guide then there is a possibility the issue is with the concentricity of the guide/valve/seat. This is typical when heads are assembled and the seats not ground.

I have experience only as Technical Superintendent but engines under my control used to run  to 25K hours plus for their 20K overhauls.

I am sure you have done so but I would give CAT (FINNINGS) a call and tell them to come and do some R&D on it.

There are other posibility associated to teh fule type and in particularly sodium vanadium deposits and corrosion.

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