Girth Gear and Pinion Damage

Good advice - also, as my consummate tinker late uncle would say, "viberation" and crystal fractionation (i.e. some amount of reversion to cast iron or other comparatively non-malleable species) of the steel due to very high point loads due to "viberation" at a frequency/amplitude that the operator may not perceive.

Is E. Coli a metaphor for "Life"?

Like most mechanical things, if you dismantle it, clean it, inspect it, lubricate it and reassemble it correctly the cause may become apparent, or if not it will probably have been removed.

Mind I s'pose it's too big to do that?

Del

Scuffing indicates there has been a failure to maintain a complete lubricant barrier between gear teeth allowing contact between asperities and possibly wear products as well, i.e. adhesive wear.

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A myriad of possibilities causes exist.

It could be a flaw in the original gear design.

The lubricant specified might not be up to the task, e.g. a higher FZG number might be called for.

The specified lubricant might be adequate, but what was obtained was not up to spec or was degraded prior to or during service.

There may have been a high temperature excursion, or extreme temperature gradient exceeding design criteria.

Original manufacture or subsequent work may have left the surface too rough or otherwise out of spec.

A disgruntled chipmunk may have dusted the pinion gear when no one is looking.

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Keeping the lubrication supply consistently at the low end of the acceptable range is one thing that can help to reduce the likelihood/severity of scuffing.

Without a picture, working parameters and dimensions it is difficult to say if it is a failure or only normal wear.

I started my comment with the intent of requesting pictures. Thank you for actually doing it.

I second the request for pictures. They may be helpful and they will definitely be appreciated.

Any chance of you posting some photos?

Seven years is a long time for a gear that has had continuous duty or even extended duty regardless of its lubrication system. Most machinery requires periodic maintenance. You do not give any history of that. More information as well as closeup photos would be very helpful.

If only "scuffing" is seen, it may just be normal wear and tear, as you say, 7 years of operation does take its toll. Nothing mechanical lasts forever, unless of course it doesn't get used.

The last time we changed a girth gear it had been in service 25 years. The pinion had been changed every 5 or 6 years.

Personally I think the OP is looking at general wear and tear. They're old and knackered like me. I'm retired, it's about time those gears were.