Industrial Engine: Ring Gaps keep Lining up

duesey8

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#1
Hi, anyone ever encountered a problem with a cylinder or piston, which would cause the rings to rotate such that the gaps would align, causing blowby to get bad?
This is an industrial, gas engine, but still a 4-cycle, non-turbo. New cylinder liner, pistons, and rings straight-cut. Take it apart, rearrange the ring gaps, put it back together, and fater a few days they gradually line back up and the blowby gets bad.
 
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#2
How much wall tension do you have on compression and oil control rings ?
 

Tony

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#3
We used to have a lot of problems on marine engines in the 70s when the grounds would go bad, the rings would line up and cause a lot of blow by.

We could usually tell when the grounds had corroded, because we had 2 engines that would start the blow by problems at the same time. ouch

That would be my first check, to make sure the grounds are good.
 
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#4
I find this one to be interesting. I hope if the issue is found it is posted.
I was leaning towards some kind of harmonics. Like using a hose clamp on a drive shaft, or balancing sand in a tire type thing.
But the electric issue Tony mentions will give me much to think about.
One of our favorite bench racing discussions has always been do rings rotate, and if so, how fast?
 
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#5
I,d have to agree with tony , I. ve seen fords and B series cummins in boats with no anodes and current through coolant systems cause a simialr problem on one or two cylinders , but that said this engine is only lasting a couple of days and then reoccuring - it,s either got very bad harmonics or cylinder problems . A bit more imformation would help ie: what sort of engine , what sort of liners ( wet or dry ) are they chrome liners ?
 

larche

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#6
What happens if you keep running the engine?
Do they "unalign" (don't worry that will be a word someday:) or do they stay aligned?
I would check the cylinder, make sure it is round, not oblong, even by the slightest amount.
Especially if they align in the same spot, or close to it every time.
All cylinders do this? Or, just one?
 

duesey8

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#7
Hi, we are still working on this, I'll be sure to let everyone know what we find. Interesting about the grounds; tis is a 480 3 phase generator that runs full-tiome, after all.
 

duesey8

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#8
For the record, this is an Ingersoll-Rand PVG-8 gas engine, driving an open-frame Westinghouse (I think) generator. 408 HP at 400 RPM
 
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#9
A generator - thats interesting , It might pay you to check to check the cycles ( 50Htz ) on the generator as I,ve seen them polarise parts of a engine when one phase is unstable or we still might have an engine problem !
 

duesey8

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#11
Ok the guys finally got inside the engine good: first they found the crankcase vent partially plugged, cleaned it out, and everything ok for a short while. Finally they pulled every piston and found one which had not been involved with the original repair, badly scuffed. Replaced this cylinder and piston, and no more problems. I think the ring gaps were jut a straw man and were not causing any problems at all, but they were certainly getting the blame.
Thanks to everyone for participating.