Particle Size Question

[ZeeOSix]

Originally Posted By: StevieC
To get the stuff smaller than 20 micron is done by either changing the oil more frequently through regular OCI's or by using Bypass filtration which then takes everything out of the oil up to 1-2 micron level.

Don't really need a by-pass filter unless you're going for relatively super long OCIs like the "big truckers" do. IMO, doing 10K mile OCIs with synthetc oil and a filter that's 99% at 20u is going to keep wear way down.

 

[Ducked]

Originally Posted By: goodtimes
There is no such thing as zero clearance in an engine. It there was the parts would molecularly bond and become essentially one piece.


I was using "clearance" probably incorrectly, to refer to the separation of parts in operation. Apologies.

I'd have thought parts in contact, protected only by boundary lubrication, will have zero separation. The model I've seen described is that asperities will "molecularly bond" (weld) , and then those bonds will break with movement. This will happen at various places and times, such as the crank at startup, cams, gears, and perhaps piston rings in normal operation.

Whatever the model, the paper I linked to reports zero thickness for oil films, based (they say) on a survey of the literature on diesel engines, and in an oil filled space this should be as the same the separation between the parts.

 

[Ducked]

Originally Posted By: ZeeOSix
Originally Posted By: Merkava_4
Originally Posted By: Nick1994
I think, say, a Fram Ultra can filter smaller than 20 microns, it's 99.9% efficiency rating is just that, a rating at that micron size. So at 15 microns maybe it's 85% efficient and at 10 microns it's 75% efficient (I totally made up those numbers BTW).

For some reason I thought that 20 microns was the smallest size that the Fram Ultra could filter out and any particle that was smaller got a free pass. It never occurred to me that it still catches smaller particles but at a lower efficiency. Silly I know, but that's what I thought.

You must not hang out in this forum enough. Efficiency vs particle size curves have bern shown and discussed a lot.

 

[goodtimes]

Originally Posted By: Ducked
Originally Posted By: goodtimes
There is no such thing as zero clearance in an engine. It there was the parts would molecularly bond and become essentially one piece.


I was using "clearance" probably incorrectly, to refer to the separation of parts in operation. Apologies.

I'd have thought parts in contact, protected only by boundary lubrication, will have zero separation. The model I've seen described is that asperities will "molecularly bond" (weld) , and then those bonds will break with movement. This will happen at various places and times, such as the crank at startup, cams, gears, and perhaps piston rings in normal operation.

Whatever the model, the paper I linked to reports zero thickness for oil films, based (they say) on a survey of the literature on diesel engines, and in an oil filled space this should be as the same the separation between the parts.

I was being picky with words. Sorry. That's the problem with timed editing, can't go back and change it. I think only the points on the metal roughness could bond, so can break easily. There is clearance, voids, due to the surface roughness and errors in manufacturing. "Perfect" contact would mean the parts become as one. It's sort of amazing actually everything is held together by forces in the atoms. I was thinking particles are all shapes, one could slide in a bearing on it's narrow axis and maybe the forces would spin it around and that could gouge a bearing too. If I had a diesel vehicle for sure I would get a Frantz or similar. Good info.

 

[SirTanon]

Originally Posted By: Leo99
I think Merk's question more along the lines of how much damage can 1 grain of sand cause should it get past the oil filter.


The answer to this question depends on WHERE in the engine the grain of sand ends up. In the sump, pretty much no damage. Lodged between a piston ring and the cylinder wall, plenty. If it makes its way into one of the oil galleys leading to a rod bearing or main bearing, lots.

 

[zeng]

Originally Posted By: CR94
Originally Posted By: Linctex
... If there are SO MANY particles in oil....
and the particles cause SO MUCH wear....
then how come we still have long lived engines?
Because there aren't as many abrasive particles in the oil of engines in good condition as there are in tests with deliberately added massive doses of dirt. It wasn't rare for engines to go over 100k back when they had no oil filters.

+1
It's the contaminants hardness that matters, and by extension contaminants abrasiveness.
Hence, a terminology in Abrasion Wear ... other than Adhesion Wear, Corrossion Wear etc.
Not saying contaminants size does not matter though.