Particle Size Question

[bullwinkle]

Originally Posted By: Ducked
Coincidentally (?) this came up just recently. Shannow posted a good overview paper for diesel engines.

http://infohouse.p2ric.org/ref/31/30453.pdf

The bulk of the wear is caused by particles below 10 microns. Since there are situations (cam lobes, gears) where the parts are in boundary lubrication with zero clearance, there is no particle size too small to cause wear.
The contamination x hours graph is interesting, on page 11 of that report-if even a Purolator made Performax filter makes that much of a difference over a standard paper/cellulose filter, imagine what an Ultra, Donaldson Blue, or Fleetguard Stratapore/Nano/Venturi could do! Granted, most of us don't operate in a molybdenum ore mine...

 

[goodtimes]

The reason 1/4-1/2 micron particles don't scratch is no surface in an engine is better than that. Can't scratch something that already has bigger scratches. May start to polish off the machining roughness scratches already there. Polishing is a strange thing, it becomes a smear effect rather than grinding, when around 1/4 micron on many materials. Using interference contrast optical microscopes to inspect. It takes something like an electron microscope to see smaller. Nothing in an engine is made that well to begin with. There is no such thing as zero clearance in an engine. It there was the parts would molecularly bond and become essentially one piece. In optics, optical contacting occurs between two very flat plates, and if near perfect the molecular attraction is so strong the other weaker bonds in the material will break before the optically contacted surfaces.

 

[CT8]

Originally Posted By: Donald
Bypass is cost effective for diesel engines that go many hundreds of thousands of miles and have large oil sumps. So oil changes are several hundred dollars.

A decent filter and reasonable OCI will allow a normal car engine to not be what causes the car to go to the boneyard. Filtering so that the engine is in pristine condition when the car goes to the boneyard makes no economic sense.
This is BITOG !

 

[Linctex]

Originally Posted By: Ducked
Coincidentally (?) this came up just recently. Shannow posted a good overview paper for diesel engines.

http://infohouse.p2ric.org/ref/31/30453.pdf

The bulk of the wear is caused by particles below 10 microns. Since there are situations (cam lobes, gears) where the parts are in boundary lubrication with zero clearance, there is no particle size too small to cause wear.


This paper raises more questions than it answers.....

According to Table 3,
a Cummins diesel engine should be completely worn out in about 1000 hours,
yet many reach 10,000 hours or more.

If there are SO MANY particles in oil....
and the particles cause SO MUCH wear....
then how come we still have long lived engines?

Something doesn't add up.

 

[MasterSolenoid]

Originally Posted By: MasterSolenoid
To put it in perspective,

.001 inch is equal to 25.4 microns


https://elsmar.com/gif/Micron-20.gif

 

[Linctex]

From that paper:

"The composite-synthetic filters were found to
maintain high filtration efficiency levels under
severe operating conditions for more than twice the
recommended service life of the standard paper
filters. "

Any self-respecting BITOG'er would never again run any paper filter element after that!

 

[ZeeOSix]

Originally Posted By: StevieC
Particles larger than 20 micron are the most damaging to an engine. Below 20 micron are less damaging until you get down to 1-2 micron range which it would take a lot of to do damage.

As far as journal bearings, it's particles 25 microns and smaller. Particles larger than the bearing's minimum runnimg clearance will typically get spit out the side clearance instead of going through the bearing. The smaller stuff can go through the minimun running clearance and do damage.

 

[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.

 

[dlundblad]

Originally Posted By: MasterSolenoid
To put it in perspective,

.001 inch is equal to 25.4 microns


No way. 1 hair is .003.

*dang you're right. That just seemed dangerously large.

 

[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.

 

[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.

 

[StevieC]

Originally Posted By: ZeeOSix
Originally Posted By: StevieC
Particles larger than 20 micron are the most damaging to an engine. Below 20 micron are less damaging until you get down to 1-2 micron range which it would take a lot of to do damage.

As far as journal bearings, it's particles 25 microns and smaller. Particles larger than the bearing's minimum runnimg clearance will typically get spit out the side clearance instead of going through the bearing. The smaller stuff can go through the minimun running clearance and do damage.


There are more parts than just Journal bearings.

 

[StevieC]

Originally Posted By: Donald
Bypass is cost effective for diesel engines that go many hundreds of thousands of miles and have large oil sumps. So oil changes are several hundred dollars.

A decent filter and reasonable OCI will allow a normal car engine to not be what causes the car to go to the boneyard. Filtering so that the engine is in pristine condition when the car goes to the boneyard makes no economic sense.


Just the same in most Gasoline engines. Not changing the oil for 60,000 miles even with top-up oil at filter change time and the filters still makes it cheaper than conventional changes. Especially when the equipment is amortized over a few vehicles because it's reusable.

 

[ZeeOSix]

Originally Posted By: StevieC
Originally Posted By: ZeeOSix
Originally Posted By: StevieC
Particles larger than 20 micron are the most damaging to an engine. Below 20 micron are less damaging until you get down to 1-2 micron range which it would take a lot of to do damage.

As far as journal bearings, it's particles 25 microns and smaller. Particles larger than the bearing's minimum running clearance will typically get spit out the side clearance instead of going through the bearing. The smaller stuff can go through the minimum running clearance and do damage.

There are more parts than just Journal bearings.

Yes, I know ... just pointing out that some engine parts are sensitive to debris 25 microns and smaller, which are the most damaging to them, not the particles that are larger than 20 microns like you stated.

From what I've seen, it seems that crank and rod journal bearings wear out more/faster than the rest of the engine parts that rely on lubrication to keep them in good shape.

 

[StevieC]

Quote:
Particles larger than 20 micron are the most damaging to an engine. Below 20 micron are less damaging until you get down to 1-2 micron range which it would take a lot of to do damage.


I didn't say that all parts were... In general 20 microns and larger are the "concern" particle size for "most" of the engine parts. Of course there will be parts that are more and parts that are less sensitive. It's why filter manufacturers use 20 micron as the standard to try and filter down to with the most efficiency without sacrificing flow.

 

[ZeeOSix]

Originally Posted By: StevieC
Quote:
Particles larger than 20 micron are the most damaging to an engine. Below 20 micron are less damaging until you get down to 1-2 micron range which it would take a lot of to do damage.

I didn't say that all parts were... In general 20 microns and larger are the "concern" particle size for "most" of the engine parts. Of course there will be parts that are more and parts that are less sensitive. It's why filter manufacturers use 20 micron as the standard to try and filter down to with the most efficiency without sacrificing flow.


Well, if you search and read all the papers/articles about engine wear and particle size, they all say that particles 25 microns and smaller are the most damaging, which is contrary to what you're saying. If you have some links to post up to show your source of info then I'd be interested in reading them.

And BTW, filters these days can be very efficient without sacrificing flow. It's pretty hard to "sacrifice flow" on an engine with a positive displacement oil pump.

 

[StevieC]

I said 20 and larger which would include your 25. Below 20 it's less of a concern but the concern never goes away until you get down to 1-2 micron and those take a while to build up in counts large enough to be a problem which is why bypass filtration works so well for a long time.

 

[ZeeOSix]

Originally Posted By: StevieC
I said 20 and larger which would include your 25. Below 20 it's less of a concern but the concern never goes away until you get down to 1-2 micron and those take a while to build up in counts large enough to be a problem which is why bypass filtration works so well for a long time.

40, 60 and 80 microns are also larger than 20 microns. From the papers I've read, below 25 is a concern because of tight clearances. The bigger stuff can't get in and do damage like the smaller particles. Go Google up some "engine wear vs particle size" papers and you'll see what I'm talking about.

 

[StevieC]

You are missing the words "LESS OF A CONCERN" I didn't say "IT IS NOT A CONCERN".

This would mean everything bigger than 20 Micron is the stuff to worry about.

Below 20 micron you should still worry but it's not as bad as the larger particles. I.e. 21,22,23,24,25 .... 500 if you like.

You are claiming 25 and bigger. I'm claiming 20 and bigger.
It encompasses your 25 and bigger!

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. This 1-2 micron level still becomes a problem over time as these particles in this size range accumulate to a level that can cause damage because there are so many of them which is why Bypass filtration filters / oil still needs to be changed eventually but not as frequently as the 20 micron oil filters filtering oil.

 

[ZeeOSix]

Originally Posted By: StevieC
You are claiming 25 and bigger. I'm claiming 20 and bigger.

No, I'm claiming 25u and SMALLER. Said it many times - go back and re-read. You are claiming 20u and BIGGER, just the opposite of what all the technical papers say. The 5u difference doesn't really matter here.

Please post up links to valid technical sources (ie, SAE papers or similar) showing that particles greater than 25u are worse for engine wear than particles smaller than 25u.