Chromium in oil sample

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waynemcc999
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Chromium in oil sample

Post by waynemcc999 »

Prior to March 2016 my Blackstone analyses consistently showed 2 parts-per-million of Chromium. The aircraft (2008 DA40 XLS) to that point had mainly been run Rich-of-Peak.

Although it may have no bearing on the issue, in late March 2016 I had the ElectroAir ignition installed as well as moved from massive to Fine Wire Plugs. The ignition/plug implementation has allowed me to reliably run LOP and that has become my standard mode of operation.

On 4 subsequent samples, my Chromium readings have increased and become steady in the range of 7-to-10 ppm (versus industry average of 3 ppm).

Compressions and borescope reports (at annuals mid-2015 and mid-2016) have been normal.

My questions:
[*] (for all DA40 IO360 aircraft) What do you measure for Chromium in your samples? Do you run LOP or ROP most of the time?
[*] (for those with ElectroAir and/or Fine Wire Plugs) What do you measure for Chromium and was there a change after the EIS/plug implementation?

Any thoughts on what level of concern, if any, I should have? My current plan is to run to next 50-hour oil service; redo the compression and borescope checks; re-analyze oil sample.

Many thanks,
Wayne
Wayne McClelland
PPL/IR, 2008 Diamond Star DA40-XLS 40.922, KSBA
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blsewardjr
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Re: Chromium in oil sample

Post by blsewardjr »

My most recent sample was 5 ppm. Have been running 6-7 ppm since 2014. Running more LOP now than before. Have Fine Wire plugs -- no change in reading.
Bernie Seward, IR, AGI
2003 DA40 N377DS
KCHO Charlottesville, VA
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theRDWRER
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Re: Chromium in oil sample

Post by theRDWRER »

My first sample and last sample before the EIS was 2. Since then it has been 3,5, and most recently 4. I'm sending in another sample this week and can report back.

I run either LOP or Peak EGT. I also have the fine wires.
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Rick
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Re: Chromium in oil sample

Post by Rick »

Another data point. I just took a look at all my results. Back in 2012, I had Chromium levels of 4.5 and 4.0, but they have been steadily decreasing since then. My last two samples this year showed 1.7 and 1.1, a bit below the industry standard level. I consistently run LOP. I added the fine wire plugs back in 2012 just prior to the first sample.
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Steve
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Re: Chromium in oil sample

Post by Steve »

Mine have run between 2 and 5, most recent is 2, but less hours on oil for that sample. I run ROP, fine wire plugs. I didn't notice any change when I switched from massive to fine wire plugs 3 years ago.
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rwtucker
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Re: Chromium in oil sample

Post by rwtucker »

My Cr ranges between 1 & 4. No difference after installing fine wires and the two lowest readings are with fine wires. Cu was high (62) on my first reading. It gradually dropped to 7.4 in the last test.

I run 70/30 ROP.

Overall, you are really not that high but the most important test is probably a close examination of your filter core. It will also be helpful to see what happens in the next oil analysis reading. The elevated readings might be the result of a self-limiting chip off of ring plating that will level off or abnormal ring wear which will persist.

Also, I note you may be running 50 hours on a change. I run between 25 & 30. I would expect your Cr to be higher than mine. Let us know what your filter looks like under a bright light and a good magnifying lens. Pry the folds apart and look along them.
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Kurt h
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Re: Chromium in oil sample

Post by Kurt h »

My Cr runs about 2 +/- ppm for the life of the engine (1900 hrs now). switched to fine wire plugs at about 700 hrs with no change in any metals. Have always run ROP, 75% cruise power.
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rwtucker
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Re: Chromium in oil sample

Post by rwtucker »

One other variable, kind of obvious but worth mentioning, is the amount of oil we maintain in the crankcase.
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Chris B
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Re: Chromium in oil sample

Post by Chris B »

waynemcc999 wrote: My questions:
  • (for all DA40 IO360 aircraft) What do you measure for Chromium in your samples? Do you run LOP or ROP most of the time?
  • (for those with ElectroAir and/or Fine Wire Plugs) What do you measure for Chromium and was there a change after the EIS/plug implementation?


Any thoughts on what level of concern, if any, I should have? My current plan is to run to next 50-hour oil service; redo the compression and borescope checks; re-analyze oil sample.
Hi Wayne -

My 1900 hour 2008 XLS runs 2-5 ppm, averaging 3. All five readings since installing the EIS (and GAMIs) are 3 to 5. The earlier "2" readings were about 10 hours less engine time, so I don't think anything has changed. FWIW, I have always run fine wire plugs, and am very aggressive with LOP ops.

Since the primary source for Chromium is piston rings, your plan makes lots of sense to me. You might consider more frequent changes (25 hr?), although that will obviously affect the ppm trends. Robert's point about oil quantity is also quite relevant, particularly with the recent discovery (link) that many of us have been flying with less oil than we thought!

Chris
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Chris B
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Re: Chromium in oil sample

Post by Chris B »

Hi Wayne -

Other considerations, since Chromium is mostly associated with rings:
  • Have you noticed any change in oil color trends?
    Often the leading indicator for ring issues is faster-to-black oil, assuming consistent ROP/LOP operation.
  • Any noticeable change in oil consumption?
    This can be another leading indicator for ring issues, but is less specific to rings than oil color.
While obviously not cylinder specific, either change is easy to monitor at short intervals.

Chris
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