Mobil monitor report says that we got a copper problem about 56ppm and lead 33ppm.
Should we be worried?Are the results too high?
The steamturbine produces approx.15MW.
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Leif.
What was previous results? Has there been an increase?
What was previous results? Has there been an increase?
quote:Originally posted by Leif:
....Are the results too high?....
Hi there Leif,
First and foremost you need to establish a benchmark for this asset.
If it already exists and no major modifications have occured then this is one of the better indicators of how the system is operating or changing with time.
Familiarise yourself with the elements within your system.
What elements make up your oil in use.
a "new oil" sample straight from the barrel (or after the filter cart if you are following best practice and filtering your oil into the resevoir) should provide an insight into the additives present before introduction into the turbinegenerator.(the lab needs to provide a comprehensive suite of elements for this to be effective).
Bearings, coolers, pipelines, valves, pumps, filters and fittings should all be considered as potential sources of the elements.
As will the contaminants from external sources.
Watch for element proportions as a good indicator of the source.
Based upon a typical setup these values are just over the thresholds and would with no other information be taken as a warning but not an indication that stripping down of the machine should begin.
Disclaimer;
This is a rule of thumb and variations between systems do mean that in this particular instance a danger limit may already have been exceeded.
You are the guru for your site and you know the history for this asset item.
Be cautious and if in doubt retest to provide trend indications.
a 2-3 week wait from the last sample should give enough time for further changes.
Last thing.
Remember to look at the oil sample before sending it away. If you can see particles then you should identify them under a microscope.
happy hunting
Thanks for the comments.
We´ve been monitoring the oil since 2003 when we changed the oil (5000 litres),and 800 litres has been added since then.
oilanalysis has shown that.
2003 Cu 16ppm Pb <1ppm
2004 Cu 51ppm Pb <1ppm
2005 Cu 54ppm Pb <1ppm
2006 Cu 56ppm Pb <33ppm water 2000ppm
We are filtering our oil and the last oilsample has been under the microscope,found some metallic particles size:15microns
As you see that the Cu haven´t changed but I´m worried about the Pb.Could it be that it comes from the bearings?
We´ve been monitoring the oil since 2003 when we changed the oil (5000 litres),and 800 litres has been added since then.
oilanalysis has shown that.
2003 Cu 16ppm Pb <1ppm
2004 Cu 51ppm Pb <1ppm
2005 Cu 54ppm Pb <1ppm
2006 Cu 56ppm Pb <33ppm water 2000ppm
We are filtering our oil and the last oilsample has been under the microscope,found some metallic particles size:15microns
As you see that the Cu haven´t changed but I´m worried about the Pb.Could it be that it comes from the bearings?
Now, water is another biggie.
As you did not list the water against previous years I will assume for now that it was either not present or tested for.
(SAME TEST POINT AND CORRECT SAMPLING PROCEEDURE ALSO ASSUMED)
As I am sure you will have completed an elemental analysis on your various water souirces onsite.
Plant water, well water, tap water, hose water, cooling water, condensate, rain water.
You should be able to use this to identify the water source.
Can you send through / attach a jpeg of the material observed? In oil analysis size DOES matter. As does shape and colour.
Also revisit the metalurgical makeup of your bearings. If the Lead is proportional to the other elements expected in the bearing type then this is an indicator.
Use Vibration monitoring to aid the process. A severe pickup or rub will generate a signal to analize.
Incidentally once a year is a bit longer than I would be comfortable with from trending of the oil condition. At present the samples are pure snapshots of condition on that date. the validity of decisions made 2 months later about the machine health based on the lab report from that date would be questionable.
A lot can happen over a month, let alone a year.
Fitch recomends that steam turbines are sampled every 500hrs (page56 of oil analysis basics - ISBN 0-9675964-1-7)
Water limits as defined by GE are 0.2% (2000ppm).
I suggest that the lead is potentially a symptom of the root-cause.
A loss of film strength is a documented effect of water in oil.
As before I do not know your system as well as you do. Document the source elements for your generator and identify where the lead, copper and water may be coming from.
The metal particles are a good indicator and I look forward to viewing the images.
As you did not list the water against previous years I will assume for now that it was either not present or tested for.
(SAME TEST POINT AND CORRECT SAMPLING PROCEEDURE ALSO ASSUMED)
As I am sure you will have completed an elemental analysis on your various water souirces onsite.
Plant water, well water, tap water, hose water, cooling water, condensate, rain water.
You should be able to use this to identify the water source.
Can you send through / attach a jpeg of the material observed? In oil analysis size DOES matter. As does shape and colour.
Also revisit the metalurgical makeup of your bearings. If the Lead is proportional to the other elements expected in the bearing type then this is an indicator.
Use Vibration monitoring to aid the process. A severe pickup or rub will generate a signal to analize.
Incidentally once a year is a bit longer than I would be comfortable with from trending of the oil condition. At present the samples are pure snapshots of condition on that date. the validity of decisions made 2 months later about the machine health based on the lab report from that date would be questionable.
A lot can happen over a month, let alone a year.
Fitch recomends that steam turbines are sampled every 500hrs (page56 of oil analysis basics - ISBN 0-9675964-1-7)
Water limits as defined by GE are 0.2% (2000ppm).
I suggest that the lead is potentially a symptom of the root-cause.
A loss of film strength is a documented effect of water in oil.
As before I do not know your system as well as you do. Document the source elements for your generator and identify where the lead, copper and water may be coming from.
The metal particles are a good indicator and I look forward to viewing the images.
quote:Pb <33ppm
?? Pb could be 1 to 32 ppm ?
If Pb=33ppm, what is tin (Sn) reading?
Pb/Sn mostly come from babbit metal layer of plain bearing for steamturbine. Pb=33 ppm is high for me. I saw a bearing high temperature alarm case, minor bearing overlay damage, took 2 days to fix, oil sample have only 6 ppm Sn. Sn is <1ppm before. The lesson is : even small ppm of Sn probably indicate significant bearing wear. Pb:Sn is about 1:8 for tin base babbit metal, Sn reading will be helpful.
quote:Familiarise yourself with the elements within your system.
Another thought prompted by Jack.
(Thank you Jack).
Are you able to identify the ASTM designation for the bearing in service.
ASTM document B23-94;
"Standard Specification for White Metal Alloys (Known Commercially as "Babbitt Metal")"
Within this document the proportions of Lead, Tin, Copper, Iron, Antimony, Arsenic, Bismuth, Zinc, Aluminium & Cadmium are detailed.
If you know the proportions of the Babbitt metal, it is possible to state categorically that this is the source.
