Hello friends,

I am performing oil particle count test for turbines and compessors. the results are going up and down and seem inconsistent, can anyone provide any explanation.

why the number of particle goes down?
cse1:
Date(dd/mm/yy) Particle count test (ISO)
14/01/08 -------------21/19/16
24/04/08 -------------17/14/8
22/05/08 -------------16/12/7
20/06/08 -------------21/17/10


Case 2:
14/01/08 --------------14/14/10
24/04/08 --------------16/13/9
22/05/08 --------------16/13/7
20/06/08 --------------17/15/12

case 3:

07/03/08 ------------14/11/6
02/04/08 ------------16/14/9
06/05/08 ------------13/10/5
02/06/08 ------------16/13/9

Cse 4:

07/03/08 ------------18/14/10
02/04/08 ------------17/14/9
06/05/08 ------------18/15/6
02/06/08 ------------19/16/8

Many thaks for your help.

Dear Motorist,

The first piece of information we have is the tolerance of the test. Each successive reading of the oil can be +/- one ISO code for oil with the same condition, and still be a valid test.

Next we need to know if all the samples were taken under the same conditions, after the machine was running (1 hour +) and was the oil sample taken at the same place?

Next water and air can cause false counts. Some labs will simply agitate the sample to thoroughly mix without regard to water or air content. Look at the other data to see where the water content is. If it is >100 ppm I would suspect water droplets. Use vacuum pump to drive of the water, then resample. (This can be done by hand if needed)

Next, were the sample containers "Ultra Clean" if not the variances in ISO Codes can be completely due to bottle contamination.

When oils have become very dark fine particle build up must be suspected. These particles can agglomerate forming what appears to be much larger particles. In the past we have used both laser particle counts and pore blockage particle counts to try to sort this out. The laser particle count will see all of the particles, the agglomerates, water droplets and emulsions, and air bubbles as particles. The pore blockage method will generally ignore the agglomerates, the water and the air. if the difference is one ISO code then this is not an issue. If the differance is 2 or more codes, then further investigation is warranted.

Good luck, write if you need more gmunson@fluid-assets.com

Check with the customer for any large amounts of top up oil, this can affect the readings.

Another more question please...

For a Particale count test:

should I use the same sample for ICP test which is taken before the filter.

or should I take another sample after the filter just for Particle count test.

Assuming that if we use the same sample of ICP test we will have a higher level of contamination than the real oil in the bearings, because the oil in the bearings is filtrated.

regards

Noureddine.T

Dear Motorist,

the sample before will take more wild excersions as conditions change, but may provide better data.

Please have someone look into sensativity for you. The lab should be able to do this. I mention this because I know normal spectroscopy can not see any particles > 10 um in size. Find out what the upper and lower lmits of detection are.

Good Luck.

Motorist, you do not state what your target cleanliness is. Variation of results not critical if it is below your target.
What is the reason for taking the particle count? Is it for cleanliness then see above, if it is for wear then you are looking for an increase in particle count, particularly in the larger size range. Take samples before the filter or why not before and after.
As stated by others earlier, OCM should look at all parameters Water, ICP, PC and judgements made after viewing all the results, current and historical.
Particle counts do vary for the reasons mentioned by others.

Roger Davies,

My limit for the P.C test is 17/15/12.
I am monitoring the other parameters (ICP,Water...) to monitor the oil properties and different mechanical parts wear.
As well as Particale count to monitor the oil cleanliness.

Motorist,

For ISO cleanliness, I've found the Filterpatch test most reliable in terms of consistency of results within a lab and comparing different labs. The most variation I've come across is by one ISO code as part of a round robin trial.
The sample is essentially washed and filtered through a filter paper. The solvent used is hexane or heptane (filtered solvent). The filter patch is compared to a comparator such as a PALL comparator and the ISO code is then determined.
Speak to the labs to see which one can offer this method. The lab will probably have a method that is somewhat a modified version to the PALL method. The lab should also be able to provide a digital photo of the patch as part of routine analysis report.
The advantage of filterpatch method is that it does eliminate some of the interference issues experienced with automatic lazer particle counters as previously mentioned. It will also give you a visual representation of why the ISO code has gone up. It may also show up any abnormal wear material. Also as the turbine oil ages, you will also notice a change in colour on the patch test as well.
As mentioned before, look at the ISO cleanliness results in conjunction with other results such as ICP wear metals, PQI, water content etc. For turbine oils it's also important to include TAN and RPVOT results as well.
Typically, a sample before the filter is taken. You can take samples post filter as well which may give you some indication of filter efficiency. However, I've come across cases where pre filter and post filter results are almost identical.

Sampling methods, sampling practices, personnel, bottle cleanliness, the list goes on. There are some many variables to collecting a representative and accurate sample.
I would look at how you sample and the procedures involved, particuarly if more than one person is collecting the samples.