Book Bits
From "Wear Debris Analysis":

The Benefits of Trending

The condition of a machine cannot usually be determined from a single analysis of wear debris. Although an experienced user of the technique may form an opinion from the size of debris - large chunks undoubtedly conveying severe fatigue, for instance - a much clearer picture is conveyed only through trend analysis.

It would be extremely convenient if an 'absolute' measure of wear debris were able to give a definitive GO/NO-GO measure of condition. But this is only possible from experience built up from trend analysis on the same or similar machinery or systems. Many other types of condition monitoring also depend on this approach because of the wide variations in signal generation with condition. Trend analysis, however, is able to provide the required background for true machine condition determination.

Today's Tip
To check the cleanliness of the inside of a new hydraulic reservoir, take a small strip of transparent adhesive tape and stick it on the surface (roof, side wall or bottom plate) of the reservoir where you want to check the surface cleanliness. Press the strip with your thumb firmly so that it is in proper contact with the surface. Now peel off the strip and paste it on a white piece of paper. You will find that the strip has sampled large particulate contaminants. You can also use it with standard visual comparitors, similar to common patch test comparitors. With this method you know whether or not your tank needs further cleaning. Also, keep in mind that the unaided eye can only see individual particles larger than about 50 microns.
(Tip submitted by P. Urushottam, Tata Steel.)

Q & A
Understanding Filter Ratings

"My filter company uses the following notation to rate one of their filters.

BX=2, B10=X, BX=75, followed by these numbers: 5, 8, and 17

I'm familiar with the Beta rating but I've never seen it shown in this way. What is meant by these numbers?" -- Michael Cowan

This system of rating a filter describes its capture efficiency at three specific points in microns. It actually has many advantages over the more common Beta rating methods used today. This is how it works:

BX=2 The X denotes the size in microns of particles above which the filter is only removing 50 percent of the particles entering, for example, 100 particles larger than X come into the filter but only 50 of them are captured. For your filter this 50 percent efficiency size is 5 microns. This is the lower limit of performance in microns for this filter.

B10=X This X in this case denotes the Beta Ratio corresponding to particles larger than 10 microns. Many hydraulic users in the past have viewed 10 microns to be a critical clearance size, above which system components are at high risk of failure. The X has to do with the capture efficiency of particles larger than 10 microns. In your example the Beta ratio at 10 microns is 8, meaning that for every 8 particles larger than 10 microns coming into the filter, one gets through uncaptured (about 88 percent capture efficiency).

BX=75 This X corresponds to the micron size above which the filter is removing 98.7 percent of all the particles, that is, the Beta ratio for the particle size (X) is 75. For every 75 particles larger than X entering the filter, only one gets through (74 are removed). Many people have informally referred to that size (X) as "absolute" although clearly, by definition, it is not. Still it is useful to know what the BX=75 rating is. In your example, the X corresponds to 17 microns.

For more information on Beta Ratings filters please refer to ISO 16889 or go to the following articles:

Clarifying the New ISO Contamination Filtration Standards

The Future of Filtration

Jim Fitch, Noria Corporation

Book Bits
From "The Practical Handbook of Machinery Lubrication":

Rules for Dealing With Aftermarket Additives and Supplemental Oil Conditioners

RULE #3

Increasing the percentage of a certain additive may improve one property of an oil while at the same time degrade another.

Example (a) Some additives compete with each other for the same space on a wear surface. If a high concentration of a special antiwear agent is suddenly added to the oil, the corrosion inhibitor may become ineffective. The result may only be an increase in corrosion related problems.

Today's Tip
Oil analysis and particle counting are very important in unfiltered compartments such as heavy equipment final drives and differentials. However if these compartments have magnetic plugs, occasionally the magnets will show a build up of fuzz and you may have the beginnings of bearing failure while the oil sample remains relatively clean. This is an example of when manual inspection is very important along with oil analysis and particle counting. (Tip submitted by Jim Groseclose, American Colloid Company. Thanks Jim!)

Q & A
Don't Overlook Air as a Contaminant

"We suspect that we have an air contamination problem in one of our hydraulic systems. What types problems can air contamination cause?"

Air contamination can cause a great deal of harm to hydraulic systems. Unfortunately, unless the machine is foaming, with oil spewing from the top of the reservoir, we sometimes overlook this potentially devastating contaminant. Here are a few ways in which air contamination can undermine your reliability effort:

Spongy hydraulics - Air is compressible. This loss of control can slow throughput, increase the percent defective rate, and, in some cases, cause injury or death.

Gaseous cavitation - Some references say gaseous cavitation causes wear, others say it just makes noise. I'd play it safe and keep oils as free from air as possible.

Oxidation - the rate of oxidation is affected by a number of factors, but all else held equal, it is proportional to the amount of oil in boundary contact with air (which, of course provides the oxygen).

Thermal degradation - Did you know that compressing an air bubble from ambient pressure to 3000 psi increases the bubbles temperature to over 2000°F? This is hot enough to thermally degrade oil at the boundary contact between the air and the bubble, which darkens the oil, sometimes giving it a sooty appearance, and causes varnish to build up on component surfaces.

So, watch for signs of air entrainment or foaming, and take occurrences seriously. Also, periodically test your oil's ability to release air and its tendency to maintain stable foam. If you have recurring problems, evaluate the lube specification and the tank design, and check for low levels and signs of a suction line leak.

Drew Troyer, Noria Corporation

Book Bits
Here's an excerpt from the Practicing Oil Analysis '99 Conference presentation entitled "Oil Reconditioning,

Reclaiming and Recycling - Understanding the Processes and the Role of Oil Analysis in Each."

Additive Refortification

The most important aspect of determining additive levels is having an overall understanding of the state of the fluid. If there are unanswered questions with the initial batch of tests that are performed, it is imperative to perform additional diagnostic tests.

Many additives are sacrificial, meaning that once they have reacted, they are no longer of value. Eventually, these additives may polarize and fall out of solution in the form of particulate or varnish. It is important that the reprocessing technology has filtration capabilities sufficient to absorb or filter out these contaminants. Some additives will decompose and change into molecular structures that act as catalysts to oxidation. Prior to the additives changing structure however, they may still be evident in the oil. Metallic additives that are detectable through spectrography may still appear in an analysis even though they are no longer providing protection. Therefore, tests in addition to a spectrograph analysis are necessary to accurately determine additive levels.

You can download this entire paper and other files from:
http://www.noria.com/secure/ebooks.asp

Today's Tip
Do not store grease gun cartridges on their side. The grease could soften due to temperature and create an air pocket that could hinder the ability of the grease gun to function properly. Store the cartridges upright. (Tip submitted by Rodger Shaffer, Timken Latrobe Steel. Thanks Rodger!)

Q & A
Take the Synthetic Challenge. Can You Tell The Difference?
"Relating to gear boxes on trucks, if the owner or the driver doesn't know if the gear lubes are synthetic, is there a fool- proof way to determine this without having to send a sample to the lab? Some oil manufacturers color their synthetic oils, while others don't. What would happen if the oils were to be mixed or topped off with the wrong oil?" -- Submitted by Craig Knight

The color of the lube, as I'm sure you are aware, is simply a dye. There are no standards, and manufacturers can and do change colors whenever they please. Unfortunately, there is no reliable way of differentiating between mineral and synthetic in the field. However, because synthetic base oils are white (meaning transparent) as compared to a mineral oil which has a darker natural color (due to aromatics, sulfur, and other impurities), this may be a distinguishing factor. Note, however, that despite the fact that the base oil of a synthetic is white, the additives can add considerable color (darkening) to the finished oil.

In the laboratory you could distinguish synthetics from mineral oil by looking at a combination of physical properties including VI, flash point, pour point, and aniline point (all standard ASTM tests). There may also be different elemental additive chemistry.

Generally, in the type of application you are talking about, the synthetic gear oil will likely be polyalphaolefin (PAO) based. PAOs are very similar chemically to mineral oils and hence mixing the two should not cause a compatibility problem (especially if both oils are the same API classification). Although, if a synthetic is required, for example for cold temperature operation, using a mineral by mistake may cause other problems.

Also be aware that in industrial applications, some synthetic gear oils are polyglycol (PAG) basestocks, which are chemically incompatible with both PAO synthetics and mineral oils. In this case, mixing will result in serious incompatibility issues.

Mark Barnes, PhD, Senior Consultant, Noria Corporation