Keeping water out of oil seems to be a never-ending battle. Water may well be the No. 1 contaminant, reducing RTF (run to failure) time by a factor of ten. Breathers with threads may allow water to wick its way down the threads, contaminating the lubricant.

Other forms of contamination such as rust and wear particles can develop around the threads. Air gaps between the threads form a hiding place where rust can develop. Overtightening, with a wrench may stop water ingression, but can cause pieces of thread to spall off and fall into the lubricant.

Placing a small amount of thread sealant on all breathers using pipe threads will greatly reduce this risk. Thread sealant will fill the air gaps, lubricate the threads, and seal out the water. (Garry L. Sands, Lube Tech, Tembec Inc.)

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From the "Lubrication Excellence 2007 Conference Proceedings":

A coal fired power plant operating in the western U.S. was experiencing short life in their bronze-on-steel gearbox used for pulverizing coal. The AGMA 6EP (ISO 320) gear oil recommended by the OEM failed to provide adequate lubrication and protection based on oil analysis results and gearbox inspection after one year of operation. This was confirmed by excessive wear metals and lower viscosity in the used oil reports. Further analyses of the used EP gear oil indicated excessive buildup of particulate contaminants in the lubricant and depletion of the EP additive package. A chain reaction of excessive wear was taking place.

Replacing the AGMA 6EP gear oil with a synthetic AGMA 7 R&O gear oil and installing a custom-tailored oil filtration system significantly reduced the wear metals and practically eliminated the wear chain reaction.

More information about the "Lubrication Excellence 2007 Conference Proceedings".

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Question: What is a common additive found in SAE 0W-30 motor oil but not found in SAE 30 motor oil?

Get the answer.

"I heard that oil has a shelf life of one to two years, but oil in service can last for several years. How is this?"

What you have alluded to is true. Oils do have a fairly short shelf life compared to the length of time they can last in service, if properly maintained.

The issue here is additive solvency as it is commonly referred to. Chemically speaking, "additive solvency" is a bit of a misnomer, as many additives are mixed or suspended, rather than dissolved in the base oil. When the lubricant is stored for an extended time, the additives can settle out. This is particularly true of lubricants that have high additive treat rates, and leaving such oils sitting for extended periods can leave a thick sludge at the bottom of a drum. The problem is exacerbated by base stocks with a high nonpolar content, given that many additives are polar in nature.

Using the oil effectively keeps the additives well mixed. If you can limit particulate and moisture contamination to the minimum you will avoid particle scrubbing, water washing and other destructive depletion reactions. As a result, your oil will likely last for a substantially longer time than its shelf life.

Ashley Mayer, Noria Corporation

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