A Different Approach to Micro-Pitting Protection

Re-evaluating the base stock to protect gear boxes

Gear box Gear box


For several years, manufacturers of industrial gear boxes have been looking to lubricant producers for a solution to micro-pitting, which sounds like a small problem but can actually lead to big operating problems and even catastrophic equipment failure.


Modern gear boxes are decreasing in size, and many are heavily loaded. This puts a lot of stress on the gear teeth, forcing microscopic surface asperities to contact each other from opposing gear teeth. Micro-pits then form on the tooth surfaces. The wind turbine industry was among the first to sound the alarm about micro-pitting due to the severe stress that turbines place on gear teeth.   


Evidence of micro-pitting appears in the form of an area of gray staining on an otherwise shiny tooth. If you look closely enough at that area, you can see a cluster of micro-pits. If it continues to develop, micro-pitting will eventually lead to macro-pitting, meaning a visible chipping of the tooth and a loss of the tooth profile. That in turn reduces the efficiency of the gear box and can lead to gear tooth breakage.


Historically, gear oils have been formulated using a polyalphaolefin base stock, more commonly called PAO. In the search for a solution to micro-pitting, other lubricant producers have experimented with various types of additives on top of the PAO stock. At Chevron, we took a different direction – re-evaluating the base stock itself.


The result of this effort produced our new Meropa EliteSyn™ XM. It utilizes a synthetic mixture of base stocks that include methacrylate and other compounds in addition to PAO. In extensive field testing, we found that this new formulation improves significantly on wear protection, and micro-pitting when compared to traditional PAO-only based oils.


One lingering question we faced before bringing this product to market was whether it would deliver comparable low-temperature fluidity to a PAO-based lubricant. PAO-based oils are known for good low-temperature fluidity in the marketplace. As a synthetic-PAO-based mixture, Meropa EliteSyn XM should offer wide temperature range performance, but we had to find out for certain. We identified a sawmill operator in far northern Canada that had some outdoor gear boxes, and they agreed to do a field test with us through the winter to see if the product encountered any low temperature issues. The good news is we saw no impediment to fluidity or gear box performance at temperatures as low as -41o Fahrenheit or -42o Celsius.


Meropa EliteSyn XM provides industrial equipment operators with a viable alternative to PAO-only based gear lubricants, one that delivers not only superior wear and micro-pitting protection, but also the wide temperature range performance customers have come to expect. 



Dan Holdmeyer
About the Author: With over 35 years in the oil and gas industry, Dan Holdmeyer has worked for Chevron the past 14 years, serving in a variety of capacities with the company in addition to his current post as Industrial and Coolants Brand Manager where he works as a lubrication engineer that supports Chevron Delo and other related lubricants brands. He plays an integral role in supporting and managing a variety of programs related to off-highway and on-highway lubrication needs. Dan also works as Chevron’s Training Specialist for their Global Lubricants division since joining the company. Prior to joining Chevron, Dan worked as a Field Engineer at Mobil Oil Corporation for 20 years (1979-99) after graduating from the University of Missouri-Columbia with a Bachelor of Science in Chemical Engineering.

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