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The gear oils of today aren't what they used to be, and with good reason: The environment in which industrial gears operate has changed, and demands on the lubricant have increased dramatically.
There are two main drivers that influence industrial gear oil trends: specifications and changes in industrial gearboxes.
There is a series of baseline gear oil standards, and among these are geographically specific specifications such as AGMA 9005-E02 EP (North America), DIN 51517-3 (Europe) and SEBI 181 226 (Germany - steel). Original equipment manufacturers (such as David Brown, Flender, Winergy and Cincinnati Machine) often use some or all of the baseline standard tests in combination with their own additional requirements, resulting in more stringent performance standards for the gear oil. In addition, there are end user-specific (such as GM LS-2) and industry-specific specifications (such as food-contact and wind turbine lubricants).
Regardless of the specification or standard, they are becoming increasingly more stringent, requiring higher quality gear oils. This has resulted in formulators taking a different approach toward meeting or exceeding these high-performance targets.
Table 1. New Technology Performance
Changes in Industrial Gearboxes
Today's gearboxes are made from new materials, which results in a lighter weight of the gearbox. They are required to produce more power and be more durable and reliable than their predecessors. In addition, the teeth and bearing loadings are also higher.
The smaller size of the gearbox means less oil and additive to lubricate the gears, which are now trying to carry higher loads. This results in higher temperatures and an acceleration of the oxidation process. Oxidation is harmful for industrial gear oils because it can form sludge, which can shorten the oil life and component life of the gearbox. This results in downtime and expenses to replace or repair components.
Elements of a Good Gear Oil
The components of a quality gear oil sometimes depend on who is leading the discussion. The lubricant manufacturer, however, is knowledgeable on all parts of the process. An understanding of gearbox design changes helps the lubricant manufacturer and additive supplier to understand the performance requirements needed for the new design. A thorough understanding of the end user's needs is required to know how the lubricant fits into the process.
Additives play a leading role in adding value by improving the properties, lubrication and performance of industrial gear oils. They provide factors such as oxidation, viscosity and thermal stability, micropitting resistance, bearing corrosion protection, foam resistance and enhanced load carrying. In addition, they provide seal protection and demulsibility (ability to shed water).
A lineup of additives is required to deliver full performance. These additives include sulfur-phosphorus chemistry for extreme pressure, antioxidants, demulsifiers, friction modifiers, viscosity modifiers, metal deactivators and others.
Additive suppliers provide the lubricant manufacturer with the technology to go beyond the universal mineral-based gear oil. With proper additive technology, the lube manufacturer can make specific performance claims and produce gear oils with certain attributes, such as higher levels of load-carrying capability, or for specific applications, such as food contact and wind turbines.
Product value and differentiation can be accomplished by selecting the proper additive technology in combination with the appropriate base fluid. Currently, new additive technology is available that delivers this value and differentiation. Formulated to provide high levels of extreme-pressure properties across a wide range of viscosities (even down to ISO VG 68), smaller gearboxes carrying high loads have extra protection.
Additives used to enhance extreme-pressure properties can be prone to thermal stability issues, resulting in the formation of sludge. This new technology has been formulated to provide the optimum balance of thermal stability for sludge-free gear sets and extreme-pressure protection for heavy-duty durability. The combination of these two factors adds value by prolonging the life of gearboxes, maximizing efficiency and eliminating downtime.
Developed with today's industrial gear operation in mind, this technology is designed to surpass the performance of the previously available suite of industrial gear oil additives. When the blender adds 1.8 percent by weight of this new additive technology to the proper base fluid, it will meet specifications DIN 51517 Part 3, U.S. Steel 224, ISO 12925-1 CKC/CKD, Cincinnati Machine, AGMA 9005-E02, and GM LS-2 and David Brown S1.53.101.
It is anticipated that future trends to lower the costs of gearbox manufacturing while increasing productivity at the end-user level will place additional demands on gear oils. High load-carrying performance capabilities while maintaining gearbox cleanliness will be the standard level of performance for gear oils. Lubricants designed to meet these performance expectations will enable end users to maximize the efficiency of their equipment and time because lubricant- related issues will be minimized.