Most individuals rely heavily on maintenance manuals and qualified product lists (QPLs) to determine the best lubricant. However, this strategy does not constantly deliver optimal lubrication for a specific gear system or maximum productivity in oil inventory management. It doesn’t help either that some OEMs only provide general specifications without particularizing operating temperatures, forcing you to choose one. Therefore, to select the suitable gearbox lubricant, you must first understand how they differ.
This article will discuss the factors to consider when selecting a lubricant, including its three basic types.
Factors To Consider in Lubricant Selection
Aside from choosing a gearbox lubricant from the maintenance manuals, there are several factors to consider. Here are a few examples:
Function
Lubricants serve a variety of purposes, including stabilizing the following:
- Friction: Reduction of heat and energy consumption
- Wear: Lessening of mechanical and corrosive wear
- Corrosion: Protection of surfaces from corrosive substances
- Contamination: Transportation of particles and contaminants to filtration and separation systems
- Temperature: Absorption and transfer of heat
You must first understand your application’s specific challenges, then choose the lubricant accordingly. For example, determine whether it will be constantly subjected to environmental conditions, such as high pressure, low temperature, and exposure to saltwater.
Ingredients
Lubricants may not appear to contain many ingredients, but there are multiple additions to the base oil that are carefully chosen, depending on how and where users will apply them.
Greases are oils with additional thickeners composed of fibrous particles that act as sponges to retain the oil and increase its viscosity. Moreover, each type of thickener has distinct advantages and disadvantages, like shear stability, permeability, and water and heat resistance.
Terminologies
You must recognize and understand the terms used to make the best lubrication selection. The following are words you might encounter:
- Viscosity: This characterizes how thick or resistant the oil or grease is to flow. Greater viscosity equals more excellent flow resistance.
- Kinematic viscosity: This refers to a fluid’s internal resistance to flow under gravitational forces.
- Weight: This pertains to how viscous an oil is or how it flows at a given temperature.
- NLGI consistency: This indicates the hardness and softness of grease. The numbers usually range from 000 (like cooking oil) to 6 (like cheddar cheese).
- Runout: This points to the ability of grease or oil to withstand higher temperatures, which generally makes lubricants less viscous.
- Shear stability: This characterizes the oil’s resistance to an adjustment in viscosity triggered by mechanical stress.
- Metal on metal: This refers to a circumstance when no lubricant is left in a bearing or other application.
Ease of Use
The specific equipment determines a gearbox lubricant’s method of application. For instance, an aerosol lubricant is enough for a simple hinge, whereas an accessible gearbox can be easily greased by hand.
On the other hand, automatic dispensers are recommended for complex or difficult-to-reach locations and must only be refilled every six months. Meanwhile, a continuous dispenser may be the best option for chains that require regular lubrication.
Longevity
Gearbox lubricants have a limited lifespan and must be replaced when it expires. Failure to do so can lead to runout, metal-on-metal contact, ruined bearings, and other problems that cause downtime and increased costs. Furthermore, monitoring the thermal performance of your equipment is a crucial way to track the lubricant’s lifespan. For example, oils are destroyed by excessive heat; therefore, it is recommended to perform heat tracking with digital calibration tools for thermal imaging and vibration analysis.
Lastly, consider knowing more about predictive maintenance (PdM). This scheduling trend is proving to be highly effective at saving costs significantly while keeping equipment operating at peak performance levels.
Cost
Some lubricants are more expensive than others, but this is because they have different ingredients and serve varying functions. Don’t just look at the container’s price tag to determine the lubricant’s actual cost. Instead, compare that figure to the cost of downtime or replacement, product loss due to halted production or contamination, labor hours, and other considerations that may be an issue for you.
Types of Gearbox Lubricant
While there are numerous variations, the types of lubricating oil used in gearboxes are generally categorized into R&O, anti-scuff, and compounded.
R&O
Rust and oxidation-inhibited (R&O) gear lubricants do not have anti-scuffing and lubricity additives, making them suitable for applications requiring chemical stability, corrosion prevention, and foam suppression.
Anti-Scuff
Anti-scuff gear lubricants contain special additives that improve film strength or load-carrying capacity. Heavy loads, slow speeds, and shock loading are machine conditions that necessitate using these lubricants.
Compounded
The compounded gear lubricant is combined with a synthetic fatty acid to improve lubricity and film strength. The most common use for this type is worm gear applications.
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