Specialty lubricants: The time has come
The extra initial cost of synthetics can be worth the improvements.
Plant operators are understandably concerned about delivering higher output over a shorter period of time. Accordingly, it's worth considering the contributions that specialty lubricants can make to enhance daily operations while investigating how machinery and productivity benefit from proper lubrication.
For example, if the equipment component is lubricated for life, selecting lubricants that employ synthetic base oils can provide benefits that include:
- Low-temperature viscosity performance
- High-temperature viscosity performance
- Decreased evaporative loss
- Reduced friction
- Reduced wear
- Improved efficiency
- Chemical stability
- Resistance to oil-sludge problems
- Extended drain intervals.
Along with these benefits, however, synthetic lubricants are more costly than nonsynthetics. But that cost is often mitigated by extended change and relubrication intervals, as synthetic and specialty lubricants with a high-quality base oil can last substantially longer than nonsynthetic lubricants. Other concerns may include potential oil-seal problems. An experienced professional can select a lubricant that will prevent these conditions.
Make the selection pay off
With regard to energy efficiency, some gear oils are more energy-efficient than others due to their lower coefficient of friction. Polyglycols, for example, are the most efficient and lowest-wear type of oils, particularly in high-sliding applications such as worm and hypoid gears. In these applications, polyalkylene glycol (PAG) offers a lower coefficient of friction within the gearbox, which often leads to requiring less power to operate resulting in a potential for higher efficiency.
Synthetic oils are more energy-efficient because they have better oxidation and thermal stability, which means the gear oil lasts much longer. In one scenario, where one could expect to change a mineral oil every 5,000 hours, a polyalphaolefin (PAO) or synthetic hydrocarbon oil could be expected to last approximately 15,000 hours before a change-out. Under the same scenario, the high-performing PAG can then last as long as 25,000 hours at that same temperature.
For OEMs, gear oil affects several design considerations, including the reliability of their final product. How much a manufacturer will increase the energy efficiency of a gearbox by using high-quality gear oil depends on the gear type.
The biggest increase can be realized in gear types that are challenged in normally lower efficiencies, such as worm drives. For example, a worm gear test rig can run at approximately 60% efficiency with a mineral oil. With a PAO, efficiency goes up to 70%, and with a PAG it rises to 78%. With the efficiency increases, the temperature of the gearbox drops. This decrease in temperature increases the life of the gear system. This may not sound significant with one or two gearboxes in a plant, but with hundreds of gearboxes that energy usage can add up.
Application factors in oil selection
The key requirement for selecting the proper lubricant is the base-oil viscosity. To select the appropriate viscosity, a supplier will need to gather information about an application, including the operating speed (variable or fixed), the specific type of friction (e.g., sliding or rolling), the load, and the environmental conditions to which the lubricant will be subjected.
For example, some lubricants, like PAG oils, are good for sliding friction but are not well-suited for rolling friction. Likewise, PAO oils are used for rolling friction and can handle some sliding friction, whereas silicon and perfluorinated polyether (PFPE) lubricants are typically used for extremely high temperatures. Industry standards may also be an important factor in lubricant selection.
During the information-gathering stage, equipment owners often make the mistake of overlooking some basic application details, which can have a significant impact on the resulting lubricant's performance. For example, a supplier might ask detailed questions about the type of gears being used or about the cavity next to a bearing. These may seem like insignificant bits of information, but the answers to these questions are just as important as specifying the load or operating speed. When responding to these types of questions, don't generalize. It's important to provide as much information as possible and to be specific, as this will help operators and suppliers identify the lubricant best-suited to the task.
Moving to a specialty lubricant
Lubrication typically costs around 1% of the operating budget for a facility. Nevertheless, that 1% impacts many areas:
- Maintenance program: Optimizing lubricant formulations and application methods is important to control the lubrication schedule when production either can't be shut down or can stop only for a very short period.
- Environmental impacts: To meet higher demand, machine temperatures, loads, and speeds may all be increased. All of these things inevitably require the use of specialty lubricants to enhance machine performance.
- Machinery uptime:
- Higher loads and speed can stress the gearbox, requiring more frequent oil changes.
- Faster-moving chains may stretch, needing more frequent replacement.
- Forces on the bearing become more extreme, causing grease to melt out or premature failure requiring bearing replacement.
The real consideration, therefore, is not the cost of lubricants but the cost per unit of lost production or downtime due to changing a bearing or gearbox that failed as a result of improper lubrication. In comparison, the time spent evaluating proper lubricant selection or lubricant application is minuscule.
Today's manufacturers face more pressure to improve and preserve productivity. The demand for more efficient and profitable output is increasing. With those demands come the need to combine the newest state-of-the-art equipment with specialty lubricants that can match the performance and keep machinery running smoothly.
Ultimately, the first step in choosing the right lubricant is choosing the right lubricant supplier. A qualified supplier will provide detailed documentation and include test data that demonstrate the consistency and quality of the product being recommended. A reputable supplier will also spend time educating, so operators can make qualified decisions about equipment lubrication. Most end users and OEMs find that the extra cost of choosing high-quality synthetic gear oil is worth the effort. Properly applied, specialty lubricants will save energy and reduce operating costs through reduced maintenance, longer oil-change intervals, and less wear.
Toby Porter is food-market manager for Klüber Lubrication NA LP.
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