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A “Greener” Hydraulic Lubricant Gets a Lift

Nov. 30, 2021
Market is changing, and fluid performance is keeping pace.

Spurred by new demands for efficiency, hydraulic equipment across the industrial and mobile markets is rapidly evolving. For hydraulic fluids and lubricants, this kind of evolution represents both a challenge and opportunity. Not only must these fluids be able to deliver robust protection under increasingly strenuous operating conditions, but they also can directly improve operational efficiency.

Among the current market trends and their implications for hydraulic fluids:

Increasing power density and internal pressures. Modern hydraulic system design increasingly prioritizes lightweighting and power density in order to best compete with electric systems that continue to gain marketplace traction. These design parameters result in much higher internal operating pressures, which can be as high as 450 bar in current mobile equipment. Pressure levels are likely to only grow higher.

However, higher pressure increases the potential for internal fluid leakage. This phenomenon can lead to a reduction in the clearances between moving parts, which can severely compromise machine durability. As such, lubrication here has needed to move from hydrodynamic protection into the mixed film region, requiring new additive technologies and formulation expertise.

Finer filtration. Higher pressures and lower clearances in hydraulic components also mean that fluids must remain very clean throughout components’ operating life. Wet filterability has become a critical fluid performance parameter for fluids because even tiny particles that may become trapped between moving parts can have serious consequences.

Smaller oil coolers and reservoirs. In order to save space and further reduce weight, the size of new oil coolers and reservoirs are smaller. The challenges here for hydraulic fluids are significant—in smaller applications, operating temperatures can increase by as much as 10°C, effectively halving the fluids’ life. Smaller cooler and reservoir sizes also mean that less fluid is doing the same amount of work, which may increase the severity of operating conditions. Such fluids must be formulated to demonstrate thermal stability, and increased additive levels will be required to maximize performance.

Increasing electronic and digital control. It’s more common for electronic control systems to match hydraulic pressure and flow to torque requirements, allowing machines to be automatically optimized for specific duty cycles. Digital valves allow more precise control of equipment both dynamically and statically. These valves are 25 to 100 times faster than analog valves and require special hydraulic lubricants. In these applications, hydraulic lubricants must demonstrate low air content and compressibility to enable such valves to function as designed.

In each of these instances, hydraulic fluid formulation must deliver new performance characteristics in order to better enable efficient hydraulic technology. Formulation expertise that combines the use of advanced additive chemistry to strike the right balance will be essential going forward.

In addition to hydraulic fluid’s ability to withstand modern hydraulic application conditions and provide robust protection, there are several areas in which the lubricant can directly contribute some important benefits. These include:

Improved machine efficiency. Hydraulic efficiency can be measured in several ways, including lowering fuel/electricity consumption, more work completed per shift, easier cold starts or some other criteria. For OEMs, specifying an upgraded hydraulic fluid that allows the machine to move more efficiently can provide instant gains at a fraction of the cost and time of reengineering the machine itself. For end-users, a higher-performance lubricant can help lower the total cost of ownership.

A good example is found in the plastic injection molding machine, a very common piece of industrial equipment that relies on hydraulic power. Projected across a consistent work rate of 24 hours per day, 365 days per year, a lubricant that provides 8.5% amount of efficiency can deliver:

  • A $98,113 annual reduction in electricity spend for end-users
  • Improved production of 566,031 units per year
  • An annual reduction of 174 tons in carbon dioxide emissions

Extended oil drain intervals. Hydraulic fluids that can provide long-term performance have a range of benefits. For operators, draining and replacing fluids can be an inconvenience, especially in autonomous applications. As such, most OEMs are investigating technology that can help extend the drain interval without compromising machine durability or performance. Fluids formulated with these needs in mind can be beneficial.

Sustainability. In hydraulic applications, large volumes of lubricant can inadvertently enter the environment via leakage or spillage, equipment breakdown or careless disposal. For these reasons, it’s increasingly important that fluids and lubricants are formulated in such a way that minimizes environmental impact. Sustainable and biodegradable formulations will likely become more common.

A lubricant solution that delivers robust protection can help a hydraulic machine live a longer and more useful life, preventing premature replacement—another way in which lubricant technology can contribute to holistic sustainability.

This article was authored by The Lubrizol Corporation.

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