Hydraulic System Maintenance: Avoid Costly Mistakes

Hydraulic systems are the backbone of countless industrial operations, delivering immense power and efficiency when maintained correctly. However, even minor oversights in operation, maintenance, or design can result in significant expenses, reduced performance, or catastrophic failures. This article delves into prevalent errors in hydraulic equipment management, offering practical advice to help you sidestep these issues and ensure your systems operate with unwavering reliability and optimal efficiency. Whether you are a seasoned expert or new to the intricacies of hydraulic systems, understanding fundamental practices, such as selecting high-quality hydraulic oil and diligently maintaining filters, can profoundly impact your system's overall performance.

Mistake No. 1 – Changing the Oil Prematurely or Infrequently

The decision to change hydraulic oil should solely be dictated by two conditions: the degradation of the base oil or the exhaustion of the additive package. Given the multitude of variables influencing the rate of oil degradation and additive depletion, adhering to a fixed service hour schedule without assessing the oil's actual condition is akin to operating blindfolded. A paramount factor is the quality of the hydraulic fluid itself. Opting for a fluid engineered to meet the demands of modern, high-precision hydraulic systems is crucial for extending oil drain intervals. Conversely, discarding oil that still possesses adequate life is a direct waste of resources. On the other side of the coin, continuing to operate with degraded base oil or depleted additives compromises the service life of every other component within the hydraulic system. The definitive method to ascertain when an oil change is necessary is through comprehensive oil analysis.

Mistake No. 2 – Improper Filter Maintenance

A parallel scenario unfolds with hydraulic filters. Changing them based on a rigid schedule often results in either premature replacement or delayed action. Replacing filters too early, before their dirt-holding capacity is fully utilised, leads to unnecessary expenditure. Conversely, changing them too late, after the filter has entered its bypass mode, allows an increase in oil particle contamination. This subtle yet insidious increase silently diminishes the service life of all hydraulic system components, ultimately incurring far greater costs in the long run. The ideal approach is to replace filters only when their dirt-holding capacity is exhausted, but critically, before the bypass valve is activated. This necessitates a mechanism to monitor the restriction to flow, typically measured as pressure drop across the filter element, and to provide an alert when this threshold is reached. While a clogging indicator offers a rudimentary form of this monitoring, a more sophisticated and reliable solution involves continuous monitoring of the pressure drop across the filter.

Mistake No. 3 – Running Too Hot

While most equipment owners and operators are vigilant about engine overheating, the same level of concern is not always extended to hydraulic systems. However, much like an engine, operating a hydraulic system at excessively high temperatures is the most rapid pathway to destroying hydraulic components, seals, hoses, and the oil itself. How hot is 'too hot' for a hydraulic system? This is largely dependent on the oil's viscosity and viscosity index (the rate at which viscosity changes with temperature), as well as the specific types of hydraulic components employed within the system. As the oil's temperature escalates, its viscosity inevitably decreases. Consequently, a hydraulic system is operating at an unsafe temperature when the oil's viscosity drops below the minimum level required for adequate lubrication. For instance, a vane pump demands a higher minimum viscosity than a piston pump, highlighting how the type of components dictates the system's safe maximum operating temperature. Beyond the critical issue of lubrication, operating temperatures exceeding 82 degrees Celsius (180 degrees Fahrenheit) can damage most seal and hose compounds and significantly accelerate oil degradation. However, for the reasons previously explained, a hydraulic system can indeed be running too hot even at temperatures well below this benchmark.

Mistake No. 4 – Using the Wrong Hydraulic Oil

The hydraulic oil is arguably the single most critical component within any hydraulic system. It functions not only as a lubricant but also as the primary medium for power transfer throughout the system. Zinc-free anti-wear hydraulic oils represent a specialised category of lubricants designed to offer exceptional protection for hydraulic systems without relying on zinc-based additives. Traditional hydraulic oils frequently incorporate zinc dialkyldithiophosphate (ZDDP) as an anti-wear additive. While effective, zinc-containing oils can present environmental and compatibility challenges in specific applications. Zinc-free oils utilise alternative chemistries, such as ashless or phosphorus-based additives, to achieve comparable or even superior performance characteristics. For example, Hyperion Synthetic Blend oils are zinc-free, anti-wear hydraulic oils formulated to meet the stringent requirements of today's high-precision hydraulic systems, turbines, and air compressors. The viscosity of the hydraulic oil is a primary determinant of the maximum and minimum oil temperatures within which the system can safely operate. If an oil with a viscosity that is too high for the operating climate is used, the oil may not flow properly or provide adequate lubrication during cold starts. Conversely, if an oil with a viscosity that is too low for the prevailing climate is used, it will fail to maintain the necessary minimum viscosity, and thus adequate lubrication, during the hottest periods of the year. Furthermore, within the acceptable range of viscosities for proper lubrication, there exists a narrower band where power losses are minimised. If the operating oil viscosity is higher than ideal, more energy is lost due to fluid friction. If the operating viscosity is lower than ideal, increased power is lost through both friction and internal leakage. Employing hydraulic oil of the incorrect viscosity not only leads to lubrication damage and premature failure of major components but also results in increased power consumption (whether from diesel or electricity) – outcomes that are highly undesirable. It is also important to note that blindly adhering to the blanket recommendations of the machine manufacturer may not always guarantee the correct viscosity oil.

Mistake No. 5 – Wrong Filter Locations

The notion that 'any filter is a good filter' is fundamentally flawed. Certain hydraulic filter placements can, in fact, be detrimental, rapidly destroying the very components they are intended to protect. Specifically, filters should be avoided on the pump inlet and on the drain lines from the housings of piston pumps and motors. This advice may seem counterintuitive to the conventional wisdom that a strainer on the pump inlet is necessary to shield it from debris. However, it's essential to recognise that a pump draws oil from a dedicated reservoir, not from a rubbish bin. Furthermore, if you consider the ingress of debris into the hydraulic tank to be a normal or acceptable occurrence, then a fundamental issue with your system's design or cleanliness protocols needs addressing. If maximising pump life is your primary concern, which it should be, then ensuring the oil can freely and completely fill the pumping chambers during each intake stroke is far more critical than protecting the pump from items like nuts, bolts, or spanners. These foreign objects pose no significant danger within a properly designed reservoir where the pump inlet is positioned at least two inches from the bottom. Research has indicated that a restricted pump intake can reduce the service life of a gear pump by as much as 56 percent. This effect is even more pronounced in vane and piston pumps, as their designs are less tolerant of the vacuum-induced forces generated by a restricted intake. Hydraulic pumps are not designed to 'suck' fluid forcefully. A different set of complications arises from filters installed on the drain lines of piston pumps and motors, but the outcome is similar to that of suction strainers. These placements can significantly reduce service life and lead to catastrophic failures in these high-value components. It is highly recommended to consult resources on 'Hydraulic Filter Location Pros and Cons' before making decisions regarding filter placement.

Mistake No. 6 – Believing Hydraulic Components are Self-Priming and Self-Lubricating

You would not knowingly start an engine without oil in the crankcase. Yet, the same oversight is surprisingly common with expensive hydraulic components. The reality is that if the correct procedures are not followed during initial start-up, hydraulic components can sustain serious damage. In some instances, they might appear to function adequately for a period, but the harm incurred at start-up ultimately dooms them to premature failure. Successfully navigating this challenge involves two key aspects: understanding the necessary steps and diligently remembering to execute them. Not knowing what to do is one issue; however, knowing but forgetting to perform a critical step can be incredibly frustrating and costly. For example, you cannot take credit for filling the pump housing with clean oil if you neglected to open the intake isolation valve before starting the engine!

Mistake No. 7 – Not Getting an Education in Hydraulics

The fundamental purpose of this article is to underscore that if you are involved in the ownership, operation, repair, or maintenance of hydraulic equipment and remain unaware of the latest best practices in hydraulic equipment maintenance, a considerable amount of money can be inadvertently lost. To further enhance your understanding and capabilities, consider exploring resources on making hydraulics more reliable, understanding the symptoms of common hydraulic problems and their root causes, the benefits of maximum efficiency hydraulic fluids, and how to define and achieve hydraulic fluid cleanliness.

Conclusion

Avoiding common mistakes in the operation and maintenance of hydraulic equipment is paramount to ensuring the reliability, efficiency, and longevity of your systems. From the judicious selection of hydraulic oil and stringent contamination control to consistent routine maintenance and comprehensive operator training, every facet plays a critical role in keeping your equipment operating at peak performance. By understanding and proactively addressing these potential pitfalls, you can significantly minimise costly downtime, enhance operational efficiency, and safeguard your valuable investment. While hydraulic systems are inherently complex, possessing the right knowledge and implementing sound practices will enable you to maximise their potential and maintain peak productivity across all your operations.