Filtering out the downtime

Shaun Skilton, product sales manager for the HFDE Condition Monitoring Business Unit of Parker Hannifin, highlights the importance of effective hydraulic oil filtration and condition monitoring in industrial settings

Maintenance and its associated downtime can represent a significant cost to manufacturing and engineering companies. In particular, the management of large, yet critical machinery, such as hydraulic systems - both static and mobile - can be time consuming and labour intensive, putting a significant drain on capital and adding to life cycle costs.

In many instances, regular maintenance of hydraulic systems is overlooked, partly because such systems tend to be difficult to access, and partly because some plant engineers mistakenly take the view that the robust nature of this technology means that it requires only minimal attention. The quality of hydraulic oil is rarely monitored effectively, with occasional oil changes being seen as the easiest, but not necessarily the cheapest, solution.

Many hydraulic devices are typically exposed to contamination and/or climatic extremes, including abrasive particulates, moisture and humidity. The danger here is that however robust a hydraulic valve, cylinder or accumulator, it will still rely on external seals, which can degrade in such conditions, allowing contamination to enter the hydraulic fluid and lubrication to be lost.

Contamination can also come from internal sources, such as the wear of moving parts, causing metallic particles to enter the oil.

Eventually this contamination means that the oil will lose its lubricating properties, leading to even more wear.

A reactive approach to maintenance means that the use of hydraulic oils can absorb considerable resources, particularly with the increasing price of this material and the costs associated with its disposal.

The monitoring of hydraulic oil condition and early identification of contamination is vital to prevent damage to seals, pumps, cylinders, valves and other components, which can degrade performance and eventually cause catastrophic failures. An efficient way to tackle this kind of predictive maintenance strategy is to use a combination of the latest condition monitoring technologies and a practical approach to filter replacement. Depending on the needs of the application there are both low and high end technology systems available. In each case, much of the equipment is automated and enables contamination levels to be accurately detected and measured easily at point of use.

Modern devices are relatively low cost and can eliminate particulates at levels far lower than was previously possible.

For applications requiring something relatively straightforward and simple to use, the latest handheld instruments provide reference correlation and repeatable results, detecting and measuring the dielectric constant of a small sample of oil to highlight changes in oil condition caused by the presence of water, particulate contamination, metallic content or oxidation. Parker's Oilcheck portable oil indicator, for example, is small, lightweight and battery powered. The most powerful version has internal memory capacity to store current calibration data and eliminate the need to recalibrate for each test sample.

Readings are displayed both as a numeric value to show positive or negative increases in dielectric and on a simple to read, circulate green/amber/red efficiency scale.

When used together, these displays allow even gradual changes in oil quality to be recorded and, in samples where contamination has reached a critical level, for a problem to be identified immediately.

Similarly, online particle detectors, such as Parker's icount series, use laser-based technologies for ultra-high precision particle detection. Once installed, these devices continuously monitor the cleanliness of the hydraulic oil, providing warnings of low, medium or high contamination levels through simple on-board LED indicators or via links to remote control systems.

Although these condition monitoring technologies can help engineers maximise the performance and service life of machinery, to be truly effective they need to be used in conjunction with efficient hydraulic filtration systems. The latest filter technology can remove exceptionally low levels of particulate and moisture contamination, while maintaining high flow rates. Such devices can prevent problems occurring by ensuring contaminants are removed before they can cause damage.

Filter elements require replacement at the intervals recommended by the manufacturer, regardless of their performance capabilities.

In some applications, with very high levels of contamination it may be appropriate to replace filters more frequently than normal, until the source of contamination has been identified and removed.

Sophisticated condition monitoring and filtration technologies, and proactive maintenance strategies, means servicing no longer needs to be something that eats away at time and profit.Maintenance can now be viewed as something that can cut costs and optimise the performance of critical equipment, which translates to significant benefits in productivity and profitability.