By Shaun Skilton, Product Manager; Andrew Baldwin, Engineering Manager; and Marc Williams, IoT Market Sales Manager, Parker Hannifin

Industry statistics show that a whopping 80% of hydraulic system failures are due to contamination. In many of these cases, undetected contaminants of various forms have clogged, blocked, or otherwise damaged fragile hydraulic system components. The result is a malfunctioning system that can lead to costly downtime and, depending on the application, possibly compromised air or water quality for workers in the area.

Contamination sources can vary. Sometimes they originate in the environment and ingress is from breathers or seals. Such is the case with moisture and/or dust. In other cases, (especially with metal fragments) there are indications that something within the system is breaking down. In either case, their presence can lead to system failure, if left unchecked, by compromising such critical components as bearings, pumps, and actuators, to name a few.

Given the narrow tolerances between most moving parts of the machine—measured in microns (0.001 mm or 0.00003937 in.) — even the smallest contaminants can prove problematic. Particularly concerning for machinery health are particles just small enough to fit between moving surfaces where they can become embedded in surfaces, propagating damage and a cascade of wear. Non-solid contaminants are also worth monitoring. Causing corrosion and lubricity issues, water, for example, in the form of excess moisture or condensation can wreak havoc with a system’s performance depending on the application and location of the machine.

It’s also worth noting that effective condition monitoring is not just about measuring contaminants or machinery wear. It can also be used to ensure that fluid quality is meeting OEM recommendations and standards. Some fluids, for example, can lose their lubrication or water retention capabilities and interfere with system performance. Viscosity also matters. If a fluid is too thick, it can’t adequately protect bearings, for example. It also requires more energy to pump. Conversely, but with similar effects, oil that’s too thin will not protect machinery either.

Smarter ways to monitor
Not so long ago, fluid analyses were done in laboratories. Maintenance crews or operators had to draw out a fluid sample and then drive or ship the sample to a contracted lab where it might take weeks to get results. Certainly, by the time the results arrive, the state of the fluid may have deteriorated. Today, readings can be displayed right on the vehicle or equipment to provide real-time results. With this approach, fluid quality is monitored continuously versus periodically, so it is easier to spot problems as they are developing rather than waiting for a potential catastrophic failure. Importantly, sensors facilitate in-service monitoring, so that systems can remain up and running at operating pressures and temperatures while analyses are being performed. In addition, there is an environmental advantage because fluid samples do not need to be removed for testing and then properly discarded.

The sensors used to monitor particle contamination are, for the most part, not new. Some of the technologies have existed for more than a decade. What is new, however, is how the monitored data is communicated. Wireless systems are more commonplace. And thanks to increased use of the Internet of Things (IoT), machines are more connected today, making remote monitoring possible and preferable. This means data can be accessed through a web-based platform from anywhere technicians, operators, or managers have an internet connection.

One of the greatest advantages of remote monitoring is around labor. Sending updates and alerts from a remote location minimizes the number of trained maintenance personnel needed onsite, whilst mitigating logistical issues and costs. It also eliminates the need to send in operators to dirty, hostile environments to perform the analysis.

Where it gets exciting is avoiding the double whammy of costly reactive maintenance and unplanned downtime/penalties. Remote monitoring helps industry shift from interval to proactive maintenance, targeting personnel at machinery in need of maintenance rather than traditional servicing of machinery that is healthy. In other words, it’s following the old adage “if it ain’t broke, don’t try and fix it.”

As monitoring systems have become more connected, they have become smarter in what they can do. For example, they can be programmed to identify predetermined levels of fluid cleanliness, as well as the threshold for deviation. Operators can be presented with a traffic-light interface, removing difficult interpretation of when parameters are out of range. With today’s greater connectivity, mounted sensors can immediately identify when hydraulic fluid quality is outside the designated threshold or is about to exceed the stated limits.

There is also value in understanding how quickly the system is getting out of its threshold, as this indicates the seriousness of the problem and determines how quickly action is required and, ideally, if intervention can be conveniently planned. Change and rate of change are valuable in making these decisions.

Depending on severity and speed with which the threshold is approached, the monitoring system can be programmed to take predetermined types of action:

1. Automatically order spares and schedule service or preventative activities
2. Send an alarm that requires more immediate human intervention
3. Slow down the system’s operation to allow time for remedial action
4. Switch to an auxiliary system that could, for example, initiate additional filtration until the quality of the fluid is restored to within its stated tolerance
5. Completely shut down the system to minimize potential damage

Since these types of decisions can be made automatically without much human intervention, the level of training and expertise required of the maintenance team is also less — an important benefit in today’s tight labor market where a large percentage of veteran technicians are retiring. The maintenance team can also focus and prioritize tasks that are demonstrably impactful to the smooth running of critical machinery.

Many of today’s advanced sensors can additionally monitor the performance of filters within a hydraulic system. Historically, filters were changed at a predetermined rate, either based on hours of use or tons of fluid processed. However, this approach does not take into account the actual performance of the filter. While filters are typically rated for specific durations or usage, it’s possible for them to outperform those ratings. Replacing a filter before it’s at full life is costly.

Differential pressure (DP) sensors are used to indicate when a filter is approaching its dirt-holding capacity. However, filters do not have a linear dirt to DP relationship. Therefore, the point at which the DP sensor will trigger is hard to predict without knowledge of particle contamination in the system, especially if something unexpected occurs. Particle contamination sensors within the hydraulic system provide real-time indications of system health, including what is removed by the filter, its efficacy, and how rapidly an issue is developing. Algorithms that predict filter blockage and servicing needs can be programmed into control systems so that appropriate action can be automatically taken. Should the hydraulic system have contamination well below limits, arguably, there is no need to pump fluid through the filter. Filtering on demand has obvious environmental and cost-saving credentials.

Looking to the future
Condition monitoring is by no means a new concept. However, as evidenced by the high percentage of system failures that can still be attributed to contamination, it is obvious that many companies are still not employing basic condition monitoring programs, let alone sensors that measure contaminants and fluid quality in real time. Regardless, remote monitoring technologies continue to advance. By connecting the monitors to the cloud using IoT connectivity, it is possible to use data captured and algorithms to predict when filters will reach capacity, when routine servicing is necessary or to avert otherwise imminent failures. Such intelligence leads to maximum uptime and more planned maintenance.

The bottom line is that, when implemented properly, the savings realized in reduced maintenance and downtime will typically far outweigh the costs of added filtration and added analytics.

Other advances to watch for in the area of remote condition monitoring include:

• Development of more low-cost, high-volume detectors, allowing for the use of sensors on more machines
• Sharing of data and analytics with third-party suppliers to collaboratively evaluate system performance and identify potential areas for design improvement
• Creation of digital twins that can be modeled on the computer to effectively push learning algorithms and reduce overall monitoring costs

Parker is an example of a company that is investing time and resources into these developments. Because of the company’s global reach, size and depth of product offering, it is well positioned to provide a full systems approach to the most cost-effective remote monitoring of hydraulic fluid particles.

Parker Hannifin
parker.com