Year in and year out, dirty hydraulic fluid is the root cause of 80% of all hydraulic system problems. If you want your hydraulic components to last longer, the most cost-effective approach is through a comprehensive fluid cleanliness program that starts with contamination and condition assessment, implements effective filtration strategy for contamination management, and continuously monitors the results with regular sampling and analysis.
A fluid lab in a suitcase contains multiple instruments to assess the condition of hydrualic fluid, making it easy to maintain condition monitoring practices.
How to measure cleanliness
In a perfect world we would use perfect technology and remove all contaminants from all of our fluids. Unfortunately, we don’t live in a perfect world, so we need to consider factors like the practical limits of filtration technology, and cost, of course, when developing a cleanliness strategy.
With today’s technology you can clean fluid to the point that contamination isn’t a factor in the failure of any system component that has not reached the end of its useful life. This is a practical and achievable goal. Reaching it begins with setting a target cleanliness level based on all the relevant factors affecting the operation of a specific hydraulic system.
In this context, cleanliness is a precisely defined quantitative value specified by ISO standard 4406 and based on the results of an approved laboratory particle counting procedure. Although the procedural details are beyond the scope of this article, the result is a cleanliness code that represents the number of particles of a specific size present in a sample of specific volume.
Determining the appropriate cleanliness level for your system is a systematic procedure. Virtually all major filtration suppliers produce charts and guidelines to assist in identifying the most contamination sensitive components in your system and defining the cleanliness levels necessary to maximize their life expectancy.
Once you have established reasonable cleanliness goals, it’s time to develop a strategy to implement them. Implementation entails two phases: contamination control, which seeks to keep contaminants from getting into your fluids, and contamination management, which seeks to remove harmful contaminants that do inevitably find their way into your system. Contamination control and contamination management are equally important, and an effective system rigorously implements both phases. However, you cannot do either effectively without measuring the current condition of your fluids.
How to monitor condition
Until recently, measuring fluid condition required taking samples and sending them to a specialized laboratory like Eaton’s Internormen Fluid Analysis Service. In the last few years, however, many manufacturers have introduced highly-capable portable systems that duplicate much of the analytical capability offered by traditional lab-based services. Note the word much, because some important tests can only can be done in a laboratory — so far, anyway. None of these systems eliminate the need for periodic laboratory tests; they simply change the frequency with which they are required and the nature of the tests performed.
Fluid conditioning system
What today’s portable systems do accomplish, however, is make scheduled condition monitoring — as opposed to simple periodic testing — a viable process for even small fleets. A condition monitoring program makes it practical to make near-real-time maintenance decisions based on the actual condition of hydraulic fluids.
The difference in results between a maintenance program based on condition monitoring and one based on traditional time or process-based preventive procedures can be significant. The goal of condition-based maintenance is to prevent system or equipment failures before they happen by replacing worn components before they fail.
Practical experience shows that condition-based maintenance can extend the useful life of equipment by 30% to 40%. That is in addition to the economic benefit of increased uptime and availability for the well-maintained equipment, and the virtual elimination of unscheduled maintenance costs.
A laboratory in a suitcase
The heart of any condition-based maintenance program is a “laboratory-in a-suitcase,” which is used to determine fluid condition in real-time in the field. One example is the OCM 01 Condition Monitoring System from Eaton’s Internormen product line. It’s flexible enough to work in suction mode, pressure mode, or for handling traditional bottle samples. This compact machine can measure:
• contamination classes according to ISO 4406:99, SAE AS 4059, NAS 1638 protocols,
• dynamic viscosity in MPa,
• temperature in °C and °F,
• percentage of water saturation,
• theoretical absolute water content in ppm when applicable, and
• relative dielectric strength.
Users get instant readings of particulate contamination and fluid ageing with a single measurement using calibrated in-line sensors. The system has a color LCD screen and software to guide operators through the calibration and test procedure. It also has integral data storage capabilities, is able to write to USB flash drives, and can communicate with other customer systems via Labview-based software and an RS 232 interface.
The system is intended to document the condition of a new system, a system that has been opened to the atmosphere for maintenance, or immediately after fluid replacement. Doing so provides a baseline for future readings. The system should be periodically re-tested according to a schedule based on operating experience and the cleanliness recommendations of component manufacturers.
It’s worth noting that condition monitoring is an important tool for extending the life of equipment other than hydraulic systems. For example, it can be used to test foamed oils in the lubrication systems of large gearboxes typically found in wind power nacelles, ships, and steel works.
Monitoring hydraulic fluids in real time enables immediate diagnosis of component and seal wear and provides a quantifiable basis for filter and fluid change intervals. Beyond that, it becomes practical to test and evaluate the impact of operational and environmental variables on overall system performance and operating cost. For example, a laboratory-in-a-suitcase can test the condition of new fluids as they are introduced into a system. Results can be used to assess the effectiveness of off-line filtration systems and the storage and transport of the fluids. The difference between knowing the condition of new fluids and waiting for a laboratory analysis could easily be the difference between an efficient, reliable system and an early failure.
The convenience and flexibility offered by these devices also eliminates many of the either/or decisions that often constrain laboratory sampling. For example, if only one sample can be sent to the laboratory, should it be taken from the reservoir, the pump outlet, the return line, or somewhere else? A fluid analysis professional will answer, “All of the above,” if you want a really useful, accurate insight into the condition of your system.
This is generally not cost-effective on a routine basis, but it is easily accomplished with a laboratory-in-a-suitcase. In many cases, an advanced warning that prevented a major field failure would more than justify the cost of the testing equipment.
A reality check
A laboratory-in-a-suitcase will not eliminate the need for routine maintenance, but it will make the process more efficient and cost-effective.
It will not eliminate normal component wear and tear, but it will make the consequences more predictable and easier to avoid.
It will not eliminate the need for detailed laboratory testing, but it will reduce the frequency with which it needs to be done.
What it will do is dramatically reduce the incidence of catastrophic equipment failures, streamline maintenance scheduling, and maximize equipment uptime and availability. Those things, of course, will have an important positive impact on your bottom line.
Rick Jacobs is president of Eaton Filtration. For more information on Eaton’s Internormen monitoring systems, visit bit.ly/MADplE.