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The hydraulic fluid 'laboratory in a suitcase'

The hydraulic fluid 'laboratory in a suitcase'

Dirty hydraulic fluid is the root cause of 80% of all hydraulic system problems. If hydraulic components are to last longer, the most cost-effective way to make that happen is through a comprehensive fluid cleanliness program.

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 when developing a cleanliness strategy. With today's technology it is possible to clean fluid to the point at which contamination is not a factor in the premature failure of any system component. This practical and achievable goal 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 very precisely defined quantitative value specified by ISO standard 4406 and based on the results of an approved laboratory particle counting procedure. It results in a cleanliness code that represents the number of particles of a specific size present in the sample. 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 maximise their useful life.

Once you have established reasonable cleanliness goals, it's time to develop a strategy to implement them. There are two phases: contamination control, which seeks to keep contaminants from getting into your fluids in the first place and contamination management, which seeks to remove those that do inevitably find their way into your system before they can damage it. An effective system rigorously implements both. But you can't do either of those things effectively if you don't have a way to measure the current condition of your fluids. Until recently, that has meant taking samples and sending them off to a specialised laboratory.

In the last few years a number of manufacturers have introduced highly capable portable systems that duplicate much of the analytical capability offered by traditional lab-based services. They make scheduled condition monitoring, as opposed to simple periodic testing, a viable process. 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.

Practical experience shows that condition-based maintenance can extend the useful life of a piece of equipment by 30-40% compared to a poorly-maintained one. That is on top of the economic benefit of increased uptime and availability for the well-maintained equipment, and the virtual elimination of unscheduled maintenance downtime.

The heart of any condition-based maintenance program is the 'laboratory-in a-suitcase' that 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 is flexible enough to work in either suction or pressure mode as well as 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 mpas
* Temperature in °C and °F
* Water saturation in % and for certain fluids the theoretical absolute water content in ppm
* Relative dielectricity

Users get simultaneous instant readings of particulate contamination and fluid ageing with a single measurement. The system has a colour LCD display and software to guide an operator through the test procedure. It also has integral data storage capabilities, is able to write to USB flash drives, and can transfer data to computers via LabVIEW-based software and an RS-232 interface.

In practice, the system is ideally used to document the condition of any new system, any system that has been opened to the atmosphere for maintenance or immediately after fluid replacement, to provide a baseline against which to compare future readings. Then, the system is periodically re-tested according to a schedule based on operating experience and the cleanliness recommendations of various component manufacturers.

The ability to monitor hydraulic and other fluids in real-time makes it possible to immediately diagnose component and seal wear, as well as providing a quantifiable basis for filter and fluid change intervals. Beyond that, the ease and simplicity of the testing procedure makes it practical to test and evaluate the impact of operational and environmental variables on overall system performance and operating cost.

For example, with a laboratory-in-a-suitcase available it is completely practical to test the condition of new fluids as they are introduced into a system to verify the effectiveness of off-line filtration systems, and the correct 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, or the pump outlet, or the return line, or somewhere else.

A fluid analysis professional will say 'all of the above' if you want a really useful, accurate insight into the condition of your system. That's probably not cost-effective on a routine basis using a professional lab, 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.

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Eaton Fluid Power

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