The hydraulic fluid "˜laboratory in a suitcase'

In a perfect world we would use perfect technology and remove all contaminants from all of our fluids. Unfortunately, we do not 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 failure of any system component that has not reached the end of its practical useful life anyway. 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 very precisely defined quantitative value specified by ISO standard 4406 and based on the results of an approved laboratory particle-counting procedure. While the procedural details are too complex to describe here, the important fact is that 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 is 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. They are equally important, and an effective system rigorously implements both.

But, you cannot 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 like Eaton's Internormen Fluid Analysis Service.

How to monitor condition

In the last few years, however, a number of 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 there still are some important tests that, so far anyway, only can be done in a laboratory. 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.

What today's portable systems do accomplish, however, is making scheduled condition monitoring, as opposed to simple periodic testing, a viable process for even small fleets. A condition monitoring programme makes it practical to make near real-time maintenance decisions based on the actual condition of hydraulic fluids and other lubricants.

The difference in results between a maintenance programme 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 and thereby ensuring system or equipment availability.

Practical experience shows that condition-based maintenance can extend the useful life of a piece of equipment by 30-40 per cent compared with 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.

A laboratory in a suitcase

The heart of any condition-based maintenance programme 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 degC and degF
• Water saturation in per cent 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.

It is worth noting that condition monitoring is an important tool for extending the life of equipment other than hydraulic systems. Eaton's Internormen OCM 01, for example, can be used to test foamed oils in the lubrication systems of large gearboxes typically found in wind power nacelles, ships and steel works.

Immediate diagnosis

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.

Key points

• 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 reduce the incidence of catastrophic equipment failures, streamline maintenance scheduling and maximise equipment uptime and availability. Those things, of course, will have an important positive impact on your bottom line.

Go to www.eaton.com/filtration to learn more about fluid cleanliness programmes with Eaton's "laboratory in a suitcase'.