An Introduction to Ferrography Techniques for Particle Size and Morphology Analysis

Oil analysis is an important predictive maintenance technology. Reliability or service professionals, whether managing a marine vessel, a locomotive or truck fleet, or fixed assets in an industrial plant, rely on oil analysis data to schedule maintenance actions.

The need to continuously improve uptime and lower maintenance costs requires in situ oil analysis results to make better decisions using oil analysis data and other predictive maintenance technologies.

However, the following challenges make it difficult to perform on-site oil analysis:

• Insufficient oil analysis instrumentation
• Lack of in-house expertise
• Logistics of handling hazardous chemicals and waste recycling

The FluidScan handheld infrared oil analyzer was specifically developed to deal with the above challenges faced by reliability professionals. It delivers fluid condition assessment based on Joint Oil Analysis Program (JOAP) and ASTM International standard practices.

The device protects machinery by determining when a lubricant has to be changed due to excessive degradation, contamination, or fluid mix ups, which are considered the most common causes of oil changes. FluidScan measures critical oil condition parameters in both synthetic and petroleum-based fluids and lubricants to detect lubricant contamination and degradation caused by other fluids (glycol, water, incorrect lubricant) at the point of use.

The FluidScan analyzes fluids and lubricants using infrared spectroscopy, a widely accepted technique used for testing contamination and degradation. It is designed to perform, display, and store the analysis with the same accuracy as lab instruments, but does so on-site in a handheld version.

The analysis information stored on the device's database can be synchronized with the FluidScan Manager software – a powerful database analysis package that runs on a PC, archives and trends data, and creates fluid condition reports.

The FluidScan lubricant condition monitor can be applied to all mechanical systems where unanticipated downtime, due to lubricant degradation and/or contamination, is unacceptable. Operators of heavy construction equipment, marine vessels, trucks, aircraft and military vehicles, power generation and mining equipment, wind turbines, or any large industrial system, can use FluidScan to establish predictive maintenance programs depending on oil condition rather than on a pre-set distance or time schedule.

The FluidScan provides instant on-site analysis of lubricant properties, and alerts users when it is time to change the lubricant due to degradation or contamination. The following are key benefits of real-time, on-site analysis:

• No waiting for laboratory analysis results
• Extended oil change intervals
• Reduction of unscheduled maintenance outages
• Prevention of catastrophic failures
• Reduced operational and maintenance costs

Figure 1. FluidScan Device

Patented Optics and Flip Top Cell

The self-contained handheld FluidScan analyzer provides rapid assessment of fluid condition to users. Sample preparation and time-consuming cleanup is eliminated with the use of a patented flip top sampling cell for quick and easy on-site analysis (Figure 2).

Figure 2. Patented flip top cell elimi¬nates the need for solvents to clean

A patented, mid-infrared spectrometer with no moving parts is the core of the FluidScan. The spectrometer collects the infrared light that is transmitted through the fluid in the flip top sampling cell into a waveguide. This waveguide then carries the light to a prism-like diffraction grating that reflects the light into a high-performance array detector, which registers the fluid’s infrared spectrum.

Figure 3. Patented wedged optical design

The waveguide fully contains the infrared signal, reducing any atmospheric interference and increasing the amount of light inside the spectrometer. In this way, the FluidScan handheld analyzer improves spectral resolution and optical throughput in a palm-sized device.

As a result, it provides a sufficient amount of resolution, signal-to-noise ratio, and spectral range for the rapid analysis of in-service lubricants. This unique technology has been optimized for low power consumption, allowing the development of a rugged, highly accurate, compact device that runs on Li-Ion batteries for up to eight hours.

Fluid status in real time is obtained using key infrared signatures of fluid condition, established by ASTM condition monitoring standards and industry norms. The user loads a sample into the patented flip top sampling cell, enters sample data, and begins an analysis using the intuitive user interface and navigation pad of the FluidScan.

Next, the status and supporting fluid condition parameters are determined and displayed to the user, and they can be stored for trending and exporting to a central database. The data stored on the FluidScan resides in a SQL database and the FluidScan Manager database software can be used to synchronize and download this data to a computer.

This software provides data logging, warning, trending, and alarm condition alerts. Although a PC is not required to operate the FluidScan, the FluidScan Manager desktop application makes data entry and reporting easier.

Multivariate Calibration and Data Correlation to Laboratory Results

Most oil analysis users will compare FluidScan results to those from a traditional off-site laboratory. Most laboratories use a combination of wet chemistry titrators and benchtop FTIR spectrometers to report lubricant condition parameters.

One benefit of the FluidScan over laboratory FTIR is that it can report absolute quantitative results for critical properties such as glycol, TBN, water, and soot for engine oils or water contaminations and TAN for industrial lubricants. Good absolute quantitative results can only be obtained through infrared spectroscopy by referencing the right fluid type and a calibration for that specific type of fluid property, as is provided with the FluidScan.

The FluidScan device classifies fluids into groups known as families according to their spectral signature, chemical makeup, and usage. In each family, the spectrum of all fluids changes in a similar way with a given amount of contamination or degradation.

These amounts are accurately measured by the assigned family-specific algorithms, which yield quantitative results for the most significant properties for the most common types of oils. Multivariate calibrations are applied so that quantitative readings can be acquired even with complex contaminated samples.

Spectro Scientific’s research, development and applications group has created an extensive library of spectra from a huge database of frequently used lubricants. Chemometric techniques are employed to automatically subtract the presence of interferents in a given calibration.

Soot is calibrated to soot percentages determined by thermo-gravimetric analysis; TBN, TAN, and water are directly calibrated to wet chemistry titration readings; and glycol and incorrect fluid percentages are calibrated to samples prepared with known concentrations of incompatible fluids and glycol. Table 1 summarizes the main FluidScan properties and the ASTM protocols to which they correlate due to this calibration process.

Table 1. Key FluidScan parameters and corresponding ASTM protocols

Table 2. FluidScan parameter settings by oil type

In order to apply the correct algorithms to a specific sample, FluidScan is used to measure the spectrum of a new oil of the same type as the in-service oil to be tested. The spectral matching software is used to analyze the new oil and the best possible match is made of the unknown sample with lubricants already stored in the FluidScan’s database.

Quantitative results can be obtained by applying the algorithms associated with that lubricant to those oil samples at any stage in its service life. An example of data correlation between the laboratory and FluidScan for TAN of in-service turbine oils is shown in Figure 4.

Figure 4. In-Service turbine oils Total Acid Number chemical titration vs. FluidScan

Alarm Limits and Reference Oil Library

In addition to reporting quantitative values for these properties, the FluidScan provides the results in an easy to understand “go”, “no go” format. This is performed by employing absolute warning and alarm values for each property. A simple green, yellow and red system is used by the report to indicate fluid within limits, over alarm limits, and near alarm state (Figure 5).

Figure 5. Go/No-go results based on alarm limits in the reference library

In addition, the system is pre-set with warning and alarm limits for properties related to each of the fluids in the FluidScan’s database. These default alarms are based on industry best practices. All alarm and warning limits can be fully customized, and every limit can be set with an upper and/or lower bound.

They can be modified to conform to particular applications or equipment manufacturer’s recommendations. A system in the FluidScan software enables users to define pieces of equipment as assets in the onboard SQL database of the device. Users can define each asset with its own set of property limits, and sample measurements are subsequently saved and associated to that piece of equipment.

The FluidScan features a built in reference oil library that is optimized for marine, automotive, railway, industrial, and military applications. The total library includes more than 450 synthetic lubricants and mineral of over 60 brands and growing. All lubricants come with starting values corresponding to data sheets or lab measurements.

The Validate Fluid function is a key feature of FluidScan, which matches the spectrum of clean samples with those in the reference library. Users can use this function to identify an incorrect lubricant before it is introduced into the system.

Conclusion

The combination of patented IR technology, unique calibration algorithms, sampling flip top cell, and large reference library with integrated alarm limits in the FluidScan puts the power of FTIR, TAN/TBN Titration, and Karl Fischer Titration into the hands of reliability engineers.

All of these are achieved without the need for expensive chemicals, lengthy measurement processes, or trained chemists to run the tests. FluidScan simplifies on-site oil analysis, allowing reliability engineers to perform oil analysis as they do thermal imaging and vibration analysis. By carrying FluidScan with them on a maintenance route, information from these three primary technologies can be easily integrated to make better predictive maintenance decisions.

This information has been sourced, reviewed and adapted from materials provided by AMETEK Spectro Scientific.

For more information on this source, please visit AMETEK Spectro Scientific.