A Dedicated Infrared Analyzer for Fluid Condition Monitoring

Infrared analysis has long been applied as a complement to wear metal monitoring. Recently, an instrument configured to meet the needs of a routine oil analysis laboratory was developed by Bio-Rad. This oil analyzer is a dedicated FT-IR oil analyzer configured for monitoring a wide variety of different lubricants and hydraulic fluids.

Infrared analysis has been applied in oil analysis laboratories for over 40 years. Originally, this was performed on slow scanning spectrometers, with the generated chart output (a plot of intensity versus wavelength, called a spectrum) interpreted by hand. This significantly limited the application of infrared analysis in routine condition monitoring, as a
through-put of approximatley 12 samples/hour was too limiting for most laboratories. With the advent of rapid scanning FT-IR, modern software algorithms for automatically interpreting the spectrum and an instrument configured with the necessary sample introduction and cleaning components, infrared analysis now becomes practical for routine and high-volume oil analysis laboratories.

The power of infrared analysis lies in the fact that every compound has a unique infrared signature. In fact, the infrared spectrum of a substance is often used in criminal cases as definitive proof of the compound's identity. In lubricant condition monitoring, this is employed to monitor key signature points in the spectrum, or integrated absorbance areas, to uniquely identify common contaminants and degradation faults particular to that type of system. For example, a petroleum based crankcase lubricant would be monitored for excessive degradation products in the oxidation and nitration areas of the spectrum, while a synthetic ester based fluid would be monitored for excessive degradation products in the ester breakdown area of the spectrum. The software on this dedicated analyzer can automatically generate an analysis report tailored specifically to the fluid or machine being monitored, without the need for an expert to interpret spectra or decide which measurements should be applied. Table 1 shows some of the most common condition signatures monitored by the FT-IR Oil Analyzer in various mechanical and fluid systems.

Typically, information from FT-IR analysis is used in the same manner as most other information generated during routine oil tests. While the individual value or magnitude of the most recent test is useful, the greatest information on the condition of the system is obtained from an analysis of the trends of the different measurements. For example, Figure 1 shows a plot of some readings from a typical diesel engine. Taking only the most recent readings, both the soot and oxidation readings would be considered excessive. However, the rapid increase in both these measurements as compared to other trends provides important diagnostic information. In this case, this combination of responses was due to a combination of the idle speed set too high and excessive idling.

The Bio-Rad Oil Analyzer is a dedicated FT-IR spectrometer incorporating the necessary optical and electronic components optimized for lubricant and hydraulic fluid condition monitoring, as well as an integral sample introduction, removal, and cleaning system. The software on the system is configured for operation by routine condition monitoring technicians, and automatically selects the correct method depending on the source of the sample. The software automatically checks to ensure that the sample has been loaded correctly, and that the system is adequately cleaned out between each sample. This unified approach results in a platform that allows an operator with minimal training to produce a complete and valid set of infrared measurements for a sample in a minute and a half or less. An optional X-Y-Z autosampler capable of holding any size field sample bottles is also available for the Oil Analyzer, with throughput of up to 60 samples/hour reported by some larger laboratories.

The Bio-Rad Oil Analyzer was originally created to meet the stringent demands of the US Department of Defense's Joint Oil Analysis Program (JOAP). This program has the objective of standardizing fluid condition monitoring techniques and instrumentation across all branches of the US military, and also serves as an important coordinating organization with allied forces. Evaluation and approval for use in the Joint Program was performed by the Technical Support Center (JOAP-TSC) in Pensacola Florida, and approval for use in the Joint Program was granted in November 1994 . Since that time, the Bio-Rad Oil Analyzer has become the choice of many commercial and in-house condition monitoring laboratories. And, the system with the high-throughput autosampler has become the standard for high-volume laboratories.

For more information on the Bio-Rad Oil Analyzer, please contact Bio-Rad Laboratories Spectroscopy Division at (800) 225-1248, or by e-mail at Oil@Bio-Rad.com.

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