Downloaded from https://www.everyspec.com ADS-79D-HDBK LNF determines particle size, count and aspect ratio to facilitate analysis of lubricant cleanliness and particle morphology of larger particles. 87 LNF is automated, relatively easy to use, and can determine the ISO particle count (cleanliness). However it is limited to particles less than 100-microns and particles are seen in silhouette, rather than color as in Ferrography. The above tests represent the most common off-aircraft laboratory tests employed by the Army for rotorcraft. These test techniques are well documented and all have ASTM standards associated with them.
The major advantage of laboratory testing is the wide variety of tests available. M.6.1.2 Off-aircraft At-line: In the past decade, demand for more immediate machine condition information has resulted in more at-line testing instruments. 88 These instruments tend to be more rugged and often are easier to use than laboratory equipment. However, the instruments are generally designed for only one aspect of oil analysis (wear or fluid condition) and may require different types of samples than the laboratory oil sample, which is utilized for all the tests and instruments mentioned in Section 6.1.1.4. For instance, in filter debris analysis, a filter is the ―sample‖, rather than the oil.
Example at-line instruments are provided in the subsequent paragraphs of this section. M.6.1.2.1 Off-aircraft At-line Testing: The major advantages of at-line testing are that the results are immediately accessible to the soldier and some of the logistical problems with laboratory testing are negated such as mixed up samples, transport to laboratory, and long lead time for results. Additionally, the instruments are typically easy to use. The disadvantage is the instruments do not necessarily correlate to laboratory instruments and some generate only a simple go/no go result.
These tests still require a sample to be taken so the inherent problems associated with all off-line sampling procedures still exist. The Army currently does not routinely utilize any of these at-line oil analysis instruments. (See section 6.1.1.1). M.6.1.2.2 Off-aircraft At-line Tests: Several at-line oil condition monitoring test available include: Hand-held FTIR detects fluid condition (degradation, loss of additives) and organic fluid contamination (water, fuel, incorrect fluid).
The device is easy to use and deploy; requires only a few drops of oil; does not require sample preparation or solvent; has a built-in reference standard; and provides results similar to laboratory FTIR instruments. As with a laboratory FTIR, knowledge of the lubricant class (e.g., gas turbine versus diesel) is required. Filter debris analysis (FDA) counts and sizes particles by ferrous and non-ferrous, prepares a patch of debris for x-ray fluorescence (XRF) analysis, and performs XRF analysis to provide elemental composition of the debris.
The filter back flushing and instrument standardization are often automated in an instrument and all particles sizes (1-1000+ microns) are analyzed by the XRF. FDA provides early fault warnings since filters contain all the wear 87 ASTM D7596-10, Standard Test Method for Automatic Particle Counting and Particle Shape Classification of Oils Using a Direct Imaging Integrated Tester. 88 Garvey, R. ―Outstanding Return on Investment When Industrial Plant Lubrication Programs are Supported by International Standards‖, JAI, Vol. 8, No. 6, JAI103526, 2011. 249