1. Scope

1.1.This test method covers the monitoring of trending breakdown of Ester I&II in ester based lubricants, such as polyol esters. The two categories are differentiated by the degradation pathway taken. Pathways may include oxidation and/or polymer formation. The former results in decomposition products, often gaseous, with lower molecular weights than the original esters of the lubricant. The latter results in heavier molecules, often liquid, that may include acids and aldehydes. Although these lubricants are more resilient to thermal degradation, heterogeneous catalytic surface reactions may accelerate the changes detected in the lubricant that may be detected by Fourier Transform Infrared Spectrometry. The changes from Ester breakdown I & II observed in FT-IR spectra will often result from the presence or absence of O-H stretches, not H-bonded and H-bonded, respectively 1.2.This method is intended to provide a consistent means of detecting the byproducts from the breakdown of Ester I&II in polyol ester lubricants. This data may then be used to monitor the operational health of machinery based on the breakdown of these lubricating constituents. 1.3.This method is based on trending differences of spectral absorbance and/or transmittance between the new lubricant reference sample and the in-service lubricant, or multiple samples over time. 1.4.Spectral data described in Practice E2412 is referenced in this method. For direct trend analysis, values are multiplied by 10 and reported in absorbance/0.1mm. 1.5.Maintenance action schedules and routines should be determined through intra-laboratory testing if possible or other methods to validate the consistency in the detection of ester breakdown by Fourier Transform Infrared Spectrometry. 1.6.This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Keywords

3.1DefinitionsFor definitions of terms relating to infrared spectroscopy used in this practice, refer to Terminology E131.:3.2Definitions::3.2.1Fourier transform infrared (FT-IR) spectrometry, na form of infrared spectrometry in which an interferogram is obtained; this interferogram is then subjected to a Fourier transform to obtain an amplitude-wavenumber (or wavelength) spectrum.:3.3Definitions of Terms Specific to This Standard::3.3.1condition monitoring, na field of technical activity in which selected physical parameters associated with an operating machine are periodically or continuously sensed, measured and recorded for the interim purpose of reducing, analyzing, comparing and displaying the data and information so obtained and for the ultimate purpose of using interim result to support decisions related to the operation and maintenance of the machine (ISO 13372).:3.3.2in-service oil, nas applied in this practice, a lubricating oil that is present in a machine which has been at operating temperature for at least one hour.:3.3.2.1DiscussionSampling a in-service oil after at least one hour of operation will allow for the measurement of a base point for later trend analysis.:3.3.2.2DiscussionAny subsequent addition of lubricant (for example, topping off) may change the trending baseline, which may lead to erroneous conclusions.:3.3.3machinery health, na qualitative expression of the operational status of a machine sub-component, component or entire machine, used to communicate maintenance and operational recommendations or requirements in order to continue operation, schedule maintenance or take immediate maintenance action.:3.3.4new oil, nan oil taken from the original manufacturers packaging, prior to being added to machinery.:3.3.5reference oil, nsee new oil.:3.3.6trend analysis, nas applied in this practice, monitoring of the level and rate of change over operating time of measured parameters.:

Rationale

Periodic testing of machine lubricants is an effective method to avoid downtime and costly repairs of parts that may be have salvaged if the health of the lubricant was known. It is particularly important to be aware of ester breakdown because these fluids are used in aircraft turbine engines where it is critical to accurately and reliably predict a fluids performance, especially in extreme environments. Fourier Transform Infrared Spectrometry typically covers a samples absorption of light between 4000 cm-1 and 550 cm-1 with varying measurement capabilities and Signal to Noise ratios (S/N), depending on instrument manufacturer. Conditions of the oil, such as oxidation, nitration and ester breakdown, and contaminates of the oil, such as water and glycols, may be detected using FTIR. These results are then compared to trending data to determine whether action should be taken to remedy an issue with the machinery.

The title and scope are in draft form and are under development within this ASTM Committee.