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Factors to Consider in Selecting Machines for Oil Analysis

Oil analysis programs are important as these can provide information on various equipment failure modes as well as on root causes of these failures. For most studies, more than 20% of oil analysis samples are non-conforming. This just tells that more than one out of every five samples show a condition needing to be addressed. For this reason, one must be careful in selecting machines that should undergo an oil analysis program.

Precision and optimization are required in the wise selection of machines to be included in an oil analysis program. This selection is a crucial attribute of the Optimum Reference State (ORS) and requires deliberate consideration.

Multiple reliability and maintenance evaluations including oil analyses and other machine condition monitoring methods rely on the assessment of Overall Machine Criticality (OMC). As a general rule, critical equipment must be checked more often than less critical ones. The OMC evaluates criticality in the terms of lubrication. This is calculated by multiplying the Machine Criticality Factor (MCF) relating to the consequences of machine failure with the Failure Occurrence Factor (FOF) corresponding to failure probability.

A machine’s standing for oil analysis can be determined through the OMC as well as the influencing factors listed below. • If the machine is exposed to failure-inducing conditions such as loads, speeds, shock, contamination, etc. • If the machine has chronic problems • If the consequences of failure are high (safety, downtime, repair costs, environmental effects, etc.) • If failures can be lubricant-induced (degraded or contaminated oil) • If failures can be discovered through the oil (e.g. wear debris from shaft misalignment) • If early detection is important

The Overall Lubricant Criticality (OLC) defines how important lubricant health is as well as its longevity affected by the probability of early lubricant failure and possible consequences for both the oil and the machine. The OLC can be used to evaluate the importance of saving oil. This is calculated by adding the OMC to the product of Lubricant Criticality Factor (LCF) and the Degradation Occurrence Factor (DOF).

The LCF explains the particular economic consequences of oil failure different from machine failure consequences. This is influenced by the lubricant cost, cost of downtime to replace the lubricant, flushing costs, as well as system disturbance costs. Units utilizing large volumes of expensive lubricants will consequently have higher LCF values.

The Degradation Occurrence Factor (DOF) is the probability of premature oil failure. Conditions affecting this include lubricant robustness, operating temperature, contaminants, and lubricant volume and makeup rate. • Lubricant robustness – Chemically and thermally robust lubricants as well as synthetics can lower the DOF • Operating Temperature – Accelerated oxidation and degradation can happen to lubricants unprotected from high operating temperatures like hot spots. These conditions can raise DOF. • Contaminants – Water, dirt, metal particles, fuel, glycol, refrigerants and other contaminants can abruptly shorten a lubricant’s service life. Presence of these exposures can raise DOF. • Lubricant Volume and Makeup Rate – Lubricant volume can be linked to the amount of additives available to avoid oil degradation, the projected runtime to complete additive depletion and contaminant density. Burning through the additives in systems with large volumes of lubricants usually lasts years. The makeup rate is the introduction of new base oil that dilutes pre-existing contaminants and the presentation of new additives that replenish the depleted ones in the system. DOF can be reduced with high oil volume and makeup rate.

Machines recommended for oil analysis are those scoring high in OMC or OLC values. Marginal OMC/OLC machines are also good candidates for a streamlined oil analysis program. Once machine has been selected, oil sample location, oil sample frequency, test slate, alarms and limits, as well as data interpretation strategy can be determined using the OMC and OLC values.

Having a great analysis program as well as utilizing high quality lubricants can help prevent potential equipment downtime that can lower plant productivity. Trust ILS to provide a comprehensive selection of high-efficiency air compressor lubricants, hydraulic oils, and gear oils guaranteed to meet requirements of various industrial applications. Browse our product offerings by visiting today!

About the Author
Randy Renick
Randy Renick has a Bachelor's degree from LSU. He is an STLE Certified Lubrication Specialist and has a 29 year work history in Industrial Lubrication. He is currently a Lubricant Consultant at The Industrial Lubricant Store.

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