What is Damaging Your Plant Machinery?

Ray Garvey Application Engineer

Ray Garvey
Application Engineer

“Why do some machines fail early, while others operate for many additional years?” Emerson’s Ray Garvey and Spectro‘s Pat Henning open with this great question in a Machinery Lubrication article, Identifying Root Causes of Machinery Damage with Condition Monitoring.

Machinery-Lubrication-Condition-MonitoringRay and Pat point to eight sources that can damage your plant’s machinery including:

…abrasion, corrosion, fatigue, boundary lubrication, deposition, erosion, cavitation and electrical discharge.

The good news is that condition monitoring can detect each of these life-shortening conditions to provide your maintenance team early warning to take corrective actions.

The authors note that four of these conditions, abrasion, corrosion, fatigue and boundary lubrication provide the majority root cause of plant asset failures. Abrasion:

…is usually a result of three-body cutting wear caused by dust contamination of the lubricating oil compartment. Dust, which is much harder than steel, gets trapped at a nip point between two moving surfaces. The trapped particles tend to imbed in the relatively softer metal and then cut grooves in the harder metal.

Stress waves are produced in the metal which can be detected [hyperlink added]:

…using high-frequency stress-wave analysis techniques such as Emerson’s PeakVue™ technology.

They highlight the importance of establishing lubrication cleanliness targets as outline in ASTM D7416, D7647 and D7596.

Corrosion:

…is a chemical reaction that is accelerated by temperature. The Arrhenius rate rule suggests that chemical reaction rates double with each increase in temperature of 10 degrees C.

It is best detected:

…using spectrometric oil analysis (SOA) such as rotrode (ASTM D6595).

Fatigue:

…is a consequence of subsurface cracking, which is caused by cumulative rolling contact loading of rollers, races and pitch lines of gear teeth… Eventually, the metallic hardening progresses to subsurface cracks accompanied by acoustic emissions like miniature earthquakes.

Ray and Pat share fatigue detection methods:

Acoustic emission or stress-wave analysis such as PeakVue is capable of detecting subsurface cracking that eventually produces fatigue wear. X-ray fluorescence spectroscopy (XRF) and ferrous density measurements are used to detect wear debris released into a lubricant….v

They point to the ASTM D7596 standard as a good approach for the particle analysis.

The fourth major root cause, boundary lubrication or adhesion:

…is a lubrication regime in which loads are transferred by metal-to-metal contact. For most machine designs, this is abnormal because preferred lubrication methods provide a lubricant film between load-bearing surfaces.

When the proper lubrication breaks down metal-to-metal contact occurs between the moving surfaces increasing friction levels. Condition monitoring to detect this condition include:

Contact ultrasonic measurements or high-frequency stress-wave analysis techniques such as PeakVue are capable of detecting friction produced by boundary lubrication (metal-to-metal contact). Oil-breakdown-related techniques such as viscometry, time-resolved dielectric (ASTM D7416), AN and BN are also relevant in this case.

You’ll want to read the article for a more detailed look at these conditions and their description of the other four application-specific wear mechanisms, which include material deposition, surface erosion, cavitation and electrical discharge.

You can connect and interact with other reliability and asset management professionals by joining the Asset Optimization, Maintenance and Reliability track in the Emerson Exchange 365 community.

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