Lube-Tech
The Case Study: Steam Turbine Failure Paul Whiting CEO of DeltaXero, a manufacturer of offline fluid conditioning systems, was servicing a Steam Turbine at a Nuclear Power Plant in the UK that had failed due to the steam encountering the oil, resulting in hydrolysis. The oil was filtered with a nano filtration system, it was observed that the oil had dark carbonous particles along with a clear lacquer like particles. POLARIS Laboratories ® was approached to help with the root cause analysis of failure but also to help determine what caused the formation of these clear like particles to form. Together, POLARIS Laboratories® has partnered with DeltaXero to identify solutions for customers experiencing varnish contamination. We had already performed standard varnish analysis testing and determined that there was a micro-dieseling issue, while helpful, it didn’t tell the full story of what caused the failure. Paul’s mission was to understand varnish in all its guises, internal tests were not robust enough to give the answers to his clients and provide capable solutions. Clear gummy-like agglomerations were also identified in the system, but it was unsure if they were indeed varnish or a reaction from the steam interacting with the oil. Paul asked if there were any other tests that could be performed to help identify what exactly caused the failure and if we can detect the clear-like varnish formation in the oil. It was extremely important for us to understand what caused the catastrophic failure. After much discussion and troubleshooting together, I suggested a Micropatch analysis. This test would provide us with a visual aid and a more in-depth look at the contamination detected.
Micropatch Analysis A Micropatch analysis utilises a patch that is a 0.8-micron size, in which we take 1 ml of oil and filter it through the patch to capture non-ferrous wear and contamination that would otherwise not be captured in an Analytical Ferrography. Once the sample has been filtered and the patch had dried, we then review
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.140 page 2
the patch under a Microscope to help identify what caused the failure. It was a long shot, but I wanted to do everything possible to help Paul and his customer. Once the testing was completed what we found was astonishing. The Micropatch ended up detecting carbon particles that were encapsulated in a varnish agglomeration, upon further review we found large wear particles that had embedded in the carbon particle itself. Figure 1 shows the carbon particle that measured at 489 microns in size and the embedded wear metal had a micron size of 186.
Figure 1
This analysis confirmed initial suspicion that the clear gummy-like agglomerations were indeed varnish, but also highlighted a severe wear-related issue that otherwise would have gone unforeseen. Unfortunately, elemental analysis has a detection size limit of up to 8 to 10 microns in size. Any larger particles would not have otherwise been captured. Microscopic analysis is a useful tool to obtain a better visual for contamination, wear regime and/or oil degradation.
After seeing the value in what Micropatch analysis can do to detect not only wear, carbon, contamination, and varnish formation and other things, it led me to ask myself, is there value in doing Micropatch analysis on these types of systems with varnish contamination? Further investigation and research were needed to verify, and so began my 2-year research and development into Micropatch analysis for varnish. Over
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