Why are my filters plugging?
Fluid Life
A leading North American provider of fluid analysis and reliability services. Always reliable. All ways.
by Mark Shierman, Corporate Director, Client Services
When a filter plugs off unexpectedly, this usually indicates one of four possibilities. It could be due to increased contaminants getting in or increased wear being generated which plug off the filter faster than normal. Plugging could also be because of the filter being in service longer than expected and is overdue for a change. And finally, the filter may not be working correctly which requires troubleshooting the filter configuration and operation.
Filter Setup Evaluation
Filters that reach their capacity will often go into bypass, leaving the system unprotected from further contamination. This can lead to accelerated wear and increased risk of failure. As such, it is important to replace filters when needed, identify the source of the issue, and address these things on a proactive basis.
Premature filter life or filter bypass alarm fault codes may indicate the need to evaluate your filtration setup and needs.
Investigating the Issue
Reviewing recent oil analysis results may provide some clues, but this data will have a few limitations. Oil sample results may be a few weeks or months old and may not reflect the current reality. Basic oil analysis tests like ICP Spectrometry mostly evaluate particles <3 microns, while the debris being trapped in the filter is usually larger.
In addition to oil analysis, performing a laboratory analysis of the filter debris can be very useful for several reasons. This can help to identify
Fluid Life recommends filters be tested using SEM-EDS (Scanning Electron Microscopy – Energy Dispersive Spectroscopy). An SEM-EDS analysis provides a powerful assessment of the debris trapped in the filter. By adopting this best practice into your standard SOP’s, you will gain valuable insights into how best to maintain your contamination control program.
NOTE: All filters should first be drained of excess oil, wrapped in plastic, and packed in absorbent materials if possible.
Examples of SEM-EDS Filter Analysis
Example 1: A major producer of fertilizers and other products approached Fluid Life with a need to find out why their filters were plugging. SEM analysis found significant quantity of Tin wear metals in the filter exhibiting a combination of laminar and cutting wear. While there were trace amounts of outside contamination (silica and NaCl salts), Tin was the primary source of debris.
Another common metal debris identified in the sample was Iron-based particles exhibiting both laminar and cutting wear along with Iron-based small diameter spheres. Spheres may be an early warning of bearing failure, are abrasive, and can cause secondary wear. The analysis also found an alloy of antimony and lead most likely due to a bearing failure dumping debris into the filter.
This case is interesting because most of the filters we see are primarily filled with outside contamination or lubricant degradation products. Here, wear debris was the number one culprit and appropriate actions were taken to correct the situation and prevent future plugging issues.
Example 2: An oil and gas plant customer was experiencing weekly plugging of a filter on their steam turbine. Using SEM-EDS analysis, we found that the majority of metal debris present in the sample was Iron-based (e.g. steel, cast iron, and other Iron-based alloys) which exhibited laminar, cutting, adhesive, and traces of severe sliding wear. The majority of these particles measure under 87um, but there are a few large particles measuring up to 211.7um long.
In addition to the Iron-based wear, Silica-based outside contamination, both in particle and fibrous forms, measuring up to 116.2um and 248.5um long respectively were found. These contaminants are abrasive, hard minerals and can cause secondary wear. Other metal debris like Zinc, Lead and Nickel were found which exhibited laminar wear.
The analysis indicated that outside contaminants were getting into the turbine. We recommended the customer inspect all areas for the source of external contamination and check the condition of breathers and filters for signs of leakage, ensuring strict contamination control for new fluids, fill and inspection points. Monthly sampling and regular filter inspections were suggested to monitor for the large wear metals which can be a sign of bearing failure.
Take action
If you’d like to learn more about triggered SEM-EDS filter analysis or how to improve filter maintenance standard operating procedures, talk to us today.
Originally published on Fluidlife.com October 22, 2021