Rotating Maching Life Is In The Oil Analysis
Industrial machines are generally supposed to have 40,000 hour (about 5 years) mean time between failures (MTBF). This only happens if you have “good lubrication”. If you have “poor lubrication” or “no lubrication” you get far shorter operating life.
How do you know when the lubrication is good or poor? There are four parts to this answer.
1. Keep the oil clean
2. Keep the oil dry
3. Keep the oil fit for use
4. Monitor the wear debris in the oil
First, keep the oil clean. “Cleanliness is next to godliness” is an old saying related to personal hygiene. Cleanliness is also very important when it comes to your lubrication systems. Graham Fogel reports that 46% of the abnormal wear debris is abrasive wear resulting from oil contaminated with dust and other hard particles. Many industry experts say that dirt-in-oil is public enemy number one. This root cause leads to many later problems when load-bearing steel is milled away by tiny quartz particles trapped between moving surfaces of bearings and gears. Be sure to monitor the particle counts and particle size distributions to validate target cleanliness levels (TCLs). If TCLs are not met, then corrective measures such as these should be implemented:
• keep oil supplies covered,
• install desiccating breathers on oil supplies and oil compartments,
• use appropriate filtration in-line, off-line, and when transferring oils.
Second, keep the oil dry. Corrosion is another major cause of early machine failure. An MIT study generalizes that 20% of all machines are taken out of service as a result of corrosion. What causes that corrosion? The most common cause is water. Other causes are coolant and process media. Lubricants are supposed to provide a sealed barrier preventing surface oxidation. Unfortunately this is ineffective when the lubricant is loaded with moisture and other corrosive materials.
Third, keep the oil fit for use. Do you have the right oil in each application? If so, has it become deteriorated? Lubricants perform a variety of functions, some of which are unique to specific applications. Following the recommendation of the original equipment manufacturers and your lubricant supplier each application is identified to receive one specific brand or mil-spec oil designation. Be sure to mark the oil supplies and oil fill points clearly and correctly. Also be sure to test viscosity and dielectric to validate correct lubricants are in use and that they remain fit for continued service.
Fourth, monitor the wear debris in the oil. Wear debris is your indication that surface damage is taking place within your machinery. Dust contamination, water contamination, and deteriorated oil are three root causes of damage to load-bearing surfaces. Misalignment, imbalance, excessive load, extreme temperatures, and many other roots also lead to internal damage that might be revealed through wear debris analysis. Wear debris analysis really is the referee you should rely upon to establish both severity and cause of problems revealed through used oil analysis.
Although blood does not actually lubricate your joints, you can imagine a variety of functional similarities between the blood in your body and oil in your plant machinery:
• Mixing different fluid "types" can be dangerous
• Systems carry fluid to all parts
• Systems transport heat
• Systems carry away solid and liquid impurities
• Fluids carry diagnostic information
• Fluid sampling is relatively non-intrusive and nearly painless
• Fluid change-out is intrusive and can introduce new problems
This analogy is intended to highlight the important fact that operational life of your machinery is largely determined by the good lubrication practices you employ. These good practices include keeping the oil clean, dry, and fit for use. In addition, you should periodically take a look at wear debris in the oil to see the nature and severity of developing problems.