We have all seen the Bathtub Curve and its application to equipment reliability. This curve shows a high failure rate early in life (Infant Mortality), low failure rate throughout the middle of life, and another high failure rate towards the end of life. For this Tip we will focus on motor life or the life expectancy of the motor. All too often once a new motor has been installed and tested to optimize reliability by removing all anomalies during the Infant Mortality phase, we stop seeing the benefits of reliability testing. Test values continue to be normal and it becomes all too easy to justify canceling or pausing the recommended test routines necessary to see the onset of anomalies leading to a premature end of life. This unplanned failure of a critical motor creates a reaction resulting in renewed reliability interest and questions about why we didn’t see this failure coming.
Don’t let the cycle begin again. Keep the reliability discussion a regular part of management review. Present and justify the return on investment of Reliability by communicating the asset health assessment of the critical motors through verbal and written reports. Track the Bathtub Curve for each critical motor and help management recognize that keeping the critical motors in the low failure (middle of life) part of the curve does not come free and requires regular testing. With time and continued attention, the End of Life will be identified early and repair/replacement can be made without impacting production. Extending the Middle of Life section of the Bathtub Curve is an often overlooked benefit of a comprehensive reliability program and should be the goal of the reliability team. Adding years onto the expected life of a critical motor should be trackable and quantifiable from a financial perspective.
To see an example of the financial impact of halting the reliability program on a critical motor watch our latest case study on the PdMA YouTube Channel at https://www.youtube.com/watch?v=fCw3VIOktHM
