Extending Electric Motor Life: Preventative, Predictive & Reliability-Based Maintenance
Extending the life of electric motors is a priority for many industries, as downtime can be costly. There are many types of maintenance that are used to extend a motor's life, yet it's not always clear what each type entails. Here, motor rewind specialist Houghton International explains what is involved in preventative, predictive and reliability-based maintenance.
Preventative Maintenance (PM)
Preventative maintenance is carried out to identify potential issues through inspections and tests before they have a chance to have an impact. It is based on a single set of readings, which clearly indicate where work is needed.
Electrical tests can include measuring IR during motor shutdown and phase voltages and currents during normal operation. Although less common, it can also involve measuring winding resistance, inductance, capacitance and motor current signature analysis (MCSA).
If mechanical assessments are carried out, they can include vibration analysis (FFT spectra) and alignment. Of course, some preventative maintenance involves small adjustments to ensure the smooth running of the motor. This can involve cleaning, lubrication and the adjustment of belt tension and bolt tightness.
Predictive Maintenance (PdM)
Although different to PM, predictive maintenance involves forecasting when corrective maintenance will be required. This is often done by assessing and trending PM activities—these are normally electrical, such as IR, polarization index (PI) tests. Occasionally, they can analyse motor circuit parameters, current and voltage levels and MCSA results.
However, mechanical routines can also be trended, including vibration spectra and thermal scan test results. Through monitoring the performance of the motor, corrective maintenance can be scheduled before issues can arise. Essentially, you can predict the lifespan of parts of the motor and determine when maintenance and repairs will be needed.
Reliability-Based Maintenance (RBM)
Reliability-based maintenance — or reliability-centred maintenance as it's also known — is a way of determining the best combination of maintenance activities to ensure the reliability of the equipment, and the likelihood that the motor will continue to perform properly under specified conditions. RBM helps reduce maintenance tasks to the most cost-effective activities, so a thorough understanding of the motor and the consequences of its failure is required.