NOVEMBER 202319MANUFACTURING TECHNOLOGY INSIGHTSTime chart). And some assets may be better suited for more cost-efficient but delayed detection or even a "run-to-failure" model due to lower cost to repair (the Prevention-2 and Repair-2 curves). There are four basic maintenance approaches: REACTIVEThe Reactive approach has low or even no cost to implement but can result in a high repair and failure cost because no action is taken until the asset has reached a fault state. This approach might be appropriate when the cost of monitoring systems is very high compared to the cost of repairing or replacing the asset. As a general guideline, the Reactive approach is not a good strategy for any critical and/or high value assets due to their high cost of a failure.PREVENTATIVEThe preventative approach (maintenance at time-based intervals) may be appropriate when failures are age related and maintenance can be performed at regular intervals before anticipated failures occur. Two drawbacks to this approach are: the cost and time of preventative maintenance can be high; and studies show that only 18 percent of failures are age related (source: ARC Advisory Group). 82 percent of failures are "random" due to improper design/installation, operator error, quality issues, machine overuse, etc. This means that taking the preventative approach may be spending time and money on unnecessary work, and it may not prevent expensive failures in critical or high value assets.CONDITION-BASEDThe condition-based approach attempts to address failures regardless of whether they are age-based or random. Assets are monitored for one or more potential failure indicators, such as vibration, temperature, current/voltage, pressure, etc. The data is often sent to a PLC, local HMI, special processor, or the cloud through an edge gateway. Predefined limits are set and alerts (alarm, operator message, and maintenance or repair) are only sent when a limit is reached. This approach avoids unnecessary maintenance and can give warning before a failure occurs. Condition-based monitoring can be very cost-effective, though very sophisticated solutions can be expensive. It is a good solution when the cost of failure is medium or high and known indicators provide a reliable warning of impending failure.PREDICTIVE ANALYTICSPredictive analytics is the most sophisticated approach and attempts to learn from machine performance to predict failures. It uses data gathered through condition monitoring, and then applies analysis or AI and machine learning to uncover patterns to predict failures. The hardware and software to implement predictive analytics can be expensive, and this method is best for high-value and critical assets and expensive potential failures.Each user must evaluate the unique attributes of their assets and decide on the best approach and trade-offs of the cost of prevention (detection of potential failure) against the cost of repair and failure. In general, a reactive approach is only best when the cost of failure is very low. Preventative maintenance may be appropriate when failures are clearly age-related. And advanced approaches, such as condition-based monitoring and predictive analytics are best when the cost of repair or failure is high.Also, note that technology providers are continually improving condition monitoring and predictive solutions. By lowering condition monitoring system costs and making them easier to set up and use, users can cost-effectively move from reactive or preventative approaches to condition-based or predictive approaches.ABOUT THE AUTHORTom Knauer has more than 25 years of experience in the industrial automation industry, with equipment/solution suppliers including GE Fanuc, Parker Hannifin, Omron STI and Balluff, where he is currently the global business strategy manager for assembly, robotics and automation. There are four basic maintenance approaches:Technology providers are continually improving condition monitoring and predictive solutions. By lowering condition monitoring system costs and making them easier to set up and use, users can cost-effectively move from Reactive reactive or Preventative preventative approaches to condition-based or predictive approaches
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