Your Asset Strategy should be Technically Feasible and Economically Valid.
January 4, 2021by
G5 Consulting & Engineering Services, David Schultz
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Asset management is one of the best areas to start an IIoT journey. Many of the concepts of IIoT have existed within asset management for many years. The journey is the fundamental basis of a Reliability Centered Maintenance strategy. To those in reliability, the journey should seem familiar. For those that are not, take note at how the strategy evolves. Once again, it starts simply and gets more complex.
Reactive maintenance is the starting point of a reliability journey. This is performing maintenance after an asset has failed. However, this can be a costly strategy in terms of both equipment and downtime costs. While it seems to go against conventional wisdom, run until failure is a valid strategy. But it applies to very few assets. Most companies have since evolved to a preventive maintenance (PM) strategy. In this model assets receive maintenance after a period of time or number of run hours. Think of it as changing the oil in your car every 5000 miles.
Historically, preventative maintenance was managed and performed using what I call the analog method. Asset information and work orders were all tracked using paper files, filing cabinets and a clipboard. Generally, there was a significant amount of tacit knowledge used for implementing this strategy. When computers became common in manufacturing it led to the advent of aComputerized Maintenance Management System(CMMS). All of the files, folders and work orders were digitalized and accessed via a computer. This as an early example of digital transformation.
Often used in tandem with a CMMS, aprocess historianis a great tool for preventative maintenance. It is also a part of yourinformation management journey. While it is generally thought of for recording process variables (pressure, temperature, level flow) it can capture data relevant to asset health. Using the same trend tools, you can monitor asset condition and start to explore the process and machine conditions prior to a functional failure. Once you understand the factors leading to the problem, you can take preventive steps to keep it from happening again. It should be noted this activity is a building block in your asset management journey.
One of the challenges with preventative maintenance is that it is performed whether the asset requires it or not. While not performing maintenance is bad, over-performing maintenance is equally bad. A common example of this is theover-greasingof bearings. Every time you work on an asset, you induce risk. But knowing when to perform maintenance can be a challenge. The next step in your asset management journey is aCondition Based Maintenance(CBM) strategy.
Condition based maintenance, as the name suggests, is performing work on equipment based on a set of defined parameters. These can be operational hours, a period of time or a machine variable, like vibration. When one or more of these conditions is satisfied, a maintenance person is alerted that maintenance is required. Rather than changing the oil in your car every 5000 miles, you now change it based on time or driving habits. The goal of condition-based maintenance is to prevent you from both under-performing and over-performing maintenance. This is the step where you apply all of the information discovered in analyzing historical trends.
The early forms of condition-based maintenance occurred reactively by viewing trends process historian. This required a maintenance person to view certain asset conditions. Unfortunately, it is difficult to monitor all of this data. The good news is condition based maintenance tools already exist. It monitors data in your process historian to automatically generate an alert. Many of these tools integrate with your CMMS to generate a work order and document the maintenance. The better news is it leverages the efforts of your information management journey through its use of a process historian. Think of it as a two for one. The best news is the same information will be used for future steps in your asset management journey.
While CBM and PM are great strategies for asset management, the activities generated are reactive and based on events that already occurred. Utilizing the data and knowledge from the previous steps, you can build models to predict future behavior. The next step in your asset management journey isPredictive Maintenance(PdM).
By capturing historian data, models of process and asset behavior are developed. What predictive maintenance tools identify is how these variables interact with each other. This correlation of data is the basis of the models. If a variable starts to exhibit behavior that is outside its normal conditions, a maintenance person is alerted to the condition. It is possible this is normal behavior in which case the model is adjusted.
Using these models, you can extrapolate the data to predict future performance. Knowing that you will need to perform maintenance on an asset four weeks from now is much better than an emergency shutdown. It also gives you the ability to plan other maintenance that might be required. If an outage or shutdown was planned for some time in the future, you can decide if that outage should be moved up. Trucking companies use this strategy for maintenance on their trucks. Current technology predicts where a driver will be and actually schedules the maintenance for them.
It should be noted that predictive maintenance has historically been reserved for critical and expensive assets. It requires a lot of data and processing power. These was also a certain amount of expertise required to build the models and evaluate the data. Now that data collection and evaluation is much less expensive, PdM makes sense for much more process equipment.
Now that you have journeyed from reactive to predictive maintenance, it is time to get intoPrescriptive Maintenance(RxM). Instead of just predicting future performance, it tries to produce outcome-based recommendations. Not only do you know when an asset will require maintenance, you know what steps need to be taken to improve its performance. This is considered a future best practice. To be sure, very few companies are at this step-in their journey.
The concept of reliability centered maintenance is ensuring you are using the correct maintenance strategy for your assets. The decision on which one to use is based on both asset cost and criticality to the process. There are capital and operational costs and benefits with all of them. For sure, asset management is a journey. But, as previouslynoted, you should heed the advice of Occam and not add complexity when it is not necessary. A simple solution may be the correct one.