This is still the elusive question and many plant operators are still confused about When and How to use Predictive Maintenance. The aim of predictive maintenance in the Chemical Process Industry is first to predict when equipment failure might occur, and secondly, to prevent occurrence of the failure by performing maintenance. Monitoring for future failure allows maintenance to be planned before the failure occurs. Ideally, predictive maintenance allows the maintenance frequency to be as low as possible to prevent unplanned reactive maintenance, without incurring costs associated with doing too much preventative maintenance.
Predicting failure can be done with one of many techniques. The chosen technique must be effective at predicting failure and also provide sufficient warning time for upcoming maintenance. Some techniques include:
- Vibration analysis
- Oil analysis
- Thermal imaging
- Equipment observation.
Choosing the correct technique for performing condition monitoring is an important consideration that is best done in consultation with equipment manufacturers and condition monitoring experts.
When predictive maintenance is working effectively as a maintenance strategy, maintenance is only performed on machines when it is required. That is, just before failure is likely to occur. This brings several cost savings:
- Minimizing the time the equipment is being maintained
- Minimizing the production hours lost to maintenance, and
- Minimizing the cost of spare parts and supplies.
These cost savings come at a price, however. Some condition monitoring techniques are expensive and require specialist and experienced personnel for data analysis to be effective.
Suitable applications for predictive maintenance include those that:
- Have a critical operational function
- Have failure modes that can be cost-effectively predicted with regular monitoring
Unsuitable applications for predictive maintenance include those that:
- Do not serve a critical function
- Do not have a failure mode that can be cost-effectively predicted
Advantages of predictive maintenance
Compared with preventative maintenance, predictive maintenance: ensures that a piece of equipment requiring maintenance is only shut down right before imminent failure. This reduces the total time and cost spent maintaining equipment.
Disadvantages of predictive maintenance
Compared with preventative maintenance, the cost of the condition monitoring equipment needed for predictive maintenance is often high. The skill level and experience required to accurately interpret condition monitoring data is also high. Combined, these can mean that condition monitoring has a high upfront cost. Some companies engage condition monitoring contractors to minimize the upfront costs of a condition monitoring program.
Not all assets have failures that may be more cost-effectively maintained using preventative maintenance or a run-to-failure maintenance strategy. Judgment should be exercised when deciding if predictive maintenance is best for a particular asset. Techniques such as reliability-centered maintenance provide a systematic method for determining if predictive maintenance is a good choice as an asset maintenance strategy for the particular asset of interest.
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