What is the difference between criticality and risk analysis with regards to maintenance and reliability?

Criticality is a measure of how important an asset is to your process. The more critical the asset, the more of an impact it will have if fails.

Risk analysis, on the other hand, deals with both the probability of a given failure and the severity of its effects. A critical asset may not be high risk if it’s not likely to fail, and an asset that’s highly likely to fail may not necessarily be critical.

Performing Criticality Analysis

There are many ways to perform criticality analysis, one of which has to do with rating an asset based on its impact on various categories. These categories may include:

  • Health and safety
  • Natural environment
  • Operations
  • Customers

Give each asset a rating (often 1-6) on how severe its failure would be for each category. For instance, a failure in your conveyor system might rank a 5 on operations, but only a 1 for the environment.

Once you’ve ranked an asset in each of these categories, you might either multiply them together or leave them as individual criticality ratings. In either case, the higher the number is, the more critical the asset will be.

Risk Analysis

Risk analysis is a measurement of the total amount of risk posed by a given asset. The process takes the odds of a failure occurring and multiplying that by the asset’s criticality. Again, you might rank the odds of failure based on a 1-6 range.

To get an idea of how likely a given failure mode would be, you can use data tracked through your CMMS. By tracking data logged into your system, you’re able to determine how frequently a given failure mode occurs and see what the risk would be for that failure in the future.

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Using the Two Together

Criticality and risk go hand in hand when making maintenance decisions. The more critical the asset is, the more you’ll want to make sure it keeps running, but if it’s also low risk, it may not be as high priority in your maintenance planning.

Likewise, an asset that’s likely to fail but not critical to your operations won’t necessarily be high risk because a failure would have negligible impact.

On the other hand, equipment that’s both highly critical and failure-prone would take higher priority, so you’ll want to schedule preventive maintenance accordingly.