Understanding and Performing Criticality Analysis in Maintenance

As the name suggests, criticality analysis is a methodical approach to identify how critical an asset is to the business. In other words, a criticality analysis aims to evaluate potential risks and highlight any business impacts associated with such risks.

While each facility handles the exact process of criticality analysis a little differently, it’s an important part of maintenance planning. When prioritizing preventive maintenance tasks, determining assets to monitor for predictive maintenance, or evaluating schedule compliance, knowing the criticality of an asset will help you take care of the most important items first.

What is criticality analysis in maintenance?

Criticality analysis is a measurement used to prioritize assets in maintenance planning. It combines the seriousness and frequency of a potential failure and uses that information to rate the level of an asset’s criticality.

What is equipment criticality?

Equipment criticality describes the significance of a piece of equipment to the business. Critical equipment can be thought of as assets that potentially have a significant impact on the achievement of an organization’s objectives.

What is a risk matrix?

Two factors that determine the level of risk are – 1) the consequence of an event and 2) the likelihood of an event. A risk matrix considers these two factors to gauge the relative gravity of each risk.

How is criticality analysis done?

The specific steps in performing criticality analysis can vary, according to the type of organization and the industry that they are in. However, some general guidelines are similarly required in performing criticality analysis.

First, the analysis starts with agreeing on a risk matrix. The levels of risk and corresponding business value are identified in this stage. Next, the team needs to accomplish an accurate record of equipment and their hierarchy – this shows which assets would potentially affect other assets. Lastly, failure risks are listed per individual asset. This builds a comprehensive body of information that enumerates potential causes and effects of failure events.

How does a CMMS system help in criticality analysis?

By now, you may have realized how much criticality analysis relies on accurate data. This is where a good CMMS system comes in.

A CMMS enables you to track each asset in your facility. Tracking assets is necessary for monitoring maintenance schedules, breakdown records, and even real-time performance data. Investing in a CMMS also shows you how to more easily track equipment hierarchies. This makes you in command of all your assets – no matter how big or small.

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.

Component 1: Seriousness

The first component of criticality analysis is the seriousness of an event. In other words, it answers the question, “If this asset were to fail, how serious would the impact be?”
Of course, this is partly dependent on how critical the asset is to your processes, but there are other factors to consider as well, such as:

• Safety implications of the failure
• Cost and time to repair
• Environmental impacts
• Effects on product quality

If an asset’s failure wouldn’t necessarily cause severe disruption to your processes, it could still be serious if it presents a significant risk to your employees or to the environment.

Component 2: Frequency

The second component of criticality analysis is the frequency of a given failure. While certain equipment failures could be quite serious, they might be highly unlikely as well. As such, it might not make as much sense to prioritize preventive maintenance.

If a given failure mode turns out to be fairly likely, it might be worth prioritizing, especially if it would have a more severe impact.

Putting the two together

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.

Neither of these two components gives a full picture of criticality analysis on its own. Just because a certain failure mode is more likely doesn’t mean it’s always worth the cost of prevention, while more severe failures may happen too infrequently to worry about.

As such, the ratings you give for both the seriousness and the frequency of a given equipment failure mode would be multiplied together to show an asset’s level of criticality.

What is an RPN?

Seriousness and frequency give us the criticality of a failure mode, but it’s possible to add a third dimension to get a risk priority number, or RPN.

The third dimension: detection

The third dimension included in an RPN is how hard a failure mode may be to detect. The harder it is to detect, the more vigilant you’ll need to be.

Using the same range of 1 through 6 for detection as we did above for severity and frequency, a detection of 1 would be easy to detect while a value of 6 would be almost impossible.

Calculating the RPN of a failure mode

The RPN of a given failure mode is calculated by multiplying seriousness, frequency, and detection values together. Using a range of 1 through 6 for each category, the minimum an RPN can possibly be is 1 (lowest possible priority) while the highest is 216 (highest possible priority).

Caveats for using RPNs

Note that your RPN shouldn’t be the only metric you use when prioritizing maintenance tasks. Take the examples of two machines, Machine A and Machine B.

A maintenance team assessing the potential failure modes of Machine A assign it the following values:

• Seriousness: 1
• Frequency: 4
• Detection: 5

For Machine B, the values are:

• Seriousness: 6
• Frequency: 1
• Detection: 2

The RPNs for each asset are:

• Machine A: 1 x 4 x 5 = 20
• Machine B: 6 x 1 x 2 = 12

Machine A has a higher RPN than Machine B. However, the seriousness of a failure for Machine B is far worse than for Machine A, which makes it more critical. While the failure may not be particularly likely, its catastrophic results would still be worth working to prevent.

Put simply, look at the whole picture when planning maintenance rather than solely the RPN of a failure mode.

4 ways criticality analysis helps your business

In terms of the benefits of criticality analysis, there are a number of ways in which it can help your business. In general, it’s often considered a crucial part of managing a facility’s assets and processes for the following reasons.

1. Focuses maintenance efforts

One of the first benefits is in the way criticality analysis helps you focus maintenance efforts on items that matter most. With it, less time is spent on tasks that don’t mitigate the risks associated with your equipment, and you’re better able to keep your bases covered.

Often, those maintenance efforts may be simple preventative maintenance, but in others, criticality analysis can reveal the need to modify or overhaul equipment and processes in order to keep risks to a minimum. In either case, your time and resources are more fully concentrated in areas where they’re needed most.

2. Improve maintenance scheduling

Another way in which criticality analysis helps you is through improving maintenance scheduling. Often, it may seem like there’s too much for your maintenance team to do. When the number of tasks far exceed the number of schedulable hours, criticality analysis can help you prioritize the most important tasks first.

Even in cases where you have plenty of man hours to get everything done, it still helps streamline the scheduling process. Your maintenance scheduler is able to make decisions more quickly since they’re based on priority, creating an easily repeatable process for them to follow each week.

Effective scheduling practices are one of the factors that help organizations improve output efficiency, which means improving them through criticality analysis should yield a return in the long run.

3. Reduce risk

The core purpose of criticality analysis is to mitigate risk, which is a significant benefit for any business. By determining where failures are likely to occur and prioritizing the ones that would be most detrimental to your business, you’re better able to plan effective maintenance and overhaul tasks.

With the correct tasks in place, the various risks associated with your operations diminish, which has natural benefits when it comes to reducing your business’s overhead costs and overall liability.

4. Streamline costs

With less time spent scheduling and performing meaningless tasks, and with a lower incidence of expensive downtime events, the costs of running your facility become more streamlined. Businesses that perform effective criticality analysis may see reduced expenditures (or at the very least, more effectively utilized resources) in the following areas:

• Maintenance planning and scheduling
• Preventive maintenance hours
• Equipment downtime
• Major repair work
• Accidents and legal liability
• Asset replacement costs

Common criticality analysis myths and mistakes

Having explained the processes, components, and benefits of criticality analysis, it’s important to recognize the potential pitfalls that many organizations run into when they try to implement it. The following are common criticality analysis mistakes and myths that should be avoided.

Assuming you know it all

One of the most common errors that maintenance and operations personnel make is to assume they already know which assets are most critical. While they will be correct most of the time, there are instances where certain risks are overlooked or where their impact isn’t immediately obvious.

Often, criticality analysis will reveal risks that the maintenance team hadn’t previously considered, or it may help correct errors in how risks are treated. In addition, it can help preserve existing knowledge about criticality in your facility in the event that key personnel leave the company.

Assuming criticality analysis is too expensive

Given the time criticality analysis takes, many facilities may feel like it’s too expensive. However, it’s worth noting that criticality analysis should take a systems-level approach, so there’s often no need to analyze every single asset in your facility.

In addition, software solutions (such as a CMMS) and advanced analytics systems can reduce the time and labor involved in criticality analysis even further, making it easier than ever to assess the criticality of your assets.

Substituting FMEA for criticality analysis

Failure mode and effects analysis is key to helping you manage your assets, but it focuses primarily on individual assets’ performance instead of on the big picture of how they impact your processes.

Criticality analysis deals with the larger perspective of how a given equipment failure might affect your facility as a whole, and it can actually help you prioritize which assets you should focus on for FMEA, making that process more streamlined.

Over-maintaining critical assets

Many facilities perform criticality analysis only to end up misusing the data by over-maintaining critical assets. While the process is supposed to reveal which assets are most critical to maintain, it’s also meant to show you which maintenance tasks will be most effective in mitigating risks, helping you prioritize the most important PMs to perform and allowing you to discard those that would be ineffective.

Confusing condition with criticality

We often refer to assets at the point of failure as being in “critical” condition, but that’s not the same as asset criticality, which refers to what impact an asset has on your facility. With that in mind, just because a machine is failing doesn’t necessarily mean it’s a priority.

That said, it is true that failing assets may sometimes represent a significant risk to your facility. If a machine’s failure would have major ramifications in terms of process downtime, safety, or environmental impact, it should be treated as critical. If not, then it’s not as much of a priority.

Confusing cost with criticality

While important assets are often expensive, that doesn’t always mean that upfront cost = criticality. Often, less expensive machines may be integral to your operations, whereas more expensive assets may not have many risks associated with them, and thus wouldn’t be as high priority when it comes to maintenance planning.

Setting and forgetting criticality analysis

Times change, and so too do regulations, business objectives, and facility processes. As such, once you’ve performed criticality analysis once, you’re not done. You’ll need to perform it again at some point in the future to make sure your maintenance tasks continue to be prioritized effectively as your company.

Conclusion

Put simply, criticality analysis compares the severity and frequency of failure modes on key assets and helps you prioritize maintenance tasks accordingly. When it’s done correctly, it helps you improve your facility’s productivity, reduce hazardous incidents, and streamline overhead costs.