Criticality assessments can be daunting even for plants with sophisticated tools at their disposal. Where to start? Which assets should you include in the assessment? This is one of the most common questions we hear. Recently, one of our customers, a large industrial facility, said that all their assets were critical. Assuming that is the case, conducting a criticality assessment would be more like an endless loop with no beginning and no end. This is not how you want to begin your criticality assessment process.

Criticality assessments - a common sense approach

Maybe a better place to start is by making a list of assumed key assets and then calculating the cost of downtime and repairs. Your asset list may be surprising. One plant we visited, a large plywood manufacturing facility, indicated that their most critical asset was not the hundreds of motors that whirr constantly. Instead, it was the boiler that makes steam for the process.

The point of this exercise is to get started. If not, you won't know where to focus Preventive Maintenance and Predictive Maintenance resources. Additionally, your maintenance procedures will be at risk of merely reacting to Corrective Maintenance issues, and unsure of where to focus the proactive portions of your maintenance plan. So, here are some practical steps you can take to start a criticality plan.

1. Plan that your "first-cut" list of critical assets will not exceed 20 percent of all assets. Best practices from companies like  Life Cycle Engineering and others confirm this 5:1, or greater, ratio.
2. Conduct a survey of plant equipment, if one doesn't already exist in the maintenance plan or elsewhere. A team composed of Operations, Maintenance, Engineering and Materials Management should come together for this project. Be sure to include equipment operators in this discussion.
3. Apply a formula for ranking the criticality of assets once your inventory is complete. The following formula from Lifetime-Reliability.com is an excellent way to calculate asset criticality rankings.
   

Equipment Criticality = Failure Frequency (/yr.) X Cost Consequence ($) = Risk in $/yr.

By way of explanation, the cost consequence is the cost of lost production plus repair costs (labor + repair parts). One customer told us their cost of machine downtime was $500/hour/machine. That plant had many nearly identical machines. It was therefore relatively easy to calculate cost consequence because of the frequency and repeatability of these type repairs. In this case, Condition Based Maintenance was being used with all high value assets, as above. The job of maintenance and the storeroom was to minimize unscheduled downtime.

If you have a large base of critical motors, consider our eBook on Condition Based Maintenance for motors. There is also a downloadable motor CBM Analysis Worksheet that will help you prioritize motor assets.

If you want to take your assessment to the next level, consider Business Wide Consequences of asset downtime. We've looked at frequency times cost without applying a weighting to reflect business impact. Some asset failures may have catastrophic consequences resulting in loss of life, legal action and reputation problems for the entire business. Problems of that level magnitude usually impact the boardroom and the bottom line of the company.

Careful planning and criticality assessment work can stave off the impact of lost production. Done well, maintenance will know where to expend resources.