Criticality Analysis Part 5: Tiered Maintenance – Matching Tools and Talent to Asset Risk

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Criticality Analysis Part 1: Why Criticality Analysis Is the First Step Toward Maintenance Maturity

Criticality Analysis Part 2: The Criticality Dilemma – So Many Assets, So Little Time

Criticality Analysis Part 3: Beyond “Critical” – A Better Way to Classify Your Assets

Criticality Analysis Part 4: What Maintenance Teams Can Learn From Healthcare Triage

Criticality Analysis Part 5: Tiered Maintenance – Matching Tools and Talent to Asset Risk

Criticality Analysis Part 6 : From Screening to Correction – The Complete Predictive Maintenance Workflow

In Part 4, we looked at how healthcare systems triage patients by matching the right level of care to the severity of the problem. Maintenance teams face the same challenge: how to manage hundreds of assets using limited staff and tools. The solution? A tiered maintenance strategy.

Let’s explore how this approach works in industrial environments—and how to apply it using the right mix of people, tools, and data.

Handling the Criticality Dilemma with Tiered Maintenance

Figure 1 illustrates how a tiered approach to maintenance addresses all the asset classes and uses a different mix of people, tools and data collection activities for each tier.

Noncritical assets may never receive care beyond simple screening and inspection. Semicritical assets only receive attention as problems arise. Critical assets are screened and inspected regularly, and problems would be escalated as needed, sometimes all the way to advanced analysis. However, notice that the star athletes actually start with advanced analysis, regardless of whether they are in poor condition or great condition. 

The machine pyramid (Figure 1) details the value and benefits of tiered maintenance. Remember the analogy of some assets as star athletes? Star athletes receive expert maintenance regardless of their condition. Notice that the star athlete is the sole domain of the expert analyst. Think of this in terms of health care:

• When do you and I get an MRI? Only if we have a problem that our doctor cannot diagnose.
• When does a professional athlete get an MRI? Every third Wednesday, regardless of whether they have adverse symptoms. 

The remaining assets would be seen by entry-level technicians that would use simple screening tools and experienced technicians using diagnostic tools. 

How to incorporate a tester into your maintenance program 

Here’s what happens if the machines in a typical plant are put into a pyramid as shown in Figure 2: 

• The few complex machines at the top level of the machine pyramid have many variables and require a vibration expert to compare, trend, analyze and diagnose the machine. The expert relies on years of training and experience to learn how to evaluate variables. On the upper right of Figure 2, notice how complex the waterfall trends and manual data analysis look. 
  
  
• Most of the remaining machines in the plant (more than 90%) are mainstream machines — motors, pumps, fans, compressors and blowers — that can effectively be diagnosed using automated diagnostic programs. The vibration tester (on the middle level) uses a database of real-world patterns developed throughout 30 years of analyzing real machines. On the center right side of Figure 2, you will see that an automated diagnostic tester provides machine faults and severity, along with a repair recommendation. 
  
  
• At the bottom level of the pyramid, the small and expendable machines that would typically be ignored can now be screened. Either remote, wireless sensors or a handheld vibration by trending overall vibration levels and using built-in machine health severity scales to indicate when more advanced tools are required. On the bottom right side of the table above, see the trend of the data from the vibration meter. 

The tiered maintenance actions for vibration are also shown in Figure 2. The Specialist using the analyzer is only needed for the star athletes or critical machines. The vibration tester can quickly be used by a technician to diagnose faults for the critical and semicritical machines. This leaves the vibration screener to cover noncritical machines. it can also be used to Screen critical machines and star athletes. 

The tiered model gives maintenance teams a realistic way to increase reliability without burning out specialists or overextending tools.

Next, we’ll show how this strategy fits into a complete predictive maintenance workflow—from screening all the way through correction and validation.

Read Part 6 : From Screening to Correction – The Complete Predictive Maintenance Workflow

Author Bio: John Bernet is a Mechanical Application and Product Specialist at Fluke Corporation. Using his 30-plus years of experience in maintenance and operation of nuclear power plants and machinery in commercial plants, John has worked with customers in all industries implementing reliability programs. He is a Certified Category II Vibration Analyst and a Certified Maintenance Reliability Professional (CMRP), with over 20 years of experience diagnosing machine faults.