Understanding the ABCs of CBM and CM

How to avoid program pitfalls and ensure condition monitoring success.

Jason Tranter has been involved with condition monitoring since 1984. He is the founder and managing director of Mobius Institute, whichis accredited to ISO 17024 and ISO 18436-1. Mobius has training centers in more than 50 countries and has trained more than 20,000 people in a classroom setting and many thousands more via e-learning. Tranter authored the majority of Mobius’ training material and is a member of ISO TC108/SC5.

During the live Q&A portion of the on-demand webinar “Setting up a condition monitoring program is easy, right? So why do so many fail?” Jason tackled several attendee questions related to core elements of a condition monitoring program that often get overlooked.

PS: Do you consider root-cause analysis a critical part of CBM?

JT: Knowing the root causes of failure is critical to successful condition based maintenance and reliability improvement. We can use our condition monitoring technologies to detect the root causes and eliminate them before the equipment is damaged. Or better yet, we can be proactive and take steps to avoid the root causes in the first place.

However, it should be said that it is better to know the root causes when we start the condition monitoring program rather than waiting for failure and then performing root cause analysis. The good news is that there is a great deal of industry knowledge about the root causes of rotating machinery and other critical equipment, and where we have gaps in our knowledge we can perform reliability centered maintenance analysis (RCM) or failure modes effects analysis (FMEA) in order to determine the root causes. Therefore we can design our condition monitoring program to detect the root causes and the failure modes, and we can design our reliability improvement program to eliminate the root causes. But when failure occurs, we can use root cause analysis and adjust our strategy to detect and proactively eliminate those root causes in the future.

PS: There are many elements of a successful CBM program. Unfortunately, not many companies are well-versed in many of the technologies. How would you suggest that a team or a person incorporate all of these technologies into a genuine plan?

JT: The first step is to develop a genuine plan. From that we can assess our current ability to implement that plan and determine what improvements are necessary.

Step one in developing the plan is to assess the criticality of each asset. That will tell us which assets absolutely must be monitored, which assets can be “run to fail” (because the consequences of failure do not warrant the effort and expense of condition monitoring), and which assets we would like to monitor if we have the resources.

Step two is to understand the root causes and failure modes (which was discussed in the first answer). That will tell us which condition monitoring technologies need to be utilized (and the time between tests). Based on the criticality, we can determine whether it is warranted to use one or more technology.

Now that we know which assets should be tested, the time between tests, and the technologies that should be used, we can determine whether we have the resources, skills and tools to perform those tests. At that point we may determine that it is necessary to add people to the condition monitoring team, train and certify those people, purchase new test equipment, or engage consultants. Utilizing consultants can help you jumpstart your program. It is up to you whether that is a long-term plan, or whether you use the consultants while you improve the knowledge and skills of the in-house team.

One thing for sure, it is critically important that all condition monitoring analysts understand more than one technology, and that the entire condition monitoring team, including the consultants, collaborate so that the earliest and most accurate diagnosis can be made.

PS: Can you describe the difference, in your experience, between condition-based maintenance and condition monitoring, or CBM and CM?

JT: Condition monitoring is me going around the planttaking measurements, getting an early warning of a problem, and hopefully getting the attention of someone to say: "Right, we have a bearing that's failing over here. We have some looseness there. We have contamination in the oil over there." And the company can then respond to that, and that's all good. In essence, though, you are just performing reactive maintenance with a longer warning time.

It is not uncommon for organizations to continue performing time-based “preventive maintenance” tasks in parallel with condition monitoring. The trouble is, not only is many of the preventive maintenance tasks unnecessary, many will also induce failure; they will be the root cause of the failures the condition monitoring team detects.

Condition-based maintenance is a very different philosophy. Utilizing the same analysis discussed in the previous question, we will determine which of the failure modes and root causes can be detected and which cannot. If we can detect the failure mode then we leave the equipment alone until we receive an early warning of failure and we plan and schedule the maintenance based on the condition. For the failure modes that cannot be detected, we may determine that they are “age related” failures (where we know with some certainty how many months, or production cycles, or miles traveled, etc. there will be between failure). For those failure modes we will perform the traditional preventive maintenance (PM) tasks based on the time to failure.

Therefore basic condition monitoring (CM) simply gives us an early warning of failure that we can react to, while condition based maintenance (CBM) ensures that no maintenance task is performed unless the condition indicates that it is necessary. We will still perform some time-based (or production cycle based, etc.) preventive maintenance tasks - and hopefully many of those will be proactive tasks that are designed to avoid failure.

When we understand criticality, the root causes, the failure modes, and the lead-time-to-failure (i.e. the P-F interval) we are in a strong position to develop an asset strategy that serves to eliminate the root causes (defect elimination), detect the root causes and failure modes and deal with them as necessary (CBM), and prevent the “age related” failure (PM).

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