Why You Should Be Using Vibration Analysis

Andy Page

Vibration analysis is the cornerstone of any condition monitoring program. The venerable Art Crawford (founder of IRD) said, "No single measurement can provide as much information about a machine as the vibration signature."

Gross defects such as severe shaft misalignment to subtle conditions such as differences in grease types can be detected with vibration analysis. As powerful as this technology is, it's often the most misapplied of the condition monitoring tools.

This article focuses on the proper philosophy behind the technology's use inside an overall condition monitoring program. While many maintenance and reliability initiatives incorporate vibration analysis, few people have a sound philosophical base for how it is to be utilized.

The proper use of a quality vibration analysis program can provide focus to the crafts personnel. The analysis of the vibration signature, when performed in a timely manner, pinpoints the precise nature and location of the problem.

This empowers the planning and scheduling process by allowing the crafts to go straight to the heart of the problem and not waste time on troubleshooting. Vibration analysis performed too late in the propagation of a defect won't help the crafts as much.

Waiting too late actually allows the defect to propagate beyond the physical part it initiated in and create even more work for technicians. An example is that, detected early enough, the shaft misalignment can be corrected before the bearing defect has even begun.

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Wait too long and not only are the shafts misaligned, but the bearings are defective and the bearing housings are damaged to the point that the bearings are loose in the housings.

At this point, it will be difficult to get a technician to extol the benefits of vibration analysis, as it has not resulted in any more efficient work or easier troubleshooting. The correct use of vibration analysis enables the crafts to focus their resources on the issues that make the greatest difference.

Another powerful benefit of vibration analysis is that it buys the planning and scheduling effort a substantial amount of time to actually work at a normal pace.

While any job can be expedited and hurried, jobs that don't require expediting are cheaper and easier by virtue of the fact that additional fees aren't paid for expediting parts, and less effort is expended in the reallocation of labor and other resources.

These activities lead to higher costs and higher stress levels within the planning effort. Having parts drop-shipped and air-freighted always cost more money. Having maintenance work teams working on machinery that hasn't already failed makes their jobs much easier.

Having a planning group and a crafts group able to take their time and not be rushed creates a less stressful environment and, thus, increases the conditional probability of correct execution of both the job plan and the job itself.

Vibration analysis identifies defects early enough to allow the planning and scheduling process the maximum amount of time to effectively and efficiently deal with the situation.

The single-largest error people make is to use vibration analysis to simply find yet another bearing fault, fix the fault and then celebrate the fact that a bearing defect was detected and corrected. This represents an incomplete understanding of the purpose of condition monitoring.

This attitude is referred to as "optimizing your run-to-failure maintenance strategy". By being satisfied with finding the defect and merely correcting it, you haven't improved your processes.

The only way lasting improvement can be made is to identify the latent root of the systemic problems that are creating these defects. Vibration analysis is a powerful tool for identifying the physical cause of the defect or the physical effect of the condition. This information empowers the root cause analysis effort.

Vibration analysis, when used incorrectly, does nothing more than optimize an organization's run-to-failure maintenance strategy. At this point, it is nothing more than a cost-added activity and not a value-added activity.

Using vibration analysis in this manner drives up costs, and direct benefits are difficult to quantify. However, used correctly, it provides some distinct benefits to maintenance and reliability efforts. It enables the crafts to focus their resources on the issues that make the most difference.

It empowers the planning and scheduling process to be able to achieve more in a shorter period of time and with less effort. And, it enables an RCA process that will allow for a much quicker and thorough identification and elimination of the root cause of the defect.

Now is the time to ask yourself, why are you performing vibration analysis?

 

Andy Page is the director of Allied Reliability's training group, which provides education in reliability engineering topics such as root cause analysis, Reliability-Centered Maintenance and integrated condition monitoring. He has spent 15 years in the maintenance and reliability field, holding key positions at Noranda Aluminum (maintenance engineer) and Martin Marietta Aggregates (asset reliability manager). Andy has an engineering degree from Tennessee Tech and is a Certified Maintenance and Reliability Professional (CMRP) through the Society for Maintenance and Reliability Professionals (SMRP). Contact him at pagea@alliedreliability.com.

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