Two Minute Tips  

Shaft Alignment Know How: Repeatability

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    We have all heard the old carpenters’ saying: measure twice, cut once. When we start a shaft alignment measurement, we take two sets of readings with the same start and stop positions, following the natural rotation of the machine. This way, we make sure that the needed alignment corrections are precise. We call this repeatability. It means achieving identical measurement results in the same way, on the same machine, under the same conditions.

    A measurement table helps to keep track of these measurements. Once rough alignment has been performed, the results should be no more than one or two-thousanths apart, which is not the case in this example. It makes no sense to proceed with the alignment until, and unless, repeatable readings have been achieved. If repeatability is poor, there may be several root causes to consider, such as loose components, worn bearings, loose anchor bolts, and vibration from nearby machines, among other causes. Once the culprit is found and addressed, take two new sets of readings to establish repeatability. Now that repeatability has been achieved, as shown in this table, proceed with the alignment. Confidently perform the alignment corrections as called for by shimming your machine vertically and moving it horizontally. We look forward to serving your maintenance and reliability needs. Keep it running!

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LUDECA is a leading provider of Preventive, Predictive, and Proactive Condition Monitoring Solutions including equipment, software, rentals, repairs, field services, and training.