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Category: Tips

Vibration Experts

rotor unbalance

Rotor unbalance

Rotor Unbalance Rotor unbalance causes premature damage to  bearings and seals and greatly reduces the mean time between failures (MTBF) of machines. The vibration from rotor unbalance can cause false brinelling in standby machines and can reduce product quality. Vibration analysis can be used to detect rotor unbalance (or imbalance if you prefer) and most…
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Machine vibration test guide – free download

Download a free vibration test guide here. When setting up or managing a vibration monitoring program or condition monitoring program, it is important to document information about the machine and create a vibration test guide. (Audit it. Improve it! Getting the most from your vibration monitoring program. Buy it here) Here are the important things…
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Log Linear or dB Scales?

Log linear or dB scales? Log linear or dB scales? Which should you use? Log and dB scales better for analyzing vibration velocity spectra. Here’s why: Log or dB scales allow you to see small amplitude peaks in the presence of large amplitude peaks. The small amplitude peaks may be your rolling element bearing defects…
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Detecting bearing defects using vibration analysis – video

Detecting bearing defects using vibration analysis Alan Friedman describes the detection of bearing defects using vibration analysis from the time waveform, the vibration spectrum and amplitude demodulation.  This video is appropriate for anyone interested in machinery vibration analysis who wants to know about detecting bearing defects using vibration analysis. Bearing defects generate pulsations each time…
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Tip: Creating baselines and alarms

Creating baselines and alarms The best alarm limit or baseline is created from data from the machine itself tested under a predetermined set of conditions including a set load, run speed, test setups and test points.  If one keeps test conditions and test procedures constant over time then one can trend data to determine if…
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Tip: Create Case Histories

When using a condition monitoring technology to diagnose faults in machines or other plant assets, it is important to create case histories of each diagnosis, whether it was correct or not. If one uses vibration analysis for example, to detect rolling element bearing wear in a machine, and if this data is trended until a…
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Tip: Create a program flow chart

There is a difference between using a predictive technology for troubleshooting and using it in the context of a condition based maintenance program. In the latter, it is extremely important to define and standardize test procedures in order to insure that the machines are always tested in exactly the same way year after year. This…
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Tip: Change test frequency based on condition

Condition monitoring is a process of using a technology to detect changes in machine health over time in order to make a prognosis about when the machine will likely fail and to plan repairs or overhaul before that point. The frequency with which one takes measurements will depend on the machine, its current condition, and…
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Tip: Performing a bump test

A bump test is used as a quick and easy method to look for natural frequencies (related to resonance) in a structure. A bump test is conducted by hitting the structure with a moderately soft object like a 2×4 in order to make it ring in the same way one would hit a bell to…
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Tip: “As-found” condition

In condition monitoring programs, a technology will be employed to detect a problem with a machine or asset and a repair or overhaul may be conducted based on that information. Unfortunately, the overhaul is often conducted by another individual in the plant and the reliability engineer may never find out if his or her repair…
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Tips for Running a Successful PdM Program: Understand the Machine

Understand the machine By Alan Friedman When using vibration analysis or other predictive maintenance technologies, it is important to first identify the problem you want to solve and then consider the appropriate test or technology to solve it. More often than not, the cart is put before the horse and a technology is used with…
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