Papers and Case Studies

Old School Vibration Analysis Technology Still Applies Today

One of the advantages to holding a side role of Mechanical Engineering Professor at Colorado State University is that alumni occasionally donate extremely cool gifts. Upon moving offices recently I came across a donated device that I didn’t really pay much attention to when it was brought to my lab there last year. The unit is a Reed Vibrometer manufactured by the Korfund Company in approximately 1955 and was used in earlier vibration analysis techniques. Essentially the sharp tip shown in Figure 1 is placed on the structure. Then the user turns the dial in order to adjust the reed length. The reed is shown protruding to the right in the image. A corresponding frequency scale is read from the cylinder shown on the left side of the unit. The idea is that the user can identify the various source frequencies by manually tuning the unit’s first natural frequency to match each one. The reed resonance makes the frequency match obvious. The frequency scale is 10 – 250 Hz normally or 2 – 10 Hz if an included weight is attached to the reed. Once the frequency is tuned the user can then measure amplitude by using the attached scale – on the right in Figure 1 - and observing the value. If a more accurate amplitude measurement is desired, the unit could be attached to an oscilloscope and the voltage produced by the internal electromagnets and coil arrangement is plotted. Figure 2 displays the output when the reed is plucked.

The Korfund Company was founded in Germany in 1898 and its name comes from two German words meaning “Cork Foundation”. The company originally focused on vibration isolation. Its founder, Dr. Hugo Stoessel, took the company to New York City in 1923. Though morphed over the years, the company still operates today under the name “VMC Group”.

Figure 1. Reed Vibrometer manufactured by the Korfund Company in approximately 1955

The objective of this short article is not necessarily meant to be a history lesson or an endorsement for The VMC Group. The purpose is to point out a couple of key principles: 1) Vibration analysis and control have been around for a very long time. These are both tried and true technologies that have proved valuable since their invention which, by the way, dates back to as early as Pythagoras. 2) The basic procedure for vibration analysis hasn’t really changed since then. First, identify the expected frequencies. Second, verify these frequencies are actually there. Third, quantify the amplitudes so that the most offensive source is identified.

While I wouldn’t advocate trying to use this unit today, managing a condition monitoring program using vibration analysis doesn’t have to be complicated even with state-of-the-art technology. Even a basic program fully implemented with absolute consistency can produce very cost effective results.

For more information on implementing cost effective vibration analysis techniques in your organization, email Red Wolf Reliability or call 970-266-9005.