MOBIUS INSTITUTE - RELIABILITY IMPROVEMENT & VIBRATION ANALYSIS TRAINING AND CERTIFICATION PER ISO 18436

Mobius Institute - Vibration Analysis

Mobius - Analysis Tools

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Calculators, Simulators & Guides

 

As part of our Crystal Clear™ training methodology, Mobius Institute uses a vast library of Adobe® Flash® visual vibration simulators and calculators that we use in our training courses and computer-based software products.  These tools are so impressive and useful, we decided to make a few of them available to you in our myMobius Multimedia Library.  Start them up, and interact with them!  If you have any questions about our simulators or calculators, please don't hesitate to contact us at learn@mobiusinstitute.com.

Additionally, we have included several vibration severity guides to this section for your reference.  Many of them are interactive!  Bookmark this page so that you can reference it when needed to compare your vibration levels against industry standards.

CALCULATOR: Bearings

This Flash® program allows you to calculate bearing defect frequencies and then view them in a spectrum. Simply enter the number of balls, ball diameter, pitch diameter and contact angle and press "calculate." The bearing defect frequency calculator will then give you options for which defect frequencies to display in the spectrum. See ball spin frequency, inner race, outer race, harmonics and sidebands. Play around with the numbers and see how they effect the bearing defect frequencies and the patterns in the spectrum.

CALCULATOR: Fmax

What is the relationship between the Fmax or frequency range you select on your data collector, the number of lines of resolution, the time waveform length, the number of samples and the number of shaft rotations the test will capture? This little calculator will help you learn about these relationships or it will help to remind you if you forget.

The time record length (waveform time) is related to how long it will take to collect the data What happens if you select a higher number of lines of resolution? Does this effect the time record length?

What happens if you increase Fmax? Does this have any effect on the time record length?

CALCULATOR: Fmax from shaft rotation

If you want to analyze a gearbox in the time waveform and wish to configure your analyzer to collect three revolutions of the shaft, this calculator will help you determine what Fmax to use and how many lines of resolution you will need.

CALCULATOR: Gearbox

This program will calculate the shaft speeds, the gearmesh frequencies, and the Gear Assembly Phase Frequencies [GAPF] (from common factors) and the Hunting Tooth Frequency [HTF]. The utility will also simulate a spectrum with the shaft frequencies and gearmesh frequencies.

CALCULATOR: Induction motor

This Flash® simulator will let you play with characteristics of an A.C. induction motor. What is the relationship to the number of poles, the actual running speed and the slip frequency? How do these characteristics appear in the spectrum when the motor has a problem? How about motor rotor bars? Where do these appear in the spectrum and what patterns do they create?

CALCULATOR: Pumps, fans and compressors

What is the relationship between the number of pump impeller and diffuser vanes and the vibration produced by the pump? What is the relationship between the number of fan blades or compressor vanes and their relationship to fan and compressor vibration? This simple Flash® simulator will allow you to explore these questions and answers on your own.  

Enter a run speed, number of vanes (blades etc.), number of diffuser vanes and then press "Calculate."

You can check the boxes next to "Show harmonics" and "Show sidebands" to see the effect this has on the spectrum at the bottom. Use the Fmax slider bar to change the frequency range of the plot at the bottom to display the information of interest.

CALCULATOR: Units conversion

This powerful units conversion calculator allows you to convert all sorts of data units.

CALCULATOR: Vibration units conversion

This easy to use program allows you to convert vibration units from acceleration to velocity to displacement in both imperial and metric units, in/s, IPS, mm/s, g, rms, pk, pk - pk.

CALCULATOR: Waveform

This program will help you determine how many cycles of the machine speed will appear in the time waveform. You should aim to have 6-10 cycles, or 20 if you are using autocorrelation.

  1. Enter the approximate running speed of the machine and select the appropriate units.
  2. Select the Fmax chosen for the spectrum, and the appropriate units.
  3. Select the LOR (lines of resolution) in the spectrum or the number of samples desired in the waveform.
  4. The number of cycles will be displayed, and it will be simulated in the window.  The number of seconds captured in the waveform will also be displayed.

SEVERITY CHART: DLI Engineering

A severity chart produced by DLI Engineering in the 1980s that has a focus on velocity decibles (VdB).

SEVERITY CHART: Entek/IRD

A basic severity chart produced by Entek/IRD.

SEVERITY CHART: ISO 10816 Displacement

ISO 10816 Displacement - interactive vibration severity chart. This chart provides vibration alarm limits as per ISO standards in units of displacement. Click on the units button on the bottom right of the chart to toggle between imperial and metric units.

SEVERITY CHART: ISO 10816 DVA Imperial

ISO 10816 DVA Imperial - This interactive ISO alarm limit chart will help you determine acceptable vibration limits. Press the down arrow at the top of the graph to change the limits based on machine type and size. Press the frequency button on the bottom of the chart to toggle between Hz and CPM.

SEVERITY CHART: ISO 10816 DVA Metric

ISO 10816 DVA Metric - interactive vibration severity chart. This interactive chart will show you alarm limits for common machines. Use the arrow at the top of the chart to change alarm limits based on machine type and size. Highlight the machine type and the mounting type (flexible or rigid) and then click on the highlighted area to overlay these limits on the alarm chart. Use the frequency button at the bottom of the chart to toggle between Hz and CPM.

SEVERITY CHART: ISO 10816 Velocity

ISO 10816 Velocity - interactive vibration severity chart. This interactive ISO vibration severity chart provides vibration limits in units of velocity for typical machines. Press the "unit" button at the bottom right of the graph to toggle betwee metric and imperial units.

SEVERITY CHART: ISO 1925 - Mechanical vibration - balancing

Use this ISO 1925 chart to determine appropriate acceptable vibration levels and criteria for your dynamic balancing projects.

SEVERITY CHART: ISO Alert

This is a simple vibration severity chart in mils peak to peak and velocity.

SIMULATOR: Fan vibration

Adjust the speed and amplitude of vibration in this animated fan and see how these two varibales effect the time waveform. As you increase the speed, the wavelength of the sine wave decreases. As you increase the amplitude, the height of the sine wave increases. This simulator will help you to understand the relationship between the movement of the fan and the vibration produced by its movement.

SIMULATOR: Field balancing

We have a new single-plane vector balance program. Simply click and drag on the “original” vector and the “trial run” vector and you can see where the correction weight should be placed. You can move the location of the trial weight and change its mass. You can even set your phase convention (with rotation or against rotation (normal)) and you can add fan blades to see how the mass should be split between them. The original version of this program was purchased from Steven Young.

SIMULATOR: Mass and spring

Slide the bars to control the mass, stiffness and damping in this one degree of freedom mass spring system.

What happens to the frequency of the vibration (the rate at which the mass bounces up and down) when you increase the mass by sliding the mass slider bar to the right? What happens to the frequency of vibration when you decrease the mass by sliding the mass slider bar to the left?

What happens when you increase the stiffness? Think about a guitar string, what happens when you tighten the string? Does the note get higher in frequency or does it get lower?

Now play with damping. Does a change in damping effect the frequency of the vibration? Try this - move the damping slider bar all the way to the right and then press the "excite" button to set the mass in motion. What happens to the vibration? Now slide the damping bar to the left and press "excite" again. What is the difference?

SIMULATOR: Phase

In this simulator you can adjust the speed, amplitude and relative phase between two fans. This will help you visualize and understand the concept of phase. Simply adjust the knobs or type in values in the fields.

Imagine that there is a sensor on the top of the top fan. This sensor measures displacement (movement) and it only measures in the vertical direction. Look now at the graph to the right of the top fan. When the weight on the fan passes by the sensor at the top, the wave on the right is at its maximum. As the weight moves around to the right 90 degrees - the waveform reads zero. This is because the weight wants to pull the shaft to the right at this point, but our sensor is only reading in the vertical direction, so it reads zero. When the weight gets to the bottom, it wants to pull the shaft down and we see the waveform is at its maximum amplitude in the negative direction.

Now look at the bottom fan and notice it is doing the same thing. So what is phase? Phase is essentially describing how the two fans vibrate in relation to one another. When the fan vibration is synchonized, we can say that the fans are vibrating in phase.

Now, try setting the phase to 180 degrees. Notice the two fans are always moving in opposite directions. We can describe this relationship by saying they are 180 degrees out of phase.

SIMULATOR: Relation between acceleration, velocity and displacement

In this simulator you can see that as the mass moves around with the shaft, it creates a vibration. We can understand this vibration or quantify it in three different ways. We can talk about how far the shaft moves up or down or side to side under the influence of the mass(displacement). We can talk about fast it is moving (velocity) or we can talk about how fast it is speeding up or slowing down (acceleration).

SIMULATOR: Signal generator

This signal generator will help you understand how the waveform relates to the spectrum. You can add two or more signals together and see the resultant spectrum. You can also play with amplitude and frequency modulation as well as see how different windows affect the signal.

SIMULATOR: Variable excitation frequency mass and spring

This simulator is different from the other resonance simulator in that you can control the input excitation frequency of the system. Imagine that your hand is holding the mass at the top and you are moving your hand up and down at a particular frequency in order to make the spring and bottom mass vibrate. You can control the frequency of your "hand" with the bottom "frequency" slider bar.

What happens when the frequency slider bar is to the left of the resonant frequency displayed in the graph? How do the top mass (your hand) and the bottom mass move in relation to one another?

Now move the frequency slider bar to the right of the resonance. Now how do the top mass and bottom mass move in relation to one another?

Lastly, place the frequency slider bar right at the resonant frequency displayed in the graph. Now how do the two masses move in relation to one another?

The relationships between the resonant frequency of the system, the excitation frequency and the relative movements the top and bottom mass, are very important!

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