Live Demonstration of ODS and Modal Analysis for Beginners: Share Your Visuals on the Forum

05-07-2024
12 comments
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357

Question:

To all proficient experts in ODS and Modal Analysis: Would it be feasible for you to share a live demonstration, such as a visual of a damaged machine component, on this forum? This would greatly benefit beginners like myself in grasping the concepts more effectively. Looking forward to your insights. - Terry O

Top Replies

Check out this animation showcasing a motor that appears to be resonating. The video is titled S31412MP290_30Hz_Movie_2.avi.

06-07-2024
Vanessa Carter

Hello Steve, could you please review the database to confirm the following: 84 and 60 are facing 180 degrees apart in the Y axis, while 83 and 59 are also 180 degrees apart in the Y direction. If these values do not align as described, please make the necessary edits in the database to rectify any out-of-phase issues. Thank you.

06-07-2024
Gavin Russell

Hey Steve, how can we determine if the system is resonating (or what leads you to suspect it)? Is it because it's moving almost perfectly in-phase? Thanks a lot for the information.

06-07-2024
Gregory Hughes

Hello Felipe, I was anticipating Steve's response to your inquiry. Vibration measurements were taken at specific numbered points, with calculations made between these points to determine average movement. Points 59 and 60 are moving in unison but opposite to the other half of the motor, suggesting misaligned DOFs. To rectify this issue, adding a minus sign in the block file is recommended. Additionally, a mode shape is evident at point 74 on the base. Below is how I interpret the animation:

07-07-2024
Rachel White

I recently rediscovered this forum after a link was shared on the vib forum. I'll attempt to help answer Felipe's question, though Steve and Jon may have more insight. It appears to be a classic case of rocking base resonance, evident by a few key factors: 1 - A significantly higher H than V indicates a directional issue. 2 - The base is moving nearly as much as the machines themselves (around 50%), which is a telltale sign of a resonant base. 3 - It seems likely that the component between the pump and motor is a gearbox, leading to differences in running speed. The vibration aligning with the motor speed suggests resonance through the base. Agreeing with Jon, points 59 and 60 appear to be abnormal.

08-07-2024
Ursula King

Hi Terry, while a live demonstration posted directly on this forum could be challenging due to technical constraints, I'd recommend checking out some engineering YouTube channels where you can find comprehensive walkthroughs and demonstrations of ODS and Modal Analysis. Also, webinars are notably beneficial for this purpose, providing interactive learning experiences with proficient experts. Remember - no question is too trivial when you're keen to learn! I'll also look into finding an appropriate video that addresses your query and will post it if I can find one. Happy to help in your journey to understanding these concepts better.

09-01-2025
Laura White

More Replies →

Thank you for your patience. I must disclose that this was my first ODS/Modal project using ME'Scope and IOTech equipment, which leaves room for errors. Moving forward, I aim to redo this project and gather more data on the motor points. Apart from the structures displayed in the model, the pump is mounted on a steel plate supported by I-Beams. Although I collected data on the plate, it didn't show significant response, so it was excluded from the animation. To collect data at points 59 and 60, I had to adjust the orientation of my accelerometer from the standard +X / -Y / +Z to the flipped +X / +Y / -Z orientation. I updated the orientation in the block file to ensure correct data, though I acknowledge it may appear confusing. The reason for suspecting resonance is the distinct horizontal versus vertical vibration at running speed, with the FRF and Coherence data indicating a peak near 30 Hz. Seeking guidance from experienced individuals like Jon to confirm the resonance would be greatly appreciated. Thank you, Steve.

08-07-2024
Kevin Griffin

Pete, it looks like you may have mistaken the pump bearing housing/pedestal for a gearbox. Please refer to the attached image of the motor/pump for clarity.

08-07-2024
Jack Parker

In analyzing the base at point 74, a mode shape does seem to be present. To enhance resolution, additional points can be included in the base. To visualize the actual movement, consider activating the options "animate/contours/fill" and "animate/contours/values". To focus on the motor end of the animation, turn off the sub-structures for the fan and bearing pedestal, and then share a quad-view for a more detailed examination. It is possible that there is erroneous data present. While points 83 and 84 appear to be correct, points 59 and 60 may have issues. Verify the block data for these points and ensure that 83 and 59 are opposite in the "Y" direction, and 84 and 60 are opposite in the "Y" direction. The reason for the reversal in the "Z" direction is still unclear.

08-07-2024
Hannah Stone

Hello Jon, I wanted to share my experience with flipping the Z-Axis using a tri-axial accelerometer and magnets. I found success by mounting the accelerometer at points 59 & 60, which required a change in orientation to achieve +X / +Y / -Z. You can find more information on this method in the link provided: http://maintenanceforums.com/e...1082983/m/8911053104. Best, Steve.

08-07-2024
Erik Rivera

Steve, I have concerns about the polarity (phase) of your measurement points on the motor. The data indicates that the motor case is distorting, but I am skeptical that this is actually happening. When looking at points 59 & 60 for horizontal motion, they should be moving outward while base points 73 & 74 for vertical motion should be moving upward. In our previous conversation referenced in the Link provided, we talked about challenges with mounting triaxial accelerometers. It can be tricky to ensure that the accelerometer axis (data channels) align properly with the structure's coordinate system (+X, +Y, +Z). I recommend checking mode shape plots (without any fancy animations) to ensure that the mode shape aligns logically. If not, further data is necessary to confirm any anomalies. Does this information resonate with you? Walt

09-07-2024
Diana Spencer

Hello Steve, I would prefer to discuss this matter privately via email, if that works for you. Your animation indicates that the horizontal radial is oriented in the "Y" direction, while the Vertical is in the "Z" direction and the Axial is in the "X" direction. This is why I have been emphasizing the importance of examining the data along the "Y" axis. I'm not sure if you've had a chance to review this conversation, but here's a valuable insight I gained through experience: Accelerometer Orientation.

09-07-2024
Penelope James

Hi Walt, I completely understand and share your concern. I will make a concerted effort to retrieve the data and pay special attention to the sensor alignment. Regarding the use of a tri-axial sensor discussed in a previous conversation, I am struggling to figure out how to capture data in all three dimensions at certain points. How is this accomplished with a single-axis transducer? Additionally, we have just completed an outage and the sister pump is now operational. Would it be beneficial to gather modal data with both pumps running? Alternatively, I could conduct an operational deflection shape analysis. It's important to note that when the turbine-generator unit is online, I am experiencing significant background vibration and interference from the main generator. Jon, I have sent an email as per our discussion. Thank you, Steve.

10-07-2024
Kyle Russell

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Frequently Asked Questions (FAQ)

FAQ: FAQs:

Answer: 1. Q: What is ODS and Modal Analysis? Operational Deflection Shape (ODS) analysis is a technique used to visualize and analyze the vibrational behavior of mechanical systems. Modal analysis is a method to determine the natural frequencies and mode shapes of a structure.

FAQ: 2. How can beginners benefit from a live demonstration of ODS and Modal Analysis?

Answer: A live demonstration can help beginners understand the practical application of these concepts by visualizing the vibrational behavior of a machine component and seeing how modal analysis techniques are used to analyze it.

FAQ: 3. Will the live demonstration on the forum provide insights into interpreting ODS and Modal Analysis results?

Answer: Yes, the demonstration can showcase how to interpret ODS and modal analysis results, helping beginners understand how to identify vibration patterns, natural frequencies, and mode shapes in real-world scenarios.

FAQ: 4. Who can participate in the live demonstration of ODS and Modal Analysis on the forum?

Answer: Proficient experts in ODS and Modal Analysis are encouraged to share their visuals and insights to help beginners grasp the concepts effectively. Beginners interested in learning more about these techniques can also join the discussion to ask questions and gain knowledge.

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