â–º Monitor the fan geometry for any signs of deformation while in motion. Additionally, conduct a vibration test by removing the impeller to identify the source of the rattling noise. For optimal performance, ensure that the fan impellers are free from pockets or areas that may accumulate dirt, debris, or water.
Dear Shanmuga, I am seeking assistance in resolving an issue with unstable vibration in air fans at a waste water treatment plant. The equipment consists of three belt-driven air fans operating at a motor speed of 1470 RPM and a fan speed of 820 RPM (overhung fan). Despite performing rotor balancing to address suspected unbalance, the vibration amplitudes continued to rise, indicating a recurring issue. The fans draw suction from the atmosphere and have multiple filters in place.
Efforts to clean and replace filters, adjust mounting locations, and check damper positions yielded no improvement. Despite intermittent operation, the vibration levels remained high. Further attempts at balancing the fans saw temporary reductions in vibration amplitudes, only for them to increase again shortly after. The wet conditions of the fan impellers due to the enclosed operation and water in the housing during startup may be contributing to the issue.
Attached is the data for the fans for your review and feedback. Kindly share your insights on how to address this ongoing vibration problem.
Thank you,
Shanmuga Sundaram Packirisamy
The data sheet indicates that the motor experiences the highest vibration, not the fan bearings. This suggests that the peak speed of 820 RPM corresponds to the fan speed. If this is the case, why is the motor vibration higher than the fan bearings if fan unbalance was initially suspected as the cause? One factor that was not mentioned is the condition of the pulleys. It is important to ensure that both the drive and driven (fan) pulleys are concentric and not bent, as any anomalies in this component could potentially transfer vibrations to the motor. Additionally, it is crucial to check that the motor foundation is securely in place.
Unstable vibration issues with air fans in a waste water treatment plant are causing concern. Despite performing balancing on the rotor, the vibration amplitudes continue to increase, with a predominant frequency of 820 CPM. Cleaning filters, confirming damper positions, and intermittent operation have not led to improvement. It may be beneficial to consider the wet conditions in the fan housing and the drainage process before starting the fans. Checking the concentricity of the pulleys and the stability of the motor foundation could also help address the vibration issues. Feel free to review the attached data and provide your insights. Thank you.
The entire system is housed within the same frame on the first floor of a building, mounted on vibration isolators to prevent transmission of vibrations. It's not surprising to observe increased motor vibration, given that both systems share the same frame and the motor lacks proper support. Since the vibration frequency matches the fan's, motor issues have been ruled out. A solo run test by the client also showed minimal vibration levels. The fan pulley is not suspected as the vibration returned to normal after balancing. Similar symptoms in Fan 1 and Fan 3 confirmed pulley eccentricity. Could the rotor balance out and show normal vibration if the pulley is eccentric? Why does the vibration fluctuate over time? For resolving unstable vibration in air fans at a waste water treatment plant, it's crucial to check for pulley condition and ensure a secure motor foundation. Following the gathering of vibration data on all three fans on December 11, 2023, subsequent actions were taken to address the issue, including rotor balancing and fan cleaning. Despite these efforts, vibration levels continued to increase, indicating a persistent problem that requires further investigation and intervention.
It appears that the entire system is mounted on a single frame, which may contribute to the higher vibration observed at the motor compared to the fan bearings. It is essential to monitor both the magnitude and phase of the vibration. Any changes in the system, either in the force or response, should be carefully observed. During the balancing process, it is crucial to note if the correction weights were placed in the same position or not. It is also important to check if the phase changes while collecting data and if it changes over time. Inspecting the impeller and frame support system for cracks is recommended. Additionally, using a strobe light to check for abnormal motion of the shaft, pulleys, and belts can provide valuable insights. Consider the previous history of the fans - have they been running smoothly before experiencing issues? Checking the condition of the snubbers supporting the system is also advised to ensure they are not worn or improperly adjusted..*;
Potential keywords: vibration monitoring, motor vibration, fan bearings, balancing correction weights, impeller inspection, fan maintenance, shaft motion, belt inspection, snubbers, vibration isolators.
Shanmuga, Your provided information has sparked further inquiries due to the various balancing efforts and water presence in the air fan system. One possible solution could involve removing the belts and conducting a static fan balance check and correction to align with an 820 RPM wheel. However, it's crucial to note that balancing may not eliminate non-mass center related forcing functions. It might be advisable to keep the housing drain slightly open during operation to prevent the fan from acting as a pump. Consideration for the fan's overall performance and efficiency is critical in resolving the unstable vibration issue in the waste water treatment plant.+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-++-++-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-Mike Barkle****************************************************************************Contact: SHANMUGA SUNDARAM PACKIRISAMYSent: 01-09-2024 15:05Subject: Unstable Vibration in Air Fan @ Waste Water PlantGreetings,I require assistance in addressing an unstable vibration problem with the air fans at a waste water treatment facility.Key information regarding the equipment includes:- Air Fans: 3 in total- Equipment Type: Belt-driven- Motor Speed: 1470 RPM- Fan Speed: 820 RPM (overhung fan)The issue arose on December 11, 2023, when vibration data was collected showing high amplitudes in motor and fan bearings. Balancing was conducted on December 12, reducing vibration levels, but the problem resurfaced with dominant 820 CPM frequency readings. Despite cleaning filters, inspecting mounts, and assessing damper positions, vibration levels remain high, with a consistent frequency of 820 CPM. Additional attempts to add correction mass and rebalance Air Fan 1 provided temporary relief, but vibration levels increased again shortly after operation commenced.Important details to note include the fan's suction from the atmosphere, resulting in constant moisture exposure. Despite efforts to drain excess water before operation, vibration issues persist.Please review the attached data and provide your insights on how to address this recurring vibration problem.Taking steps to optimize the fan's performance and efficiency is crucial for resolving this issue.Your cooperation is greatly appreciated.Sincerely,SHANMUGA SUNDARAM PACKIRISAMYContact: +96569678166****************************************************************************
I conducted a static unbalance check prior to the initial balancing attempt by removing the belts, revealing no static unbalance in the system. The housing drain remained open, allowing water to be pumped out during pump start-up. Despite the fan housing being wet, there was no water present during normal operation.
In response to your query regarding unstable vibration in the air fans at a waste water treatment plant, I suggest performing a static fan balance check and correction by removing the belts. This method should help achieve balance, particularly with an 820 rpm wheel. It's crucial to address any forcing functions that may not be related to the mass center aligning with the center of geometry. Additionally, consider leaving the housing drain slightly open during operation to prevent the fan from turning into a pump.
If you need further assistance or guidance on resolving the vibration issue, feel free to reach out. Shanmuga Sundaram Packirisamy.
Hello Shanmuga,
I have a few questions regarding the unstable vibration issue in the air fans at the waste water treatment plant:
1. Is there any debris present in the wet airstream?
2. Did the problem start on December 11th?
3. Can you control the motor speed using a variable frequency drive? If so, does the imbalance improve? Is the issue only present at 820 fan speed?
4. Is the fan blade hollow foil? Could it have holes, cracks, or welds that allow water or debris to collect in the blades?
Matt Reynolds
Original Message:
Hi Shanmuga,
I attempted a static unbalance check before the first balancing attempt by removing the belts, and there was no static unbalance in the system. The housing drain was kept open, and the water was pumped out during startup. I don't think there was any water in the fan housing during normal operation.
SHANMUGA SUNDARAM PACKIRISAMY
Original Message:
Shanmuga,
You have provided enough information to raise more questions. Considering the multiple balancing attempts and the presence of water, I suggest removing the belts and conducting a static fan balance check and correction to address the issue at 820 rpm.
Mike Barkle
Original Message:
Hi,
I need help resolving an unstable vibration problem with air fans at a waste water treatment plant. Three air fans are belt-driven with a motor speed of 1470 RPM and fan speed of 820 RPM. On December 11, 2023, vibration data showed high amplitudes, suspected unbalance, and performed rotor balancing. Despite cleaning filters and checking mounting locations, the issue persists.
Please see the attached data and share your insights.
Shanmuga
- 07-08-2024
- Frances Fisher
When troubleshooting unstable vibrations in an air fan at a waste water treatment plant, it is crucial to consider potential issues such as a loose foot or insecure sheeve. The vibrations may be caused by the entire frame vibrating at fan RPM, but it is more likely due to a loose foot on the motor or pillow blocks. Performing a static fan balance check, especially after multiple balancing attempts and water presence in the system, can help pinpoint and correct any unbalance issues. Additionally, maintaining an open housing drain during operation can prevent the fan from functioning like a pump. For further support in resolving vibration problems in air fans, reach out for expert assistance.
Hello Shanmuga,
After reviewing all the comments and responses, it appears that you have covered a lot of troubleshooting options for the issue at hand. Drawing from my experience with fan unbalance and related vibrations, here are my insights:
When it comes to vibration analysis, simplicity is key. Overcomplicating things can lead to analysis paralysis and steer us off course. Keeping it simple means trusting and relying on your vibration data. High readings at 1x frequency usually indicate unbalance issues (around 90% of the time). The focus should be on understanding what is causing this unbalance.
In your case, for overhung fans, if it's purely an unbalance issue, the highest readings should be in the Axial direction on the fan pedestal bearings. Since this isn't the case here, it's important to concentrate on the factors contributing to the unbalance rather than solely focusing on balancing the fan itself. It seems unlikely that the issue lies with the balancing process.
Possible underlying causes could include:
i) Foundation
ii) Resonance
iii) Temperature variations during operation
It's recommended to closely examine the foundation, even if the rubber mounts appear to be in good condition externally. Consider motion amplification to observe relative movement. Conduct a bump test to rule out resonance issues. Investigate if temperature fluctuations or process changes are affecting the equipment.
Given the gradual increase in vibration/unbalance over one to two days, it wouldn't hurt to double-check the alignment, specifically the pulley alignment.
Regards,
Ahmad Kidwai
Original Message:
Sent: 01-09-2024 15:05
From: SHANMUGA SUNDARAM PACKIRISAMY
Subject: Unstable vibration in Air Fan @ Waste Water Plant
Hi,
I require assistance in resolving an unstable vibration problem with air fans at a waste water treatment plant.
Equipment:
- Air Fans
- Number of Fans: 3
- Equipment type: belt-driven
- Motor Speed: 1470 RPM
- Fan Speed: 820 RPM (overhung fan)
Issue:
On December 11, 2023, I conducted vibration measurements on all three fans. Two out of three fans exhibited high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings. FFT analysis revealed a predominant frequency of 820 CPM in both the motor and fan bearings. Suspecting unbalance, I balanced the rotor on December 12, 2023, resulting in vibration amplitudes of approximately 3 mm/s and 2 mm/s in both fans.
However, within a day of operation, the vibration amplitudes in both fans started increasing again, with 820 CPM being the dominant frequency. Despite cleaning and replacing filters, as well as checking mounting locations and damper positions, there was no improvement.
On December 16, 2024, vibration amplitudes in both fans measured around 16 mm/s (motor) and 8 mm/s (fan), with the predominant frequency still at 820 CPM. Despite operating the fans intermittently and monitoring vibration levels, the issue persisted.
As a next step, I attempted to balance Air Fan 1 by adding a correction mass of 170 grams. This temporarily reduced the vibration to 4 mm/s in the motor and 2 mm/s in the fan, but the amplitudes once again escalated to around 12 mm/s within a couple of days.
Additional Details:
- Suction for the fans is from the atmosphere, minimizing wear.
- Discharge is for removing gases from wastewater, causing the fan impellers to be constantly wet.
- Water accumulation in the housing during startup is drained by the client before operating the fans.
Attached is the data for these fans. I would appreciate your insights on this matter.
Shanmuga
+96569678166
Hello Shanmuga,
I recently encountered a similar issue with our hood exhaust fan, and I believe there may have been a misdiagnosis of the problem. Prior to balancing on 11/12/2023, the axial reading on the fan was unusually low for an overhung fan, indicating that the main issue may not have been an unbalanced force. It is crucial to recognize that attempting to balance a fan without addressing the underlying forcing frequency can lead to recurring problems. I have dealt with a resonance issue in the past, and while balancing initially provided results, the problem resurfaced in a more pronounced manner after 24 hours of operation, mirroring your current situation.
To address the problem effectively, it is essential to conduct additional tests to rule out structural looseness and resonance as potential issues. A balanced fan should not become unbalanced unless external factors like dropped weight or debris accumulation occur during operation. Also, consider monitoring the vibration amplitude post-balancing, as it may increase over time.
To eliminate resonance and structural looseness, consider the following steps:
1. Analyze the waveform of the spectrum to gain insights.
2. Vary the speed if possible and monitor the resulting vibration amplitude. For unbalance, the amplitude varies with the square of the speed, while resonance will cause drastic changes in amplitude. Structural looseness, on the other hand, may not significantly impact the amplitude.
3. Conduct a bump test if you have the necessary equipment.
4. Inspect the structure and reinforce the support around the motor.
I hope these suggestions help in resolving the issue with the air fans at the waste water treatment plant.
Best regards,
Shittu Olakunle
Reliability Engineer
United Kingdom
- 07-08-2024
- Wesley Jenkins
It appears that there may be a resonance issue with the fan volute panels, possibly due to their composition being fiberglass/composite in a water treatment setting. Considering the corrosive nature of the process, it is likely that the repeated balance failures are a result of a natural frequency problem. As suggested earlier, it would be wise to inspect the condition of the anti-vibration feet and assess the structure of the volute for any signs of flexing.
It seems like you might have misdiagnosed the vibration issue with the air fans at the waste water treatment plant. Before the balancing, the axial reading was unusually low for an overhung fan, indicating that the problem may not be related to unbalanced forces. Balancing a fan without addressing the underlying resonant frequency could lead to temporary results, as experienced firsthand. To rule out structural looseness and resonance, conduct additional tests and analyze the spectrum waveform. Varying the speed and performing a bump test, if possible, can help pinpoint the root cause of the vibration issue.
In summary, it is crucial to address potential resonance and structural issues to ensure the fans operate smoothly. By conducting thorough testing and analysis, you can identify and resolve the underlying problems causing the unstable vibration in the air fans at the waste water plant.
Attached please find (2) Shanmuga, could you provide a high-resolution spectrum analysis to verify the presence or absence of sidebands on both sides of the Fan's 1x rpm? Please refer to the image attached from your original post. Thank you, Ralph Stewart
Original message:
Subject: Unstable vibration in Air Fan @ Waste Water Plant
Hello, I am seeking assistance with resolving an issue of unstable vibration in the air fans at a waste water treatment facility.
Equipment:
- Air Fans
- Number of Fans: 3
- Equipment type: belt-driven
- Motor Speed: 1470 RPM
- Fan Speed: 820 RPM (overhung fan)
The problem:
On December 11, 2023, vibration data was collected on all three fans, with 2 out of 3 fans showing high vibration levels of approximately 10 mm/s in the motor and 7 mm/s in the fan bearings. The FFT analysis identified a predominant frequency of 820 CPM in both the motor and fan bearings. Unbalance was suspected, and rotor balancing was performed. After balancing on December 12, 2023, vibration levels decreased to around 3 mm/s and 2 mm/s in both fans. However, within a day of operation, the vibration levels started to rise again, with a dominant frequency of 820 CPM.
The client cleaned and replaced all filters, checked the mounting locations, and confirmed the damper positions were correct, but the issue persisted.
Further testing on December 16, 2024, showed vibration levels of approximately 16 mm/s (motor) and 8 mm/s (fan) with the same dominant frequency of 820 CPM.
Repeated attempts at balancing Fan 1 by adding a correction mass of 170 grams temporarily reduced vibration levels, but they increased again within a day.
Some key points:
- The fans intake air from the atmosphere, so minimal wear is expected.
- The fans discharge gases from waste water, leading to wet impellers during operation.
Please review the attached data for these fans and provide your insights.
Thank you.
Shanmuga +96569678166
SHANMUGA, I have reviewed the "before" and "after" balance files for Fan #1 and Fan #3 in detail. It appears that both fans transition from balanced to out-of-balance around the same time. Are all three fans mounted on the same suspended (isolated) platform base? Additionally, please clarify the motor speed of each fan and whether they operate at a 50 Hz or 60 Hz Line Frequency. Do all three fans run at the same speed of 820 rpm? Is there any issue with Fan #2, or is it not in use at all? It would be helpful if you could provide waveform and spectrum data from both motors. Thank you, Ralph.
Original Message:
Hello, I am facing vibration instability issues with air fans in a waste water treatment plant. I have conducted vibration analysis on three fans, and two of them showed high vibration levels in both the motor and fan bearings. After performing rotor balancing, the vibration levels temporarily reduced but increased again shortly after. The client has cleaned and replaced filters, checked mounting locations, and verified damper positions, but the issue persists. I conducted further testing, and despite additional balancing efforts, the vibration levels continue to rise. The fans operate intermittently, with vibration levels consistently higher than acceptable. The fans draw air from the atmosphere, and the impellers are continuously moist due to the enclosed environment. Please review the attached data and provide your insights. Shanmuga +96569678166.
Rephrased Message:
Greetings, I am encountering unstable vibration problems with the air fans at a waste water treatment facility. After analyzing the vibration of three fans, it was observed that two fans exhibited elevated vibration levels in both the motor and fan bearings. Despite conducting rotor balancing, the vibration levels decreased temporarily but resurfaced shortly afterward. Despite thorough cleaning, filter replacements, and checks on mounting locations and damper positions by the client, the issue persists. Subsequent testing showed that vibration levels continued to rise despite additional balancing attempts. The fans are operated intermittently, and the vibration levels remain consistently higher than desired. The fans draw air from the atmosphere, and the impellers are continuously damp due to the enclosed environment. Kindly review the attached data and provide your insights. Shanmuga +96569678166.
Hey Shanmuga, When dealing with the sudden increase in fan vibrations post-balancing, it's essential to consider common process factors. Have you looked into dampers / actuators? Make sure to confirm if everything is functioning normally post-balancing. In the past, I've experienced issues where balancing was done, but changes occurred when dampers were later opened down the line. Just a suggestion to consider. Best regards, Colin
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Colin Leigh
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Original Message:
Sent: 01-09-2024 15:05
From: SHANMUGA SUNDARAM PACKIRISAMY
Subject: Unstable vibration in Air Fan @ Waste Water Plant
Hello, I'm seeking assistance to address the unstable vibrations in air fans at a wastewater treatment plant.
Equipment: Air Fans
Number of Fans: 3
Equipment type: belt-driven
Motor Speed: 1470 RPM
Fan Speed: 820 RPM (overhung fan)
Issue: On December 11, 2023, vibration data was gathered on all three fans, revealing high vibration levels in 2 out of 3 fans - around 10 mm/s in the motor and 7 mm/s in the fan bearings. FFT analysis indicated a predominant 820 CPM in both motor and fan bearings. Suspecting unbalance, rotor balancing was performed on December 12, 2023, reducing vibration amplitudes to approximately 3 mm/s and 2 mm/s in the fans. However, vibrations increased again within a day of operation, with a dominant frequency of 820 CPM.
The fan takes in atmospheric suction and has multiple filters. Although the client cleaned and replaced filters, checked mounting locations, and confirmed damper positions were correct, there was no improvement. On December 16, 2023, vibration levels were measured at approximately 16 mm/s (motor) and 8 mm/s (fan) with the predominant frequency still at 820 CPM. Despite operating fans intermittently and monitoring vibration levels, no significant improvement was observed.
To address the issue, balancing was attempted on Air Fan 1 by adding a correction mass of 170 grams, temporarily reducing vibration to 4 mm/s (motor) and 2 mm/s (fan). However, vibrations increased once again, reaching around 12 mm/s after a couple of days. Notably, as the fans draw in atmospheric suction, minimal wear is expected. The fan impellers remain wet due to the enclosed operation, with water in the housing during startup, drained by the client before fan operation.
Please review the attached data for the fans and share your insights.
Shanmuga
+96569678166
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SHANMUGA SUNDARAM PACKIRISAMY
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- 07-08-2024
- Quentin Foster
Have you tried using a strobe light to identify and resolve vibrations in your equipment? This was a handy technique for me when facing difficult vibrations. If you're experiencing unstable vibrations in the air fans at your waste water treatment plant, I'm here to help. You mentioned issues with three belt-driven air fans, with two of them showing high vibration levels in the motor and fan bearings. Even after performing balancing on the rotor, the vibrations persisted, with a predominant frequency of 820 CPM. The client has checked filters and damper positions, but the issue remains. Despite my attempts to balance the air fans, vibrations continue to increase, indicating a persistent problem. The wet environment of the fan impellers may be contributing to the issue. Feel free to share your thoughts on the attached data. Contact me for further assistance at +96569678166.
To resolve unstable vibration issues with air fans in a waste water treatment plant, clean the fan wheel, remove old balance weights, rebalance the fan, and install a drain valve at the bottom of the fan housing connected to a pump to remove water. Consider using a strobe light to pinpoint vibrations in the structure. Ensure that the fan is properly balanced to reduce vibration amplitudes and frequency. Regularly monitor vibration levels and address any recurring issues promptly. Additionally, check the fan intake for any obstructions or blockages that may contribute to vibration. Regular maintenance and monitoring are crucial to preventing vibration issues in industrial equipment.
- 07-08-2024
- Heather Coleman