vibration/alignment/balance

Hi

I need your support in resolving an unstable vibration issue with air fans in 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)

Problem:

On December 11, 2023, I initially collected vibration data on all three fans; 2 out of 3 fans showed high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings.

FFT showed a predominant 820 CPM in both motor and fan bearings. Suspected unbalance and performed balancing of the rotor.

After balancing on December 12, 2023, the vibration amplitude was around 3 mm/s and 2 mm/s in both fans.

But, within a day of operation, the vibration amplitude at both fans started increasing with a predominant frequency of 820 CPM again.

The suction for this fan is from the atmosphere, and there are multiple filters. The client cleaned all filters, replaced the damaged filters, checked the mounting locations, and confirmed that the damper positions were okay, but still there was no improvement.

I once again tested the equipment on 16 Dec 2024. Vibration amplitudes at both fans were around 16 mm/s (motor) and 8 mm/s (fan), with the same dominant frequency of 820 CPM.

Client operated the fans intermittently and checked the vibration levels, but it was on higher side only. Since I was left with no other actions, I once again attempted balancing Air Fan 1 by adding a correction mass of 170 grams, and vibration dropped once again to 4 mm/s in the motor and 2 mm/s in the fan.

Once again, vibration amplitudes started increasing within a day and reached around 12 mm/s in a couple of days.

A couple of points:

1. The suction for these fans is from the atmosphere; hence, no significant wear is expected.
2. The discharge is to remove gases from waste water, but due to enclosed operation, the fan impellers are always wet, and there is some water in the housing during start up and the client is draining the same before starting the fans.

Please find attached the data for these fans and share your thoughts.

Shanmuga

+96569678166

Hi Shanmuga, for this overhung fan, the blade looks a little bit wider. If confirmed it is unbalance issue, does it exist couple-unbalance. I supposed you performed the single plane balancing, may consider two plane for both static and couple unbalance.

Hi

I need your support in resolving an unstable vibration issue with air fans in 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)

Problem:

On December 11, 2023, I initially collected vibration data on all three fans; 2 out of 3 fans showed high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings.

FFT showed a predominant 820 CPM in both motor and fan bearings. Suspected unbalance and performed balancing of the rotor.

After balancing on December 12, 2023, the vibration amplitude was around 3 mm/s and 2 mm/s in both fans.

But, within a day of operation, the vibration amplitude at both fans started increasing with a predominant frequency of 820 CPM again.

The suction for this fan is from the atmosphere, and there are multiple filters. The client cleaned all filters, replaced the damaged filters, checked the mounting locations, and confirmed that the damper positions were okay, but still there was no improvement.

I once again tested the equipment on 16 Dec 2024. Vibration amplitudes at both fans were around 16 mm/s (motor) and 8 mm/s (fan), with the same dominant frequency of 820 CPM.

Client operated the fans intermittently and checked the vibration levels, but it was on higher side only. Since I was left with no other actions, I once again attempted balancing Air Fan 1 by adding a correction mass of 170 grams, and vibration dropped once again to 4 mm/s in the motor and 2 mm/s in the fan.

Once again, vibration amplitudes started increasing within a day and reached around 12 mm/s in a couple of days.

A couple of points:

1. The suction for these fans is from the atmosphere; hence, no significant wear is expected.
2. The discharge is to remove gases from waste water, but due to enclosed operation, the fan impellers are always wet, and there is some water in the housing during start up and the client is draining the same before starting the fans.

Please find attached the data for these fans and share your thoughts.

Shanmuga

+96569678166

Dear Kevin

Thank you for your response. Valid point.

But, will the vibration ever drop to normal level if the unbalance is still present? Air Fan 1 was running normal for almost a day (11th December evening to 12th Dec evening). I feel that even couple balancing also (even if it brings the vibration to normal) will not resolve the issue.

Is there any effect of wet conditions in blower rotor. Some water droplets are always found in the rotor due to humid conditions. Does anyone have any experience or idea on this?

Hi Shanmuga, for this overhung fan, the blade looks a little bit wider. If confirmed it is unbalance issue, does it exist couple-unbalance. I supposed you performed the single plane balancing, may consider two plane for both static and couple unbalance.

Hi

I need your support in resolving an unstable vibration issue with air fans in 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)

Problem:

On December 11, 2023, I initially collected vibration data on all three fans; 2 out of 3 fans showed high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings.

FFT showed a predominant 820 CPM in both motor and fan bearings. Suspected unbalance and performed balancing of the rotor.

After balancing on December 12, 2023, the vibration amplitude was around 3 mm/s and 2 mm/s in both fans.

But, within a day of operation, the vibration amplitude at both fans started increasing with a predominant frequency of 820 CPM again.

The suction for this fan is from the atmosphere, and there are multiple filters. The client cleaned all filters, replaced the damaged filters, checked the mounting locations, and confirmed that the damper positions were okay, but still there was no improvement.

I once again tested the equipment on 16 Dec 2024. Vibration amplitudes at both fans were around 16 mm/s (motor) and 8 mm/s (fan), with the same dominant frequency of 820 CPM.

Client operated the fans intermittently and checked the vibration levels, but it was on higher side only. Since I was left with no other actions, I once again attempted balancing Air Fan 1 by adding a correction mass of 170 grams, and vibration dropped once again to 4 mm/s in the motor and 2 mm/s in the fan.

Once again, vibration amplitudes started increasing within a day and reached around 12 mm/s in a couple of days.

A couple of points:

1. The suction for these fans is from the atmosphere; hence, no significant wear is expected.
2. The discharge is to remove gases from waste water, but due to enclosed operation, the fan impellers are always wet, and there is some water in the housing during start up and the client is draining the same before starting the fans.

Please find attached the data for these fans and share your thoughts.

Shanmuga

+96569678166

Hi

I need your support in resolving an unstable vibration issue with air fans in 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)

Problem:

On December 11, 2023, I initially collected vibration data on all three fans; 2 out of 3 fans showed high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings.

FFT showed a predominant 820 CPM in both motor and fan bearings. Suspected unbalance and performed balancing of the rotor.

After balancing on December 12, 2023, the vibration amplitude was around 3 mm/s and 2 mm/s in both fans.

But, within a day of operation, the vibration amplitude at both fans started increasing with a predominant frequency of 820 CPM again.

The suction for this fan is from the atmosphere, and there are multiple filters. The client cleaned all filters, replaced the damaged filters, checked the mounting locations, and confirmed that the damper positions were okay, but still there was no improvement.

I once again tested the equipment on 16 Dec 2024. Vibration amplitudes at both fans were around 16 mm/s (motor) and 8 mm/s (fan), with the same dominant frequency of 820 CPM.

Client operated the fans intermittently and checked the vibration levels, but it was on higher side only. Since I was left with no other actions, I once again attempted balancing Air Fan 1 by adding a correction mass of 170 grams, and vibration dropped once again to 4 mm/s in the motor and 2 mm/s in the fan.

Once again, vibration amplitudes started increasing within a day and reached around 12 mm/s in a couple of days.

A couple of points:

1. The suction for these fans is from the atmosphere; hence, no significant wear is expected.
2. The discharge is to remove gases from waste water, but due to enclosed operation, the fan impellers are always wet, and there is some water in the housing during start up and the client is draining the same before starting the fans.

Please find attached the data for these fans and share your thoughts.

Shanmuga

+96569678166

Hi

I need your support in resolving an unstable vibration issue with air fans in 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)

Problem:

On December 11, 2023, I initially collected vibration data on all three fans; 2 out of 3 fans showed high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings.

FFT showed a predominant 820 CPM in both motor and fan bearings. Suspected unbalance and performed balancing of the rotor.

After balancing on December 12, 2023, the vibration amplitude was around 3 mm/s and 2 mm/s in both fans.

But, within a day of operation, the vibration amplitude at both fans started increasing with a predominant frequency of 820 CPM again.

The suction for this fan is from the atmosphere, and there are multiple filters. The client cleaned all filters, replaced the damaged filters, checked the mounting locations, and confirmed that the damper positions were okay, but still there was no improvement.

I once again tested the equipment on 16 Dec 2024. Vibration amplitudes at both fans were around 16 mm/s (motor) and 8 mm/s (fan), with the same dominant frequency of 820 CPM.

Client operated the fans intermittently and checked the vibration levels, but it was on higher side only. Since I was left with no other actions, I once again attempted balancing Air Fan 1 by adding a correction mass of 170 grams, and vibration dropped once again to 4 mm/s in the motor and 2 mm/s in the fan.

Once again, vibration amplitudes started increasing within a day and reached around 12 mm/s in a couple of days.

A couple of points:

1. The suction for these fans is from the atmosphere; hence, no significant wear is expected.
2. The discharge is to remove gases from waste water, but due to enclosed operation, the fan impellers are always wet, and there is some water in the housing during start up and the client is draining the same before starting the fans.

Please find attached the data for these fans and share your thoughts.

Shanmuga

+96569678166

Hi

I need your support in resolving an unstable vibration issue with air fans in 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)

Problem:

On December 11, 2023, I initially collected vibration data on all three fans; 2 out of 3 fans showed high vibration amplitudes of around 10 mm/s in the motor and 7 mm/s in the fan bearings.

FFT showed a predominant 820 CPM in both motor and fan bearings. Suspected unbalance and performed balancing of the rotor.

After balancing on December 12, 2023, the vibration amplitude was around 3 mm/s and 2 mm/s in both fans.

But, within a day of operation, the vibration amplitude at both fans started increasing with a predominant frequency of 820 CPM again.

The suction for this fan is from the atmosphere, and there are multiple filters. The client cleaned all filters, replaced the damaged filters, checked the mounting locations, and confirmed that the damper positions were okay, but still there was no improvement.

I once again tested the equipment on 16 Dec 2024. Vibration amplitudes at both fans were around 16 mm/s (motor) and 8 mm/s (fan), with the same dominant frequency of 820 CPM.

Client operated the fans intermittently and checked the vibration levels, but it was on higher side only. Since I was left with no other actions, I once again attempted balancing Air Fan 1 by adding a correction mass of 170 grams, and vibration dropped once again to 4 mm/s in the motor and 2 mm/s in the fan.

Once again, vibration amplitudes started increasing within a day and reached around 12 mm/s in a couple of days.

A couple of points:

1. The suction for these fans is from the atmosphere; hence, no significant wear is expected.
2. The discharge is to remove gases from waste water, but due to enclosed operation, the fan impellers are always wet, and there is some water in the housing during start up and the client is draining the same before starting the fans.

Please find attached the data for these fans and share your thoughts.

Shanmuga

+96569678166