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Dear All,

We are using Vibexpert II from pruftechnik for vibration measurements,while i took phase readings from one of our asset the phase angle is fluctuating continuously(Fluctuation is above 10 degree) during continuous measurement,and also we tried to take different readings from same measuring point and we are getting different phase angles during each measurement.

i)is that an issue with the device or asset?

ii)If this is an issue with the asset what are all things i need to consider while diagnosing unbalance?

iii)If this is in issue with the Device can anyone advise me?

iv)What is the acceptable phase angle fluctuation during continuous mode measurement?

Any help would be great!Thanks!

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Dear Becar,

Thank you for the response,Fluctuation issue is happening with more than 1 asset on different locations including indoor equipment's.Please find the attached images showing the tacho mounting positions.

File_000

Vibration velocity at 1X was 7.604mm/sec and overall RMS was 8.89mm/Sec,Phase angle measurements were taken to see if there is any imbalance but phase angle is not stabled so we couldn't able to see whether the equipement is unbalanced

OCUWe are also coordinating with the supplier about this issue ,they are looking into device settings for any abnormality!!

Best Regards,

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VIDEO-2021-03-01-15-39-46
@Registered Member posted:

Dear Becar,

Thank you for the response,Fluctuation issue is happening with more than 1 asset on different locations including indoor equipment's.Please find the attached images showing the tacho mounting positions.

Looking at the picture you have posted, the ratio between the motor sheave and the driven equipment (which appears to be a fan) appears to be very near a 1:1 ratio (based on the angle the belt appears to be showing in the picture). With a belt drive system, it is almost impossible to get the rpms the exact same speed and If is very close to 1:1, the speed difference in the motor and the "fan" may be just enough to cause the phase change.

Does the 1x vibration fluctuate (increase and decrease) also as you monitor the system?

The motor mounting assembly appears as though it may be a little "weak", especially the long "thread-all" studs and the angle iron the studs are fastened to.

Have you tried to check the phase on the "fan" bearing or what ever the driven part is?

Are the motor and "fan" running close to the same speeds?

Is the phase problem showing in the "fan" also?

Does the phase problem show if you place the transducer on the fan (in the same direction as the motor) instead of the motor and leave the tach light on the motor?

Just some thoughts.

File_000

Vibration velocity at 1X was 7.604mm/sec and overall RMS was 8.89mm/Sec,Phase angle measurements were taken to see if there is any imbalance but phase angle is not stabled so we couldn't able to see whether the equipement is unbalanced

We are also coordinating with the supplier about this issue ,they are looking into device settings for any abnormality!!

Best Regards,

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