Background

The following case shows the findings of the Vibration Analysis study done on the Agitator FD-431-AG1 that was completed by Eastway on the 16th of July 2019 in a pharmaceutical manufacturing plant located in Ireland, Europe. Eastway has carried out a range of condition monitoring services for this client since 2012.

Case description

The purpose of the survey was to assess the health status of the unit, which was reported by the operators after detecting an abnormal sound coming from the gearbox. Bearing housing vibration was collected from the field with a portable FFT analyzer.

The agitator was tested on five locations: Motor NDE (radial), Motor DE (radial), Gearbox Top 1 (Horizontal), Gearbox Bottom 2 (Horizontal) and Gearbox Side 3 (Horizontal) at three separate running speed: 5 RPM, 10 RPM and 15 RPM. For each measurement, the vibration was recorded in both time and spectrum overalls of:

 – The velocity amplitude (mm/s rms)

 – The acceleration amplitude (g rms)

Machine line sketch:

As there was not enough history of data on this unit, there was not a full alarm system set on the database. 

Therefore the analysis of the machine was based on comparing the machine performance at the different speeds and on the several locations taken. And the following table can be used as a guideline.

   A: The vibration of newly commissioned machines

   B: Accepted for unrestricted long-term operation

   C: Unsatisfactory for long-term continuous operation

   D: Vibration can cause damage to the machine

Results

The table below displays all the vibration values across the unit. The major increase in the values were found on the Gearbox as the machine speed was increased.

The graph below shows a significant impacting on the Gearbox. The peak-peak value (8.308g) is around 2660% higher than the overall vibration value (0.3123g). In normal this peak-peak value is expected to be max 500% higher than the overall.

The demodulation graph, see below, shows low frequency related peaks, because of the low RPM these are likely to be related to the bearings condition on the Gearbox. There is no evidence of high frequency peaks that could be associated to gear teeth wear.

Recommendation

It was recommended to schedule a bearing replacement on the Gearbox at the next available opportunity and avoid the long-term continuous operation of the unit under high load and speed conditions (>15RPM).

Action taken

GB shaft 3 Top and Bottom bearings replaced from side view hole and oil top up done. This was completed on 17 July 2019 by plant maintenance personnel. After corrective action the Agitator start up taken at 5,10,15&20 RPM found significant reduction of vibration readings up to 95% in Gearbox, abnormal noise and acceleration reduced and equipment was running normal. See the Bearing housing – FFT Spectrums below for Gearbox comparing changes in amplitude.

Bearing housing – FFT Spectrums:

Velocity before and after GB TOP 1

Acceleration before and after GB Top 1

Results: Estimated* cost savings associated with avoidance of unplanned downtime, emergency repair costs & secondary damage:

Downtime avoided:

4 hours

Downtime cost per hour

€10,000

Total Savings:

€40,000