Case Study
Advanced Fault Diagnosis for Roller
Press
Gearbox in Cement Industry
1. Abstract
Gearbox failure is one of the highest risk events in the Cement Industry. In most of the Roller Presses in Cement Industry planetary gearboxes are preferred over conventional gearboxes due to their significant advantages. Fault diagnosis of planetary gearboxes is always a challenge given the complex gear arrangement. This paper demonstrates the use of Infinite Uptime’s auto-diagnostics features to help detect faults for complex gear train designs.
2. Introduction
The roller press indicated in the Figure 1 (schematic) is installed at 2MTPA cement grinding unit & it’s a high-pressure Roller Press manufactured by Polycom. Roller Sensor nodes enabling fault diagnosis for this gearbox are mounted at positions marked by White dots. These sensor nodes communicate to a cloud dashboard and
provided comprehensive vibration signal analysis and fault diagnosis.
Figure 1: Roller Press Construction & Sensor Positions
3. Background
3.1 Roller Press
Construction
Roller press gearboxes rotate in two opposite directions, so that small, dry particles are crushed into powder or uniform shapes. Extremely high pressure needs to be generated. Planetary gearboxes with high reduction ratios are mounted over the individual rollers. The drive from the main motor to the gearboxes is obtained by having a connection Cardan shaft with universal coupling between the motor shaft and the
gear shaft.
3.2 Sequence
of Events
Figure 2 shows the sequence of events in a summarized way.
4. Solution
The Infinite Uptime’s Advanced Fault Diagnosis had predicted the fault. Figure 3, Figure 4, and Figure 5 show the increase in trends and rise in spectrums on the respective dates.
Advanced Fault Diagnosis in IDAP Platform
A. Increase in Total Acceleration from 2/11/2021 to 10/05/2022.
Figure 3: Increase in Total Acceleration
B. Rise In Velocity Values from 20/12/2021 to 10/05/2022 in all 3 directions.
Figure 4: Rise in Velocity Values
C. Shockwave Spectrum- Outer Race defects Observed in the spectrum.
Figure 5: Bearing Outer Race defect in Shockwave Spectrum
D. Reduction in Total Acceleration Trend After Maintenance on 13th May 22.
Figure 6: Reduction in total acceleration
5. Site Inspection and Findings
Inspection of Gearbox I/P stage done by Maintenance & OEM team, Replacement carried out for Gearbox I/P stage Bearing no. 32240 on May 13. The disassembled bearing as shown in Figure 7 has the indications of “Line Marks” and “Circumferential
Grooving Marks”.
Figure 7 shows the abrasive wear of the rolling element particle due to fine particle contamination. Extremely heavy wear from chips or metal particles can cause grooving. These contaminants become wedged in the soft cage material and cut grooves in the rolling elements. This condition generates improper rolling contact geometry and can reduce service life. Possible remedy is use of lubricants containing anti-wear additives.
Figure 7: Viewing “Line Marks” and “Circumferential Grooving Marks” in Rollers
Figure 8: Viewing Line Marks in Outer Raceway
Figure 8 show Line Marks on outer raceway which is the case of false brinelling that occurs when there is small relative motion between the rollers and raceways during non-rotation times, characterized by elliptical wear marks in the axial direction at each roller position. When the bearing is not turning, an oil film cannot be formed to prevent
raceway wear. Possible remedy is eliminating external vibration.
6. Conclusion
The breakdown of such a gearbox will lead to a breakdown of the roller press resulting in a production loss of up to 36 hours.
The paper serves to demonstrate that bearing and gear faults in a complex planetary gear train can be monitored and effectively diagnosed with parameters of Total Acceleration and Shockwave with the Infinite Uptime auto-diagnostics features. Thus, preventing
unplanned downtime for this equipment.
