Diagnostics and Condition Prediction on the Kotlas Paper and Pulp Mill using Bruel & Kjaer Type 2515 Portable Signal Analyzer with DREAM
The Kotlas Paper and Pulp Mill is one of the largest plants in Russia. The paper and carton machines were delivered in the 1960s by Swedish firms. A program was installed in the plant in 1991 for monitoring two carton and four paper making machines. Each machine has over 2000 bearings. Many bearings worked for more than 10 years. The program was used for monitoring 5000 bearings. During the program operation about 200 bearings were replaced. Ninety per cent of those had the type of defects that coincided with the diagnosis given by the program (180 bearings) and about 70% of them (140) had the depth of the defect that was defined by the program. No one bearing that was monitored by the program failed. All of them were replaced before failure. At the same time there were bearings which the operator did not have access for monitoring. More than 25 of them failed during this time. Below there are some examples of the replaced bearings.
1. The first case was on the third carton making machine. The bearing was on the short shaft No 94. The Measurement Point ID was 3-9-94, the designation 113618, the rotation frequency - 7.03 Hz.
Fig. 1 (above). The envelope spectrum of the vibration of the bearing with revolution around the outer race (medium defect), a severe cavity on the outer race, and a medium cavity on the inner race.
2. The second case was with the bearing mounted on the drying shaft No 70. The Measurement Point ID was 3-11-70, the designation 73617, the rotation frequency - 6.95 Hz.
On June 12th, the first measurement was made. The program showed that the bearing had severe wear of the rolling elements and the cage (the depth of modulation 19%). There were also the beginnings of the development of cavities and spalls on the rolling elements. The envelope spectrum of this case is shown in Fig. 2(below). The program gave the recommendation to replace the bearing. During the dismounting the defects were confirmed.
Fig.2(above). The envelope spectrum of a bearing with the severe wear of the rolling elements and cage and cavities and spalls on the rolling elements.
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