Diagnostics and Condition Prediction on the Balakovskaja Nuclear Power Plant using a Bruel & Kjaer Type 2515 Portable Signal Analyzer with DREAM
In the Balakovskaja Nuclear Power Plant, the program using DREAM for rolling element bearing diagnostics has been in operation for 3 years. About 1000 bearings are controlled by the DREAM Software and the Bruel & Kjaer model 2515 Analyzer. Using the advanced technique of long term condition prediction implemented in DREAM, only 10-20 of them are measured during one week. During three years, according to the recommendations of DREAM program, nearly 100 bearings were replaced. None of the bearings under the control of the DREAM complex failed during that time. The Director of the technical diagnostics laboratory, Mr. Kochanov, says that the usage of DREAM during one year covered all the expenses of DREAM purchase and installation on the enterprise. Below are shown the examples of the bearings diagnostics, which gave the recommendations to replace the bearings.
On February 25th 1993, a bearing in the first cooling loop pump in the reactor plant was diagnosed. The designation of the bearing was 314. The rotation speed of the pump was 1500 RPM. The program has shown a severe cavity (spall) on the outer race (the depth of modulation 23%). The recommended date of the next measurement was March 26th 1993.
On March 26th the diagnostic measurement had detected an increase of the cavity on the outer race (the depth of modulation 40%), an appearance of a severe revolution around the outer race (the depth of modulation 18%) and an incipient defect of lubrication (3 dB). The program recommended making the next diagnostic measurement in 4 days (March 30th). During this period of time the pump was stopped, the bearing was dismounted, and the diagnosis was confirmed by the visual inspection. The envelope spectrum measured on March 26th is shown in Fig. 1(below).
Fig. 1(above). The envelope spectrum of a bearing with a severe cavity on the outer race and revolution around the outer race.
On the 16th of April 1993 a bearing with designation 314 which was mounted on the pump supplying the turbine condenser by the washing water solution was diagnosed in the chemical plant. The rotation speed of the pump was 3000 RPM. By the diagnostic measurement it was automatically detected by the program that the bearing has a severe wear of the outer race (the depth of modulation 13%), a severe defect of the inner race (the depth of modulation 28%) and severe deep cavity on the inner race ( the depth of modulation 40%). After dismounting the bearing the diagnose was confirmed visually. The envelope spectrum of this bearing is shown on Fig. 2 (below).
Fig. 2(above). The envelope spectrum of a bearing with wear of the outer race, inner race and a severe cavity on the inner race.
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