Development of maintenance technology for rotating equipment; Condition based maintenance by shock pulse method

Takeuchi, Kenji ; Sanyoshi, Hirotaka; Fukuari, Yoshihiro; Inami, Shinichi

In the Tokai Reprocessing Plant (TRP), lots of blowers are used for enclosing radioactive materials in a controlled area, and pumps are used for circulating cooling water to keep temperature under appropriate conditions of vessels, which contain high-level radioactive liquid waste. These rotating equipments play an important role in safety management of the nuclear facilities, where they are required stable conditions all the time. To improve the reliability of rotating equipments, the condition based maintenance for detecting the deterioration is one of the effective measures. According to the analyses of the past maintenance data obtained in TRP, it has been found that about 90% troubles related to the rotating equipment are caused in the bearing works, in which the lubrication was defective in almost every case. So, it is very important for stable operation of the rotating equipment to monitor the lubrication conditions in bearings. The vibration method facilitates to detect defects and abrasion of bearings by measuring a vibration signal. However, this method has a disadvantage that quantitative management for the lubrication conditions of bearings is not possible. Therefore, the shock pulse method, which is widely used for diagnosis of the bearings, is applied to assess the deterioration of rolling bearing. The shock pulse method can detect the change of the lubrication condition and the presence of defects in bearings, by a pressure wave generated from rotating rolling bearing. The method can also evaluate the oil slick thickness and the condition of deterioration in the bearing. As one of maintenance activities performed after monitoring, replenishment with a suitable amount of oil for a lubricant was able to be conducted with a proper timing. As a result, the number of the troubles on bearings has significantly reduced because proper maintenance for keeping the oil slick thickness can be carried out, which resulted in stable operation of the rotary equipmen