Vibration analysis of water cooling towers' defective fan bearing units at J-PARC RCS

Fujirai, Kosuke; Suganuma, Kazuaki ; Yamazaki, Yoshio 

The J-PARC (Japan Proton Accelerator Research Complex) 3-GeV RCS (Rapid Cycling Synchrotron) has many devices such as Radio-Frequency components, electromagnets and power supplies. These devices use 17MW of electricity during operation, most of which is consumed as thermal energy. Therefore, cooling water equipment is indispensable for the operation of the accelerator and its stability affects the operation rate of the accelerator. Due to resent operation experience, the bearing unit of the cooling tower fan, which is also an important part of the cooling water equipment, broke down. This accident leads to the suspension of the J-PARC operation. In order to investigate the cause of the failure, we tried to measure vibration for the defective bearing and the bearing unit were cut and observed damaged surface. As a result of the vibration measurement, it was found that vibration frequency depends on the presence or absence of scratches on the bearing. We found surface of the outer ring had scratches called flaking.