Large-scale hydro-formed bellows with inner-surface polishing, as flexible as welded bellows

溶接ベローズ並みの柔軟性を有する大口径内面研磨成形ベローズの開発

小泉 欧児*; 井上 勝*; 荻原 徳男; 神谷 潤一郎   ; 金正 倫計  

Koizumi, Oji*; Inoue, Masaru*; Ogiwara, Norio; Kamiya, Junichiro; Kinsho, Michikazu

In the 3 GeV Rapid Cycling Synchrotron (RCS) in the Japan Accelerator Research Complex (J-PARC) project, large-scale bellows were needed to adjust the gap between the ceramic ducts and between the ceramic ducts and the transport ducts. The space for setting the bellows are so narrow that the requirements for the bellows were severe. Typical free length and inner diameter of the bellows were 100 mm and 300-400 mm, respectively; nevertheless, the spring rate of less than 100 N/mm was needed. Then pure Ti and SUS 316L steel were selected as materials for bellows; Ti bellows were set in the high radiation field because of its small residual radioactivity, and the SUS 316L bellows in the other area. We have developed the hydro-formed bellows as flexible as welded bellows. Then, we have developed the new polishing method "wet mechanical polishing". Using the fluid containing the minute particles of abrasive we have succeeded to polish the inner-surface of the complicated shape. The average roughness factor Ra of 0.05 m was obtained. After assembling, mainly to reduce the hydrogen inventory in the bellows, all the bellows have been vacuum-fired for 10h at 650C for Ti bellows, and at 750C for SUS316L bellows, respectively. Thus we have succeeded in developing the large-scale hydro-formed bellows with the inner-surface polishing, as flexible as welded bellows.