Fracture analysis and improvement of PTO shaft on marine gearbox for an offshore supply vessel

ZHOU Xiao-mei， HUANG Jiang-xing， DAI Hong-chang， SHEN Xian
（Hangzhou Advance Gearbox Group Co. Ltd.， Hangzhou 311203， China）

Abstract： Aiming that PTO shafts fracture occurring during operation of a marine gearbox on an offshore supply vessel，in the case of the high flexible coupling is damaged because of the bad alignment of the high flexible coupling，through making mechanical model together with measuring technique and material metallographic analysis，all possible causes resulting to the fracture were found out. On the basis of mechanics analysis of the PTO shaft，stress condition of the sink groove of the PTO shaft were studied mainly and the two dimensional stress state of the weakest point was analyzed，when the high flexible coupling became cantilever load. Then，several precautions of improving strength of the PTO shaft were raised. The research result proves that， the strength of the PTO shaft is affected quite by installation accuracy of the high flexible coupling， and the improvement actions presented can eliminate the broken shaft event from happening again，ensure the normal operation of equipment.
Key words： marine gearbox； PTO shaft； fracture； improvement actions