back-up roll bearing

例句：

1. 1.The engineer replaced the old back-uproll bearing with a new one.
   工程师用一个新的备用滚珠轴承替换了旧的。
2. 2. The machine's back-uproll bearing failed during operation.
   机器在运行过程中，备用滚珠轴承失效了。
3. 3.The technician quickly identified the problem and replacedthe back-up roll bearing.
   技术员迅速诊断出问题并更换了备用滚珠轴承。