| 摘要 |
A top drive (10) for use in wellbore operations above a well, which top drive comprises: a main body, a main shaft (16) extending from the main body, said main shaft (16) comprising a flow bore through which drilling fluid is flowable in use, a main shaft housing (17) enclosing a portion of the main shaft (16), the main shaft having a non-loaded position relative to the main shaft housing, and sensing apparatus (24) located for sensing bending of the main shaft (16) away from the non-loaded position.
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