| 摘要 |
Apparatus for cementing a string of tubulars in a borehole comprises an enclosure having a bore therethrough, an axially fixed sphere canister having a sphere aperture therethrough, a sphere valve member having a valve body disposed internally of said bore, and a sphere disposed in said sphere aperture, wherein said sphere valve member has a hold position closing said sphere aperture and a drop position opening said sphere aperture to release said sphere.
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