| 摘要 |
A slip die with a substantially smooth pipe contact surface (26a) is employ ed in a conventional slip assembly as a primary mechanism (34) for gripping pip e (13). A second conventional slip assembly with conventional dies having penetratin g die teeth (37) on their contact surfaces is employed as a secondary gripping mechanism to automatically grip the pipe in the event the primary mechanism loses its grip. The smooth slip elements (26a) are constructed of a malleable material which tends to conform to surface irregularities on the outer surface of the pipe to increase the gripping force on the pipe. In the method, the pipe is initially gripped by the primary slip mechanism (34) before the secondary mechanism is actuated t o contact the pipe (13). The slips (36, 37) are set by downward pipe forces acting on the dies so that the die teeth of the secondary mechanism (37) do not gri p the pipe unless the primary slip mechanism fails. The system and method permit t he pipe to be gripped without producing damaging die teeth marks on the pipe during normal pipe handling operations while providing a secondary mechanism which will automatically grip the pipe if the primary gripping mechanism fails.</S DOAB>
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