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A multi position safety valve retainable within an internal portion of a drill string casing and responsive to the greater differential pressure in an internal fluid passage to displace a valve head r

An improved safety valve includes piston-actuated provisions for gradually pressurizing a fluid-actuated motor during start-up of the system, preferably by way of a changeable flow restriction. In add

Lock-open mechanism for surface controlled subsurface safety valves. A lock-open sleeve can be positioned by wireline techniques to hold open the valve closure means for a subsurface safety valve. The

A new and improved subsurface safety valve which is inserted into well tubing without requiring removal of the tubing, and which replaces worn, deteriorated and fully or partially inoperative safety v

A safety valve for use with horizontal subsea trees as described which uses a two-part safety valve system. The first part containing a valve mechanism remains in the wellhead and is normally biased t

A safety valve for use in a wellbore formed in an earth formation, comprising a valve body having a fluid passage for passage of a stream of hydrocarbon fluid flowing from the earth formation via the

A wellbore safety valve system includes a plug held by a retention spider, a plug seat separated from and located above the plug, and a controlled release section for separating the spider from the pl