AUSBLAS-PREVENTER MIT ABSCHERVORRICHTUNG.

摘要

A ram-type shearing apparatus for a wellhead having a body with a vertical bore therethrough and aligned, opposed ram guideways extending outward in the body from the bore, a ram assembly in each of the guideways, each of the ram assemblies having a ram body with a shearing blade on the face of the ram and means for moving the ram inward and outward in the guideway, the cutting edge of the upper shear blade and the face of the ram assembly below the upper shear blade being concave to support the string during shearing sufficiently to constrain the string below the upper shear blade as it is sheared to a shape suitable for receiving an overshot type of retrieving tool and to allow flow therein, the lower shear blade having at least one node extending toward the upper shear blade so that when a pipe is being sheared the node engages and penetrates the pipe prior to other shearing of the pipe to thereby reduce the force used for such shearing.