Patent ID: 6752212
Filing Date: 2004-06-22
Classification: E21B,F16K

Abstract:
An operator controlled, selectively actuatable downhole dump valve unit for selective draining of pumping liquid from a producing oil well downhole pipe string, said pipe string having an elongated, tubular pipe section connection body attached to a pipe section that is located in general proximity to and above a pump unit connected to the pipe string, said connection body having a sidewall with opposed inner and outer faces presenting a generally cylindrical interior having a selected internal diameter, said connection body being provided with a threaded opening extending through the sidewall between the inner and outer faces thereof, said dump valve unit comprising;an integral, externally threaded pressure activated fitting adapted to be threaded into the threaded opening in the connection body in disposition extending between the inner and outer faces of the connection body to form a thread to thread, complemental, metal to metal, liquid tight seal between the fitting and the sidewall, said fitting having a tubular housing which has wall structure presenting a central liquid discharge passage therethrough, said wall structure having a circular inner edge portion defining the pumping liquid entrance of the passage that is adjacent the inner face of the connection body, said circular inner edge portion of the wall structure being of a diameter approximately equal to the diameter of said passage, said fitting being provided with a thin, metallic, frangible, shape-retaining rupture disc having an outer circular marginal portion welded to the inner circular edge of the wall structure defining said passage through the tubular fitting, the disc upon rupture presenting an opening therethrough having an effective diameter at least about as great as the diameter of the passage through the housing of the fitting, the diameter of said opening through the disc upon rupture thereof being at least about one-fourth times the internal diameter of the connection body, said disc being bulged inwardly of the passage to present opposed concavo-convex surfaces such that the concave surface thereof directly faces the interior of the connection body, said disc being provided with at least one line of weakness extending across the disc, said disc being of a thickness and having at least one line of weakness such that the disc thickness and line of weakness depth are correlated to impart a predetermined pumping liquid withstand pressure to the disc sufficient to withstand the pressure of pumping liquid normally contained in a particular length of pipe string when the pipe string is inserted in and extends along the length of the well casing, thereby preventing pumping liquid flow through the passage in the housing under normal production operating conditions, the disc thickness and the line of weakness depth being further correlated to reliably effect operator-actuated rupture of the disc when a predetermined disc activation pressure is applied to the pumping liquid in the pipe string to drain all of the pumping liquid from the pipe string through the opening in the disc and thence through the discharge passage of the fitting prior to removal of the pipe string from the well.