Dump valve assembly for selective draining of liquid from an oil well pipe stream

A dump valve assembly for operator controlled, selective full drainage of pumping liquid from a producing oil well downhole pipe string formed of end to end pipe sections and having a pump unit at the lower end thereof, which permits conventional pulling of the pipe string from the oil well as the pipe sections are successively disassembled without significant spillage of pumping liquid contained in the pipe string onto the area surrounding the oil well, said assembly comprising;

• an elongated pipe section connection body having a sidewall and end structure for connection of the body to the lower part of the pipe string above the pump unit, said sidewall of the connection body having opposed inner and outer faces presenting a generally cylindrical internal diameter, said connection body being provided with an internally threaded opening therethrough between said faces;
• and
• an integral fitting having a tubular housing having an outer cylindrical wall surface and an inner tubular wall surface presenting a central pumping liquid discharge passage through the housing, said inner wall surface defining the passage having generally axially aligned, spaced pumping liquid entrance and pumping liquid exit edge portions respectively, a portion of the outer wall surface of the housing being provided with external threads for complementally engaging the threads of the threaded opening in the sidewall of the pipe section, the pumping liquid entrance edge portion of the fitting being of a diameter approximately equal to the diameter of said passage,
• said fitting being sealingly and removably threaded into the opening in the sidewall of the pipe section,
• said housing being provided with a thin, metallic, frangible, shape-retaining, passage-closing rupture disc having an outer circular marginal portion welded to the housing adjacent said entrance edge portion of the passage, 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 with the concave surface thereof facing the interior of the connection body in disposition directly exposed to pumping liquid in the connection body,
• 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 liquid withstand pressure to the disc sufficient to withstand the pressure of 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 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 activation pressure is applied to the pumping liquid in the pipe string, said activation pressure being selectively applied to cause said rupture of the disc in order to drain all of said pumping liquid from the pipe string through the opening in the disc and the discharge passage of the fitting prior to removal of the pipe string from the well,
• the diameter of the disc and said line of weakness in the disc being of a pattern such that upon operator-selected rupture, the disc splits into individual petals that are in relatively close, generally conforming proximity to the inner wall surface of the passage.

A dump valve assembly for operator controlled, selective full drainage of pumping liquid from a producing oil well downhole pipe string formed of end to end pipe sections and having a pump unit at the lower end thereof, which permits conventional pulling of the pipe string from the oil well as the pipe sections are successively disassembled without significant spillage of pumping liquid contained in the pipe string onto the area surrounding the oil well, said assembly comprising;

• an elongated pipe section connection body having a sidewall and end structure for connection of the body to the lower part of the pipe string above the pump unit, said sidewall of the connection body having opposed inner and outer faces presenting a generally cylindrical internal diameter, said connection body being provided with an internally threaded opening therethrough between said faces;
• and
• an integral fitting having a tubular housing having an outer cylindrical wall surface and an inner tubular wall surface presenting a central pumping liquid discharge passage through the housing, said inner wall surface defining the passage having generally axially aligned, spaced pumping liquid entrance and pumping liquid exit edge portions respectively, a portion of the outer wall surface of the housing being provided with external threads for complementally engaging the threads of the threaded opening in the sidewall of the pipe section, the pumping liquid entrance edge portion of the fitting being of a diameter approximately equal to the diameter of said passage,
• said fitting being sealingly and removably threaded into the opening in the sidewall of the pipe section,
• said housing being provided with a thin, metallic, frangible, shape-retaining, passage-closing rupture disc having an outer circular marginal portion welded to the housing adjacent said entrance edge portion of the passage, 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 with the concave surface thereof facing the interior of the connection body in disposition directly exposed to pumping liquid in the connection body,
• 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 liquid withstand pressure to the disc sufficient to withstand the pressure of 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 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 activation pressure is applied to the pumping liquid in the pipe string, said activation pressure being selectively applied to cause said rupture of the disc in order to drain all of said pumping liquid from the pipe string through the opening in the disc and the discharge passage of the fitting prior to removal of the pipe string from the well,
• the diameter of the disc and said line of weakness in the disc being of a pattern such that upon operator-selected rupture, the disc splits into individual petals that are in relatively close, generally conforming proximity to the inner wall surface of the passage.