Bulged single-hinged scored rupture having a non-circular varying depth score line

Apparatus for testing the integrity of a sectional tubing string within an oil well casing, said apparatus comprising:

• a tubular holder presenting a passage therethrough and having opposed open ends, one of said holder ends being adapted for attachment to an end of one section of the tubing string;
• a rupture disc within said holder in normally closing relationship to said passage, said disc including an outer annular peripheral flange portion having a first annular face, an opposed second annular face and an inner circular margin, an inner concavo-convex, generally hemispherical bulged region inboard of and projecting away from said first annular face of the flange portion, said bulged region having opposed convex and concave faces and provided with an outer circular margin, and a unitary, annular, transversely arcuate transition region integral with and joining the outer circular margin of the bulged region with the inner circular margin of the flange portion,
• said bulged region being provided with a continuous score line in the concave face thereof adjacent the outer circular margin of the bulged region in proximal spaced relationship to said transition region, said score line defining a burst region and having a semi-circular segment of major length, and a generally curvilinear score line cam segment of minor length with respect to the length of said semi-circular score line segment, said cam score line segment projecting outwardly of the diameter of said major score line segment and located inboard of said transition region,
• said score line varying in depth along the length thereof with the score line being of greatest depth along said cam score line segment and of shallowest depth in substantially direct opposition to said cam score line segment to define a hinge portion of the score line,
• said disc being openable under the influence of liquid overpressure directed against the concave face of the disc to allow flow of the liquid past the disc, the cam score line segment being of a depth relative to the remaining portion of the score line to cause the cam score line segment to rupture first under said liquid pressure while the major score line segment is of a varying depth which allows the burst region to swing to a fully opened rupture position without severing of the hinge portion of the score line with the edge of the burst region disposed in generally perpendicular relationship to said flange portion of the disc,
• said tubular holder being provided with sidewall structure configured to generally complementally receive and, allow sufficient full opening of the rupture disc under said liquid overpressure to thereby permit full, substantially unimpeded bi-directional flow of liquid through the tubular holder after rupture of the disc.