Pressure relief valve assembly and methods

A pressure relief valve assembly defining a longitudinally-extending center axis, the pressure relief valve assembly comprising:

• a female sub defining a first internal fluid passage, the first internal fluid passage being generally coaxial with the center axis, the female sub comprising a counterbore, a first internal annular shoulder defined by the counterbore, and an internal threaded connection formed in an interior of the female sub at the counterbore;
• a male sub coupled to the female sub and defining a second internal fluid passage, the second internal fluid passage being generally coaxial with the center axis and thus with the first internal fluid passage, the male sub comprising a first external threaded connection formed in an exterior surface of the male sub threadably coupled to an internal threaded connection formed in an interior surface of the female sub, wherein the male sub is entirely housed within the female sub;
• and
• a rupture disc clamped between the male sub and the first internal annular shoulder of the female sub so that the rupture disc is positioned axially between the first and second internal fluid passages, the rupture disc being adapted to rupture when a pressure in the second internal fluid passage exceeds a pressure in the first internal fluid passage by a predetermined pressure differential, so that the second internal fluid passage communicates fluid into the first internal fluid passage;
• wherein the first external threaded connection of the male sub is threadably engaged with the internal threaded connection of the female sub to connect the male sub to the female sub and clamp the rupture disc between the male sub and the female sub;
• and
• wherein the first internal fluid passage of the female sub adjacent the rupture disc comprises a frusto-conical segment flaring radially outward from the first internal fluid passage, and diameters of the frusto-conical segment being substantially greater than a diameter of the first internal fluid passage to increase a likelihood that shrapnel from the ruptured rupture disc will flow out of the female sub.