Pressure-compensated rupture disk assembly for subsea protection of a pressure vessel

A pressure-compensated rupture disk assembly for subsea protection of a pressure vessel, comprising:

• a rupture disk having a first side configured to be in fluid communication with interior fluid within the pressure vessel and having a second side that forms a first wall of a gas-filled, compressible enclosure, the rupture disk being configured to burst when a predetermined pressure within the pressure vessel is exceeded;
• a piston having a first end that is configured to be exposed to ambient seawater and a second end that forms a second wall of the compressible enclosure, wherein the piston is configured to move toward the rupture disk a predetermined distance as ambient pressure increases up to a particular ambient pressure above which further movement of the piston is stopped such that the piston's second end does not come in contact with the rupture disk wherein the piston comprises a fluid communication channel between the first and second ends;
• a dynamic piston seal configured to prevent leakage of the ambient seawater into the compressible enclosure when the rupture disk is intact and to allow movement of the piston away from the rupture disk when the rupture disk bursts, wherein the dynamic piston seal is also configured to allow movement of the piston toward the rupture disk such that gas pressure within the compressible enclosure changes in response to changes in ambient pressure;
• and
• a removable piston plug configured to seal the fluid communication channel to prevent fluid transfer through the fluid communication channel.

A method for providing subsea protection of a pressure vessel using a rupture disk assembly, comprising:

• mounting a rupture disk on the pressure vessel such that a first side of the rupture disk is in fluid communication with interior fluid within the pressure vessel and such that a second side of the rupture disk forms a first wall of a compressible fluid enclosure;
• positioning a piston on the pressure vessel at a predetermined distance from the rupture disk with a dynamic seal such that a first end of the piston is configured to be exposed to ambient seawater and a second end of the piston forms a second wall of the compressible fluid enclosure and such that the dynamic seal prevents leakage of the ambient seawater into the compressible fluid enclosure when the rupture disk is intact and allows movement of the piston away from the rupture disk and leakage of ambient seawater into the compressible fluid enclosure when the rupture disk bursts, wherein the dynamic seal is also configured to allow movement of the piston toward the rupture disk such that fluid pressure within the compressible fluid enclosure changes in response to changes in ambient pressure;
• mounting a removable piston plug on the piston so as to seal a fluid communication channel between the first and second ends such that fluid transfer through the fluid communication channel is prevented;
• and
• mounting a perforated safety cap to the pressure vessel so as to allow ambient seawater communication with the piston's first end and to secure the piston to the pressure vessel in the event of rupture disk failure.