Dual stage pressure relief valve

A plug system for sealing a pipeline, the plug system comprising:

• an inflatable plug including:
• a tubular member having an outer surface that extends from a first end to a second end;
• and
• a first plate and a second plate secured to the first end and the second end of the tubular member respectively, such that the first plate, the second plate, and the inner surface of the tubular member together define a central chamber of the inflatable plug, and
• a dual stage pressure relief valve coupled to at least one of the first plate and the second plate, the dual stage pressure relief valve configured to release a pressure within the inflatable plug after a desired upper pressure limit is achieved within the inflatable plug, wherein the dual stage pressure relieve valve comprises:
• a main body,
• a pilot piston defining a reset channel in fluid communication with the central chamber of the inflatable plug, and
• a poppet cap defining a cap channel in fluid communication with the reset channel of the pilot piston and with a pressure cavity defined by the poppet cap and an end of the main body,
• wherein in a closed position of the pressure relief valve, fluid communication between the pressure cavity and atmosphere is substantially prevented, and wherein in an open position of the pressure relief valve, the pilot piston is spaced from the poppet cap defining a pressure relief channel therebetween, the pressure relief channel being in fluid communication with the pressure cavity and atmosphere.

A pressure relief valve comprising:

• a main body having a first portion and a second portion, the first portion defining a main channel that extends from a first opening to a second opening, the second portion defining a component chamber;
• a poppet bulb positioned within the component chamber, the poppet bulb defining a first flow channel being in fluid communication with the main channel;
• a pilot piston positioned adjacent to the poppet bulb within the component chamber, the pilot piston defining a reset channel, the reset channel being in fluid communication with the first flow channel of the poppet bulb;
• and
• a poppet cap defining a cap channel, the cap channel being in fluid communication with the reset channel of the pilot piston, the cap channel having a diameter that is greater than a diameter of the reset channel, an opening of the cap channel being in fluid communication with a pressure chamber defined by the poppet cap, the second portion of the main body, and a body cap,
• wherein the pressure relief valve is operable between a closed position and an open position, wherein in the closed position the poppet bulb is located adjacent to the second opening of the main channel and in contact with an inner surface of the main channel such that a fluid flow through the main channel is substantially prevented, and wherein in the open position the pilot piston, the poppet bulb, and the poppet cap are spaced away from the second opening of the main channel such that a fluid flow through the second opening to atmosphere is allowed wherein in the closed position of the pressure relief valve, fluid communication between the pressure chamber and atmosphere is substantially prevented, and wherein in the open position fluid communication between the pressure chamber and atmosphere is allowed.