A pressure relief valve to balance the pressure between a cargo tank and the ambient atmosphere is described. The valve is so arranged that the velocity of the out flowing gas jet at no time is under a preset value when the valve is in open position. The valve comprises a valve body (2) designed to act against a valve seat (1) located in a structural outlet (5a) from the cargo tank, which valve body (2) is connected to a rod (7) extending into the structural outlet (5a) opening (5). The rod (7) is being supported and guided by a frame structure (6) extending into the structural outlet (5a) opening (5) and fixed to the structural outlet (5a).

A thief hatch assembly for a storage tank includes a housing and a cover that rests on an upper surface of the housing to seal and maintain a pressure within the storage tank. The thief hatch cover is configured to open at a predetermined set pressure to relieve excess pressure from the storage tank. The thief hatch assembly is attached to the storage tank using blind threaded mounting holes to prevent escape of gases from the storage tank through the mounting holes. In one embodiment, the blind threaded holes are provided in a flange adapter that mounts between the thief hatch housing and the storage tank. In another embodiment, the blind threaded holes are provided in a flange adapter that is welded to the storage tank. In another embodiment, the blind threaded holes are provided in the base of the thief hatch housing. Seals are provided between the mounting surfaces.

A thief hatch assembly for a storage tank includes a housing and a cover that rests on an upper surface of the housing to seal and maintain a pressure within the storage tank. The thief hatch cover is configured to open at a predetermined set pressure to relieve excess pressure from the storage tank. The thief hatch assembly is attached to the storage tank using blind threaded mounting holes to prevent escape of gases from the storage tank through the mounting holes. In one embodiment, the blind threaded holes are provided in a flange adapter that mounts between the thief hatch housing and the storage tank. In another embodiment, the blind threaded holes are provided in a flange adapter that is welded to the storage tank. In another embodiment, the blind threaded holes are provided in the base of the thief hatch housing. Seals are provided between the mounting surfaces.

A storage tank isolation system for a storage tank includes a vertical riser attached to a top of the storage tank and having a cover with an aperture and a connecting member extending from a side of the vertical riser. A distal end of the connecting member is parallel to the top of the storage tank and attached to a storage hatch. The storage tank isolation system includes a valve assembly, which includes a stem extending through the aperture in the cover, a valve plate attached to the stem, and a valve seat sealed to the vertical riser at a position below a connection to the connecting member. The valve plate is moves with the stem from an open position in which the valve plate is held within the vertical riser at a position equal to or above the connection to the connecting member and a closed position.

A storage container for storing quantities of acids and other volatile liquids is described having a recirculation system that can include a recirculation pump and a recirculation line that goes from a bottom end of the container toward a top end of the container, where the recirculation line has a plurality of pressure relief valves spaced along its length. The storage container may also include a leak detection system and a high level warning system.

A storage container for storing quantities of acids and other volatile liquids is described having a recirculation system that can include a recirculation pump and a recirculation line that goes from a bottom end of the container toward a top end of the container, where the recirculation line has a plurality of pressure relief valves spaced along its length. The storage container may also include a leak detection system and a high level warning system.

A vent valve includes an outer frame, a ventilation box movable in the outer frame, a sealing cover, a buoyant box and elongate sliding members. The ventilation box has an interior space. The sealing cover has a cover opening, and closes/opens a surrounding space defined by the ventilation box and the outer frame. The buoyant box is disposed within the interior space. When the buoyant box abuts the sealing cover and closes the cover opening, the cover opening is disconnected from the interior space. When the buoyant box moves away from the sealing cover, the interior space communicates the cover opening. The sliding members slidingly contact the outer frame and ventilation box to guide sliding movements.

A vent valve includes an outer frame, a ventilation box movable in the outer frame, a sealing cover, a buoyant box and elongate sliding members. The ventilation box has an interior space. The sealing cover has a cover opening, and closes/opens a surrounding space defined by the ventilation box and the outer frame. The buoyant box is disposed within the interior space. When the buoyant box abuts the sealing cover and closes the cover opening, the cover opening is disconnected from the interior space. When the buoyant box moves away from the sealing cover, the interior space communicates the cover opening. The sliding members slidingly contact the outer frame and ventilation box to guide sliding movements.

A system for controlling an environment within a fuel tank is provided. The system includes a conduit with a plurality of vents, wherein the conduit defines a path through the fuel tank, and wherein the conduit is configured to direct a flow of air along the path and out the plurality of vents.

A system for controlling an environment within a fuel tank is provided. The system includes a conduit with a plurality of vents, wherein the conduit defines a path through the fuel tank, and wherein the conduit is configured to direct a flow of air along the path and out the plurality of vents.