Patent ID: 8104296

Claim:
A cryogenic storage tank comprises: (a) a cryogen space defined by a thermally insulated vessel for storing a cryogenic fluid; (b) a partition dividing said cryogen space into a main storage space and an auxiliary space; (c) a conduit connecting said main storage space with a coupling outside said storage tank; (d) a first valve disposed inside said cryogen space and associated with a first fluid passage through said partition, said first fluid passage being in fluid communication with a lower region of said auxiliary space and said first valve comprising a first valve member that is actuatable by fluid forces within said cryogen space to move from an open position to a seated position when said fluid forces within said main storage space are higher than fluid forces within said auxiliary space by a predetermined amount; (e) a second fluid passage through said partition, wherein said second fluid passage comprises a restricted flow area that is dimensioned to have a cross-sectional flow area that is smaller than that of said conduit such that there is a detectable increase in back-pressure in said conduit when said cryogenic fluid is being introduced into said main storage space and said main storage space is filled with liquefied gas; and (f) a second valve disposed in said second fluid passage, said second valve comprising a second valve member that is actuatable by fluid forces within said cryogen space to move between an open position and a seated position, wherein closing forces acting on said second valve member associated with said second valve urge said second valve member to said seated position when fluid pressure within said main storage space does not exceed fluid pressure within said auxiliary space by a predetermined amount.