All-attitude cryogenic vapor vent system

Claim 2

In a cryogenic liquid storage-gas supply system including a thermally insulated cryogenic liquid storage-dispensing containing having top and bottom ends and being invertible between top-up dispensing and bottom-up filling positions, gas vent-liquid fill conduit means with a first end terminating in the container top end and a second end outside said container top end, liquid withdrawal-gas vent conduit means with a first end terminating in the container bottom end and a second end outside said container top end, an invertible liquid vaporizing-gas vent control circuit outside the container and joined at a first inlet end to the liquid withdrawal-gas vent conduit means second end and including a first atmospheric vaporizer, and gas flow regulating means between said first atmospheric vaporizer and the gas discharge other end of said circuit: the improvement of an all-attitude gas relief circuit for said container comprising (a) first pressure relief means between said first atmospheric vaporizer and said gas flow regulating means, (b) branch conduit means having one end in flow communication with the gas ventliquid fill conduit second end, (c) second flow restrictionpressure relief means in branch conduit (b) constructed to vent gas at lower pressure than said first pressure relief means and at maximum rate between 3 and 25 times the normal evaporation rate from the container, and (d) a second atmospheric vaporizer in flow communication at its inlet end with the branch conduit (b) one end and in flow communication at its discharge end with the second flow restriction-pressure relief means, and constructed with a heat transfer capacity not greater than onethird the first atmospheric vaporizer capacity and also sufficient to vaporize cryogenic liquid entering its inlet end and discharge gas at rate between 1.04 and 1.30 times the maximum vent rate of (c).

Claim 3

A cryogenic liquid storage-gas supply system according to claim 1 wherein the second flow restriction-pressure relief means (c) is constructed to vent gas at maximum rate between 5 and 20 times the normal evaporation rate from the container.

Claim 4

A cryogenic liquid storage-gas supply system according to claim 1 wherein the second atmospheric vaporizer heat transfer capacity is not greater than one-fifth the first atmospheric vaporizer capacity.

Claim 5

A cryogenic liquid storage gas supply system according to claim 1 wherein the second atmospheric vaporizer heat transfer capacity is sufficient to vaporizer cryogenic liquid entering the inlet end and discharge gas at rate between 1.08 and 1.25 times the maximum vent rate of (c).

Claim 6

A cryogenic liquid storage-gas supply system according to claim 1 wherein a pressure relief valve and a separate flow restriction element in flow communication with each other comprise the second flow restriction-pressure relief means (c).

Claim 7

A cryogenic liquid storage-gas supply system according to claim 1 wherein a pressure relief valve and a porous member in downstream flow communication with said pressure relief valve comprise the second flow restriction-pressure relief means (c).

Claim 8

A cryogenic liquid storage-gas supply system according to claim 1 wherein the second flow restriction-pressure relief means is constructed to vent gas at maximum rate between 5 and 20 times the normal evaporation rate from the container, the second atmospheric vaporizer is constructed with a heat transfer capacity not greater than one-fifth the first atmospheric vaporizer capacity and also sufficient to vaporize cryogenic liquid entering its inlet end and discharge gas at rate between 1.08 and 1.25 times the maximum vent rate of (c), and wherein a pressure relief valve and a porous member in downstream flow communication with said pressure relief valve comprise the second flow restriction-pressure relief means (c).

Claim 9

In a method for supplying gas from a thermally insulated cryogenic liquid-storage-dispensing container having top and bottom ends and being invertible between top-up dispensing and bottom-up filling positions and wherein during the gas supplying step cryogenic liquid flows by overhead vapor pressure upwardly from the lowest zone of the container, discharged from the container top end and vaporized by atmospheric heat to form the gas supply, the improvement comprising: in a top-up dispensing position, a. when gas is not being supplied, venting vapor through a passage from the highest zone of the container, at flow-restricted maximum rate between 3 and 25 times the normal evaporation rate from the container, warming the vapor by atmospheric heat and discharging the warmed vapor when the container pressure is above a first lowest superatmospheric relief pressure; and b. when gas is being supplied, flowing cryogenic liquid by overhead vapor pressure upwardly from the lowest zone of the container, discharging such liquid from the container top end, vaporizing the so-discharged liquid by atmospheric heat, warming the vapor and withdrawing the warmed vapor as the gas supply and simultaneously venting vapor in accordance with step (a); and c. in a non-vertical position such that liquid flows through the passage of step (a) and the container gas pressure rises above the first lowest superatmospheric relief pressure: discharging first liquid from the normally top end of the container at a first lower flow restricted rate, vaporizing the discharged first liquid, warming the cold first vapor to ambient temperature and releasing the warmed first vapor at pressure above said first lowest superatmospheric relief pressure; and when the container pressure rises to a second higher superatmospheric relief pressure between 1.08 and 1.75 times the first superatmospheric relief pressure on an absolute basis, simultaneously discharging second liquid from the normally bottom end of the container at a second higher rate, vaporizing the discharged second liquid by atmospheric heat, warming the cold second vapor and releasing the warmed vapor at pressure above said second superatmospheric relief pressure.

Claim 10

In a method for supplying gas from a thermally insulated cryogenic liquid-storage-dispensing container having top and bottom ends and being invertible between top-up dispensing and bottom-up filling positions and wherein during the gas supplying step cryogenic liquid flows by overhead vapor pressure upwardly from the lowest zone of the container, discharged from the container top end and vaporized by atmospheric heat to form the gas supply, the improvement comprising: in a top-up dispensing position, a. when gas is not being supplied, venting vapor through a passage from the highest zone of the container, at flow-restricted maximum rate between 3 and 25 times the normal evaporation rate from the container, warming the vapor by atmospheric heat and discharging the warmed vapor when the container pressure is above a first lowest superatmospheric relief pressure; and b. when gas is being supplied, flowing cryogenic liquid by overhead vapor pressure upwardly from the lowest zone of the container, discharging such liquid from the container top end, vaporizing the so-discharged liquid by atmospheric heat, warming the vapor and withdrawing the warmed vapor as the gas supply and simultaneously venting vapor in accordance with step (a); and c. in a non-vertical position such that liquid flows through the passage of step (a) and the container gas pressure rises above the first lowest superatmospheric relief pressure: discharging first liquid from the normally top end of the container at a first lower flow restricted rate, vaporizing the discharged first liquid, warming the cold first vapor to ambient temperature and releasing the warmed first vapor at pressure above said first lowest superatmospheric relief pressure; and when the container pressure rises to a second higher superatmospheric relief pressure between 1.08 and 1.75 times the first superatmospheric relief pressure on an absolute basis, simultaneously discharging second liquid from the normally bottom end of the container at a second higher rate, vaporizing the discharged second liquid by atmospheric heat, warming the cold second vapor and releasing the warmed vapor at pressure above said second superatmospheric relief pressure.

Claim 11

A method according to claim 8 wherein vapor is vented during step (a) at flow-restricted maximum rate between 5 and 20 times the normal evaporation rate from the container.

Claim 12

A method according to claim 8 wherein said second higher superatmospheric relief pressure is between 1.15 and 1.4 times the superatmospheric relief pressure on an absolute basis.