Method for leak testing a sealed and thermally insulating tank for storing a fluid
AssigneeGaztransport Et Technigaz
InventorsMaxime Champagnac, Pierre Jolivet, Mael Bleomelen
Life of this patent
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Abstract
A method is described for checking the sealing of a sealed and thermally insulating tank for storing a liquefied gas at low temperature. The tank has a primary space and a secondary space where, in order to perform the check, a difference in pressure is created between the two spaces at least some of the inert gas injected into the primary space is recovered via at least one secondary outlet of the secondary space so as to be reinjected into the primary space.
Claims16
A method for checking the sealing of a sealed and thermally insulating tank (1) for storing a liquefied gas at low temperature (30), the tank (1) being at low temperature (30), the tank (1) comprising a carrier structure which has an inner hull (2) and an outer hull (3), a confined space (4) between the inner hull (2) and the outer hull (3), a primary sealing membrane (9) which is intended to be in contact with the liquefied gas at low temperature (30) contained in the tank (1), and a secondary sealing membrane (7) which is arranged between the primary sealing membrane (9) and the inner hull (2), a primary space (8) between the primary sealing membrane (9) and the secondary sealing membrane (7) and a secondary space (6) between the secondary sealing membrane (7) and the inner hull (2), the primary space (8) and the secondary space (6) comprising insulating materials, the primary space (8) comprising at least one primary gas inlet (18) and the secondary space (6) comprising at least one secondary gas outlet (19), said primary sealing membrane resting directly on the insulating materials contained in the primary space and said secondary sealing membrane resting directly on the insulating materials contained in the secondary space, the method comprising the following successive steps for detecting the location of a sealing defect of the secondary sealing membrane (7) in the form of a cold spot on the outer surface of the inner hull (2):
- a step referred to as main step in which the secondary space (6) is brought to a pressure lower than the pressure of the primary space (8), with a pressure differential P1, by injecting an inert gas into the primary space via the primary gas inlet (18) and causing gas to be expelled or drawn from the secondary gas outlet (19) of the secondary space and then by measuring the temperature of an outer surface of the inner hull (2) from the confined space (4) situated around the inner hull (2);
- a step referred to as a subsequent step in which the temperature of the outer surface of the inner hull (2) is measured from the confined space (4) under the normal operating conditions of the tank (1);
- characterized in that, during the main step, at least some of the inert gas injected into the primary space (8) is recovered by at least one secondary outlet (19, 20 or 23) of the secondary space (6) and is reinjected into the primary space (8).
A floating or onshore storage installation for a liquefied gas at low temperature (30), comprising:
- a tank (1) at low temperature (30) comprising a carrier structure which has an inner hull (2) and an outer hull (3), the space between the inner hull (2) and the outer hull (3) being referred to as the confined space (4), a primary sealing membrane (9) which is intended to be in contact with the liquefied gas at low temperature (30) contained in the tank, and a secondary sealing membrane (7) which is arranged between the primary sealing membrane (9) and the inner hull (2), the space between the primary sealing membrane (9) and the secondary sealing membrane (7) is referred to as the primary space (8) and the space between the secondary sealing membrane (7) and the inner hull (2) is referred to as the secondary space (6), the primary space (8) and the secondary space (6) comprising insulating materials, the primary space (8) comprising at least one primary gas inlet (18), the secondary space (6) comprising at least one secondary gas outlet (19), said primary sealing membrane resting directly on the insulating materials contained in the primary space and said secondary sealing membrane resting directly on the insulating materials contained in the secondary space,
- an inert gas reservoir (16) which is arranged in order to inject inert gas into the primary space (8) through the primary gas inlet,
- an injection device (45) which is capable of injecting inert gas of the inert gas reservoir (16) via the primary gas inlet (18), and thus placing the primary space (8) under pressure relative to the secondary space (6),
- a suction device (80, 80′) which is connected to the secondary gas outlet (19) in order to generate a lower pressure in the secondary space (6) than the pressure in the primary space (8),
- a device for measuring the temperature of the outer surface of the inner hull (2),
- a system for displaying the temperature measurements in order to locate a sealing defect of the secondary sealing membrane (7) in the form of a cold spot on the outer surface of the inner hull (2),
- characterized in that the suction device comprises at least one suction means (80) consisting of a pump that draws at least some of the inert gas out of the secondary space (6) and reinjects it into the primary space (8) via the aforesaid injection device (45).
Dependencies are inferred from the claim text.