JPH0231330B2 - NIJUKAKUTEIONTANKUNOGASUROEIKENCHISOCHI - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to an apparatus for sampling gas from between the inner and outer tanks of a double-shelled cryogenic tank, performing gas detection, and detecting leakage of stored low-temperature liquefied gas from the inner tank. .

Conventional technology Double-shell cryogenic tanks that store low-temperature liquefied gases such as LPG and LNG have a storage capacity of tens of thousands of tons in large-scale tanks, and contain an extremely large amount of energy, making safety management extremely important. be. Therefore, in order to prevent disasters due to tank destruction, it is important to detect cracks in the inner tank wall at an early stage. The occurrence of cracks is generally detected by sampling the seal gas between the inner and outer tanks, which serve as a cold insulation layer, and detecting the gas.

By the way, it is an important matter in the operation of the tank which part of the tank the leakage point is. for example,
The degree of potential danger differs greatly depending on whether the leak point is the inner tank roof or the side plate. Furthermore, the degree of danger is different depending on whether the leakage point is relatively upper or lower than the inner tank side plate. Therefore, the method of countermeasures and the level of urgency will differ depending on where the leak is.

Therefore, it is very important to detect where leakage has occurred in the height direction of the side panels and roof of the inner tank.

Now, if the low-temperature liquefied gas stored in the double-shell low-temperature tank leaks from the inner tank into the cold insulation layer and vaporizes, its specific gravity is greater than the specific gravity of the nitrogen gas used as the seal gas in the cold insulation layer. In the case of propane, butane, etc., the leaked gas descends along the outer surface of the inner tank through the ventilation gap of the cold insulation material of the cold insulation layer.

Purpose: In view of the above-mentioned requirements for leakage detection in a double-shell cryogenic tank, the present invention provides an inner tank of a double-shell cryogenic tank that stores a low-temperature liquefied gas whose specific gravity when vaporized is greater than the specific gravity of the seal gas in the cold insulation layer. An object of the present invention is to provide a gas leakage detection device capable of early detecting gas leakage by appropriately sectioning side plates and a roof.

Configuration The gas leak detection device according to the present invention that achieves this objective has ring-shaped weirs for the flow from above, for example L-shaped weirs with upwardly facing flanges, installed on the outer surface of the inner tank side plate at a plurality of positions in the height direction. A plurality of ring-shaped weirs with different radii are provided concentrically on the upper surface of the inner tank roof, and gas sampling means are provided at the lower corner of the side dammed by these weirs and at the lowest part of the side cold insulation layer. A gas detection instrumentation device is provided to separately detect sample gases corresponding to each weir.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

The attached drawing shows an embodiment in which the present invention is applied to an LPG tank with a double shell flat bottom structure, and shows a space 3 between an inner tank side plate 1 and an outer tank side plate 2 and an inner tank roof 4.
The space 6 between the tank and the outer tank roof 5 both serves as a cold insulation layer, and the inside of the inner tank serves as an LPG storage space 7. The cold insulation layers 3 and 6 are filled with a cold insulation material 8 and nitrogen gas as a seal gas. Note that a bottom cold insulation 11 is formed between the inner tank bottom plate 9 and the outer tank bottom plate 10 using a relatively hard cold insulation material.

Ring-shaped members 12 having an L-shaped cross section with flanges facing upward are attached to the inner tank side plate 1 at a plurality of positions in the height direction by welding with the toes on the opposite side of the flange abutting against the outer surface of the inner tank 1. It forms a dam. Furthermore, a plurality of ring-shaped weirs 13 having different radii are provided concentrically on the upper surface of the inner tank roof. The weir 12 can also use a stiffener in the inner tank.

A gas sampling device 14 for gas detection is provided at the lower corner of the side where a gas having a higher specific gravity than the sealing gas is dammed by these weirs 12 and 13 and at the lowest level of the side cold insulation layer. If the gas sampling device is a dotted suction port, it is necessary to provide a plurality of them along a ring-shaped weir in one weir. As the gas sampling device 14, a ring-shaped pipe having a large number of small holes in the pipe wall may be provided along the weir. Gas detection instrumentation is provided that can individually detect the gas sampled by the sampling device corresponding to each weir and the bottom of the cold storage layer. To do this, for example, the instrumentation piping from the gas sampling device installed at each weir can be connected to individual gas detection instrumentation, or it can be switched at a predetermined timing with a switching valve to one gas detection instrumentation. This is achieved by connecting.

Since this device is configured as described above, for example, if a crack occurs somewhere in the inner tank roof and the gas in the inner tank leaks into the cold insulation layer 6, the leaked gas will be affected by the difference in specific gravity from the seal gas. As a result, the water flows radially outward in the cold insulation layer along the upper surface of the dome-shaped inner tank roof 4, is stopped by the first weir 13, and accumulates inside the weir. In addition, the stored gas that leaked from cracks that occurred somewhere on the shoulder of the inner tank and the side plate 1 evaporates within the cold insulation layer 3, and due to the difference in specific gravity with the nitrogen gas that is the sealing gas, it leaks onto the outer surface of the inner tank side plate 1. It descends along the line, is stopped by the first weir 12 it encounters, and accumulates at the bottom of the space surrounded by the flange of the weir 12, the horizontal part, and the inner tank side plate 1.

Therefore, by continuously sampling the seal gas from the gas sampling device 14 corresponding to each weir 12 and 13 and performing gas detection, it is possible to detect the stored gas in the gas drawn by the gas sampling device corresponding to a certain weir. If the component is detected, it is determined that the leakage location is within the range between the weir and the weir adjacent to the upstream side of the weir (that is, the center side of the roof 4, and the upper part of the weir of the side plate 1). Ru.

In addition, when using a granular cold insulating material that does not have good ventilation, such as perlite, as the cold insulating material for the cold insulating layers 3 and 6, a certain thickness of material is used along the outer surface of the inner tank to facilitate the movement of leaked gas. It is effective to provide a layer of air-permeable cold insulation material such as glass wool in the area. In that case, it is more effective to limit the movement range of the leaked gas by covering the outer surface of the glass wool layer with a suitable film such as polyethylene film, polyester film, or vinyl chloride film.

Effects As described above, according to the present invention, leakage from the inner tank of a double-shell cryogenic tank can be detected early along with the range of the leakage point, so appropriate measures can be taken to ensure safety. Significant management effects can be obtained.

[Brief explanation of drawings]

The attached drawings are cross-sectional views showing embodiments of the present invention. 1... Inner tank side plate, 2... Outer tank side plate, 3... Side cold insulation layer, 4... Inner tank roof, 5... Outer tank roof, 6...
...Roof cold insulation layer, 7...Stored low-temperature liquefied gas, 8...
Cold insulation material, 12, 13... weir, 14... gas sampling device.

Claims (1)

[Claims] 1 Gas is detected by sampling gas from between the inner and outer tanks of a double-shelled flat-bottomed cryogenic tank, which stores low-temperature liquefied gas in the inner tank and fills cold insulation material and seal gas between the inner and outer tanks to form a cold insulation layer. In a device for detecting gas leakage from the inner tank, where the specific gravity of the low-temperature liquefied gas when vaporized is greater than the specific gravity of the seal gas, there is a mark on the outer surface of the inner tank side plate in the height direction. Ring-shaped weirs are provided at multiple locations to prevent the flow from above, and multiple ring-shaped weirs with different radii are provided concentrically on the upper surface of the inner tank roof, and the lower corners and sides of the side that are dammed by these weirs are A gas leak detection device characterized in that a gas sampling means is provided at the lowest part of a cold insulation layer, and a gas detection instrumentation is provided to separately detect sample gas corresponding to each weir.