JPS60219533A - Gas sampling apparatus for detecting leakage of gas of double shell low temperature tank - Google Patents

Abstract

PURPOSE:To make it possible to detect the leakage of gas with high reliability, by attaching a pipe provided with a large number of small holes by drilling in close vicinity to the outer surface of an inner tank. CONSTITUTION:A ring-shaped pipe 2 is attached in extremely close vicinity to the outer surface of an inner tank 1 in a horizontal plane and a large number of small holes 3 are provided to the wall of the pipe 2 opposed to the outer surface of the inner tank 1 by drilling. Therefore, when a crack is generated to the inner tank 1 and low temp. liquefied gas is leaked to be gasified in a cool keeping layer, the formed gas is moved along the outer surface of the wall of the inner tank 1 by the difference of specific gravity with seal gas and the rising or falling leaked gas is sucked through small holes 3 and the generation of a crack can be detected by detecting the stored gas component.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a waste leak detection system that samples waste from the inside and outside of a double-shell cryogenic tank and performs gas detection to detect leakage of stored low-temperature liquefied gas from the inner tank. This relates to a detection gas sampling device '6.

Conventional technology The large-sized two-shell low-temperature tanks used to store low-temperature liquefied waste such as LPG, LN, and G have a storage capacity of 100,000 tons, and contain a very large amount of energy, making safety management extremely difficult. is important. Therefore, in order to prevent disasters due to tank destruction, the internal Jc! ! It is important to detect the occurrence of cracks in the r-wall. 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.

Now, if a well-ventilated material such as glass wool is used as the cold insulation material for the cold insulation layer, at least in the part that contacts the outer surface of the inner tank, cracks will form in the inner tank and the stored liquefied gas will leak from the inner tank wall to the cold insulation layer. If the gas leaks into the air, it is relatively easy for the vaporized liquefied gas to descend or ascend through the breathable layer due to the difference in specific gravity with the sealing gas, but it hardly spreads in the horizontal direction. Conventionally, gas sampling for leak detection was performed at points, but for large tanks, it is necessary to arrange many sampling devices circumferentially and connect them to the detection instrumentation, which reduces costs. The disadvantage was that it was expensive.

Purpose The present invention provides a gas sampling device that eliminates the above-mentioned drawbacks of conventional sampling devices for gas leak detection in double-shell cryogenic tanks, has a simple configuration, and is capable of covering a wide range. An object of the present invention is to provide a gas sampling device that can detect leakage by dividing the surface of an inner tank into a plurality of parts.

Structure The gas sampling device of the present invention which achieves the above object has a large number of small holes bored in the tube wall, and the tube connected to the gas detection instrumentation is placed in contact with the outer surface of the inner tank and immersed in water l'+fij. Hereinafter, based on the embodiments of the present invention shown in the drawings, (゛CC
10 Explain.

FIGS. 1(a) and 1(b) are a sectional view and a perspective view showing a part of a gas sampling device according to an embodiment of the present invention.
It consists of a tube 2 cut out in a ring shape in a horizontal plane very close to the outer surface of the inner tank, and a large number of small holes 6 are bored in the tube wall of the portion of the tube 2 facing the outer surface of the inner tank. It is set up. The ring-shaped pipe 2 is connected to a gas detection J1 device via a pump (not shown).

Therefore, if a crack occurs somewhere in the inner tank 1 and the low-temperature liquefied gas 4 stored in the inner tank leaks through the crack, it will vaporize within the cold insulation layer between the inner and outer tanks.

Due to the difference between the specific gravity and the specific gravity of the seal gas, the inner tank Ijt
j Descend or rise along the outer surface of 1. therefore,
If the gas sampling ring tube 2 is provided at the location where the descending or ascending leaked gas accumulates or along the route, the leaked gas will be sucked into the tube 2 along with the sealing gas.
The gas flows horizontally through the pipe and is sent to a gas detection system to detect stored gas components and detect gas leaks, ie, the occurrence of cracks.

If the specific gravity of the stored low-temperature liquefied gas vaporized with LPG such as propane or butane is greater than the specific gravity of nitrogen gas normally used as sealing gas, the leaked gas will accumulate at the bottom of the space between the inner and outer tank side plates. Therefore, if the ring-shaped pipe 2 for gas sampling is installed in contact with the outer surface of the lowest part of the inner tank side plate 1, gas sampling will be possible no matter where a leak occurs on the inner 4'rt side plate or the inner tank roof. Since it is taken in from the pipe 2 along with the seal gas, leakage can be detected early and reliably.

If the stored low-temperature liquefied gas is vaporized, such as LNG (mainly metasogas), and its specific gravity is lower than the specific gravity of nitrogen in the sealing gas, the leaked gas will rise inside the cold storage jVt along the outer surface of the inner tank, causing the gas to The ring-shaped sampling tube may be provided near the top of the dome-shaped inner tank roof.

Furthermore, as in the embodiment shown in Fig. 2, if a plurality of ring-shaped pipes 2 for gas sampling are provided at a plurality of positions in the height direction of the inner tank, the gas rises and falls from the point of leakage '+tt. The ring-shaped tube that passes through the process first is sampled and detected quickly, making it possible to detect leaks quickly. If connected to detection instrumentation, the inner tank surface can be sectioned in the height direction, making it possible to limit the estimated range of leakage locations.

Depending on the specific gravity of the stored liquefied gas when it is vaporized and the specific gravity of the nitrogen gas, a ring-shaped weir 5 is installed on the outer surface of the inner tank 1 to collect leakage gas as shown in FIG. When the gas sampling ring-shaped pipe 2 of the present invention is installed inside the tank, the leaking gas is blocked by the weir 5 and does not move above or below it, so this weir is installed in the height direction of the inner tank. If it is provided in multiple positions, it will be more useful for sectioning the inner tank wall surface.

In addition, one ring-shaped tube is partitioned into a plurality of parts in the circumferential direction of the ring, and the gas detection system is configured such that the gas sampled by each partitioned part is detected separately. By connecting, the inner tank wall surface can be sectioned into a plurality of parts in the circumferential direction to detect leakage. Therefore, by further partitioning a plurality of ring-shaped tubes provided in the height direction into a plurality of parts in the circumferential direction as shown in FIG. 2, it is possible to section the inner tank wall surface into a plurality of parts in a base 1 This is useful for limiting the estimated range of gas leaks, especially for large tanks.

The ring-shaped pipe for gas sampling of the present invention can be processed by simple bending along the outer surface shape of the inner tank, and can be simply installed on the outer surface of the inner tank by attaching it to the side plate block in advance. .

Effects As described above, according to the present invention, gas leakage can be detected at an early stage with high reliability with a simple configuration, so that a remarkable effect on safety management can be obtained.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view showing an embodiment of the gas sampling device of the present invention, FIG. 1(b) is a perspective view showing a part thereof,
FIG. 2 is a sectional view showing an example of the arrangement of the gas sampling device of the present invention, and FIG. 6 is a sectional view showing another embodiment. 1... Inner tank 2... Gas sampling tube 3...
Small hole 4...Low temperature liquefied gas 5...Weir Figure 3

Claims (5)

[Claims] (1) In a gas sampling device for gas leak detection, which samples gas from between the inner and outer tanks of a double-shell cryogenic tank and performs gas detection to detect leakage of stored low-temperature liquefied gas from the tank, there are many small holes on the pipe wall. A gas sampling device characterized in that a tube having a hole and connected to a gas detection instrument is provided in a ring shape in a horizontal plane in contact with the outer surface of an inner tank. (2) The gas sump song device according to claim 1, wherein the ring-shaped pipe is provided at the lowest position of the inner tank side plate. (3) The gas sampling device according to claim 1, wherein the ring-shaped pipe is provided near the top of the dome-shaped roof of the inner tank. (4) The ring-shaped pipe mentioned above is the fu of the height direction of the inner tank.
A plurality of gas detectors are installed at the position M, and each gas sampled by the container tube is detected separately.
The dregs sampling device according to claim 1, characterized in that the dregs sampling device is connected to one unit. (5) The ring-shaped tube is partitioned into a plurality of parts in the circumferential direction of the ring, and partitions 1. 1. Any one of claims 1 to 4, characterized in that the gas sampled by each portion is connected to a gas detection instrumentation so that gas detection is performed separately. Gas sampling device described in.