JP2015020752A - Leak detector installation structure in low temperature tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leak detector installation structure in a low temperature tank capable of accurately and quickly detecting leak of low temperature liquefied gas from an inner tank.SOLUTION: A leak detector installation structure in a low temperature tank is a structure for installing a leak detector 9 having a wiring part 9a, and a temperature measurement part 9b provided at the leading end of the wiring part 9a on a bottom plate 6 of an annular space part of a low temperature tank provided with a metal inner tank for storing liquefied gas, an outer tank surrounding the inner tank, the annular space part between the inner tank and the outer tank, and the metal bottom plate 6 provided at the bottom of the annular space part. The temperature measurement part 9b is arranged on the bottom plate 6 of the annular space part in a state of being separated from the bottom plate 6 through a heat shielding material 12.

Description

  The present invention relates to an installation structure of a leak detector in a low temperature tank.

  As a low-temperature tank for storing a low-temperature liquefied gas such as LNG, LPG, or liquefied ethylene, a double-shell structure having a metal inner tank and an outer tank covering the metal inner tank is known. In such a low temperature tank, when the low temperature liquefied gas stored in the inner tank leaks to the outside, it is necessary to immediately detect this and repair the leaked portion. However, in the low temperature tank, the annular space between the inner tank and the outer tank is filled with a cold insulating material such as pearlite, so it is not possible to detect low temperature liquefied gas that leaks from the inner tank and accumulates in the annular space. difficult.

Conventionally, based on such a background, a liquid collecting tub that is held at a predetermined position and moves from the predetermined position by receiving a leaked liquid, and a detecting unit that detects the movement of the liquid collecting tub is provided. A liquid leakage detection device has been proposed (see, for example, Patent Document 1).
However, such a detection device is difficult to install in an annular space filled with a cold insulating material such as pearlite as described above.

  Therefore, a leakage detector that detects leakage of low-temperature liquefied gas by detecting temperature (low temperature) is usually installed (installed) in the annular space. This leakage detector has a wiring part and a temperature measuring part provided at the tip thereof, and detects the temperature change when the low-temperature liquefied gas leaks in the temperature measuring part.

JP 2000-9300 A

  However, conventionally, the temperature measuring part of the leak detector is welded onto a metal bottom plate plate provided at the bottom of the annular space via a metal plate, so that the low-temperature liquefied gas in the inner tank The cold is transmitted through the bottom plate and the plate, so that the temperature measuring unit detects a low temperature close to the temperature of the low-temperature liquefied gas.

  As described above, when the temperature measuring unit (leakage detector) detects a low temperature close to the temperature of the low-temperature liquefied gas, even if the low-temperature liquefied gas actually leaks from the inner tank, the leak is simply a heat. It is difficult to determine whether the temperature is low due to conduction. Therefore, conventionally, it has been difficult to accurately and quickly detect the leakage of the low-temperature liquefied gas from the inner tank.

  The present invention has been made in view of the above circumstances, and its object is to install a leak detector in a low-temperature tank that can accurately and quickly detect leakage of low-temperature liquefied gas from the inner tank. To provide a structure.

The installation structure of the leak detector in the low temperature tank of the present invention includes a metal inner tank for storing liquefied gas, an outer tank surrounding the inner tank, and an annular provided between the inner tank and the outer tank. A low-temperature tank comprising a space portion and a metal bottom plate plate provided at the bottom of the annular space portion, on the bottom plate plate of the annular space portion, a wiring portion and a temperature measurement provided at the tip of the wiring portion. A leak detector having a portion,
The temperature measuring unit is arranged on the bottom plate in the annular space so as to be separated from the bottom plate via a heat shield.

  Further, in the installation structure of the leak detector in the low temperature tank, the heat shield material is formed by a cylindrical heat shield material formed in a cylindrical shape, and the leak detector has the wiring section or the temperature measuring section described above. It is preferable to be inserted into the hole of the tubular heat shield.

  In the leak detector installation structure in the low-temperature tank, the leak detector has the wiring portion inserted into the hole of the cylindrical heat shield, and the temperature measuring portion is a hole of the cylindrical heat shield. It is preferable that it is pulled out and exposed.

  Further, in the leak detector installation structure in the low-temperature tank, a metal pad plate is provided on the bottom plate, and the tubular heat shield is provided on the pad plate and is fixed to the plate. It is preferable that the jig is pressed against the pad plate by a tool, and the fixing jig is welded to the pad plate in a state where the cylindrical heat shield is pressed.

  According to the installation structure of the leak detector in the low temperature tank of the present invention, the temperature detector of the leak detector is arranged on the bottom plate plate of the annular space portion so as to be separated from the bottom plate plate via a heat shield. Therefore, it can suppress that the cold heat | fever of the low temperature liquefied gas in an inner tank is transmitted to a temperature measurement part via a baseplate plate by a heat shield. Therefore, at a steady time when there is no leakage of the low-temperature liquefied gas from the inner tank, the temperature measuring unit of the leak detector is not affected by heat conduction, and therefore detects a relatively high temperature in the annular space. Therefore, when the low temperature liquefied gas leaks from the inner tank, the temperature detector of the leak detector detects a sufficiently low temperature compared to the steady state, so the low temperature liquefied gas leaks from the inner tank accurately. And can be detected quickly.

It is side sectional drawing which shows schematic structure of an example of the low temperature tank to which the installation structure of this invention is applied. It is a perspective view which expands and shows the principal part shown to A in FIG. (A)-(c) is a figure which shows one Embodiment of the installation structure based on this invention, (a) is a top view, (b) is a front view, (c) is a side view.

Hereinafter, the installation structure of the leak detector in the low temperature tank of the present invention will be described in detail with reference to the drawings. In the following drawings, the scale of each member is appropriately changed to make each member a recognizable size.
First, an example of a low temperature tank to which the installation structure of the present invention is applied will be described. Reference numeral 1 in FIG. 1 is a ground-type low temperature tank (hereinafter referred to as a low temperature tank) as an example of a low temperature tank according to the present invention.

  The low temperature tank 1 is provided on the ground 2 and is a metal (for example, steel) inner tank 3 for storing a low temperature liquefied gas L such as LNG, and a concrete outer tank covering the inner tank 3. 4 of a double shell structure. That is, the outer tub 4 having a bottom portion 4 a, a side wall portion 4 b, and a roof portion 4 c is installed on the ground 2, and the inner tub 3 is accommodated on the bottom portion 4 a in the outer tub 4.

The inner tub 3 has a bottom 3a and a side wall 3b made of a metal plate, and a lid 5 is provided so as to cover the upper opening. The lid 5 serves as a roof portion of the inner tub 3. ing. Further, glass wool (not shown) is laid on the lid member 5 as a lightweight cold insulation material.
The bottom part 3a of the inner tank 3 is formed to extend outward from the side wall part 3b of the inner tank 3, and the extended part, that is, the part continuing to the bottom part 3a is separated from the side wall part 3b of the inner tank. A bottom plate plate 6 made of a metal plate that constitutes a bottom portion between the side wall portion 4 b of the tank 4 is provided. An annular space 7 is formed between the side wall 3b of the inner tub 3 and the side wall 4b of the outer tub 4. The annular space 7 has a granular shape as a cold insulating material on the bottom plate plate 6. The pearlite 8 is filled.

In the low-temperature tank 1 having such a configuration, a leak detector is installed in the annular space portion 7 in order to detect when the low-temperature liquefied gas L stored in the inner tank 3 leaks.
2 is an enlarged perspective view showing a main part indicated by A in FIG. In FIG. 2, the pearlite 8 filled in the annular space 7 is not shown.

As shown in FIG. 2, a leak detector 9 is installed on the bottom plate 6 in the annular space 7.
As shown in FIGS. 3A to 3C, the leak detector 9 is connected to the wiring portion 9a, the temperature measuring portion 9b provided at the tip of the wiring portion 9a, and the rear end portion of the wiring portion 9a. And a detector main body (not shown).

  The temperature measuring unit 9b has a conventionally known configuration such as a thermocouple, and is a temperature sensor that generates an electromotive force corresponding to the temperature of the environment to be detected. The wiring portion 9a has a certain degree of flexibility in that a conducting wire connected to the temperature measuring portion 9b is arranged in a protective tube (sheath) and the periphery thereof is hermetically sealed with an inorganic insulator. The detector body detects the temperature of the environment to be detected by the temperature measuring unit 9b when the electromotive force corresponding to the temperature detected by the temperature measuring unit 9b is transmitted through the conductor in the wiring unit 9a, and outputs the detected temperature. To do.

  That is, for example, when the detector body detects a temperature lower than a preset temperature or detects a temperature drop more than a preset temperature, it recognizes that there is a leak (detects a leak) and detects this by an alarm or the like. Configured to inform. Therefore, when the detector main body is installed in, for example, the central control room, the temperature in the central control room detects the environment in which the temperature measuring unit 9b is installed, that is, the temperature on the bottom plate 6 of the annular space part 7, and thereby the temperature is lowered. The presence or absence of leakage of the liquefied gas L can be detected.

Such leak detectors 9 are installed at a plurality of positions on the bottom plate 6 of the annular space 7 formed in an annular shape (ring shape) in plan view, for example, at four positions at equal intervals.
At that time, the leakage detector 9 has its wiring portion 9a drawn from the roof portion 4c of the outer tub 4 and hung along the inner surface of the side wall portion 4b as shown in FIG. 2, and is held by the holding member (not shown). It is fixed to the inner surface of the part 4b.

  Then, the tip side is rolled on the bottom plate 6. A nitrogen purge pipe 10 is provided on the bottom plate 6 along the circumferential direction thereof. The pipe 10 is installed to replace the air in the annular space 7 with nitrogen when the low temperature tank 1 is completed, and is left without being removed even when the low temperature tank 1 is operated. Therefore, in the present embodiment, the wiring portion 9 a of the leak detector 9 is disposed so as to get over the pipe 10 and have its tip side close to the side wall portion 3 b side of the inner tank 3.

  A metal pad plate 11 is disposed on the bottom plate 6 on the side wall 3 b side of the inner tank 3 from the pipe 10. The pad plate 11 is used to install the temperature measuring unit 9b side of the leak detector 9 on the bottom plate 6 and is fixed to the bottom plate 6 by welding in advance. Such a pad plate 11 is subsequently welded to a preset position on the bottom plate 6 when the outer tub 4 and the inner tub 3 are constructed in the low temperature tank 1, that is, when the bottom plate 6 is formed.

  By performing the welding of the pad plate 11 following the construction of the bottom plate plate 6, in parallel with the inspection of the bottom plate plate 6, that is, the inspection of the welded portion of the joint portion when the bottom plate plate 6 is constructed. Inspection of welds can be performed. As described above, when the welded portion of the pad plate 11 is inspected in parallel with the welded portion of the bottom plate plate 6 and a weld failure is recognized in the welded portion of the pad plate 11, the repair processing is performed. This can be carried out in parallel with the welding failure location of 6 and becomes efficient.

  Although the temperature measuring part 9b side of the leak detector 9 is arranged on the pad plate 11, the pad plate 11 is made of metal, and if the temperature measuring part 9b is arranged directly on this, the heat conduction is large as in the conventional case. Become. Therefore, in the present embodiment, as shown in FIGS. 3A to 3C, the temperature measuring unit 9 b is arranged in a state of being separated from the bottom plate 6 and the pad plate 11 via the heat shield 12.

  As the heat shielding material 12, a resin heat insulating material such as polystyrene foam or polyurethane resin, or a mineral heat insulating material such as glass wool or rock wool is preferably used. Moreover, if it is comprised so that heat conductivity may become low enough, the heat-shielding material formed by laminating | stacking aluminum foil and a polyethylene sheet can also be used.

  In the present embodiment, in particular, as the heat insulating material 12, a heat insulating material formed into a cylindrical shape or a sheet-shaped material wound in a cylindrical shape, that is, a cylindrical heat insulating material (cylindrical heat insulating material) 12R is provided. Used. The cylindrical heat insulating material 12R has a radial thickness of, for example, about 2 to 8 cm in order to exhibit a function as a spacer as will be described later.

  And the temperature measuring part 9b side of the leak detector 9 is inserted in the hole 12a of this cylindrical heat insulating material 12R. That is, a part of the temperature measuring part 9b and the wiring part 9a are inserted into the hole 12a of the cylindrical heat insulating material 12R, and a part or all of the temperature measuring part 9b (all in the present embodiment) extends from the hole 12a. It is pulled out and exposed. Here, the hole 12a is formed so that the inner diameter thereof is substantially the same as the outer diameter of the temperature measuring part 9b and the wiring part 9a of the leak detector 9. Since the temperature measuring unit 9b has a length of about several centimeters to 10 cm, the tip end side hardly hangs down, and therefore is held in a state of being separated from the pad plate 11 and the bottom plate 6.

  Further, since the cylindrical heat insulating material 12R is formed in a cylindrical shape and its posture is not stable, in this embodiment, it is pressed by the fixing jig 13 and fixed to the pad plate 11. The fixing jig 13 is a rectangular metal plate, and holds the upper part of the cylindrical heat insulating material 12R at the center in the long side direction, and in this state, both end sides are bent as shown in FIG. Both end portions are welded to the pad plate 11, respectively.

  Thus, the cylindrical heat insulating material 12R is held and fixed on the pad plate 11 by fixing the cylindrical heat insulating material 12R with the fixing jig 13. Therefore, the temperature measuring part 9b side of the wiring part 9a of the leak detector 9 inserted into the hole 12a of the cylindrical heat insulating material 12R is also held and fixed on the pad plate 11 via the cylindrical heat insulating material 12R. As a result, the temperature measuring section 9b of the leak detector 9 is pulled out from the hole 12a of the cylindrical heat insulating material 12R as described above and is held in an exposed state. At that time, as described above, the lower half portion of the cylindrical heat insulating material 12R functions as a spacer and lifts the vicinity of the temperature measuring portion 9b of the wiring portion 9a of the leak detector 9, so that the temperature measuring portion 9b is a pad. The plate 11 and the bottom plate 6 are arranged in contact with each other without contacting the plate 11 and the bottom plate 6.

  The temperature measuring unit 9b is in contact with or cooled to the low-temperature liquefied gas when the low-temperature liquefied gas leaks from the inner tank 3 and accumulates on the bottom plate 6 or is vaporized therefrom. It is necessary to detect the temperature change of the environment quickly by touching. Therefore, it is not preferable to dispose it at a position higher than necessary above the bottom plate 6, and for example, the tubular heat insulation so that the temperature measuring unit 9 b is disposed at a height of about several cm to several tens of cm from the bottom plate 6. It is preferable to prescribe the dimensions and shapes of the material 12R and the pad plate 11.

  In the installation structure of the leak detector 9 in the present embodiment, the leak detector is separated from the pad plate 11 and the bottom plate plate 6 via the cylindrical heat insulating material 12R on the bottom plate 6 of the annular space 7. Since the nine temperature measuring parts 9b are arranged, the cylindrical heat insulating material 12R suppresses the cold heat of the low-temperature liquefied gas in the inner tank 3 from being transmitted to the temperature measuring part 9b via the bottom plate 6 and the pad plate 11. be able to.

  Therefore, at the time of steady state where there is no leakage of the low-temperature liquefied gas from the inner tank 3, the temperature measuring unit 9 b of the leak detector 9 is affected by the heat conduction that the cold of the low-temperature liquefied gas L in the inner tank 3 is transmitted through the bottom plate 6. Therefore, a relatively high temperature in the annular space 7 is detected. Therefore, when the leakage of the low-temperature liquefied gas L from the inner tank 3 occurs, the temperature measuring unit 9b of the leak detector 9 detects a sufficiently low temperature compared with the normal time, so the low-temperature liquefaction from the inner tank 3 Gas leakage can be detected accurately and quickly. Thereby, for example, in the central control room where the detector body of the leak detector 9 is installed, the temperature on the bottom plate 6 of the annular space portion 7 is detected, so that the presence or absence of leakage of the low-temperature liquefied gas L can be accurately and quickly detected. Can be detected.

  Moreover, the cylindrical heat insulating material (cylindrical heat insulating material) 12R formed in a cylindrical shape is used as the heat insulating material, and the wiring portion 9a of the leak detector 9 is inserted into the hole 12a of the cylindrical heat insulating material 12R. Therefore, in particular, the temperature measuring unit 9b of the leak detector 9 can be held in a stable state by the cylindrical heat insulating material 12R, and further, the wiring unit 9a and the temperature measuring unit 9b can be handled when the leak detector 9 is installed. Since it becomes easy, installation work can be made easy.

  Moreover, since the temperature measuring part 9b of the leak detector 9 is arranged in a state where it is pulled out from the hole 12a of the cylindrical heat insulating material 12R and exposed, the temperature measuring part 9b directly controls the temperature of the annular space part 7 in which the temperature measuring part 9b is arranged. Therefore, the temperature change due to the leakage of the low-temperature liquefied gas can be detected accurately and quickly.

  Further, the cylindrical heat insulating material 12R is disposed on the bottom plate 6 via the pad plate 11, and this cylindrical heat insulating material 12R is pressed against the pad plate 11 side by the plate-shaped fixing jig 13, and in this state. Since the fixing jig 13 is welded to the pad plate 11, the leak detector 9 held in the hole 12a of the cylindrical heat insulating material 12R can be stably fixed on the pad plate 11. Further, since the fixing jig 13 is fixed to the pad plate 11 by welding, the influence of the welding of the fixing jig 13 on the bottom plate 6 can be reduced. Therefore, after the fixing jig 13 is welded, The re-examination of the bottom plate plate 6 can be omitted or simplified.

  Moreover, since the temperature measuring part 9b of the leak detector 9 is arranged on the inner tank 3 side from the pipe 10, when the low-temperature liquefied gas leaked from the inner tank 3 is collected on the bottom plate 6, the low-temperature liquefied gas is The temperature measuring unit 9b can detect the leakage of the low-temperature liquefied gas accurately and quickly because it contacts the temperature measuring unit 9b without being blocked by the pipe 10 or approaches the lower end of the temperature measuring unit 9b.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.
For example, in the above-described embodiment, the cylindrical heat insulating material 12R is cylindrical, but a rectangular tube or the like may be used. Furthermore, without using a cylindrical material as the heat shielding material, simply use two plate-shaped or sheet-shaped materials, and sandwich the wiring part 9a or the temperature measuring part 9b of the leak detector 9 between them. May be held.

  Further, when a protective tube (sheath) made of metal is used as the wiring portion 9a of the leak detector 9, a heat shielding material is disposed between the protective tube and the temperature measuring portion 9b, and measurement is performed from the protective tube. It is preferable to suppress heat conduction to the warm part 9b. Or it is preferable to arrange | position also about the wiring part 9a passed on the baseplate plate 6 on the baseplate plate 6 via a heat shield, in order to suppress the heat conduction from the baseplate plate 6 to a protective tube.

DESCRIPTION OF SYMBOLS 1 ... Low temperature tank, 3 ... Inner tank, 4 ... Outer tank, 6 ... Bottom plate plate, 7 ... Annular space part, 9 ... Leak detector, 9a ... Wiring part, 9b ... Temperature measuring part, 10 ... Piping, 12 ... Interception Heating material, 12R ... cylindrical heat insulating material (cylindrical heat insulating material), 12a ... hole, 13 ... fixing jig

Claims (4)

A metal inner tank for storing liquefied gas, an outer tank surrounding the inner tank, an annular space provided between the inner tank and the outer tank, and a bottom of the annular space A structure of installing a leak detector having a wiring portion and a temperature measuring portion provided at the tip of the wiring portion on the bottom plate plate of the annular space portion of the low temperature tank provided with a metal bottom plate plate,
An installation structure of a leak detector in a low-temperature tank, wherein the temperature measuring unit is arranged on a bottom plate of the annular space portion so as to be separated from the bottom plate via a heat shield. The heat shield is formed by a cylindrical heat shield formed in a cylindrical shape,
The leak detector installation structure in a low temperature tank according to claim 1, wherein the leak detector has the wiring portion or the temperature measuring portion inserted into a hole of the cylindrical heat shield.   The leak detector is characterized in that the wiring portion is inserted into a hole of the cylindrical heat shield, and the temperature measuring unit is drawn out from the hole of the cylindrical heat shield. Item 3. A leakage detector installation structure in a cryogenic tank according to Item 2. A metal pad plate is provided on the bottom plate,
The cylindrical heat shielding material is provided on the pad plate and pressed against the pad plate side by a plate-shaped fixing jig,
The installation structure of a leak detector in a low temperature tank according to claim 2 or 3, wherein the fixing jig is welded to the pad plate in a state where the cylindrical heat shield is pressed.

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