JPS6044558B2 - double shell cryogenic tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a double-shell cryogenic tank that has a horizontal movement restraining member interposed between the inner and outer tanks to prevent horizontal movement of the inner tank due to an earthquake. In particular, the horizontal movement restraining member is composed of a plate body, and the expansion portion having a structure to resist horizontal force during an earthquake absorbs the contraction of the inner tank in the radial direction, and This invention relates to a double-shell cryogenic tank designed to prevent sliding.

Conventional technology Conventionally, as shown in Fig. 1, a low-temperature tank for storing liquid such as LPGNLNG has an outer tank 2 installed on a foundation 1 with a heat insulating material 3 such as perlite concrete and a heat insulating material 4 such as perlite interposed therein. A dome-roof type double-shell tank with an inner tank 5 installed inside, and a suspended deck type tank with a heat insulating material 6 such as glass wool placed on the inner tank 5 as shown in Figure 2. Double-shell cryogenic tanks and the like have been widely used.

As a result, the safety of these types of double-shell cryogenic tanks, especially flammable and storage tanks, has come to be seriously reconsidered, and regulatory conditions have been set in terms of seismic resistance. It is starting to be reconsidered.

In other words, for the previous tanks of this type, the design conditions for earthquakes were on the order of a horizontal seismic intensity of O, 3G or less, without taking vertical seismic intensity into account, but due to the close-up of the J pollution problem caused by recent disasters, and the tank capacity. From the perspective of increase, for example, horizontal seismic intensity 0.7-0.8G) vertical seismic intensity 0.25-0.3G
More and more severe design conditions are being taken into consideration.

By the way, a flat bottom cylindrical double shell tank for storing low temperature liquids such as -4.5°C (7) LPG) -162'C LNG) -183°C LOX has the following characteristics due to its function and structure. I have a problem.

The problem to be solved by the invention is that the tank inner tank 5 unavoidably contracts in the radial direction during the cool-down at startup after tank construction;
Therefore, even if it is possible to anchor in the vertical direction, the anchor cannot be removed in the radial direction during construction, and as a result, there is a drawback that it is basically prone to sliding in the horizontal direction.

As shown in Figures 1 and 2 above, a heat insulating material 4 such as perlite concrete or foam glass is interposed at the bottom, but thermal insulation and strength are in a contradictory relationship.
If we prioritize insulation, which is primarily necessary for a low-temperature storage tank, we will inevitably have to sacrifice some strength, and in addition, insulation is essential, so horizontal anchors are It could not be removed from the insulation material, and the structure had many disadvantageous conditions from an earthquake resistance standpoint.

(Depending on the design, it is possible to take the vertical anchors from the foundation.) By the way, horizontal The coefficient of friction is usually only about 0.4 to 0.5, and therefore, as shown in Figure 3, when an earthquake with a horizontal seismic intensity of 0.7 to 0.8 G occurs, the mass M of the inner tank 5 containing the accumulated material decreases. When the horizontal force H acts, the horizontal force H exceeds the frictional force N and the inner tank 5
It becomes impossible to restrain the sliding movement of the

To deal with this, if a structure is designed in which the frictional force N is larger than the horizontal force H, an excessive shearing force is applied to the bottom insulation material 3, as shown in FIG. ,
The conventional heat insulating materials 3, such as pearlite concrete and foam glass, were insufficient in terms of strength and had the disadvantage of seriously affecting the safety of the tank.

As shown above, in a flat bottom cylindrical double shell tank, it is difficult to restrain the inner tank from sliding during an earthquake, and if the inner tank does slide,
The bottom insulation material 3 is likely to be damaged, and in extreme cases, there is a possibility that the entire tank may collapse.

The purpose of this invention is to solve the technical problem of the earthquake resistance of the double-shell cryogenic tank based on the above-mentioned conventional technology, and to solve the problem of earthquake resistance of the double-shell cryogenic tank based on the above-mentioned conventional technology. This system prevents internal tank sliding and prevents damage to pipes, insulation materials, etc. between them, preventing leakage of stored liquid and resulting disasters, loss of tank function, and damage to plant safety. It is an object of the present invention to provide an excellent double-shell cryogenic tank that will benefit the field of storage utilization technology in the energy industry by avoiding the above problems.

Means and Effects for Solving the Problems In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims, is to provide a structure between the inner tank and the outer tank of the double-shell cryogenic tank. The expansion part of the restraint plate provided has rigidity to withstand horizontal force during an earthquake, and can absorb the radial thermal expansion and contraction of the inner tank.
Furthermore, the shear rigidity of the restraint plate is made to resist the horizontal force applied to the inner tank, and as a result, the outer tank is made effective to prevent horizontal sliding of the inner tank. This is a technical measure.

Embodiment 1 Configuration Next, an embodiment of the present invention will be described below based on the drawings from FIG. 5 onwards.

Note that the same parts as in FIGS. 1 to 4 will be described with the same reference numerals. In the embodiment shown in FIGS. 5 to 7, the flat-bottom cylindrical dome-roof type double-shell cryogenic tank has an outer tank 2 on a foundation 1, as in the conventional design, and a bottom plate of the outer tank 2. An inner tank 5 is provided via a heat insulating material 3 such as foam glass, a side plate, and a roof type heat insulating material 4 such as perlite.

In the lower part between the inner tank 5 and the outer tank 2, there is a horizontal movement restraint plate 6 as a horizontal movement restraint member, or a cross-sectional shape having a single upward convex expansion 7 in the center. It is welded and fixed via an outer tank side attachment member 8 and an inner tank side attachment member 8″, and is installed in a ring.

Note that A is a low-temperature liquid such as LPG or LNG stored in the inner tank 5.

For convenience of illustration, equipment such as anchors, nozzle piping, and stairs provided in the inner and outer tanks 5 and 2 are omitted.

Embodiment 1 Effect In the above-described configuration, after the tank is constructed, it receives a low-temperature liquid such as LPG, cools down, and starts up. As shown in FIG. 8, the inner tank 5 changes from the solid line state to the dotted line state 5''.
However, in this case, the friction of the bottom plate of the inner tank 5 against the heat insulating material 3 during contraction is mainly due to the weight of the bottom plate, and there is no need to worry because the static frictional force is small.

The contraction behavior without deviation is stably performed without being restrained in strength through the bellows action caused by the expansion of the expansion portion 7 of the horizontal movement/motion restraining member 6.

Also, the thermal behavior when the tank is opened is completely reversed.

Next, when an earthquake occurs and the horizontal force H acts on the total mass M of the storage liquid A and the inner tank 5 as shown by the arrow, as shown in FIG. As shown in FIG. 10, a shearing force γ acts on the inner tank side plate 5 as shown by the arrow, and its magnitude is in the direction perpendicular to the horizontal force H, that is, in the 900 direction on both sides, as shown in the figure. Maximum effect.

Therefore, the shearing force τ similarly acts on the horizontal restraining plate 6 which is fixed to the inner tank 5 in a series.

However, as shown in FIG.
has a large shearing rigidity in the X-Y plane, that is, it has a large rigidity in the direction in which the shearing force τ generated by the horizontal force H is generated, and the inner tank 5 can sufficiently resist the horizontal force. It is possible to restrain the sliding movement of the In addition, the outer tank 2 is fixed in the first
Hooking the bottom plate flange 9 of the outer tank 2 to the foundation 1 as shown in Figures 3, 14, and 15, fixing the bottom plate to the bottom plate with an anchor 11 from the foundation 1, and fixing the bottom plate with separate restraints 12 and 13, etc., as appropriate. I can do it.

Therefore, the horizontal restraining plate 6 sufficiently resists the horizontal force H, prevents displacement and sliding of the inner tank, and also prevents shearing deformation and damage of the bottom heat insulating material 3.

Of course, as mentioned above, the plate pressure of the horizontal movement restraining plate 6 and the design of the expansion part 7, which have the rigidity to resist 0.7 to 0.8 G horizontal force during an earthquake, are determined as appropriate. As shown in FIG.
It is also possible to design the horizontal movement restraint plates 6'' and 6'''' in a multi-row manner as shown in FIGS. 16 and 17.
Circumferential stiffeners 14 and 15 may be provided outside the plane to prevent buckling as a shape against shearing forces, and as shown in FIG. A slope may be provided.

The horizontal restraint plate 6 can also be connected to the outer tank bottom plate and the inner tank bottom plate, and it is also possible to connect the inner tank side plate to the outer tank bottom plate, or vice versa.

In addition, vertical anchors, piping, nozzles,
Of course, additional equipment is included.

More than the effects of the invention, according to the present invention, in a double-shell low-temperature tank in which a heat insulating material is interposed between the inner and outer tanks, a horizontal movement restraint plate is provided between the inner and outer tanks in at least one expansion section in the circumferential direction. By reinstalling the expansion part with the expansion part, the elastic deformation of the expansion part acts evenly during thermal behavior such as contraction during start-up during cool-down after tank construction, resulting in center-symmetrical displacement. Therefore, there is an advantage that deviation between the inner tank and the outer tank does not occur, and therefore, deviation does not occur beyond the permissible range of fluctuations of piping, nozzles, etc.

In addition, even if there is a risk of an earthquake with a horizontal seismic intensity of 0.7 to 0.8G, which exceeds the conventional design limit seismic intensity of 0.8G, the horizontal movement restraint plate will prevent the circumference generated in the inner tank. By creating a shearing resistance that resists the directional shearing force, no sliding occurs, and therefore, even if a horizontal force due to the horizontal seismic intensity that exceeds the frictional force between the insulation material and the like acts, stable displacement is achieved. In addition, as far as this is concerned, there is no need to create a structure that generates shearing force in the heat insulating material, and both the inner tank and the heat insulating material can perform good earthquake-resistant operation.

Therefore, it is stable even if an earthquake horizontal force that exceeds the frictional force with the bottom insulation material acts, or an earthquake horizontal force that exceeds the strength of the bottom insulation material, so it is necessary to have a specially designed structure for strength. It has the advantage of being easy to obtain both in terms of cost and results.

The present invention is of course applicable not only to the double shell dome roof tank of the illustrated embodiment but also to a double shell suspended deck type tank.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of a double-shell cryogenic tank based on conventional technology, Figure 3 is a cross-sectional view of the tank shown in Figure 1 on which the horizontal force and frictional force act when an earthquake occurs, and Figure 4 is a cross-sectional view of the bottom of the tank. 5 and the following are explanatory diagrams of embodiments of the present invention, FIG. 5 is a sectional view of one embodiment, and FIG. 6 is a partially enlarged perspective sectional view of FIG. Figure 7 is the cross-sectional plan view of Figure 5.
Figure 8 is a cross-sectional view of thermal behavior, Figure 9 is a cross-sectional view of horizontal force action during an earthquake, Figure 10 is a cross-sectional view of shear force action in the X-X cross section of Figure 9, and Figure 11 is a horizontal restraint plate circumferential shear. Force, shear reaction force perspective view, Figure 12 is a perspective view of another embodiment of the horizontal restraint plate, Figure 1
3, 14, and 15 are fixed sectional views of the outer tank, FIGS. 16 and 17 are perspective views of different horizontal restraining plates, and FIG. 18 is a sectional view of another embodiment of the installation of the horizontal restraining plates. 5...Inner tank, 3...Insulation material, 6,6″
．． 6″, 6″″″, 6″″″″...Horizontal restraining plate (member), 7, 7Z... Expansion.

Claims (1)

[Claims] 1. In a double-shell cryogenic tank in which a horizontal movement restraining member is interposed between an inner tank having an inner tank bottom plate and an outer tank having an outer tank bottom plate provided to the inner tank via a heat insulating material, the above-mentioned horizontal movement The restraining member is a ring-shaped plate provided between the inner tank and the outer tank, and includes at least one stage of expansion portions having rigidity to withstand horizontal forces such as earthquakes in the radial direction. A double shell low temperature tank is provided at a lower portion between the inner and outer tanks.