JP3978892B2 - Tank pump pit and its construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tank pump pit that is provided at a predetermined depth from a tank bottom surface and accommodates a liquid discharge pump, and a construction method thereof, and particularly to a case where a pit body thermally expands and contracts depending on the temperature of a liquid to be stored. However, it relates to the one that does not put a burden on the membrane on the inner surface of the tank.
[0002]
[Prior art]
In general, in a membrane type low temperature tank, a liquid discharging pump is installed in a pump barrel in the tank. FIG. 4 is a cross-sectional view showing a conventional tank. This tank is an underground storage type low temperature tank for storing LNG, LPG, etc., and a membrane (not shown) is disposed on the inner surface of the casing 101. This membrane is attached to the same level without providing discontinuous parts. The liquid discharge pump 102 is housed in the lower end of the barrel 104 penetrating the roof 103, and sucks LNG from the lower end of the barrel 104.
[0003]
For example, in the case of a tank having a liquid depth of 35 m, the pump 102 cannot discharge the liquid by sucking vortices and bubbles unless the liquid level is at a height H of about 2 to 3 m from the suction port. That is, the liquid corresponding to the position and height H of the pump 102 cannot be dispensed from the tank, resulting in a decrease in the effective storage amount of the tank. In order to cope with this, it is conceivable to form a tank pump pit as shown in FIG.
[0004]
In this case, a hole 106 is formed in the bottom 101 a of the casing 101, and a bottomed cylindrical pit body 107 is installed in the hole 106 via a cold insulating material (for example, polyurethane foam) 108. The lower end portion of the barrel 104 is disposed inside and the installation position of the pump 102 is lowered to increase the liquid discharge amount and increase the effective storage amount. Note that the upper end of the pit body 107 is connected to the membrane 105.
[0005]
[Problems to be solved by the invention]
In the above-described conventional tank pump pit, the pit body 107 is simply installed in the hole portion 106. Therefore, when storing a low temperature liquid such as LNG, the pit body 107 is heated downward with the bottom as a reference. As shown in FIG. 5B, the membrane 105 is contracted and deformed so as to be pulled downward. The membrane 105 is provided with a cross-sectional chevron portion (not shown) for absorbing deformation (stretching) in the in-plane direction, usually called corrugation.
[0006]
However, if the membrane 105 is deformed in an out-of-plane direction that bends downward as described above, the peripheral corrugation is likely to exhibit unstable behavior, and as a result, the basic performance of the tank may be hindered. Absent. Conversely, when storing a high-temperature liquid, the pit body thermally expands upward and deforms so as to lift the membrane 105 upward, so that the membrane 105 is similarly deformed out of plane.
[0007]
The present invention has been made in view of such problems, and even when the pit body thermally contracts due to the temperature of the liquid stored in the tank, the membrane is not deformed in the out-of-plane direction, It is an object of the present invention to provide a tank pump pit capable of clarifying the behavior of a membrane and corrugation and a construction method thereof.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is a tank pump that is provided at a predetermined depth from a bottom surface of a tank formed by disposing a membrane on the inner surface of the housing and accommodates a liquid discharge pump. The pit is composed of a hole provided at a predetermined position on the bottom of the housing, and a bottomed cylindrical pit main body that is connected to the membrane and is placed on the bottom surface of the hole. A technique is adopted in which the connecting portion is set higher than the position in the surface direction of the membrane by the amount of heat shrinkage corresponding to the stored liquid temperature. In this tank pump pit, the connection part between the pit body and the membrane is set higher than the surface direction position of the membrane by the amount of heat shrinkage corresponding to the stored liquid temperature, so the pit depends on the liquid temperature stored in the tank. When the main body is thermally shrunk, the connecting portion is lowered downward to match the surface direction position of the membrane. Therefore, since the membrane is not deformed in the out-of-plane direction during liquid storage, the behavior of corrugation can be clarified, and the basic performance of the tank can be maintained.
[0009]
The invention according to claim 2 is applied to the tank pump pit according to claim 1 in which the pit body is installed between corrugations formed on the membrane. In this tank pump pit, since the pit main body is installed between the corrugations formed on the membrane, it is possible to absorb the contraction or expansion in the bottom direction of the upper end portion of the pit main body by the peripheral corrugation.
[0010]
The invention according to claim 3 is a construction method of a tank pump pit that is provided at a predetermined depth from the bottom surface of a tank formed by arranging a membrane on the inner surface of the housing and accommodates a liquid discharge pump. The step of installing a bottomed cylindrical pit body on the bottom surface of the hole provided at a predetermined position on the bottom of the housing, and a position higher than the position in the surface direction of the membrane by the amount of heat shrinkage according to the stored liquid temperature A technique comprising a step of connecting the pit main body and the membrane and a step of thermally contracting the pit main body by receiving a liquid in the tank and positioning the connection portion in the surface direction of the membrane is adopted. In this tank pump pit construction method, the pit body and the membrane are connected at a position higher than the surface direction position of the membrane by the amount of heat shrinkage corresponding to the stored liquid temperature, and the pit body is heated by the stored liquid temperature. By shrinking and lowering the connection part downward, the connection part matches the position of the membrane in the surface direction, so that the corrugation behavior can be clarified without deforming the membrane in the out-of-plane direction when storing the liquid. Thus, the basic performance of the tank can be maintained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a tank pump pit according to the present invention. The tank to which the tank pump pit is applied is, for example, a low-temperature liquid storage underground tank such as LNG or LPG as shown in FIG. 4, but is not limited thereto, and may be a ground tank. This tank is constructed by a concrete segment, and a hole 2 is formed in the bottom 1 of the casing. The hole 2 is provided at a position where the lower end of the barrel 4 that accommodates the pump 3 can enter, for example, at a position below the barrel 4 in the vertical direction.
[0012]
As shown in FIGS. 1 and 2, a membrane 6 having a cross-sectional mountain-shaped corrugation 7 is laid on the bottom 1 via a cold insulating material 5 such as polyurethane foam. And the part corresponding to the hole part 2 of the membrane 6 is notched, and the hole part 2 is exposed. The membrane 6 is preliminarily calculated and laid so that the position where the membrane 6 is cut out is between the corrugations 7. As the membrane 6, a stainless plate having a thickness of about 2 mm is used, and corrugations 7 are formed in a lattice shape. Further, similarly to the cold insulation material 5, cold insulation materials 8 and 8 a such as polyurethane foam are provided on the inner side surface 2 a and the bottom surface 2 b of the hole portion 2.
[0013]
As shown in FIG. 1, the pit main body 9 is installed in the hole 2 in a state of being placed on the cold insulating material 8a. The pit main body 9 is formed in a bottomed cylindrical shape by a stainless plate having a thickness of about 10 mm so as to withstand the hydraulic pressure, and a flange 10 is provided at the upper end toward the outside. Moreover, although the bottom part 11 of the pit main body 9 is formed in flat plate shape, it may replace with this and may be a semi-elliptical shape, a semicircle shape, and a taper shape. However, in any case, it is still the same that it is placed on the cold insulating material 8a (bottom 2b).
[0014]
Thus, since the pit main body 9 is installed in a state of being placed on the bottom surface 2b of the hole 2, the vertical contraction is considered with the bottom 11 as a reference position. The pit body 9 is not fixed in the horizontal direction and is not restricted from contracting in the horizontal direction. The gap 12 between the cold insulating material 8 and the pit body 9 is filled with glass wool, pearlite, or the like.
[0015]
The height of the pit body 9 (the height from the bottom 11 to the flange 10) is determined by the amount of heat shrinkage at room temperature in consideration of the amount of heat shrinkage in the vertical direction of the pit body 9 when the liquid is stored in the tank. The length L is determined in advance so as to be higher than the position in the surface direction of the membrane 6.
[0016]
The length L is, for example, about 6 mm when it is desired that the pit body 9 has a height of about 1500 mm due to thermal contraction during storage of LNG (liquid temperature is about −162 ° C.). In the case of the pit body 9 having a diameter of about 1200 mm by a stainless plate having a thickness of about 10 mm). However, the value of the length L is appropriately determined depending on the liquid temperature to be stored and the shape of the pit body 9.
[0017]
Then, by installing the pit body 9 in the hole 2, the flange 10 is in a state of protruding from the hole 2. Since the flange 10 and the membrane 6 are connected by welding or the like in this state, when the pit body 9 is installed (at room temperature), the membrane 6 is lifted from the cold insulation material 5 as shown in FIG. ing.
[0018]
However, in the case shown in FIG. 1, the membrane 6 is lifted from the corrugation 7 portion, but as described above, the lift amount (length L) is very small (according to the above example, the pit body 9 It is also conceivable that the membrane 6 is lifted up except for the corrugation 7 and bent upwards with respect to the height of about 1500 mm. However, in any case, since the length L disappears during storage of the liquid as described later, the membrane 6 remains unchanged in the out-of-plane direction.
[0019]
As shown in FIG. 1, the pump 3 is arranged in a state of being accommodated in the pit body 9 by inserting the lower end of the barrel 4 into the pit body 9. The pump 3 includes a lid portion 3b that opens and closes by operating the driving portion 3a to form a liquid suction port. By opening the lid portion 3b and sucking in liquid as indicated by an arrow, the liquid is It is paid out of the tank through the barrel 4.
[0020]
The pump 3 (barrel 4) is arranged so as to be shifted from the center of the hole 2 as shown in FIGS. This is because it is possible to form a gap into which an operator enters by shifting the pump 3, and it is not necessary to provide a hole 2 larger than necessary, and the effective storage amount of the tank is unnecessarily reduced. There is an advantage that it can be avoided. However, it is arbitrary whether the pump 3 is shifted from the center of the hole 2.
[0021]
Then, the construction method of this tank pump pit is demonstrated. First, the hole part 2 is formed in the bottom part 1 of the tank which is a housing. The hole 2 is formed by a concrete segment as in the case of the other casings, and is formed by placing a formwork and hitting the concrete in the field. Next, after the cold insulation materials 8 and 8 a are pasted on the inner side surface 2 a and the bottom surface 2 b of the hole portion 2, the membrane 6 having a part cut away corresponding to the diameter of the hole portion 2 is laid on the cold insulation material 5. .
[0022]
Next, the pit body 9 is installed in the hole 2. As described above, the pit body 9 is formed in advance with a predetermined height. And the notch edge part of the membrane 6 is lifted and this edge part and the flange 10 of the pit main body 9 are connected by welding etc. FIG. This completes the installation work of the tank pump pit.
[0023]
It should be noted that a part of this installation order may be changed to install the pit body 9 in the hole 2 and then lay the membrane 6 with a part cut away. According to this method, by making the notch inner diameter of the membrane 6 smaller than the outer diameter of the flange 10, when the membrane 6 is laid, the notch end portion is locked to the flange 10 and is naturally raised. The lifting work of the part can be omitted, and the subsequent welding work is facilitated.
[0024]
In the tank pump pit installed as described above, when LNG is received in the tank, the LNG is a low-temperature liquid of about −162 ° C., so that the pit body 9 is thermally contracted by the reception of this LNG. FIG. 3 shows a state in which the pit body 9 is thermally contracted. As described above, the pit body 9 is thermally contracted by the length L in the vertical direction due to the temperature of the LNG, so that the height of the flange 10 that is a connection portion with the membrane 6 coincides with the surface direction of the membrane 6. (See also dotted line in FIG. 1).
[0025]
Accordingly, the membrane 6 is not deformed out of the plane during storage of the liquid, and the membrane 6 and the peripheral corrugation 7 are prevented from exhibiting unclear behavior. Thus, the installation position of the pump 3 is lowered to increase the liquid discharge amount in the tank, and the membrane 6 is effectively prevented from being deformed in the out-of-plane direction. In addition, after paying out LNG from the tank, the pit body 9 is released from the heat shrinkage and returns to the original state shown in FIG.
[0026]
The pit body 9 is thermally contracted not only in the vertical direction but also in the radial direction. This radial thermal contraction is caused in the in-plane direction of the membrane 6 by the flange 10 being positioned in the surface direction of the membrane 6. It is considered as a deformation and is appropriately absorbed by the peripheral corrugation 7.
[0027]
It should be noted that the various shapes and combinations of the constituent members shown in the above embodiment are merely examples, and various modifications can be made based on design requirements and the like without departing from the spirit of the present invention. For example, when the membrane 6 is connected to the upper surface of the flange 10, the periphery of the pit body 9 on the upper surface of the cold insulating material 5 is recessed, and the flange 10 at the time of heat shrinkage is fitted into the recessed portion. The deformation of the membrane 6 in the out-of-plane direction may be avoided. Furthermore, a cylindrical body having a square cross section may be used as the pit body 9, and a corrugation 7 portion may be used as an installation position of the pit body 9.
[0028]
【The invention's effect】
As described above, in the tank pump pit according to the first aspect, the connection portion between the pit body and the membrane is set higher than the position in the surface direction of the membrane by the amount of heat shrinkage corresponding to the stored liquid temperature. Therefore, when the pit body is thermally contracted due to the temperature of the liquid stored in the tank, the connecting portion is lowered downward to coincide with the surface direction position of the membrane. Therefore, since the membrane is not deformed in the out-of-plane direction during liquid storage, the behavior of the membrane and corrugation can be clarified, and the basic performance of the tank can be maintained.
[0029]
Since the tank pump pit according to the second aspect is installed between the corrugations in which the pit main body is formed on the membrane, the shrinkage or expansion in the bottom direction of the upper end portion of the pit main body can be absorbed by the peripheral corrugation.
[0030]
The construction method of the tank pump pit according to claim 3 connects the pit body and the membrane at a position higher than the surface direction position of the membrane by the amount of heat shrinkage corresponding to the stored liquid temperature, and depending on the stored liquid temperature. The pit body is thermally shrunk to lower the connection part downward so that the connection part conforms to the position of the membrane in the surface direction. It can be clarified and the basic performance of the tank can be maintained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a tank pump pit according to the present invention.
FIG. 2 is a plan view of the tank pump pit shown in FIG.
FIG. 3 is a cross-sectional view showing a state where a pit body is thermally contracted.
FIG. 4 is a cross-sectional view showing a general tank.
5A and 5B show a conventional tank pump pit, in which FIG. 5A is a cross-sectional view in a normal state, and FIG. 5B is a cross-sectional view in a state where a pit body is thermally contracted.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bottom part 2 Hole part 2b Bottom face 3 Pump 6 Membrane 7 Corrugation 9 Pit main body 10 Flange (connection part)
11 Bottom

Claims (3)

A tank pump pit provided at a predetermined depth from the bottom surface of a tank formed by arranging a membrane on the inner surface of the housing, and accommodating a pump for discharging liquid,
It is composed of a hole provided at a predetermined position of the bottom of the housing, and a bottomed cylindrical pit body that is connected to the membrane and placed on the bottom of the hole,
The tank pit is characterized in that the connecting portion with the membrane is set higher than the position in the surface direction of the membrane by the amount of heat shrinkage corresponding to the stored liquid temperature. The tank pit according to claim 1, wherein the pit body is installed between corrugations formed on the membrane. A construction method of a tank pump pit provided at a predetermined depth from the bottom surface of a tank formed by arranging a membrane on the inner surface of the housing, and accommodating a pump for liquid discharge,
A step of installing a bottomed cylindrical pit body on the bottom surface of a hole provided at a predetermined position of the bottom of the housing;
Connecting the pit body and the membrane at a position higher than the surface direction position of the membrane by the amount of heat shrinkage corresponding to the liquid temperature to be stored;
A method for constructing a pump pit for a tank, comprising the step of thermally contracting the pit main body by receiving a liquid in a tank and positioning the connecting portion in a surface direction of the membrane.

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