JP2001322697A - Fabrication method of floating-roof type tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently prevent a floating roof from being broken when the floating roof is lifted pneumatically. SOLUTION: A plurality of annular spaces X, Y, Z are formed by means of a plurality of concentric circumferential partition walls 6a, 6b at the bottom within a tank body 1 to assemble a floating roof 2, and a lifting gas is supplied to the rear side of the roof 2 to lift it, while an adjusting gas is fed into the outermost space X to raise the inner pressure thereof corresponding to the pressure rise on the rear side of the roof 2, and the adjusting gas is fed into the inner side spaces Y and Z to keep the pressure therein lower than that of the space X.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a floating roof tank in which a liquid is stored in a tank body and a floating roof floating on the liquid surface is provided.

[0002]

2. Description of the Related Art Floating roof tanks have been proposed for storing liquids such as volatile oil. This floating roof tank is constructed by floating the floating roof on the liquid surface so as to cover the upper space of the stored liquid, and the floating roof moves up and down according to the liquid level change, so that the liquid in the tank is removed. It suppresses volatilization. In order to build this floating roof tank, first, a gantry is temporarily installed on the bottom of the constructed tank body, a floating roof is assembled on this gantry, and then a floating roof is supported at the time of landing. A plurality of rod-shaped members called roof supports are attached to the floating roof. The roof support is inserted into each of the plurality of through holes provided in the floating roof, and is fixed to the floating roof with a lower portion protruding below the floating roof. After that, it is completed by removing the temporary base.

[0003]

However, such a conventional method for building a floating roof tank requires a great deal of labor and cost for installation and removal of a temporary base, and thus has a problem that the construction period is prolonged and the construction cost is increased. Was. To cope with this, instead of using a temporary base, after assembling the floating roof, pour water into the tank, float the floating roof on the water surface and position it at a predetermined height, and attach the roof support to the floating roof in this state A method is also conceivable. However, this method requires a large amount of water to float the floating roof, and requires a long time for wastewater treatment after the completion of the work, and construction costs such as the necessity of additional equipment for a series of work. Is difficult to reduce.

Therefore, a technique has been proposed in which the floating roof is floated by using gas pressure such as air or nitrogen gas instead of floating the floating roof with water. However, since the floating roof has a diameter of several tens of meters and is designed to float it on the liquid surface, even if the internal space is divided into a plurality of sections by partition walls, one space (one section) of the outer peripheral part is The strength of the outer peripheral portion is not always high. As a result, when the floating roof is lifted by the gas pressure, there is a problem that the roof is deformed from the outer peripheral portion (a portion where strength is insufficient) and is further damaged.

[0005] The present invention solves the above-mentioned problems, and of course reduces the construction cost and the construction period.
An object of the present invention is to provide a method for constructing a floating roof tank that can efficiently prevent breakage of the floating roof when the floating roof is floated by gas pressure.

[0006]

In order to achieve the above object, the invention according to claim 1 is directed to a floating roof type tank in which a liquid is stored in a tank body and a floating roof floating on the liquid surface is disposed. A method of building, in which a floating roof having a plurality of annular spaces is assembled by a plurality of concentric circumferential partition walls at the bottom of a tank body, and a floating gas is supplied to the back side of the floating roof to lift the floating roof. In addition to the above, the adjusting pressure is supplied to the outermost annular space of the floating roof in accordance with the pressure rise on the back side of the floating roof to increase the internal pressure, and the inner annular space is lower than the outermost annular space. It is characterized in that an adjusting gas is supplied so as to have an internal pressure.

According to a second aspect of the present invention, in the method for constructing a floating roof tank according to the first aspect, a technique is used in which a part of the floating gas is used as the adjusting gas. Claim 3
In the invention according to claim 1, in the method for constructing a floating roof tank according to claim 1 or 2, a technique is applied in which the supply amount of the adjusting gas to the inner annular space is determined according to the strength of the circumferential partition. . The invention according to claim 4 is the invention according to claim 1, 2, or 3.
In the method of building a floating roof type tank, a plurality of compartments are formed by providing a radial partition having a communication hole in an annular space, and adjusting gas is supplied to some compartments. A technique of supplying the adjusting gas through the communication hole is applied.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for constructing a floating roof tank according to the present invention will be described with reference to the drawings. FIG. 1 is a process chart showing an embodiment of a method for building a floating roof tank T. As shown in FIG. 1 (c), the floating roof tank T stores a liquid such as volatile oil in the tank 1, and has a floating roof so as to cover the upper space of the stored liquid. 2 is floated on the liquid surface, and the floating roof 2 moves up and down according to the liquid level change, thereby suppressing the volatilization of the liquid in the tank body 1.

The floating roof 2 is provided with a plurality of roof supports 3 for supporting the floating roof 2 at the time of landing, ie, when the amount of stored liquid decreases and the floating roof 2 approaches the bottom plate. The roof support 3 is inserted into each of a plurality of through holes 4 vertically penetrating the floating roof 2, and is fixed so as to protrude downward by a predetermined length below the floating roof 2.

In order to construct this floating roof type tank T, first, as shown in FIG. 1 (a), a cylindrical tank body 1 having an open top and a bottom is constructed above or below the ground. Subsequently, a board 5 having a predetermined height is installed to assemble the floating roof 2 on the bottom plate 1a of the tank body 1. The height of the board 5 may be such that the gas for assembling the floating roof 2 and a floating gas to be described later can be supplied, and need not be a height at which the roof support 4 can be attached. Needless to say, the height of the board 5 is lower than that of the conventional temporary mount. Further, a protective sheet (not shown) can be laid on the bottom plate 1a in order to protect the bottom plate 1a from sparks or the like generated by welding work when assembling the floating roof 2.

As shown in FIG. 2, the floating roof 2 to be assembled is provided with a plurality of annular spaces X, Y, and Z by a plurality of concentric circumferential partition walls 6a and 6b, and a plurality of annular spaces is provided in each of the annular spaces. Radial bulkhead (bulkhead) 7
Sections Xa, Ya, and Za are formed by providing a, 7b, and 7c. Each of the sections Xa and the like serves as a floating body for the stored liquid, and the floating roof 2 can be said to be an aggregate of a large number of sections (floating bodies). This is to prevent the floating roof 2 from sinking even if a part of the floating roof 2 is damaged.

The floating roof 2 has openings 8a, 8b, 8c for supplying an adjusting gas, which will be described later, in each section Xa and the like, and a plurality of through holes 4 for inserting the roof support 4. (Not shown in FIG. 2) are provided in a predetermined arrangement. However, the through hole 4 is in a closed state when the floating roof 2 to be described later floats.

The volume of each section Xa and the like is different for each annular space. This is a result of designing the floating roof 2 to obtain the necessary strength in the use state (floating on the liquid surface). It is. That is, in the use state of the floating roof 2, although a large force is applied near the center, the strength needs to be increased, but the strength is not so required near the periphery. Therefore, the section Za near the center has a smaller volume to increase its strength, while the section Xa near the periphery, which does not require strength, is formed with a larger volume. As a result, this floating roof 2
As a whole, the strength is high near the center and can withstand a large external force, but conversely, the strength is low in the peripheral portion, and there is a possibility of deformation and breakage due to the external force.

Next, returning to FIG. 1, the floating roof 2 is provided with a sealing member 9 so as to close a gap between the outer peripheral surface and the inner wall of the tank body 1, and is suspended by wires 10 from a plurality of peripheral portions. Can be lowered. The wire 10 is wound up at an upper portion of the tank body 1 by a winch or the like (not shown). In this state, as shown in FIG. 1 (b), a gas for floating is supplied from the gas supply device 11 such as a blower to the back side of the floating roof 2 (between the floating roof 2 and the bottom plate of the tank 1), and the internal pressure is increased. Is raised, and the floating roof 2 is levitated by the gas pressure (floating pressure). Although air is used as the floating gas, it is not particularly limited.

An adjusting gas is supplied from a gas supply system 12 to each section Xa of the floating roof 2 in response to the supply of the floating gas (corresponding to an increase in the floating pressure). FIG. 3 is a schematic diagram showing the gas supply system 12. As shown in FIG. 3, the gas supply system 12 has a pipe (pressurizing hose) 14 connected to a cylinder 13 in which the adjusting gas is stored in a pressurized state.
A plurality of pipes (pressurizing hoses) 16a, 16b, 16c,...
A plurality of pipes (pressurizing hoses) 18a, 18b, 18c are provided downstream of the pressure reducing valves 17a, 17b, 17c. Reference numeral 19 denotes a pressure release valve.

As shown in FIG. 2, the gas supply system 12 is provided in the opening 8a (ie, the annular space X) of each section Xa.
Of the gas supply system 12 in the opening 8b of the section Ya (that is, the annular space Y), and piping of the gas supply system 12 in the opening 8c of the section Za (that is, the annular space Z). 18c is connected. As a connection portion, a nozzle 19 is provided in each of the openings 18a to 18b,
Pipes 18a to 18a sandwiching the three-way pipe 20 and the nozzle base valve 21
8c is attached. Note that reference numeral 2
2 is a pressure gauge. In addition, as the adjusting gas, air, nitrogen gas, or the like is used.

The supply amount of the adjusting gas to each of the sections Xa to Za is determined by the first and second pressure reducing valves 15 and 17a.
~ 17c is set. In the section Xa (annular space X), the supply amount corresponding to the rise of the levitation pressure is such that the internal pressure P1 is the same as the levitation pressure or the internal pressure P1a is lower (higher) than the levitation pressure in consideration of the strength of the section Xa. Is set to The supply amount is set to the section Ya (annular space Y) such that the internal pressure P2 is lower than the internal pressure P1, and the section Za is set to the supply amount such that the internal pressure P3 is equal to or lower than the internal pressure P2. That is, the adjustment gas is supplied to each section Xa and the like under the condition that the relationship of P1 (P1a)> P2 ≧ P3 is satisfied. In this relational expression, the internal pressures P2 and P3 each include 0, though not depending on the strength of each section, and do not prevent a negative pressure.

As described above, by setting the internal pressure of the section Xa located at the outermost periphery of the floating roof 2 to the same internal pressure P1 as the floating pressure, the internal pressure P1 and the floating pressure are canceled, and the section Xa having a low strength floats. It effectively prevents deformation and breakage due to pressure. In the section Ya and the section Za, the internal pressures P2 and P3 are set lower than the floating pressure. However, since the volume of each section is smaller than that of the section Xa and the strength is correspondingly higher, the internal pressure P1 is unnecessary. is there. Therefore, section Y
Since the supply amount of the adjustment gas to the section a and the section Za can be reduced, the amount of the adjustment gas required when floating the floating roof 2 is reduced, and the cost can be reduced. Further, at the time of supplying the adjusting gas, it is only necessary to supply the gas to the section Ya or the section Za so as to be lower than the internal pressure P1 of the section Xa, and only the supply to the section Xa needs to be strictly monitored. The burden can be reduced.

The difference in the supply amount to the section Ya with respect to the section Xa is such that the circumferential partition 6a is not deformed or damaged by the differential pressure between the internal pressure P1 and the internal pressure P2, that is, the circumferential partition 6a.
Preferably, it is determined based on the intensity of a. This is because if the differential pressure is increased, the circumferential partition 6a may be deformed or damaged, and each section may lose its function as a floating body. Similarly, section Za for section Ya
Is preferably determined based on the extent to which the circumferential partition 6b is not deformed or damaged by the differential pressure between the internal pressure P2 and the internal pressure P3, that is, the strength of the circumferential partition 6b.

Returning to FIG. 1B, when the floating roof 2 floats, a plurality of winches are driven so that the wire 10 is always stretched. Thereby, the floating roof 2 is prevented from being inclined by the plurality of wires 10. In this way, the floating roof 2 is floated up to a predetermined height while stabilizing its posture. When the floating roof 2 reaches a predetermined height, that is, a height at which the work for fixing the roof support 3 can be performed, the driving of the gas supply device 11 is stopped to stop the floating, and in this state, each of the through holes 4 is Insert the roof support 3 and fix it.

Next, the floating gas is exhausted to the outside of the tank body 1 to lower the floating roof 2 so as to land on the bottom plate 1a. When the floating roof 2 is lowered, the adjusting gas is discharged so as to lower the internal pressure P1 of the section Xa in accordance with the drop in the floating pressure. Similarly, the adjusting gas is also released from the section Ya and the section Za. At this time, the differential pressure between P1 and P2 and the differential pressure between P2 and P3 are determined based on the strength of the circumferential partition walls 6a and 6b. Operate not to exceed the value.

Then, the construction of the floating roof type tank T is completed by removing the board 5 and the protective sheet.
FIG. 1C shows a state in which the liquid is stored in the floating roof tank T. In addition, the nozzle 19 of each section Xa or the like is detached from the three-way tube 20 and thereafter, and instead, a closing flange (not shown) is attached to seal each section Xa.

As described above, the floating roof 2 is attached to the bottom plate 1a of the tank body 1.
After assembling, the floating roof 2 is lifted by using gas pressure, so that the roof support 3 can be attached without using a large temporary base as in the related art. By omitting it, it is possible to reduce the construction cost and the construction period. Further, when the floating roof 2 is levitated with the liquid, the scale of the equipment is smaller than that required for supplying and discharging the liquid, and the cost can be reduced.

FIG. 4 is a schematic view showing another embodiment of a method of constructing a floating roof type tank. In FIG. 4, a part of a pipe from a gas supply device 11 that supplies a floating gas is branched, and the branch pipe 23 is connected to an annular space X (section Xa) of the floating roof 2. According to this, since a part of the floating gas is used as the adjusting gas and both are discharged from the same gas supply system, the rise in the pressure of the floating gas and the rise in the internal pressure P1 of the section Xa are synchronized. Thus, the monitoring of the internal pressure P1 is facilitated. Although not shown, the branch pipe 23 may be further branched to supply a part of the floating gas to the annular spaces Y and Z as the adjusting gas. In this case, it goes without saying that the pressure of the adjusting gas to the annular spaces Y and Z is reduced.

FIG. 5 is a plan view showing another embodiment of the floating roof 2. This floating roof 2 is, like FIG.
a, 6b, a plurality of annular spaces X, Y, Z are provided, and radial partitions 7a, 7b, 7c are provided to define a section X.
a, Ya and Za are formed. The differences from FIG. 2 are as follows. As shown in FIG. 5, in the annular space X, the radial partitions 7aa lacking except for the two radial partitions 7ab.
A communication hole 24 is formed, and an opening 25a for supplying the adjusting gas is provided for each region partitioned by the radial partition 7ab.

Similarly, in the annular space Y, the communication holes 24 are formed in the radial partitions 7ba which are missing except for the two radial partitions 7bb.
Is formed, and an opening 25b for supplying the adjusting gas is provided for each region partitioned by the radial partition 7bb. In the annular space Z, the communication holes 24 are formed in all the radial partitions 7c, and one opening 25c is provided. That is, the adjusting gas is supplied to the section without the opening 25a or the like through the communication hole 24, and the connecting portion for supplying the adjusting gas to the plurality of sections is shared. is there.

Thus, the number of pipes to be used can be reduced as compared with connecting pipes to each section, and the supply of adjusting gas due to a reduction in cost, a reduction in the number of inspection points for pipe connections, and collapse of pipes, etc. The number of defective parts can be reduced. However, it is optional to divide the annular space into what area, and to form two or more openings 25a and the like in one area. Further, after the floating work of the floating roof 2 is completed, a function as a floating body such as each section Xa can be secured by attaching a closing flange to each communication hole 24.

The various shapes and combinations of the constituent members shown in the above-described embodiment are merely examples, and can be variously changed based on design requirements without departing from the spirit of the present invention. For example, the number of circumferential partitions and radial partitions on the floating roof 2, that is, the shape (volume) of each partition can be arbitrarily changed depending on the size of the tank to be built.

[0029]

As described above, according to the construction method of the floating roof type tank according to the first aspect, the internal pressure and the floating pressure are made to correspond to the internal pressure of the outermost annular space of the floating roof by the floating pressure. It is possible to efficiently prevent the sections having low strength from being offset and deformed or damaged by the floating pressure. Further, since the supply of the adjusting gas to the inner annular space can be reduced, the amount of the adjusting gas necessary for floating the floating roof can be reduced, and the cost can be reduced. Further, at the time of supply of the adjusting gas, the supply to the inner annular space may be simply performed to be lower than the inner pressure of the outermost annular space, and only the supply to the outermost annular space may be strictly monitored. The monitoring burden during work can be reduced.

In the construction method of the floating roof tank according to the second aspect, since a part of the floating gas is used as the adjusting gas, the pressure of the floating gas against the floating roof and the internal pressure of the outermost annular space rise. Can be easily synchronized with each other, and the monitoring of the internal pressure in the outermost peripheral annular space is facilitated. In the method for constructing a floating roof tank according to claim 3, since the supply amount of the adjustment gas to the inner annular space is determined according to the strength of the circumferential partition, the adjustment gas is supplied when the floating roof floats. Inadvertent deformation and breakage of the circumferential partition wall due to the supply can be avoided. The construction method of the floating roof tank according to claim 4 supplies the adjusting gas to some sections,
Since the adjusting gas is supplied to the remaining sections through the communication holes, the number of pipes used can be reduced as compared with connecting pipes to each section, which reduces costs and reduces the number of pipe connection inspection points. It is possible to reduce the number of defective supply portions of the adjustment gas due to the decrease, the collapse of the pipe, and the like.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a process chart of a method of constructing a floating roof tank according to the present invention, wherein (a) shows a state of assembling the floating roof, (b) shows a state of floating the floating roof, and (c) shows a state of storing liquid. .

FIG. 2 is a structural view of the floating roof shown in FIG.

FIG. 3 is a schematic diagram of a gas supply system for supplying an adjustment gas.

FIG. 4 is a schematic diagram showing another supply path of the adjustment gas.

FIG. 5 is a plan view showing another structure of the floating roof.

[Explanation of symbols]

 T Floating roof tank X, Y, Z Annular space Xa, Ya, Za Section P1, P2, P3 Internal pressure 1 Tank body 1a Bottom plate 2 Floating roof 6a, 6b Circumferential partition 7a, 7b, 7c Radial partition 24 Communication hole

Claims (4)

[Claims] 1. A method of constructing a floating roof type tank in which a liquid is stored in a tank body and a floating roof floating on a liquid surface is provided, wherein a plurality of concentric circumferential directions are formed at a bottom portion of the tank body. The floating roof having a plurality of annular spaces is assembled by partition walls, and a floating gas is supplied to the back side of the floating roof to float the floating roof, and the floating roof is raised in response to a pressure increase on the back side of the floating roof. An adjusting gas is supplied to the outermost annular space of the floating roof to increase the internal pressure, and the adjusting gas is supplied to the inner annular space so that the inner pressure is lower than that of the outermost annular space. A method for constructing a floating roof tank. 2. The method according to claim 1, wherein a part of the floating gas is used as the adjusting gas. 3. The floating roof tank according to claim 1, wherein an amount of the adjusting gas supplied to the inner annular space is determined according to a strength of the circumferential partition. Construction method. 4. A plurality of partitions are formed by providing a radial partition having a communication hole in the annular space, and the adjusting gas is supplied to some of the partitions, so that the communication holes are provided in the remaining partitions. The method for constructing a floating roof type tank according to claim 1, wherein the adjusting gas is supplied via a control valve.