JPS63178982A - Sloshing preventive method of liquid storage tank - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a sloshing prevention method for preventing sloshing that occurs in a liquid storage tank during an earthquake, and is controlled by expanding and contracting an expandable member in the storage tank.

(Conventional technology) Various types of storage tanks are used to store liquids such as crude oil and petroleum products.

It is known that sloshing occurs when seismic forces act on such liquid storage tanks, and sloshing itself is being analyzed and countermeasures are being researched.

As a countermeasure against sloshing, a bulkhead plate may be installed on the underside of the floating roof of a floating roof type storage tank where sloshing is likely to occur. The pulley A73 is placed across the floating roof 4 so that it passes between the pulleys 5, allowing the floating roof 4 to move up and down while restricting its swinging.

(Problems to be solved by the invention) However, 1. None of the conventional measures against sloshing can be said to be sufficient, and when using the wire 3, it is necessary to reinforce the attachment part of the wire 3, and the floating roof also needs to be reinforced, leading to the problem of increased layering.

The present invention has been made in view of the problems of the prior art, and it is an object of the present invention to provide a method for preventing sloshing in a liquid storage tank, which can effectively suppress sloshing.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a
Detects the change in the level of the stored liquid, and based on this detection signal, controls the expandable members installed in the storage tank such that the one on the side where the liquid level is rising is contracted, and the one on the side where the liquid level is falling is closed. It is characterized by:

[For production]

Detect the liquid level in the liquid storage tank with a pressure sensor, wave height sensor, etc.
Based on this detection signal, among the plurality of telescoping members such as telescoping bellows provided in the storage tank, the one on the side where the liquid level is halfway up and down is contracted to apply a downward force. The purpose is to actively prevent sloshing by extending the telescopic member on the side that is on the way down to apply upward force.

〔Example〕

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

The floating roof type storage tank 10 to which the method for preventing sloshing of a liquid storage tank of the present invention is applied includes a storage tank main body 12 on which a floating roof 11 is floated. A large number of telescopic bellows 13 are attached so that they can expand and contract in the vertical direction. A pressure sensor 4 for detecting the liquid level of the stored liquid as a head pressure is attached to each of these telescoping bellows 13, and pressures P and P2 are detected, and a control computer 15 is installed.
It is now entered into A rotary pump 17 is connected to these telescopic bellows 13 via a flow rate regulating valve 16, and supplies and discharges a fluid for expansion and contraction, such as air or N2 gas, to and from the telescopic bellows 13.

Furthermore, a pressure sensor 8 for detecting internal pressure is attached to at least one of the telescoping bellows 13, and the telescoping bellows 13 is kept extended to the middle regardless of the liquid level of the storage liquid, and the extended side The sensor can be moved either to the contraction side or to the contraction side. The detection signal 1]3 of the pressure sensor 8 is inputted to the control computer 5.

Next, along with the functions of the control computer 5.

A method for preventing threading will be explained.

In this 5N light sloshing prevention method, the retractable bellows in the part where the liquid level of the stored liquid is rising upwards are retracted, and the retractable bellows in the part where the liquid level of the stored liquid is going down. 13 to suppress sloshing.

For this reason, as shown in the flowchart in FIG. 2, the current liquid level is measured from the pressure sensor 4, and the detection signal FjP
, P2 are input into the computer 5.

Then, the computer 5 compares the pressures P and P2 of the left and right pressure sensors 4 to determine whether sloshing has occurred, and if 1) = P2 within a certain setting error, the liquid level is horizontal and no sloshing occurs. Assuming that it has not occurred, P
If 1≠P2, it is determined that the liquid level is inclined and sloshing is occurring.

If sloshing does not occur, retractable bellows 1
3 is detected by a pressure sensor 8 and input into the computer 5.

In the computer 5, the telescoping bellows 13 is set in advance to be at an intermediate position regardless of the liquid level, p3v=
It is compared with a constant value, and if it is a constant value, it returns to the beginning and monitors P, P, . - On the other hand, if the product of the measured pressure P3 and the volume V of the telescoping bellows 13 when extended to the intermediate position is not a constant value, calculate the pressure to make P3v constant.

Then, based on the calculation result of this pressure, the rotary pump 1
7 operation and the opening/closing command for the flow rate regulating valve 16, all telescoping bellows 13 are extended to the middle, and placed in a standby state in which they can be further extended or contracted, and pressure is applied to maintain this state. Always with sensor 8,
Monitor pressure P3.

In this way, when sloshing due to a normal earthquake does not occur, control is performed to always maintain the telescoping bellows 13 in the mid-stretched state even if there is a change in the liquid level or leakage of the fluid supplied to the telescoping bellows 13.

On the other hand, by monitoring the pressures P and P2 by the pressure sensor 4, if P ≠ P2 and it is determined that sloshing has occurred, then after deducing the pressure difference P −P, P
- Calculate the change in P2 over time to find out which side the liquid level is rising or falling.

Then, the required amount of air to be supplied to and discharged from each telescoping bellows 13 is calculated, and based on this, the rotation speed and rotation direction of the rotary pump 17 (this determines the discharge side and the suction side).

After that, a control command for controlling the operation of the rotary pump 17 and the opening/closing of the flow rate adjustment valve 16 is output, and the telescoping bellows 13 on the side where the liquid level is rising upward is contracted to apply a downward force to the stored liquid. At the same time, the telescoping bellows 13 on the side where the liquid level is falling is extended to apply an upward force, and the expansion and contraction of the telescoping bellows 13 is controlled so as to suppress sloshing.

After performing the first sloshing prevention control in this way, the pressures P and P2 corresponding to the liquid level are monitored again in order to respond to the next liquid level change, and the pressure difference P corresponding to the liquid level change is monitored again.
- Continue control to prevent sloshing until P falls below a certain value.

By performing sloshing prevention control in this manner, sloshing can be actively suppressed, and damage to the floating roof 11 and leakage of the stored liquid can be prevented.

In the above embodiment, the pressure sensor rotates twice, and the detected values P 1 , P 1 . ：Although we have explained the control based on this, it is also possible to calculate the slope of the liquid level from pressure sensors installed diagonally, or to use all the detected values of multiple pressure sensors in calculations at the same time based on three-dimensional changes in the liquid level. It may also be controlled.

Further, the extensible member is not limited to an extensible bellows, but may be a fluid pressure cylinder or the like, as long as it can control expansion and contraction.

In addition, a rotary pump is used to expand and contract the expandable member.
Although the suction side and the discharge side are changed depending on the direction of rotation, it is also possible to install a pump for each telescoping member, or to create a large air reservoir and distribute it through piping. After filling with air or the like, the conduit may be sealed so that the contraction of one of the opposing positions corresponds to the expansion of the other.

〔Effect of the invention〕

As specifically explained in conjunction with Example 1-1 below, according to the method for preventing sloshing in a liquid storage tank of the present invention, a change in the liquid level of the stored liquid is detected, and based on this detection No. 15, a Among the multiple elastic members, the one on the liquid level jacket side is controlled to contract, and the one on the liquid level decreasing side is controlled to extend, so a downward force due to its own weight acts on the liquid level rising side, causing the liquid level to decrease. On the descending side, an upward force is applied by the elastic member, and sloshing can be suppressed more reliably and easily than in the conventional method.

In addition, conventional sloshing prevention methods using bulkhead plates or wires passively suppress the liquid level fluctuations that occur, but this invention's method actively prevents sloshing by applying direct force to the fluctuating liquid level. It can be suppressed.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the method for preventing sloshing in a liquid storage tank according to the present invention, and FIG. 1 is a schematic configuration diagram;
FIG. 2 is a flowchart of the secondary method, and FIG. 3 is a schematic explanatory diagram of the conventional sloshing prevention method. 10... Floating roof type storage tank, 11... Floating roof, 12...
-Storage tank body, 13...Extendable bellows, 14...Pressure sensor, 15...Control computer, 16...
・Flow rate adjustment valve, 17...0-tally bomb, 18...
pressure sensor. Applicant Ishikawajima Harima Heavy Industries Co., Ltd. Figure 2 Figure 3

Claims (1)

[Claims] To detect a change in the level of the stored liquid during an earthquake and, based on this detection signal, control the expandable members installed in the storage tank to contract those on the side where the liquid level is rising and extend those on the side where the liquid level is falling. A method for preventing sloshing in a liquid storage tank.