JPH0314713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting subsidence of a floating roof in a floating roof tank.

For storage tanks such as crude oil and volatile flammable liquids, so-called floating roof storage tanks with roofs floating above the surface of the stored liquid are used to minimize the formation of dangerous atmospheres due to evaporation of the stored liquid and mixing with air. It has been adopted. This type of storage tank is very large, with a floating roof diameter of 70 to 80 meters or more, making it structurally difficult to avoid deflection of the floating roof itself.

In such a storage tank, when a load such as snow accumulation, particularly an uneven load, is applied to the floating roof, the floating roof may flex or tilt as a whole, causing a portion to sink into the stored liquid. If the stored liquid leaks onto the floating roof due to such subsidence, it will lead to an extremely dangerous situation, so detection and countermeasures are important.

Conventionally, the following method has been adopted for this detection.

(1) During patrol inspections, lifeguards will visually check snow conditions on the floating roof.

(2) Appropriately install detection means such as a liquid level detection switch on the floating roof to detect overflow of stored liquid.

(3) As shown in Figure 1, a gauge head 1 of the type generally used for float-type liquid level gauges, etc. is installed at the top or bottom (indicated by dotted lines) of the tank side wall 2, and a wire 4 connected to the floating roof 3 is installed. The height position of the floating roof 3 is detected at multiple appropriate positions in the circumferential direction based on the amount of feeding, and the sinking is determined by comparing it with the liquid level measured by a separately installed liquid level gauge. To detect.

(4) As shown in FIG.
A so-called capacitive liquid level gauge 7 having a capacitive liquid level detection probe 6 is provided to directly detect the liquid level with respect to the floating roof 3 and detect subsidence.

However, although method (1) is advantageous in that it can prevent overflow, it can be dangerous when there is heavy snowfall or strong winds, and it may be practically impossible to remove snow and climb to the top of the tank. There are many drawbacks.

Method (2) only detects the presence or absence of overflow, and has the disadvantage that the maximum subsidence position and the amount of subsidence cannot be accurately estimated.

In method (3), the maximum sinking position and the amount of sinking can be detected remotely by providing a large number of gauge heads 1, but the structure of the detection device is very complicated, leading to increased costs, and a separate Subsidence cannot be detected unless a surface gauge is provided. Furthermore, snow or the like may freeze on the wire 4, causing trouble in winding the wire 4 by the gauge head 1, and the wire 4 may be measured in a bent state, resulting in a large error.

Method (4) has no moving parts and is said to be advantageous in terms of measurement span and accuracy; however, some stored liquids (such as crude oil) may adhere to the probe 6 and form a lump, which may affect the measurement accuracy. It has the disadvantage that it gets extremely worse.

In view of the current situation, the present invention has a simple structure that can be applied to all kinds of stored liquids, allows the situation of subsidence to be directly grasped from a remote location, and allows for easy and accurate estimation of the maximum subsidence position and amount of subsidence. The purpose is to provide equipment.

To this end, the present invention provides float or displacer type liquid level gauges arranged appropriately in the circumferential direction on the floating roof so that the liquid level position relative to the floating roof can be directly measured. is converted into an electrical signal or a pneumatic signal and transmitted to a monitoring room at a remote location, making it possible to calculate the maximum sinking position and maximum sinking amount based on the measured values from each liquid level gauge. .

Embodiments of the present invention are shown below in FIGS. 3 and 4.
This will be explained with reference to the figures.

In FIG. 3, numerals 2, 3, and 5 indicate the tank side wall, floating roof, and well, respectively, as in FIGS. 3 and 2. A plurality of these wells 5 are provided along the circumferential direction of the floating roof 3 at appropriate angular intervals, and each well 5 is provided with a liquid level gauge generally indicated by the reference numeral 10.

The liquid level gauge 10 has a gauge head 11 and a wire 1.
2, a float 13, and a transmitter 14. The gauge head 11 has a winding mechanism for the wire 12, and is adapted to measure the position of the float 13 added to the liquid level in the well 5 by the amount of feeding out of the wire 12, that is, the amount of rotation of the winding of the wire 12. The transmitter 14 converts the liquid level position measured by the gauge head 11 into an electrical or pneumatic signal and transmits it to a monitoring room at a remote location. In the case of an electrical signal, it is preferably of an intrinsically safe explosion-proof structure. . Here, pneumatic means, for example, to create a conductive state according to a predetermined code by providing multiple air passages, blocking any of the air passages, and forming a conductive state according to a predetermined code, and then transmitting this conductive state to a remote location using air pressure. It includes a method of detecting based on changes, etc. Such gauge head 11 and transmitter 14 can be easily constructed using well-known techniques, and therefore will not be described in detail.

According to the sinking device as described above, since the liquid level meter 10 measures the liquid level on the floating roof 3, the liquid level position with respect to the floating roof 3 can be directly detected. Therefore, if the appropriate amount of wire to be fed out in the state shown in Figure 3 is, for example, 0, then if subsidence occurs, the amount of wire to be fed out will be reduced to the ``-'' side, and conversely, if lifting occurs, Increases to the “+” side. This decrease/increase amount directly indicates the amount of sinking and lifting amount of the floating roof 3, respectively.

The values measured by the gauge head 11 in this manner are converted into electrical or pneumatic signals by a transmitter and sent to the monitoring room. Therefore, in the monitoring room, the amount of subsidence of each part can be directly detected at any time based on the signals from each subsidence detection device.

Here, since the position of the well 5 is known in advance and a plurality of detection devices are provided to measure the amount of sinking or lifting at each position, using this measurement value, which position in the circumferential direction is the most It becomes possible to easily calculate whether subsidence is occurring and the amount of subsidence. Therefore, based on this result, treatment can be performed more appropriately and quickly. For this reason, although not specifically shown, when subsidence occurs, it not only issues an alarm, but also displays the status of the floating roof 3 on a display device based on the amount of subsidence at each location, etc. It is advantageous to have a visual representation of the condition. In addition, it is advantageous to carry out subsidence prevention measures at the maximum subsidence position.

FIG. 4 shows another embodiment, in which float 2
0 is suspended by link members 21 and 22, and the link member 22 is pivoted about the fulcrum P by the float 20 that follows the liquid level, and based on this pivot amount θ, the liquid relative to the floating roof is It can be configured to measure the surface position. It is also possible to use a displacer instead of the float 20 and detect changes in buoyancy based on changes in the draft of the displacer. Furthermore, the float 20 is screwed onto a fixed screw instead of the link member 21, and the float 20
It is also possible to measure the relative position by rotating the robot and measuring the rotation angle when it goes up and down.

An example of measuring and calculating the settlement, inclination, and deflection deformation state of a floating roof using the above-mentioned well and float or displacer will be shown below.

On the circumference of a floating roof with radius ro and radius r, n wells are provided at equal intervals with n≧3, and W ₁ , W ₂ . . .
Let W _i , W _i+1 , W ₊₂ ...Wn.

In this case, it is advantageous to install a well and a float instead of using a capacitance method and measure the relative movement of the float to the floating roof because it can prevent crude oil in the tank from sticking to the detection unit and causing errors. .

To find the maximum inclination angle α or maximum sinking (or rising) amount Z _nax of the floating roof using W ₁ ~ Wn,
If r is the distance between the center of the floating roof and each well W, and ro is the radius of the floating roof, then ro tanα + Zo = max... (1) However, Zo is the amount of sinking (or rising) at the center of the floating roof α and It is assumed and introduced as an auxiliary number in the calculation.

A certain position A on the concentric circle of radius r now sinking amount Z
and the plane coordinates x, y with the maximum settlement point Z _nax as the x axis
The relationship between θ is from the center to the reference well.
Let the angle formed by the line to W _i+1 and the line from the center to A,
If φ is the angle between the reference well W _i+1 from the center and the X axis, then x=rcos(θ−φ) y=rsin(θ−φ) Z=xtanα+Zo ……(2) ∴Z=rtanα・cos(θ−φ)+Zo...(3) The central angle β between two adjacent wells is β=360°/n, and the amount of subsidence of each well is Z _i , Z _i+1 , Z _i+2 ,
When expressed in polar coordinates using W _i+1 as the standard of cylindrical coordinates, W _i ... (r ₁ , -θ) W _i+1 ... (r, o) W _i+2 ... (r ₁ + θ) Equation ( 3), the amount of settlement Z _i , Z _i+1 , Z _i+2 in wells W _i , W _i+1 , W _i+2 is Z _i = rtanα・cos(−β−φ)+Zo ∴Z _i ＝rtanα(cosβcosφ −sinβsinφ)＋Zo ……(4) Z _i+1 ＝rtanαcos(o−φ)＋Zo ∴Z _i+1 ＝rtanαcosφ＋Zo ……(5) Z _i+2 ＝rtanαcos(β−φ)＋Zo ∴ Z _i+2 = rtanα (cosβcosφ − sinβsinφ) + Zo ...(6) Calculating equation (6) - equation (4)/2sinβ, rtanαsinφ=Z _i+2 −Z _i /2sinβ ...(7) Equation ( 6) + Equation (4)/2cosβ is calculated as rtanαcosα=Zo/cosβ=Z _i+2 −Z _i /2cosβ ……(8) Equation (8)−Equation (5) (1/cosβ−1)Zo =Z _i+2 +Z _i /2cosβ−Z _i+1 ∴Zo=Z _i+2 +Z _i /2−Z _i+1 cosβ/1−cosβ ……(9) Substitute formula (9) into formula (5) By substituting, rtanαcosφ=Z _i+1 −Z _i+2 +Z _i /2−Z _i+1 cosβ/1−
cosβ ∴rtanαcosφ＝2Z _i+1 −Z _i+2 −Z _i /2(1−cosβ)
...(10) (Formula (7)) ² + (Formula (10)) ² r ² tan ² α= (Z _i+2 −Z _i /2sinβ) ² + {2Z _i+1 −Z _i+2 − Z _i /2(1−cosβ)} ² ……(11
) From formulas (1), (9), and (11), Z _nax = ro/2r {(Z _i+2 −Z _i /sinβ) ² + (2Z _i+1 −Z _i+2 −Z _i / 1−cosβ) ² } ^1/2 +Z _i+2 +Z _i /2−Z _i+1 cosβ/1−cosβ ...(12) The inclination angle α can be obtained from equation (11). The maximum settlement position can be determined by the angle φ with W _i+1 from equation (7). When n = 3 and β = 120° When n=4 and β=90°, sinβ=1, cosβ=0 Z _nax = ro/2r {(Z _i+2 −Z _i ) ² + (2Z _i+1 −Z _i+2 −Z _i )
^1/2 +Z _i+2 +Z _i /2...(14) For 1=1.2.3.4, four different Z _nax values are obtained and, for example, a warning is issued based on the largest one of them.

i ⁼ _{1Z nax} =ro/r( _Z22 +( _Z82 + _Z12 / ₂ - _Z2Z8 ^{- Z2}
BZ ₁ ) ^1/2 +Z ₈ +Z ₁ /2 i=2Z _nax =ro/r (Z ₈ ² +Z ₄ ² +Z ₂ ² /2-Z ₈ Z ₄ -Z ₈ Z ₂
) ^1/2 +Z ₄ +Z ₂ /2 i=3Z _nax =ro/r (Z ₄ ² +Z ₁ ² +Z ₈ ² /2-Z ₄ Z ₁ -Z ₄ Z ₈
) ^1/2 +Z ₁ +Z ₈ /2 i=4Z _nax =ro/r (Z ₁ ² +Z ₂ ² +Z ₄ ² /2-Z ₁ Z ₂ -Z ₁ Z ₄
) ^1/2 +Z ₂ +Z ₄ /2 When n=6 and β=60° According to the subsidence detection device of the present invention as described above, the following effects can be obtained.

(1) By installing the detection device on the floating roof, changes in the liquid level can be measured over a small range, making the detection device smaller and cheaper.

(2) It can be easily applied to existing tanks by making some modifications to the floating roof.

(3) Dozens of tanks can be easily monitored.

(4) By installing multiple units in the circumferential direction, it becomes possible to calculate the amount of subsidence at any position, and it becomes possible to take subsidence prevention measures at desired positions. Therefore, treatment can be performed quickly, easily, and accurately.

(5) Since the detection device is a float type, there are no problems with liquid adhesion or sticking.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic diagrams of a conventional subsidence detection device. FIG. 3 is a schematic diagram of an embodiment of the subsidence detection device according to the present invention. FIG. 4 is a schematic diagram of another embodiment of the invention. 2... Tank side wall, 3... Floating roof, 5... Well, 10... Detection device, 11... Gauge head,
12...Wire, 13...Float, 14...
Transmitter, 20... float, 21, 22... link member.

Claims (1)

[Claims] 1. A device for detecting subsidence of a floating roof in a floating roof tank, in which a plurality of float wells are provided in the circumferential direction of the floating roof, and a liquid level detection device having a float or a displacer is attached to each well. The liquid level position relative to the floating roof is measured at each position, and the measured values are transmitted to a monitoring room by a transmitter, and the maximum sinking position and sinking amount can be calculated in the monitoring room. Floating roof subsidence detection device.