JPH0375432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a floating roof type liquid tank, and more particularly, to a safety device for a liquid tank that stores two liquids having different maximum storage amounts, particularly where the two liquids are petroleum products. be.

(Prior Art) Various liquid tanks capable of storing different liquids have been proposed. Among them, in a liquid tank for liquid B having a floating roof 1, a partition membrane (hereinafter abbreviated as diaphragm) 6 made of a flexible membrane material is provided on the lower side of the floating roof.
There is a structure in which the space surrounded by the lower deck plate 3 of the floating roof, the partition plate 4 lowered downward from the lower deck plate, and the diaphragm 6 is used as a new storage chamber for other liquid A. .

An example is shown in FIG.
This is a diagram seen from the side. Figure b shows the cross section AA' in Figure a, with another liquid A8 inside the storage chamber 5 and a liquid B9 outside.
indicates a situation. Normally, the specific gravity of liquid A is smaller than that of liquid B. The arrangement of each storage chamber 5 and the distribution of the amount of liquid A in each storage chamber 5 are such that the floating roof does not become unbalanced and tilted. Figure c shows the diaphragm 6 itself, and the outer circumference of the diaphragm shows its attachment line 7. Figure d
6(M-(0) indicates the movement of the diaphragm 6 when the storage chamber 5 for liquid A is substantially empty.
(v)) is 6 when the amount of liquid A in the liquid A storage chamber 5 is v.
(M(1)) indicates when the amount of liquid A in the storage chamber 5 for liquid A is full to the designed level. Note that 2 in Figure 1 is the upper deck board of the floating roof.

(Problems to be Solved by the Invention) The problem with the structure described above is that the amount of liquid A stored can actually be ascertained only by a flowmeter. For this reason, if the amount of liquid A is not properly grasped by the flowmeter, there is a risk that the full amount will exceed the designed full amount at the time of injection. If the amount is exceeded, excessive tension will be applied to the diaphragm, and if injection continues, in the worst case, the diaphragm partition plate etc. will be destroyed.

In view of the above, the present invention was developed to solve these problems.

(Means for Solving the Problem) That is, the safety device for a floating roof type liquid tank of the present invention includes a partition made of at least a flexible membrane on the underside of the floating roof of a certain liquid B liquid tank having a floating roof. In a liquid tank that forms a new storage chamber for another liquid A using a thin tube that is open towards B and allows another liquid A to flow through it towards a certain liquid B;
A liquid level detector and a signal transmission line attached to the thin tube that detect when the liquid level of another liquid A passes a preset position in the thin tube and send a signal to stop the injection pump of the other liquid A; It is characterized by having the following.

(Function) As shown in Fig. 2, a thin tube 12 with one end opened in another liquid A storage chamber 5 is erected upward, bent at an appropriate height, and the other end is placed above the liquid level 11 of a certain liquid B. The cap is kept open toward the liquid B while being kept high, but the other end may have a lid that opens with a small force.

Normally, a small amount of liquid A is contained within the tube to a certain height while satisfying the relationship of hydraulic pressure.

The capillary has a liquid level detector 13, which detects when the liquid A in the capillary exceeds a preset height and transmits a signal to the liquid A pump to stop the pump. It's becoming like that. The preset height is a height that the liquid A does not reach until it exceeds the set full amount, and is a height that the liquid A reaches in the event of an abnormality of exceeding the amount. Usually the preset height is located below the bend of the capillary. Therefore, liquid A
When exceeds the designed full amount, the liquid level 10 of the liquid A in the capillary rises, and first, when it passes a preset height, the liquid level detector 13 detects this and is activated,
A signal is then sent through the transmission line to stop the pump. However, an excess amount of liquid A due to an error such as a slight time delay passes through the bent portion of the thin tube and flows into the liquid B side. Of course, it is assumed that no abnormal reaction will occur even if liquid A and liquid B are mixed. Note that 14 is a signal transmission path.

Now, a more detailed explanation will be given with reference to FIG. When the other liquid A storage chamber 5 is substantially empty, the diaphragm is 6 (M
(0)), the liquid level of liquid B is 11 (H(0)), and the liquid level of liquid A in the capillary is 10 (h(0)).The injection rate of liquid A is The liquid level height 10 (h (v) is a range that does not exceed the preset height 10 (h) at which the liquid level detector operates. When the liquid A storage chamber 5 reaches the designed full level, the normal liquid The pump for A stops, the diaphragm becomes 6 (M(1)), the liquid level of liquid B becomes 11H(1)), and the liquid level of liquid A becomes 10 (h(1)).

However, if the stored amount is not properly grasped and the injection continues, the pressure in the storage chamber 5 suddenly begins to rise, and the liquid level of the liquid A in the thin tube also rises rapidly.

However, when the liquid level 10 (h(v)) of liquid A reaches 10(h), the liquid level detector detects and operates, a signal is transmitted, and the pump for liquid A stops. A slight excess amount of liquid A due to errors such as time delays can be poured into the liquid B side through the thin tube. In addition, 1 in Figure 2
4 is a signal transmission path.

(Example) In order to further enhance the safety of the safety device shown in FIG. 2, it is effective for oil tanks and the like to use an optical system for the liquid level detector and the signal transmission line, and to use an explosion-proof type. An example of this safety device is shown in FIG. When the injection amount of liquid A exceeds a set height of 10 (h), the float type optical interrupter 13a interrupts the signal transmission path through which light had passed until then. This is used as a signal to stop the liquid A pump. In Fig. 3, 14a is an optical fiber (light transmitting), 14b is an optical fiber (light receiving), 14c is a light, 14d is a light emitting part, 14e is a light receiving part, and the same symbols as in Fig. 2 refer to the same parts. It shows.

Note that each liquid level height mentioned above is considered based on the floating roof (lower deck board of the floating roof), not the tank floor level, because the entire floating roof moves up and down depending on the amount of liquid B. For reference, let's design a model using the simplest system.

Figure 4 shows a storage chamber 5 for liquid A under the center of the floating roof.
This is based on the following. In this example, since the floating roof is wide, the other end of the thin tube of the safety device passes through the floating roof and opens toward the liquid B. Now, assume the following.

(1) Total weight of the floating roof, partition plate, diaphragm, and safety device M (2) The area of the floating roof viewed from above is S (constant in the height direction) (3) The area of the storage chamber for liquid A is Z when viewed from above (Constant height direction) (4) The thickness of the partition plate and diaphragm is thin, and their volume can be ignored compared to the volume of the floating roof immersed in liquid B.

(5) Specific gravity ρ _A of liquid A, specific gravity ρ _B of liquid B, and ρ _A is smaller than ρ _B. (6) The liquid level of liquid B is always assumed to be between the upper and lower deck plates.

(7) The diaphragm separates liquid A and liquid B horizontally. In addition, the intermembrane (or storage chamber 5) is long and narrow, and the influence of the ends at both ends in the length direction can be ignored.

The height of each liquid level is based on the lower surface of the lower deck board.

From the relationship between buoyancy and liquid pressure, M=SH(0)ρ _B M+vρ _A = {SH(v))+v}ρ _B h(0)ρ _A =H ₀ ρ _B {h(v)+v/Z}ρ _A ={H(v)+v/Z}ρ BHeight H(v) of liquid _B is H(v)=H ₀ −ρ _B −ρ _A /ρ _B・v/S Height h(v) of liquid A ) is h(v)=ρ _B /ρ _A H ₀ +ρ _B −ρ _A /ρ _A・S−Z/SZ
v That is, the liquid level of liquid B falls linearly as the injection amount of liquid A increases (in other words, the floating roof rises)).

The level of liquid A in the thin tube becomes higher as the amount of liquid A injected increases. The above situation is shown in Figure 5. When the designed full amount is exceeded, the liquid level of liquid A rises suddenly. The height 10 (h) at which the liquid level detector operates can be set higher than 10 (h (1)), but this can be determined by considering the strength of the diaphragm, etc.

In the above description of the present invention, the specific gravity of liquid A is normally smaller than the specific gravity of liquid B in a liquid tank as shown in Figure 1, but the specific gravity may be reversed if a certain degree of strength is provided to the diaphragm, etc. . Safety devices can also be applied in that case. Further, there are methods of providing a diaphragm under the lower deck board of the floating roof as illustrated in FIGS. 6a, b, and c.

(Effects of the Invention) According to the safety device for the floating roof type liquid tank of the present invention as described above, (1) Excessive injection of liquid A is prevented.

(2) (1) prevents excessive force from being applied to the diaphragm or partition plate. Therefore, it is systemically safe.

(3) The thin tube can also be used to vent gas from storage chamber A.

There are advantages to this.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a different floating roof type liquid tank for storing two liquids. Figure a is a plan view seen from the new storage chamber side, Figure b is a cross-sectional view taken along line A-A' in Figure a, and Figure c is a diagram of the diaphragm. Perspective view,
Figure d is a diagram explaining the situation in which the diaphragm is displaced, Figure 2 is a diagram explaining the safety device of the floating roof tank of the present invention used in Figure 1, and Figure 3 is a diagram of the liquid level detector of Figure 2. Detailed example diagram, Figure 4 is a diagram explaining the safety device model design of the present invention, Figure 5 is a relationship diagram between the amount of liquid A and the liquid level height showing the result of the model design in Figure 4, Figure 6 a , b, and c are diagrams each illustrating how to provide a diaphragm in the present invention. 1... Floating roof, 2... Upper deck board of floating roof,
3... Lower deck board of floating roof, 4... Partition plate, 5
... Storage chamber for liquid A, 6 ... Partition membrane (diaphragm), 6 (M
(0))...When storage chamber A is substantially empty, 6(M
(v))...When the amount of liquid A in storage chamber A is v, 6(M
(1))...When the amount of liquid A in storage chamber A is full to the design, 7
...Outer circumference of partition membrane (installation line), 8...Liquid A,
9...Liquid B, 10...Liquid level in the capillary of liquid A, 10
(h(0))...When storage chamber A is substantially empty, 10
(h(v))...When the amount of liquid A in storage chamber A is v, 10
(h)...When the liquid level detector is activated, 10(h)(1)
...When the liquid level detector is full to the designed level, 11...Liquid B
11(H(0))...When storage chamber A is substantially empty, 11(H(v)...The amount of liquid A in storage chamber A is v.
When, 11 (H(1))...When the amount of liquid A in storage chamber A is full to the designed level, 12...Thin tube, 13...Liquid level detector, 13a...Float type optical interrupter, 14... Signal transmission path, 14a... Optical fiber (light transmission), 14b
...Optical fiber (light receiving), 14c...Light, 14
d... Light emitting section, 14e... Light receiving section.

Claims (1)

[Claims] 1. A new storage chamber for another liquid A is constructed by using a partition made of at least a flexible membrane under the floating roof of a liquid tank for liquid B that has a floating roof. In a liquid tank, one end opens into a storage chamber for another liquid A, and the other end opens toward liquid B, which is kept higher than the liquid level of liquid B. a thin tube that allows liquid B to flow through it,
A liquid level detector and a signal transmission line attached to the thin tube that detect when the liquid level of another liquid A passes a preset position in the thin tube and send a signal to stop the injection pump of the other liquid A; A safety device for a floating roof liquid tank characterized by comprising: 2. Safety of the floating roof type liquid tank according to claim 1, in which a new storage chamber for another liquid A is constructed below the floating roof using a partition made of a flexible membrane and a partition plate. Device.