JPS6335518B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a floating roof sealing mechanism.

Floating roof type liquid storage tanks are used to store evaporable liquids, and in order to minimize the amount of evaporation, various improvements have been made to the sealing mechanism of the floating roof.

However, when it comes to large-diameter tanks made of thin plates, the floating roof sealing mechanism is made highly flexible, and even if airtightness is achieved between the tank side wall and the surrounding wall of the floating roof, there is no loss due to evaporation of the stored liquid. I have not yet succeeded in doing so.

Nowadays, as the problem of pollution has become more and more serious,
When the stored liquid became petroleum, even the emission of hydrocarbon vapor from the sealing mechanism of a floating roof, which is technically extremely small, came to be monitored as a source of air pollution.

As a result of actually measuring the amount of emissions in floating roof oil storage tanks, the following facts were discovered. That is, (i) the amount of emission depends on the type of seal mechanism, e.g. mechanical show seal type (see Figure 1) or tube seal type (see Figure 2)
It also varies depending on the size of the seal gap actually formed on the seal surface, the wind speed, and the type of oil stored.

(ii) Actual emissions are shown in the American Petroleum Institute's booklet "API Bulletin 2577 (published February 1962)"
Approximately 50~ of the estimated emission amount listed in
It was 60%.

(iii) For mechanical show seals, there is no correlation between the amount of emission and the seal gap. In other words, the seal gap reaches 50mm,
Even if it is actually visible, the amount of emission is almost the same as that of a normal seal gap of about 3 to 5 mm, or an area that is considered to have no gap in engineering terms.

(iv) A poorly maintained seal mechanism has a large amount of emissions.

(v) Mechanical seal type seal mechanism has a considerable seal gap, tube seal type has no gap,
Or the amount of emission should be comparable to that of a microgap.

(vi) The mechanical seal type seal mechanism has a more effective evaporation prevention effect than the tube seal type.

That's what I was saying. Of the above, the most noteworthy is: In other words, before actual measurements, the tube seal type seal mechanism was more effective.
It seems to be superior in terms of flexibility than the mechanical show-seal type, so it is thought to adapt well to the deformation of the tank side plate and come into close contact with the inner wall of the side plate, resulting in an excellent sealing effect. However, the actual measurement results were the opposite.

Also, surprisingly, as the wind speed increases, the amount of emission becomes larger in the tube seal type than in the mechanical show seal type, as shown in FIG. In Figure 3, the liquid stored in the tank was gasoline.

However, in Japan, which is an earthquake-prone country, mechanical show-seal type floating roofs have rarely been manufactured in recent years due to the risk of them colliding with the inner side walls and catching fire during an earthquake. Recently, they have been replaced by flexible tube seal types.

However, from the point of view of the amount of emission, the use of a tube seal type floating roof seal mechanism requires consideration.

Now, in light of the above measurement results, we consider the superiority of the conventional mechanical seal type over the tube seal type in terms of preventing emissions.The one shown in Figure 1 is a typical mechanical It is a U-seal type seal mechanism, with A as a floating roof, B as a tank side plate, C as a seal fabric, D as a mechanical shoe, E as a Pandagraph type hanger, F as a counterweight, and G as an oil level. However, in the mechanical seal type, the seal is fully immersed in oil, so the floating roof moves due to wind, etc., creating a seal gap, which induces evaporation and generates hydrocarbon emissions. Even under these conditions, the hydrocarbon vapor in space A surrounded by the tank, seal fabric, and floating roof side wall will not participate in the emission, and the gap consisting of the tank side plate and the tank will not participate in the emission. Because of its long length, there is resistance to the emission, so evaporation does not progress much. However, with the tube seal type, the roof moves due to wind etc., creating a seal gap, which induces evaporation and generates hydrocarbon emission. In such a situation,
In the tube seal type shown in Fig. 2, the hydrocarbon vapor in the space B surrounded by the tank side plate, the tube seal, and the floating roof side wall immediately participates in the emission. It was determined that the seal gap, which is made up of a tube seal and a tube seal, is short and does not offer much resistance to the emission, and that the amount of evaporation progresses as the wind speed increases.
In addition, there is a type between the tube seal type and the mechanical seal type.
No. 15986 uses a liquid instead of the cloth inside the tube, and a floating body installed at the bottom of the tube causes the liquid to generate pressure in the radial direction of the tank, and the inner wall of the tank and the annular tube The upper and lower ends of the sealing strip between the floating roof and the floating body are fixed to the other end of an elastic steel piece, but the structure is extremely complicated, and the lower end of the sealing strip is fixed to the floating roof. It had the disadvantage that it moved with the roof and tried to separate from the inner wall of the tank. In view of the above facts, this invention does not use a mechanical shoe, but by applying the structure that is effective for emissions in a mechanical shoe seal type to a soft tube seal type, it is safe from ignition and has an extremely high emission level. The purpose is to provide a floating roof sealing mechanism that is at least simple in construction.

The gist of the present invention is that a ring-shaped body 5 is attached to the outer peripheral side wall 2 of the floating roof 1, and the ring-shaped elastic cushion body is used as a core material 3, and the surface of the core material 3 is covered with an oil-resistant film 4.
A wall curtain 7 made of the same or different material as the coating 4 and covering the upper surface 6 of the ring-shaped body 5.
The upper end is fixed to the outer circumferential side wall 2, and is suspended between the outer circumference of the ring-shaped body 5 and the tank inner wall 8, and the lower end of the hanging part 11 is long immersed in the storage liquid, and a protrusion is formed on the inner wall of the hanging part 11. The floating roof sealing mechanism is characterized in that the floating roof seal mechanism 12 is provided in a protruding manner.

The structure will be explained based on an embodiment shown in FIG. 4. A ring-shaped elastic lining material, for example, a soft synthetic resin foam such as urethane foam, is used as a core material 3 on the outer peripheral side wall 2 of the floating roof 1. A ring-shaped body 5 covered with an oil-resistant film 4 is attached to the surface of the core material 3, and the film 4 is applied so as to cover the upper surface 6 of the ring-shaped body 5.
The upper end of the wall curtain 7 made of the same or different material is fixed to the outer circumference side wall 2 of the floating roof 1, and is suspended between the outer circumference of the ring-shaped body 5 and the tank inner wall 8, and the inner wall of the hanging part 11 has a projection. 12 is provided in a protruding manner, and the lower surface of the hanging portion 11 extends to a point 1 below the oil level 9.

Incidentally, the length of l changes as the floating roof 1 moves up and down. That is, when the floating roof 1 is lowered, the wall curtain 7 tends to remain due to the frictional force acting between it and the inner wall 8 of the tank, and the ring-shaped body 5 easily slides on the inner surface of the wall curtain 7, so that it is most likely to be shortened. In addition, the vapor pressure of the stored liquid acts on the space C formed between the upper part of the wall curtain 7 and the membrane 4 and tends to lift the wall curtain 7, so the length l tends to become shorter from both sides.
Since the length of the curtain wall existing between the wall curtain 7 and the tank side wall 8 is shortened, it is better to make it at least longer than the head due to the vapor pressure of the stored liquid in the operating temperature range of the tank. However, in this embodiment, a protrusion 12 is provided on the inner surface of the hanging portion 11 to serve as a lift stopper for the hanging portion 11.

Since this embodiment has the above-mentioned configuration, the floating roof 1 moves due to the wind, etc., and a seal gap is created between the wall curtain 7 and the tank inner wall 8, evaporation is induced from there, and the vapor of the built-in liquid is emitted. Even if such a situation occurs, the steam in the space D surrounded by the wall curtain 7, the lower side of the ring-shaped body 5, and the floating roof outer periphery 10 does not participate in the emission, and the wall curtain 7 automatically In addition, the curling up that occurs when the so-called floating roof is lowered is eliminated, and the liquid immersion length is increased to help prevent emissions, and the length between the wall curtain 7 and the tank inner wall 8 is reduced to a normal soft seal, etc. In comparison, the ring-shaped body is much longer and has resistance to the emission, so evaporation does not progress much. Also, since the ring-shaped body is covered with an oil-resistant film 4 with an elastic cushion as a core material, it does not collide with the inner wall 8 of the tank. There is no fear of fire at all.

In addition, when the seals are in close contact with each other, when the floating roof 1 descends, the wall curtain tends to curl up, but in this invention, when the floating roof 1 descends, the drooping portion 11 tends to shorten. 12 acts as a stopper and does not shorten beyond a certain level.

Since this invention has the above-mentioned structural effect,
When the floating roof is lowered, the hanging part of the wall curtain will not be shortened beyond a certain level due to the protrusions, and the generation of wrinkles can be prevented, which can sufficiently prevent the emission of flammable vapors such as hydrocarbon vapor. To provide a floating roof sealing mechanism for a floating roof tank that can safely store and store even storage liquid that generates.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a typical example of a mechanical shoe seal mechanism, Fig. 2 is an explanatory diagram of a typical example of a tube seal mechanism, and Fig. 3 is an explanatory diagram of a typical example of a tube seal type and a mechanical shoe type seal mechanism. The evaporation amount diagram and FIG. 4 each show a longitudinal sectional front view of a part of an embodiment of the floating roof sealing mechanism according to the present invention, where 1 is the floating roof, 2 is the outer peripheral side wall, 3 is the core material, and 4 is the floating roof sealing mechanism.
5 indicates an oil-resistant film, 5 indicates a ring-shaped body, 6 indicates an upper surface, and 7 indicates a wall curtain.

Claims (1)

[Claims] 1 A ring-shaped elastic cushion is used as a core material 3 on the outer peripheral side wall 2 of the floating roof 1, and the surface of the core material 3 is coated with an oil-resistant film 4.
A ring-shaped body 5 covered with
The upper end of a wall curtain 7 made of the same or different material as the coating 4 is fixed to the outer peripheral side wall 2 so as to cover the upper surface 6, and is suspended between the outer periphery of the ring-shaped body 5 and the tank inner wall 8, The floating roof sealing mechanism is characterized in that the lower end of the hanging part 11 is immersed in the storage liquid for a long time, and a protrusion 12 is provided on the inner wall of the hanging part 11 to protrude.