JP2013018320A - Oil tank structure of tanker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil tank structure that can control any local corrosion in the oil tank of a tanker having a double hull structure.SOLUTION: An oil tank in an oil tanker having a double hull structure constituted of a bottom shell plate and an inner bottom plate 11, is formed by joining stiffeners 40 with drain holes 42 formed therein to a longitudinal bulkhead 30 along the longitudinal direction of a hull. The oil tank has distributing members 43 that can prevent any direct collision of crude oil flowing down toward the inner bottom plate 11 via the drain holes 42 with an upper surface of the inner bottom plate 11. The distributing members 43 are provided below the drain holes 42.

Description

  The present invention relates to an oil tank structure of a tanker having excellent corrosion resistance.

  For tankers that transport crude oil, etc., a double hull structure is required to prevent the crude oil loaded on the tanker from flowing out of the ship when the bottom skin or ship side skin of the tanker is damaged. Yes.

  In this double hull tanker, seawater is loaded in a ballast tank that is configured between the bottom shell plate and the inner bottom plate and between the ship side outer plate and the inner side wall, and is constituted by the inner bottom plate and the inner side wall. Since the crude oil is loaded in the oil tank, the steel plate constituting the inner bottom plate and the inner wall is exposed to a corrosive environment by seawater and crude oil.

  For this reason, it is known that local corrosion with a relatively high corrosion rate of about several mm / year occurs on the inner bottom plate and the inner side wall, and anticorrosion coating is applied as a countermeasure against this corrosion. Furthermore, in order to reduce the frequency of maintenance such as repainting, the inner bottom plate and the inner side wall are formed of a special steel plate having high corrosion resistance (for example, Patent Documents 1 to 4).

JP 2001-214236 A JP 2004-204344 A Japanese Patent Laid-Open No. 2005-23421 JP 2007-270196 A

  The inventors of the present invention conducted intensive research on the occurrence of local corrosion in an oil tank of a tanker composed of a coated steel plate with anticorrosion coating or a special steel plate (corrosion resistant steel plate) having high corrosion resistance. As a result, it was found that local corrosion was concentrated on the surface of the inner bottom plate on the oil tank side and concentrated in the vicinity of the longitudinal partition wall dividing the oil tank into a plurality of compartments.

  This invention is made | formed in view of this point, and makes it a subject to provide the oil tank structure which can suppress the corrosion which arises locally in the oil tank of a tanker.

  The present inventors further investigated the local corrosion that is concentrated on the surface of the inner bottom plate on the oil tank side and concentrated in the vicinity of the longitudinal partition wall that divides the oil tank into a plurality of compartments. As a result, the location where local corrosion occurs almost coincides with the position directly below the drain hole formed in the stiffener provided as a reinforcement for the longitudinal partition wall, and at locations other than the position directly below the drain hole. It was found that local corrosion hardly occurred.

  The present inventors have found that the fact that the crude oil flowing down from the drain hole directly collides with the inner bottom plate is a cause of local corrosion occurring in the oil tank. Furthermore, the present inventors have provided a collision prevention structure in the oil tank and succeeded in suppressing corrosion in the tanker's oil tank, that is, local corrosion caused by the flow of crude oil from the drain hole. The present invention is based on such knowledge.

In order to achieve the above object, the present invention provides an oil tanker having a double hull structure composed of a ship bottom outer plate and an inner bottom plate, and a plurality of stiffeners having drain holes formed therein. It is a structure of an oil tank formed by joining to a longitudinal partition wall along a direction,
The oil tank has a collision preventing structure that prevents oil flowing down through the drain hole of the stiffener from directly colliding with the upper surface of the inner bottom plate.

  The collision prevention structure may be a structure in which a dispersion member that disperses oil flowing down from the drain hole is provided below the drain hole of the stiffener.

  The collision preventing structure may be a structure provided with a closing member that closes a drain hole of the stiffener.

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion which arises locally in the oil tank of a tanker can be suppressed.

It is a longitudinal cross-sectional view which shows schematic structure of the tanker which has the oil tank concerning this Embodiment. It is explanatory drawing which shows the outline of the structure of the stiffener provided in the longitudinal partition, and the dispersion member vicinity. It is a transverse cross section showing the outline of the composition near a stiffener. It is explanatory drawing which shows the outline of a structure of the dispersion member vicinity concerning other embodiment. It is explanatory drawing which shows the outline of a structure of the stiffener vicinity concerning other embodiment. It is explanatory drawing which shows the outline of a structure of the stiffener vicinity concerning other embodiment.

  Embodiments of the present invention will be described below. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a tanker having an oil tank according to the present embodiment.

  As shown in FIG. 1, the bottom of the tanker 1 is composed of a ship bottom skin 10 and an inner bottom plate 11, and the ship side has a double hull structure composed of a ship side skin 12 and an inner wall 13. An upper deck 14 is provided at the upper ends of the ship side outer plate 12 and the inner side wall 13, and a ballast tank 20 is formed by a space surrounded by the ship side outer plate 12, the inner side wall 13 and the upper deck 14. The space surrounded by the inner wall 13 and the upper deck 14 forms an oil tank 21.

  The oil tank 21 is provided with, for example, two longitudinal partition walls 30 along the length direction of the tanker. The oil tank 21 is divided into a center tank 31 and a wing tank 32 by the longitudinal partition walls 30.

  On the surface of the inner bottom plate 11 and the inner wall 13 on the ballast tank 20 side, a plate-like stiffener 40 is provided along the length direction of the tanker as a reinforcing material for increasing the rigidity of the inner bottom plate 11 and the inner wall 13. A plurality of sheets are joined at predetermined intervals in the vertical direction. Also, a plurality of stiffeners 40 are provided on the surface of the longitudinal partition wall 30, for example, on the center tank 31 side, similarly to the inner wall 13.

  FIG. 2 is an explanatory diagram showing an outline of the configuration in the vicinity of the stiffener 40 provided on the longitudinal partition wall 30. As shown in FIG. 2, a plurality of partition cross beams 41 are provided in the longitudinal partition wall 30 along the vertical direction of the longitudinal partition wall 30. The stiffeners 40 are provided with ren holes 42 on the same vertical line so that the positions of the drain holes 42 of the stiffeners 40 arranged vertically in the plan view coincide with each other. The drain hole 42 is configured to prevent crude oil sludge from accumulating at the joint between the stiffener 40 and the longitudinal partition wall 30 when, for example, loading / unloading crude oil into / from the oil tank 21. .

  A flat plate-like dispersion member 43 is provided at a position between the stiffener 40 and the stiffener 40 provided in the vertical direction and directly below the drain hole 42. The dispersion member 43 is welded to the longitudinal partition wall 30. As shown in FIG. 3, the dispersion member 43 is formed with a diameter larger than the diameter of the drain hole 42, and is disposed so that the outer peripheral portion of the drain hole 42 is located inside the dispersion member 43 in plan view. .

  For example, when the crude oil flows down from the drain hole 42 when the crude oil is loaded and unloaded into the oil tank 21, the crude oil that has flowed down from the drain hole 42 once collides with the dispersion member 43 and is dispersed. Dispersed at the upper surface, the dispersed crude oil flows down from the dispersing member 43 and then reaches the inner bottom plate 11. Therefore, a collision preventing structure for preventing the crude oil flowing down from the drain hole 42 from directly colliding with the inner bottom plate 11 is formed in the oil tank 21 by the dispersion member 43.

  The dispersion member 43 has a stiffener in plan view so that the dispersion member 43 does not disturb the flow of the crude oil in the oil tank 21 when the crude oil is loaded onto the oil tank 21. It is preferable to form it so as to be positioned on the longitudinal partition wall 30 side with respect to the end portion of 40. Moreover, as for the member which comprises the above-mentioned tanker 1, ship steel plates, such as a coated steel plate and a corrosion-resistant steel plate, are used for all.

  According to the above embodiment, since the dispersion member 43 is provided below the drain hole 42 formed in the stiffener 40, the crude oil flowing down from the drain hole 42 directly collides with the upper surface of the inner bottom plate 11. Can be prevented. Therefore, local corrosion of the inner bottom plate 11 caused by the flow of crude oil from the drain hole 42 can be suppressed.

  Here, considering the investigation results of the inventors that local corrosion is hardly observed except for the position directly below the drain hole 42, the crude oil flowing down from the end of the stiffener 40 on the center direction side of the center tank 31 is considered. Depending on the flow F, it can be said that local corrosion does not occur. Therefore, in the above embodiment, the dispersion member 43 is provided for each stiffener 40. However, the dispersion member 43 is located at the lowest level, that is, the drain hole 42 of the stiffener 40a facing the inner bottom plate 11. You may make it provide only below. Also in this case, the dispersion member 43 can prevent the crude oil flowing down from the drain hole 42 of the stiffener 40a from directly colliding with the upper surface of the inner bottom plate 11.

  Further, in order to prevent the crude oil flowing down from the drain hole 42 from directly colliding with the upper surface of the inner bottom plate 11 using the dispersing member 43, for example, as shown by the broken line in FIG. It is also conceivable to directly join the dispersion member 43a as a sacrificial material at a position directly below the hole 42. However, at present, according to the classification rules, it is obliged to regularly check whether the thickness reduction of the inner bottom plate 11 is within the specified value, and the dispersing member 43a as a sacrificial material is an obstacle to the plate thickness measurement. It may become. Therefore, although implementation is restricted under the current classification rules, it is understood that the mode of directly joining the dispersion member 43a as a sacrificial material belongs to the technical scope of the present invention.

  In the above embodiment, the anti-collision structure is formed using the flat dispersion member 43. However, the shape of the dispersion member 43 is not limited to the flat plate shape. For example, as shown in FIG. A dispersion member 50 having a shape may be used.

  Further, instead of a collision prevention structure for preventing the crude oil flowing down from the drain hole 42 from directly colliding with the upper surface of the inner bottom plate 11, a structure for suppressing the flow velocity of the crude oil reaching the upper surface of the inner bottom plate 11 to a certain speed or less. It is considered that the same effect can be achieved by forming. Therefore, in order to reduce the flow rate of the crude oil passing through the drain hole 42, for example, a slit-shaped drain hole 60 may be provided instead of the drain hole 42 as shown in FIG. Even in such a case, when the oil passes through the drain hole 60, the flow rate of the crude oil decreases due to the resistance of the slit, and thus the same effect as that obtained when the dispersion member 43 is used can be obtained.

  In the above embodiment, the drain holes 42 are arranged so as to be arranged in the same vertical line. Generally, the stiffener 40 having the same shape is used for such an arrangement. This is because a plurality of stiffeners 40 are welded and joined to the longitudinal partition wall 30 in the vertical direction, leading to a reduction in construction costs. Therefore, the drain holes 42 do not necessarily have to be arranged in the same vertical line shape. For example, as shown in FIG. 6, the position of the drain hole 42 in the stiffener 40 arranged at the lowest level is shown in plan view. You may arrange | position alternately so that it may not mutually overlap with the drain hole 42 of the stiffener 40 located above.

  In such a case, the crude oil flowing into the drain hole 42 of the stiffener 40a located at the lowest level flows down from the drain hole 42 above the stiffener 40, and then once collides with the upper surface of the stiffener 40a to reduce the flow velocity. Therefore, similarly to the case where the slit-shaped drain hole 60 is used, the flow-down speed of the stiffener 40a from the drain hole 42 can be reduced. Therefore, as shown in FIG. 6, by arranging the stiffeners 40, 40a, the same as when preventing the crude oil flowing down from the drain hole 42 from directly colliding with the inner bottom plate 11 without providing the dispersing member 43, is provided. An effect can be obtained.

  Further, as shown in FIG. 6, when the stiffeners 40 and 40a are arranged, the dispersion member 43 is not necessary, so that welding work and the work at a high place associated therewith are also unnecessary. The work cost and safety at the construction site are improved. In this case, the flow rate of the crude oil from the drain hole 42 of the stiffener 40a can be further reduced by moving the stiffener 40a in the height direction toward the inner bottom plate 11 side. The effect of suppressing local corrosion of the bottom plate 11 can be further enhanced.

  In addition, when the drain holes 42 are alternately arranged as shown in FIG. 6, the crude oil flowing down from the drain hole 42 provided above the upper surface of the stiffener 40 collides. In this case, local corrosion may occur in the stiffener 40, which is a structural member. When corrosion occurs, the stiffener 40 needs to be replaced. Thus, the sacrificial material 61 may be provided at a position directly below the drain hole 42 to prevent the stiffener 40 from being corroded.

  In the above embodiment, the dispersion member 43 is disposed between the stiffeners 40 disposed so as to face each other. For example, instead of the dispersion member 43, the top surface or the bottom surface of the stiffener 40 is provided. A closing member that closes the drain hole 42 may be provided at a position corresponding to the drain hole 42.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  The present invention is useful in suppressing corrosion in a tanker oil tank.

DESCRIPTION OF SYMBOLS 1 Tanker 10 Ship bottom skin 11 Inner bottom plate 12 Ship side skin 13 Inner side wall 14 Upper deck 20 Ballast tank 21 Oil tank 30 Longitudinal bulkhead 31 Center tank 32 Wing tank 40 Stiffener 41 Bulkhead cross beam 42 Drain hole 43 Dispersing member 50 Dispersion Member 60 Drain hole 61 Sacrificial material F Flow

Claims (4)

In an oil tanker with a double hull structure consisting of a ship's outer skin and an inner floor, a stiffener with a drain hole formed is joined to a longitudinal bulkhead along the length of the hull. The structure of the oil tank,
An oil tank structure for a tanker, wherein the oil tank has a collision prevention structure for preventing oil flowing down through the drain hole of the stiffener from directly colliding with the upper surface of the inner bottom plate. 2. The tanker oil tank structure according to claim 1, wherein the collision prevention structure is a structure in which a dispersion member for dispersing oil flowing down from the drain hole is provided below the drain hole of the stiffener. . A plurality of the stiffeners are provided at predetermined intervals in the vertical direction,
The said collision prevention structure is a structure where the said drain hole of the stiffener arrange | positioned adjacent to the up-down direction is arrange | positioned in the position which does not mutually overlap in planar view, Either of Claim 1 or 2 characterized by the above-mentioned. Tanker oil tank structure according to the above. The oil tank structure for a tanker according to claim 1, wherein the collision preventing structure is a structure provided with a closing member that closes a drain hole of the stiffener.

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