WO2014112822A1

WO2014112822A1 - Method for manufacturing large diameter pipe using internal frame

Info

Publication number: WO2014112822A1
Application number: PCT/KR2014/000502
Authority: WO
Inventors: Hyeon Ju Kim; Dong Ho Jung; Ho Saeng Lee; Deok Soo Moon; Young Seok Kim
Original assignee: Korea Institute Of Ocean Science & Technology
Priority date: 2013-01-17
Filing date: 2014-01-17
Publication date: 2014-07-24
Also published as: KR101423937B1; KR20140093129A

Abstract

Disclosed herein are a large diameter pipe for connecting a floating marine structure to the deep seafloor and a method for manufacturing the large diameter pipe. According to the present invention, a large diameter pipe can be manufactured such that the specific gravity thereof is entirely or partially adjusted. In addition, the large diameter pipe is configured such that large diameter pipes can be easily successively connected to each other and the coupling strength between the large diameter pipes can be markedly enhanced. Moreover, large diameter pipes may be directly manufactured above the sea and the manufactured large diameter pipes can be installed under the sea in such a way that they are successively connected to each other. Therefore, the installation efficiency of the large diameter pipes can be improved.

Description

METHOD FOR MANUFACTURING LARGE DIAMETER PIPE USING INTERNAL FRAME

The present invention relates generally to large diameter pipes and methods for manufacturing the large diameter pipes and, more particularly, to a large diameter pipe which connects floating marine equipment to the deep seafloor, and a method for manufacturing the large diameter pipe.

Generally, pipes are made of materials such as metal, PE (polyethylene), GFRP (glass fiber reinforced plastic), etc. Such materials are mainly used to manufacture small and medium sized pipes having diameters of 1 m or less.

However, in the case of large diameter pipes of, for example, 5 m to 10 m in diameter, there is a limit to manufacture if a single material is used. Even if manufacture is possible, the production period is excessively increased, and it is economically infeasible.

That is, such a large diameter pipe must be designed such that as the diameter thereof increases, the thickness thereof is very largely increased to maintain the circular cross-sectional shape of the pipe. However, an increase in the thickness of the pipe increases the production cost, thus manufacture becomes economically infeasible. Also, there is a problem of an increase in the weight of the pipe.

With regard to piping materials for connecting a floating marine structure to the deep seafloor, materials which have high strength and superior electric insulation performance and are corrosion-resistant in a chemical environment are required.

Therefore, in the conventional technique, when pipes for connecting a floating marine structure to the deep seafloor are manufactured, steel pipes have been mainly used in consideration of the above-mentioned requirements, economic feasibility, workability, etc.

For example, a representative example of submarine steel pipes was proposed in Korean Patent Application No. 10-2002-0062684, entitled “STEEL PIPE COATED WITH COMPOSITE FRP RESIN”.

FIG. 1 is a view showing the general structure of a conventional submarine steel pipe.

In detail, as shown in FIG. 1, a steel pipe coated with composite FRP (fiber reinforced plastic) resin of No. 10-2002-0062684 is configured in such a way that a surface of a steel pipe 10 is coated with vinylester resin 12, and composite FRP (fiber reinforced plastic) resin 14 for preventing sea pollution and increasing corrosion resistance covers the outer surface of the vinylester resin layer.

According to the steel pipe coated with coated with composite FRP resin of No. 10-2002-0062684, because FRP resin is applied to the outer surface of the steel pipe, the strength of the steel pipe is increased, and corrosion of the steel pipe can be prevented, whereby the lifetime thereof can be extended. In addition, compared to a prior method using ceramic coating, the production cost can be reduced by 50% or more.

However, the conventional submarine steel pipe of No. 10-2002-0062684 lacks the strength to embody a large diameter pipe. Further, difficulty lies in bonding between synthetic resins. Therefore, there is a problem in that it is impossible to manufacture a large diameter pipe or an extra-large diameter pipe. It is also difficult to successively connect pipes to each other.

That is, typically, steel pipes are connected to each other by welding. If single pipes are manufactured with a large diameter, it is very important to connect the pipes to each other. As the diameter of each pipe increases, welding becomes more difficult, and the cost required for welding is also greatly increased.

If a typical simple connection method, in lieu of welding, is used to overcome the above-mentioned problems, the coupling strength between the pipes may not be sufficient.

In an effort to overcome the above-mentioned problems of the conventional technique, a method for manufacturing a large diameter pipe which is configured such that pipes can be easily successively connected to each other and ensured satisfactory coupling strength is required. However, until now, there has been no method for manufacturing a large diameter pipe which satisfies the above requirements.

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a large diameter pipe which connects a floating marine structure to the deep seafloor and is configured such that large diameter pipes can be successively connected to each other, the specific gravity of the pipe can be adjusted, and the coupling strength between the pipes is satisfactory, and a method for manufacturing the large diameter pipe.

In order to accomplish the above object, in an aspect, the present invention provides a method for manufacturing a large diameter pipe, including: an internal frame preparation operation of preparing cylindrical members that form a multilayered structure, each of the cylindrical members being made of at least one metal panel, and inserting reinforcing members between the cylindrical members such that the cylindrical members are spaced apart from each other by a predetermined distance, thus forming an internal frame; a filler charging operation of charging a filler between the reinforcing members to adjust a specific gravity of the internal frame; a hole forming operation of forming a plurality of holes passing through the internal frame; a fiber arrangement operation of arranging longitudinal reinforcing fibers or fiber mats on an outer or inner surface of the internal frame in a longitudinal direction of the internal frame or in a direction inclined to the longitudinal direction; a fiber connection operation of arranging circumferential reinforcing fibers in a circumferential direction of the internal frame in such a way that the circumferential reinforcing fibers pass through the holes and connecting the circumferential reinforcing fibers to the longitudinal reinforcing fibers or the fiber mats; a resin application operation of applying resin to a circumferential surface of the reinforcing fibers or the fiber mats so that the internal frame is integrated with the reinforcing fibers or the fiber mats; and an internal frame connection operation of connecting a plurality of internal frames to each other and forming a large diameter pipe having a desired length, each of the internal frames to which the resin has been applied in the resin application operation.

In another aspect, the present invention provides a method for manufacturing a large diameter pipe, including: an inner mold preparation operation of forming a cylindrical frame using a plurality of reinforcing plates, each of the reinforcing plates being recessed in a medial portion thereof by bending opposite ends thereof in a perpendicular direction, and of laminating a plurality of reinforcing fibers or fiber mats on a recessed portion of an outer circumferential surface of the cylindrical frame, thus forming an inner mold; a reinforcing member arrangement operation of longitudinally arranging a plurality of reinforcing members, each of the reinforcing members being wrapped by a multilayered fiber mat, wrapping a wire mesh around the reinforcing members, and disposing the reinforcing members on the recessed portion of the outer circumferential surface of the inner mold; a fiber mat providing operation of wrapping a multilayered fiber mat around outer circumferential surfaces of the reinforcing members that have been arranged in the reinforcing member arrangement operation; an outer mold disposition operation of disposing an outer mold on the outer circumferential surfaces of the reinforcing members; a forming operation of applying resin among the outer mold, the inner mold and the reinforcing members and forming a cylindrical internal frame through an FRP (fiber reinforced plastic) forming process; and an internal frame connection operation of connecting a plurality of internal frames formed in the forming operation to each other and forming a large diameter pipe having a desired length.

In a further aspect, the present invention provides a method for manufacturing a large diameter pipe, including: an inner mold preparation operation of laminating a multilayered fiber mat and a wire mesh on an outer surface of the inner mold, the inner mold being formed in a cylindrical shape using at least one panel; a reinforcing member arrangement operation of arranging a plurality of reinforcing members, each of the reinforcing members being wrapped by a multilayered fiber mat, on the outer surface of the inner mold in a longitudinal direction and wrapping a wire mesh around each of the reinforcing members; a fiber mat providing operation of wrapping a multilayered fiber mat around each of the reinforcing members that have been arranged in the reinforcing member arrangement operation; an outer mold disposition operation of disposing an outer mold on outer circumferential surfaces of the fiber mats that have been wrapped around the reinforcing members in the fiber mat providing operation; a forming operation of forming a cylindrical internal frame using the outer mold, the inner mold and the reinforcing members through an FRP (fiber reinforced plastic) forming process; and an internal frame connection operation of connecting a plurality of internal frames formed in the forming operation to each other and forming a large diameter pipe having a desired length.

The resin application operation may include: disposing an inner mold on an outer surface of the reinforcing fibers or fiber mats formed on the inner circumferential surface of the internal frame; disposing an outer mold on an outer surface of the reinforcing fibers or fiber mats formed on the outer circumferential surface of the internal frame; and charging resin between the inner mold and the outer mold through a vacuum suction method or a combination of vacuum suction and injection methods, the outer mold being airtightly sealed with the internal frame. In the fiber connection operation, while the circumferential reinforcing fibers are wound around the internal frame, the resin may be applied between the inner mold and the outer mold so that an integrated structure is formed.

The inner mold disposed on the inner surface of the internal frame may include a plurality of arc-shaped plates configured such that a diameter of a circle defined by the arc-shaped plates can be expanded to make internal pressurization possible, whereby the inner mold can be brought into close contact with the inner surface of the internal frame. The outer mold disposed on the outer surface of the internal frame may include a plurality of arc-shaped plates configured such that a diameter of a circle defined by the arc-shaped plates can be reduced to make internal pressurization possible, whereby the outer mold can be brought into close contact with the outer surface of the internal frame.

Each of the cylindrical members may be formed by rolling a single metal panel and bonding opposite ends of the metal panel to each other or by bonding a plurality of arc-shaped metal panels to each other. The reinforcing members may include corrugated plates, V-shaped or L-shaped bars, or circular or rectangular pipes that are interposed between the cylindrical members to maintain a distance between the cylindrical members constant.

The filler may comprise at least one of urethane foam, polystyrene, mortar and sand.

The reinforcing fibers may be formed of at least one of glass fibers, carbon fibers, metal fibers and basalt fibers, and the longitudinal reinforcing fibers of the fiber arrangement operation and the circumferential reinforcing fibers of the fiber connection operation may intersect with each other to increase tensile strength and shear strength, thus forming a fiber layer. The fiber layer may comprise at least one of a fiber mat, a woven roving mat and chopped strand mat.

The reinforcing member arrangement operation may include winding the fiber mats one to five turns around the reinforcing members, and the fiber mat providing operation may include winding two to twenty sheets of fiber mats.

The forming operation may include forming the internal frame by molding FRP (fiber reinforced plastic) as a filler through a resin transfer molding (RTM) method, a vacuum assisted resin transfer molding (VARTM) method or a RTM-VARTM method

Each of the reinforcing members may have a bar shape and is made of polyurethane, wood, ferroconcrete or metal. A specific gravity and a strength of the internal frame for forming the large diameter pipe may be adjusted by selecting the kind of reinforcing member.

The method may further include a covering material application operation of applying covering material to the outer circumferential surface of the internal frame to prevent biofouling or block ultraviolet rays.

Each of opposite ends of the internal frame may have a stepped structure to increase a coupling strength between internal frames when the internal frames are longitudinally connected to each other to extend a length of the large diameter pipe.

In yet another aspect, the present invention provides a method for connecting large diameter pipes, the method including: forming stepped parts on opposite ends of each of the large diameter pipes, the stepped parts having shapes corresponding to each other or being oriented in a same direction, and inserting an internal frame piece between the stepped parts of the large diameter pipes, and respectively fixing fiber-reinforced plastic bonding panels to outer and inner circumferential surfaces of a junction between the large diameter pipes longitudinally connected to each other, and charging resin into the junction through a vacuum suction method or a combination of vacuum suction and injection methods.

The fiber-reinforced plastic bonding panels may be transparent to enable observation and inspection of internal coupling conditions or to determine whether bubbles are generated.

Each of opposite ends of each of the large diameter pipes may have a protrusion, and the protrusions of the large diameter pipes may be coupled to each other by bolting or using a fiber bundle so as to increase a coupling strength between large diameter pipes.

In still another aspect, the present invention a method for installing large diameter pipes in such a way that the large diameter pipes that are vertically connected to each other are vertically moved downwards from a platform of an installation ship or marine structure, the method including: a heating and pressing band attachment operation of attaching a heating and pressing band to an outer circumferential surface of each junction between a plurality of large diameter pipes; a hardening operation of applying heat and pressure to the heating and pressing band and hardening the junction between the large diameter pipes; and a moving-down operation of tautly connecting a plurality of winches provided on the platform to the heating and pressing band using a plurality of wires so as to prevent deformation of the large diameter pipes and maintain a coupling strength between the large diameter pipes and vertically moving the large diameter pipes downwards.

The heating and pressing band may have a removable structure such that the heating and pressing band can be removably attached to the outer circumferential surface of the corresponding junction of the large diameter pipes.

The heating and pressing band may comprise a plurality of heating and pressing bands, wherein when a lower end of the large diameter pipes are moved to a predetermined depth while the large diameter pipes are longitudinally connected to each other, a lowermost heating and pressing band is removed from the large diameter pipes, is drawn upwards, and is attached to an uppermost junction of the large diameter pipes, whereby the large diameter pipes can be connected to each other using a predetermined number of heating and pressing bands without limiting a length of the large diameter pipes.

As described above, a large diameter pipe using an internal frame and a method of coupling large diameter pipes to each other according to the present invention can be provided. Furthermore, a large diameter pipe can be manufactured by connecting a plurality of internal frames to each other. In addition, the present invention can also provide a method of installing the large diameter pipe under the sea.

In a method of manufacturing a large diameter pipe which connects floating marine equipment to a deep seafloor according to the present invention, large diameter pipes which can be entirely or partially adjusted in specific gravity can be manufactured and successively connected toeach other. Furthermore, coupling strength between large diameter pipes can be markedly enhanced. As such, the present invention can provide a large diameter pipe having an improved structure and a method for manufacturing the large diameter pipe using an internal frame.

Moreover, in the present invention, because large diameter pipes may be

directly manufactured above the sea and the manufactured large diameter pipes can be installed under the sea in such a way that they are successively connected to each other, the installation efficiency of the large diameter pipes can be improved.

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view showing the general structure of a conventional submarine steel pipe;

FIG. 2 is a flowchart showing a method for manufacturing a large diameter pipe according to a first embodiment of the present invention;

FIGS. 3A through 3C are views illustrating the constructions of metal panels constituting an internal frame according to the present invention;

FIG. 4 is a view illustrating the structure of a reinforcing member of the internal frame according to the present invention;

FIG. 5 is a view showing a plurality of holes formed in the internal frame according to the present invention;

FIG. 6 is a view showing the construction of an inner mold disposed on an inner surface of the internal frame to apply resin thereto according to the present invention;

FIG. 7 is a view showing the construction of an outer mold disposed on an outer surface of the internal frame to apply resin thereto according to the present invention;

FIG. 8 is a sectional view showing the structure of an internal frame formed in accordance with an embodiment of the present invention;

FIG. 9 is a flowchart showing a method for manufacturing a large diameter pipe using an internal frame according to a second embodiment of the present invention;

FIG. 10 is a sectional view showing the construction of the internal frame according to the second embodiment of the present invention;

FIG. 11 is a sectional view showing the construction of an internal frame according to a third embodiment of the present invention;

FIG. 12 is a flowchart showing a method for manufacturing the internal frame according to the third embodiment of the present invention;

FIG. 13 is a view showing the construction of a coupling part for connecting a plurality of internal frames to each other according to the present invention;

FIG. 14 is a view showing the construction of another example of a coupling part for connecting a plurality of internal frames to each other according to the present invention;

FIG. 15 is a view showing the construction of a further example of a coupling part for connecting a plurality of internal frames to each other according to the present invention;

FIG. 16 is a view showing the construction of yet another example of a coupling part for connecting a plurality of internal frames to each other according to the present invention;

FIG. 17 is a flowchart showing a method of installing a large diameter pipe according to an embodiment of the present invention; and

FIG. 18 is a view showing installation of the large diameter pipe manufactured by the method according to an embodiment of the present invention.

Hereinafter, a method for manufacturing a large diameter pipe using an internal frame according to the present invention will be described in detail with reference to the attached drawings.

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

The present invention relates to a large diameter pipe which connects a floating marine structure to the deep seafloor and is configured such that large diameter pipes can be successively connected to each other and the coupling strength between the large diameter pipes is satisfactory, and a method for manufacturing the large diameter pipe using an internal frame.

Moreover, the present invention provides a method for manufacturing a large diameter pipe using an internal frame in which because large diameter pipes may be directly manufactured above the sea and the manufactured large diameter pipes can be installed under the sea in such a way that they are successively connected to each other, the installation efficiency of the large diameter pipes can be improved.

Hereinafter, embodiments of the large diameter pipe manufacturing method according to the present invention will be described in detail with reference to the attached drawings.

FIG. 2 is a flowchart showing a method for manufacturing a large diameter pipe using an internal frame according to a first embodiment of the present invention.

As shown in FIG. 2, the large diameter pipe manufacturing method according to the first embodiment includes: an internal frame preparation operation S21 of preparing cylindrical members which form a multilayered structure and each of which is made of at least one metal panel and inserting reinforcing members between the cylindrical members such that the cylindrical members are spaced apart from each other by a predetermined distance, thus forming an internal frame; a filler charging operation S22 of charging a filler between the reinforcing members to adjust the specific gravity of the internal frame; a hole forming operation S23 of forming a plurality of holes passing through the internal frame; a fiber arrangement operation S24 of arranging reinforcing fibers or fiber mats on an outer or inner surface of the internal frame in a longitudinal direction of the internal frame or in a direction inclined to the longitudinal direction; a fiber connection operation S25 of arranging reinforcing fibers in a circumferential direction of the internal frame in such a way that the reinforcing fibers pass through the holes and connecting the circumferential reinforcing fibers to the longitudinal reinforcing fibers or the fiber mats; and a resin application operation S26 of applying resin to a circumferential surface of the reinforcing fibers or the fiber mats so that the internal frame is integrated with the reinforcing fibers or the fiber mats.

In more detail, in the internal frame preparation operation S21, each of the cylindrical members which form a multilayered structure is formed by rolling a single metal panel in a cylindrical shape and bonding connected ends thereof to each other, or by bonding a plurality of metal panels that have a predetermined curvature radius to each other.

FIG. 3 is a view showing the construction of the metal panel.

As shown in FIG. 3A, the metal panel 31 may comprise a single steel plate. Alternatively, as shown in FIG. 3B, the metal panel 31 may be configured in such a way that a plurality of steel plates 32 are bonded to each other, and a plurality of reinforcing members 33 are interposed between the steel plates 32 to form a sandwich structure. As a further alternative, as shown in FIG. 3C, the metal panel 31 may be configured in such a way that a plurality of steel plates 32 are bonded to each other, and the space between the steel plates 32 is filled with a filler 35.

Here, the

metal panel

32 or 34 which has a sandwich structure or is provided with the filler 35 has increased strength, because the section modulus thereof is increased. Furthermore, in the case of such structures, adjustment in specific gravity can be also facilitated.

Using such a metal panel, an internal frame is formed. In other words, a cylindrical internal frame may be formed by rolling a single metal panel in a roll shape. Alternatively, e.g., a double-cylindrical internal frame including a plurality of cylinders having different diameters may be formed by coupling a plurality of metal panels to each other, for example, using nuts and bolts,

FIG. 4 is a view illustrating the structure of a reinforcing member 41 according to the present invention.

As shown in FIG. 4, the reinforcing members 41 may be formed of composite aluminum or steel to have a honeycomb structure or triangle-cluster structure. Alternatively, the reinforcing members may comprise corrugated plates, V-shaped or L-shaped bars, or circular or rectangular pipes which are interposed between the cylindrical members to maintain the distance between the cylindrical members constant and increase the shear rigidity.

As such, in the internal frame preparation operation S21, a multilayered cylindrical structure having at least two layers is formed by bonding a plurality of metal panels having the above-mentioned structure. The reinforcing members 33 are interposed between the cylindrical members of the cylindrical structure such that the distance between the cylindrical members is maintained constant, thus forming the internal frame having the multilayered cylindrical member.

Thereafter, in the filler charging operation S22, the filler 35 is charged into space between the cylindrical members and the reinforcing members 33, thus adjusting the specific gravity of the internal frame. The filler 35 is formed of at least one of urethane foam, polystyrene, mortar and sand and functions to adjust the specific gravity of the internal frame such that it preferably becomes 0.2 to 5.0.

In the hole forming operation S23, the holes are formed through the cylindrical members of the internal frame.

That is, as shown in FIG. 5, the holes 51 are formed in the internal frame 50 having a cylindrical shape.

The hole forming operation S23 may be performed after the internal frame has been completely manufactured, as illustrated in this embodiment. Alternatively, the hole forming operation S23 may be performed during the internal frame preparation operation in such a way that holes are previously formed in the metal panels. That is, the metal panels that have holes therein may be used to form the internal frame. As such, a sequence of the operations of the manufacturing method may be changed, as needed.

In the fiber arrangement operation S24, to increase tensile strength and shearing strength, a reinforcing fiber layer is formed on the surface of the internal frame 50 in such a way that reinforcing fibers are wrapped or fiber mats are arranged on the outer or inner surface of the internal frame 50 in the longitudinal direction or in a direction inclined to the longitudinal direction.

In the fiber connection operation S25, reinforcing fibers are arranged through the holes 51 formed in the hole forming operation S23 in such a way that each reinforcing fiber passes through the corresponding holes 51 alternately between the inside and outside of the internal frame 50 as if the cylindrical members that form the multilayered structure are sewn by the reinforcing fibers.

Through the fiber arrangement operation S24 and the fiber connection operation S25, the reinforcing fibers formed in the fiber arrangement operation S24 and the reinforcing fibers formed in the fiber connection operation S25 are cross-coupled to each other, thus forming a fiber layer. Therefore, the tensile strength and the shearing strength of the internal frame with respect to not only the circumferential direction but also the axial direction can be enhanced.

For example, the reinforcing fibers are formed of at least one of glass fibers, carbon fibers, metal fibers and basalt fibers. The fiber layer is formed of at least one of a fiber mat, woven roving, chopped strand mat and a fiber bundle.

Hereinafter, the resin application operation S26 will be explained in detail with reference to FIGS. 6 and 7.

FIG. 6 is a view showing the construction of an inner mold 70 disposed inside the internal frame to apply resin thereto.

FIG. 7 is a view showing the construction of an outer mold 80 disposed on the outer surface of the internal frame to apply resin thereto.

In the resin application operation S26, resin is applied to the reinforcing fiber layer which is formed on the internal frame through the fiber arrangement operation S24 and the fiber connection operation S25, thus forming a fiber-reinforcing plastic layer which integrates the reinforcing fiber layer with the internal frame.

The resin application operation S26 may be conducted after the reinforcing fibers or fiber mats are arranged to form the reinforcing fiber layer. Alternatively, in the fiber connection operation, the resin application operation S26 may be conducted simultaneously with the arrangement of reinforcing fibers.

In detail, in the resin application operation S26, as shown in FIG. 6, the inner mold 70 is located adjacent to the outer surface of the reinforcing fibers or fiber mats formed on the inner circumferential surface of the internal frame 50. As shown in FIG. 7, the outer mold 80 is located around the outer surface of the reinforcing fibers or fiber mats formed on the outer circumferential surface of the internal frame 50.

Thereafter, for example, through VARTM (vacuum assisted resin transfer molding) or VARTM+RTM (resin transfer molding), resin is charged into space between the internal frame 50 and the inner and

outer molds

70 and 80 which are airtightly sealed with the internal frame 50, thus integrating the reinforcing fiber layer with the internal frame.

To bring the inner mold 70 into close contact with the inner surface of the internal frame 50, the inner mold 70 which is located around the inner surface of the internal frame 50 is provided with a plurality of arc-shaped plates which are configured such that the diameter of a circle defined by the arc-shaped plates can be expanded to make internal pressurization possible. Furthermore, to bring the outer mold 80 into close contact with the outer surface of the internal frame 50, the outer mold 80 which is located around the outer surface of the internal frame 50 is provided with a plurality of arc-shaped plates which are configured such that the diameter of a circle defined by the arc-shaped plates can be contracted to make internal pressurization possible.

In more detail, as shown in FIG. 6, the inner mold 70 includes a central member 71, a plurality of elastic members 72 which are connected to the central member 71, and a plurality of support members 73 which are connected to ends of the respective elastic members 72.

The number of elastic members 72 corresponds to that of the support members 73. Further, the shapes of the support members 73 correspond to the shape of the internal frame 50.

In the above-mentioned structure, each support member 73 can be moved by variation in length of the corresponding elastic member 72. By virtue of expansion and contraction of the elastic members 72, the process of locating the inner mold 70 inside the internal frame 50, bringing the inner mold 70 into close contact with the internal frame 50, applying resin to the inner surface of the internal frame 50 and removing the inner mold 70 therefrom can be facilitated.

As shown in FIG. 7, the outer mold 80 is provided around the internal frame 50 in a shape in which the outer mold 80 encloses the outer surface of the internal frame 50. In the same manner as the inner mold 70, a process of locating the outer mold 80, bringing the outer mold 80 into close contact with the internal frame 50, applying resin to the outer surface of the internal frame 50 and removing the outer mold 80 therefrom can be easily performed.

After the resin application operation S26, the method according to the present invention may further include a covering material application operation of applying covering material to the outer surface of the hardened resin layer to prevent seawater from permeating the large diameter pipe and prevent biofouling on the outer surface of the large diameter pipe.

Through the above-mentioned process, the internal frame 50 according to this embodiment of the present invention can be formed.

FIG. 8 is a sectional view showing the structure of the internal frame 50 formed by the method according to the embodiment of the present invention.

As shown in FIG. 8, in the internal frame 50 manufactured by the method according to the embodiment of the present invention, the reinforcing member 92 and the filler 93 are interposed between the cylindrical members 91 which form a multilayered structure. The fiber layers formed of reinforcing fibers or fiber mats 94 are formed on the outer and inner circumferential surfaces of the cylindrical members 91. The second reinforcing fibers 95 are arranged through the cylindrical members 91 and the fiber layers formed of reinforcing fibers or fiber mats 94. The fiber layers are integrated with the cylindrical members 91 by applying resin thereto. As needed, the covering layers 96 are formed on the resin layers, thus completing the manufacture of the internal frame 50.

In the above-stated embodiment, although the internal frame 50 has been illustrated as having a double cylinder structure in which a plurality of cylindrical members made of steel are coupled to each other, the present invention is not limited to this structure.

Hereinafter, a method for manufacturing a large diameter pipe using an internal frame according to a second embodiment of the present invention will be described in detail with reference to FIGS. 9 and 10.

FIG. 9 is a flowchart showing the method for manufacturing a large diameter pipe using an internal frame according to the second embodiment of the present invention.

As shown in FIG. 9, the large diameter pipe manufacturing method according to the second embodiment of the present invention includes an inner mold preparation operation S91 of forming a cylindrical frame using a plurality of reinforcing plates, each of which is recessed in a medial portion thereof by bending opposite ends thereof in the perpendicular direction, and laminating a plurality of reinforcing fibers or fiber mats on the recessed portion of the outer surface of the cylindrical frame, thus forming an inner mold; a reinforcing member arrangement operation S92 of longitudinally arranging a plurality of reinforcing members each of which is wrapped by a fiber mat in layers, wrapping a wire mesh around the reinforcing members, and disposing them on the recessed portion of the outer surface of the inner mold; a fiber mat providing operation S93 of wrapping a fiber mat in layers around outer circumferential surfaces of the reinforcing members that have been arranged in the reinforcing member arrangement operation S92; an outer mold disposition operation S94 of disposing an outer mold on the outer circumferential surfaces of the reinforcing members; and a forming operation S95 of forming a cylindrical internal frame using the outer mold, the inner mold and the reinforcing member through an FRP (fiber reinforced plastic) forming process.

Unlike the internal frame according to the first embodiment, the internal frame according to the second embodiment is formed by forming a cylindrical member using at least one FRP plate, which is bent on opposite ends thereof, arranging the reinforcing members each of which is wrapped by a fiber mat in layers, disposing the outer mold at a predetermined position, and then molding FRP through a resin transfer molding (RTM) method, a vacuum assisted resin transfer molding (VARTM) method or a RTM-VARTM method.

FIG. 10 is a sectional view showing the construction of the internal frame 110 according to the second embodiment of the present invention.

As shown in FIG. 10, the internal frame 110 according to the second embodiment includes a fiber-reinforced plastic (FRP) panel 111 which is recessed in the medial portion thereof by bending the opposite ends thereof, a fiber layer 112 which is formed in the recessed portion of the fiber-reinforced plastic (FRP) panel 111 by laminating the reinforcing fibers or fiber mats, reinforcing members 113 which are arranged on the fiber layer 112 and each of which has a bar shape extending a predetermined length in the longitudinal direction, and an outer mold 114 which is disposed on the outer circumferential surfaces of the fiber-reinforced plastic (FRP) panel 111 and the reinforcing members 113.

Each reinforcing member 113 has a bar shape and is made of polyurethane, wood, ferroconcrete or metal. The specific gravity and strength of the internal frame 110 for the large diameter pipe can be easily adjusted by appropriately selecting the kind of reinforcing member 113.

Furthermore, each reinforcing member 113 is wrapped one to five turns with a fiber mat, and then the reinforcing members 113 are arranged in the longitudinal direction before they are wrapped by a wire mesh.

That is, in the internal frame according to the first embodiment, a multi-cylindrical structure is formed by a single panel or coupling a plurality of arc-shaped steel plates. However, in the internal frame according to the second embodiment, as shown in FIG. 10, a cylindrical structure is formed by coupling a plurality of fiber-reinforced plastic (FRP) panels 111, each of which has a recessed shape in a medial portion thereof, to each other. A plurality of reinforcing fibers or fiber mats are laid on the recessed portion of each fiber-reinforced plastic (FRP) panel 111, thus forming the fiber layer 112. Thereafter, the reinforcing members 113 are arranged in the recessed portion of the fiber-reinforced plastic (FRP) panel 111. Subsequently, the outer mold 114 is disposed on the outer circumferential surfaces of the fiber-reinforced plastic (FRP) panels 111 and the reinforcing member 112. The FRP molding process is thereafter conducted, thus completing the internal frame. Therefore, unlike the first embodiment, the internal frame 110 can be formed without requiring the operations of forming holes and arranging reinforcing fibers.

As such, according to the second embodiment of the present invention, the internal frame 110 having a cross-sectional structure shown in FIG. 10 can be formed by arranging the fiber-reinforced plastic (FRP) panels 111 and the reinforcing members 112 and FRP-molding, without conducting the hole forming operation S103, the fiber arrangement operation S104, the fiber connection operation S105 and the resin application operation S106 of the first embodiment. As a result, the process of manufacturing the internal frame 110 can be simplified.

Hereinafter, the construction of an internal frame 170 according to a third embodiment of the present invention will be described in detail with reference to FIGS. 11 and 12.

FIG. 11 is a sectional view showing the general construction of an internal frame 170 according to the third embodiment of the present invention.

As shown in FIG. 11, the internal frame 170 according to the third embodiment of the present invention includes a plurality of reinforcing members 171 which form a main body of the internal frame 170, a multilayered first fiber mat 172 which encloses each reinforcing member 171, a multilayered wire mesh 173 which encloses each reinforcing member 171 that has been wrapped by the first fiber mat 172, a multilayered second fiber mat 174 which encloses the wire mesh 173, and an inner mold 175 and an outer mold 176 which are respectively disposed on inner and outer circumferential surfaces of the second fiber mats 174.

In the same manner as the second embodiment, each reinforcing member 171 has a bar shape and is made of polyurethane, wood, ferroconcrete or metal. The specific gravity and strength of the internal frame 170 for the large diameter pipe can be easily adjusted by appropriately selecting the kind of reinforcing member 171.

Each multilayered first fiber mat 172 may be formed by wrapping a fiber mat one to five turns around the corresponding reinforcing member 171. Each multilayered second fiber mat 174 may be formed by wrapping two to twenty fiber mats around the corresponding reinforcing member 171.

FIG. 12 is a flowchart showing a method for manufacturing the internal frame 170 having the above-mentioned construction according to the third embodiment of the present invention.

As shown in FIG. 12, the method for manufacturing the internal frame 170 according to the third embodiment of the present invention includes: an inner mold preparation operation S121 of laminating a multilayered fiber mat and wire mesh on an outer surface of the inner mold which is formed in a cylindrical shape using at least one panel; a reinforcing member arrangement operation S122 of arranging a plurality of reinforcing members, each of which is wrapped by a multilayered fiber mat, on the outer surface of the inner mold in the longitudinal direction and wrapping a wire mesh around each reinforcing member; a fiber mat providing operation S123 of wrapping a multilayered fiber mat around each reinforcing member; an outer mold disposition operation S124 of disposing the outer mold on the outer circumferential surfaces of the fiber mats wrapped around the reinforcing members; and a forming operation S125 of forming a cylindrical internal frame using the outer mold, the inner mold and the reinforcing members through an FRP (fiber reinforced plastic) forming process.

In detail, in the inner mold preparation operation S121, fiber mats and wire meshes are placed on the inner mold in two to twenty layers. In the reinforcing member arrangement operation S122, the reinforcing members each of which is wrapped one to five layers by fiber mats are arranged in the longitudinal direction and are wrapped by wire meshes. In the fiber mat providing operation S123, fiber mats are wrapped, in two to twenty layers, around the outer circumferential surfaces of the reinforcing members that have been wrapped by the wire meshes.

Thereafter, in the outer mold disposition operation S124, the outer mold is disposed on the outer circumferential surfaces of the reinforcing members that have been wrapped with the fiber mats. In the forming operation S125, an internal frame is formed by molding FRP through a resin transfer molding (RTM) method, a vacuum assisted resin transfer molding (VARTM) method or a RTM-VARTM method.

In the above-mentioned ways, the internal frames according to the first through third embodiments of the present invention can be manufactured. Furthermore, such internal frames are configured such that they are connected to each other to form a large diameter pipe having a desired length.

Through the above-stated process, the internal frames according to the first through third embodiments of the present invention and a large diameter pipe using the internal frames can be embodied.

Meanwhile, for the sake of manufacture, it is preferable that a large diameter pipe be manufactured using the internal frames of the present invention as the unit of about 5 m to about 10 m.

In the case of a single pipe using a single internal frame, for example, it may be manufactured to have a length of about 5 m. Such pipes may be successively connected to each other to have a desire length by longitudinally bonding a plurality of internal frames to each other.

To connect the internal frames in the longitudinal direction, in the same manner of the method of manufacturing the internal frame, the cylindrical internal frames may be connected to each other into a single body by bolting. Alternatively, the ends of each internal frame may be configured to have stepped structures, and the stepped ends of the internal frames may be bonded to each other using fiber materials and resin.

In detail, FIGS. 13 through 16 are views showing the structure of a coupling part for connecting the internal frames to each other.

As shown in FIG. 13, when the internal frame 120 according to the first through third embodiments of the present invention is manufactured, a coupling protrusion 121 may be formed on each end of each internal frame 120 so that the internal frames 120 can be fastened to each other by tightening a fastening bolt 122 into the coupling protrusions 121 of the internal frames 120.

As such, nuts and bolts can be used to couple the metal panels to each other or fasten the large diameter pipes to each other. In this case, there is an advantage in that a large diameter pipe having a predetermined diameter can be formed in a short time.

However, if only nuts and bolts are used to connect the internal frames to each other, there is the possibility of breakage because of comparatively low coupling strength. Therefore, to enhance the coupling strength, as shown in FIG. 14, coupling parts 131 are formed in the opposite ends of each internal frame in such a way that stepped parts that have shapes corresponding to each other or are oriented in the same direction are formed in the opposite ends of each internal frame. A coupling protrusion 132 is provided on each coupling part 131 having the stepped structure. The internal frames 120 are coupled to each other by winding a reinforcing fiber 133 around the coupling protrusions 132 of the internal frames 120.

As shown in FIG. 15, in lieu of the above-mentioned coupling protrusion 132, a coupling bolt 134 may be pegged into a predetermined portion of each coupling part 131, and the reinforcing fiber 133 may be wound around the coupling bolts 134, whereby the adjacent internal frames can be fastened to each other.

Thereafter, an internal frame piece 135 having a shape corresponding to the coupling parts 131 is inserted between the stepped portions of the coupling parts 131 of the internal frames. Bonding panels 136 made of fiber-reinforced plastic are respectively fixed to the outer and inner circumferential surfaces of the junction between the internal frames that are longitudinally connected to each other. Subsequently, resin is charged into the junction between the internal frames by a vacuum suction method or a combination of vacuum suction and injection methods. In this way, the coupling strength between the internal frames can be enhanced.

Preferably, the bonding panels 136 are made of transparent fiber-reinforced plastic to allow a worker to observe and inspect internal coupling conditions or to detect whether bubbles are generated.

In another way, referring to FIG. 16, each coupling part 131 of each internal frame has a stepped structure. The stepped coupling parts 131 of the internal frames engage with each other. Bonding panels 136 are thereafter fixed to the junction between the internal frames. Subsequently, resin is charged into the junction between the internal frames by a vacuum suction method or a combination of vacuum suction and injection methods. In this case, compared to the forgoing coupling methods, the internal frames can be more easily coupled and bonded to each other.

Meanwhile, a large diameter pipe having a predetermined length can be manufactured by repeatedly conducting the above-mentioned process of coupling the internal frames to each other. For example, a large diameter pipe having a length of 100 m or more can be manufactured by successively conducting the above-mentioned coupling process.

Next, a method of installing such a large diameter pipe under the sea will be described in detail with reference to FIG. 17.

FIG. 17 is a flowchart showing a method of installing a large diameter pipe according to an embodiment of the present invention.

As shown in FIG. 17, the method of installing a large diameter pipe according to an embodiment of the present invention includes: operation S152 of attaching a heating and pressing band to an outer circumferential surface of each junction between a plurality of large diameter pipes; operation S152 of heating and pressing the junction between the large diameter pipes using the heating and pressing band and hardening the junction; and operation S153 of tautly connecting a plurality of winches provided on a platform of a ship or marine structure to the heating and pressing band using a plurality of wires so as to prevent deformation of the large diameter pipes and maintain the coupling strength between the pipes and immersing the large diameter pipes under the sea.

As shown in FIG. 18, in the installation method of the large diameter pipe according to the present invention, heating and pressing bands 162 are attached to an outer circumferential surface of the large diameter pipes. The heating and pressing bands 162 are heated and pressurized so as to harden the junctions between the large diameter pipes. The heating and pressing bands 162 are connected to winches (not shown) provided on a platform 163 by a plurality of wires 164. In this state, the wires 164 are unwound from the winches while being maintained taut so as to prevent deformation of the large diameter pipes 161. Thereby, the large diameter pipes which are connected to each other in the vertical direction are moved downwards under the sea from the platform of an installation ship or marine structure. Each heating and pressing band 162 has a removable structure such that it can be removably attached to the outer circumferential surface of the corresponding junction of the large diameter pipes 161.

Furthermore, the heating and pressing bands 162 may be provided on the respective junctions of the large diameter pipes 161. Preferably, when the lower end of the large diameter pipes 161 is moved to a predetermined depth while the large diameter pipes 161 are longitudinally connected to each other, the lowermost heating and pressing band 162 is removed from the large diameter pipes 161, is drawn upwards, and is attached to the uppermost junction of the large diameter pipes 161. In this way, large diameter pipes can be connected to each other only using a predetermined number of heating and pressing bands without limiting the length of the large diameter pipes.

In a method of manufacturing a large diameter pipe which connects floating marine equipment to a deep seafloor according to the present invention, large diameter pipes which can be entirely or partially adjusted in specific gravity can be manufactured and successively connected to each other. Furthermore, coupling strength between large diameter pipes can be markedly enhanced. As such, the present invention can provide a large diameter pipe having an improved structure and a method for manufacturing the large diameter pipe using an internal frame.

Moreover, in the present invention, because large diameter pipes may be directly manufactured above the sea and the manufactured large diameter pipes can be installed under the sea in such a way that they are successively connected to each other, the installation efficiency of the large diameter pipes can be improved.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

10. steel pipe 12. vinylester resin

14. FRP resin 31. metal panel

32. metal panel 33. reinforcing member

34. metal panel 35. filler

41. reinforcing member 50. internal frame

51. hole 61. first reinforcing fiber

70. inner mold 71. central member

72. elastic member 73. support member

80. outer mold 91. cylindrical member

92. reinforcing member 93. filler

94. first reinforcing fiber 95. second reinforcing fiber

96. covering layer 110. internal frame

111. FRP panel 112. fiber layer

113. reinforcing member 114. outer mold

120. internal frame 121. coupling protrusion

122. fastening bolt 131. coupling part

132. coupling protrusion 133. reinforcing fiber

134. coupling bolt 135. internal frame piece

136. bonding panel 161. large diameter pipe

162. heating and pressing band 163. platform

164. wire 170. internal frame

171. filler 172. first fiber mat

173. wire mesh 174. second fiber mat

175. inner mold 176. outer mold

Claims

A method for manufacturing a large diameter pipe, comprising:

an internal frame preparation operation of preparing cylindrical members that form a multilayered structure, each of the cylindrical members being made of at least one metal panel, and inserting reinforcing members between the cylindrical members such that the cylindrical members are spaced apart from each other by a predetermined distance, thus forming an internal frame;

a filler charging operation of charging a filler between the reinforcing members to adjust a specific gravity of the internal frame;

a hole forming operation of forming a plurality of holes passing through the internal frame;

a fiber arrangement operation of arranging longitudinal reinforcing fibers or fiber mats on an outer or inner surface of the internal frame in a longitudinal direction of the internal frame or in a direction inclined to the longitudinal direction;

a fiber connection operation of arranging circumferential reinforcing fibers in a circumferential direction of the internal frame in such a way that the circumferential reinforcing fibers pass through the holes and connecting the circumferential reinforcing fibers to the longitudinal reinforcing fibers or the fiber mats;

a resin application operation of applying resin to a circumferential surface of the reinforcing fibers or the fiber mats so that the internal frame is integrated with the reinforcing fibers or the fiber mats; and

an internal frame connection operation of connecting a plurality of internal frames to each other and forming a large diameter pipe having a desired length, each of the internal frames to which the resin has been applied in the resin application operation.
A method for manufacturing a large diameter pipe, comprising:

an inner mold preparation operation of forming a cylindrical frame using a plurality of reinforcing plates, each of the reinforcing plates being recessed in a medial portion thereof by bending opposite ends thereof in a perpendicular direction, and of laminating a plurality of reinforcing fibers or fiber mats on a recessed portion of an outer circumferential surface of the cylindrical frame, thus forming an inner mold;

a reinforcing member arrangement operation of longitudinally arranging a plurality of reinforcing members, each of the reinforcing members being wrapped by a multilayered fiber mat, wrapping a wire mesh around the reinforcing members, and disposing the reinforcing members on the recessed portion of the outer circumferential surface of the inner mold;

a fiber mat providing operation of wrapping a multilayered fiber mat around outer circumferential surfaces of the reinforcing members that have been arranged in the reinforcing member arrangement operation;

an outer mold disposition operation of disposing an outer mold on the outer circumferential surfaces of the reinforcing members;

a forming operation of applying resin among the outer mold, the inner mold and the reinforcing members and forming a cylindrical internal frame through an FRP (fiber reinforced plastic) forming process; and

an internal frame connection operation of connecting a plurality of internal frames formed in the forming operation to each other and forming a large diameter pipe having a desired length.
A method for manufacturing a large diameter pipe, comprising:

an inner mold preparation operation of laminating a multilayered fiber mat and a wire mesh on an outer surface of the inner mold, the inner mold being formed in a cylindrical shape using at least one panel;

a reinforcing member arrangement operation of arranging a plurality of reinforcing members, each of the reinforcing members being wrapped by a multilayered fiber mat, on the outer surface of the inner mold in a longitudinal direction and wrapping a wire mesh around each of the reinforcing members;

a fiber mat providing operation of wrapping a multilayered fiber mat around each of the reinforcing members that have been arranged in the reinforcing member arrangement operation;

an outer mold disposition operation of disposing an outer mold on outer circumferential surfaces of the fiber mats that have been wrapped around the reinforcing members in the fiber mat providing operation;

a forming operation of forming a cylindrical internal frame using the outer mold, the inner mold and the reinforcing members through an FRP (fiber reinforced plastic) forming process; and

an internal frame connection operation of connecting a plurality of internal frames formed in the forming operation to each other and forming a large diameter pipe having a desired length.
The method for manufacturing a large diameter pipe as set forth in claim 1, wherein the resin application operation comprises:

disposing an inner mold on an outer surface of the reinforcing fibers or fiber mats formed on the inner circumferential surface of the internal frame;

disposing an outer mold on an outer surface of the reinforcing fibers or fiber mats formed on the outer circumferential surface of the internal frame; and

charging resin between the inner mold and the outer mold through a vacuum suction method or a combination of vacuum suction and injection methods, the outer mold being airtightly sealed with the internal frame, and

in the fiber connection operation, while the circumferential reinforcing fibers are wound around the internal frame, the resin is applied between the inner mold and the outer mold so that an integrated structure is formed.
The method for manufacturing a large diameter pipe as set forth in claim 4, wherein

the inner mold disposed on the inner surface of the internal frame comprises a plurality of arc-shaped plates configured such that a diameter of a circle defined by the arc-shaped plates can be expanded to make internal pressurization possible, whereby the inner mold can be brought into close contact with the inner surface of the internal frame, and

the outer mold disposed on the outer surface of the internal frame comprises a plurality of arc-shaped plates configured such that a diameter of a circle defined by the arc-shaped plates can be reduced to make internal pressurization possible, whereby the outer mold can be brought into close contact with the outer surface of the internal frame.
The method for manufacturing a large diameter pipe as set forth in claim 1, wherein each of the cylindrical members is formed by rolling a single metal panel and bonding opposite ends of the metal panel to each other or by bonding a plurality of arc-shaped metal panels to each other,

the reinforcing members comprise corrugated plates, V-shaped or L-shaped bars, or circular or rectangular pipes that are interposed between the cylindrical members to maintain a distance between the cylindrical members constant.
The method for manufacturing a large diameter pipe as set forth in claim 1, wherein the filler comprises at least one of urethane foam, polystyrene, mortar and sand.
The method for manufacturing a large diameter pipe as set forth in claim 1, wherein the reinforcing fibers are formed of at least one of glass fibers, carbon fibers, metal fibers and basalt fibers, and the longitudinal reinforcing fibers of the fiber arrangement operation and the circumferential reinforcing fibers of the fiber connection operation intersect with each other to increase tensile strength and shear strength, thus forming a fiber layer, and

the fiber layer comprises at least one of a fiber mat, a woven roving mat and chopped strand mat.
The method for manufacturing a large diameter pipe as set forth in claim 2 or 3, wherein the reinforcing member arrangement operation comprises winding the fiber mats one to five turns around the reinforcing members, and

the fiber mat providing operation comprises winding two to twenty sheets of fiber mats.
The method for manufacturing a large diameter pipe as set forth in claim 2 or 3, wherein the forming operation comprises forming the internal frame by molding FRP (fiber reinforced plastic) as a filler through a resin transfer molding (RTM) method, a vacuum assisted resin transfer molding (VARTM) method or a RTM-VARTM method.
The method for manufacturing a large diameter pipe as set forth in any one of claims 1 through 3, wherein each of the reinforcing members has a bar shape and is made of polyurethane, wood, ferroconcrete or metal, and

a specific gravity and a strength of the internal frame for forming the large diameter pipe can be adjusted by selecting the kind of reinforcing member.
The method for manufacturing a large diameter pipe as set forth in any one of claims 1 through 3, further comprising;

a covering material application operation of applying covering material to the outer circumferential surface of the internal frame to prevent biofouling or block ultraviolet rays.
The method for manufacturing a large diameter pipe as set forth in any one of claims 1 through 3, wherein each of opposite ends of the internal frame has a stepped structure to increase a coupling strength between internal frames when the internal frames are longitudinally connected to each other to extend a length of the large diameter pipe.
A method for connecting large diameter pipes, the method comprising:

forming stepped parts on opposite ends of each of the large diameter pipes, the stepped parts having shapes corresponding to each other or being oriented in a same direction, and inserting an internal frame piece between the stepped parts of the large diameter pipes, and

respectively fixing fiber-reinforced plastic bonding panels to outer and inner circumferential surfaces of a junction between the large diameter pipes longitudinally connected to each other, and charging resin into the junction through a vacuum suction method or a combination of vacuum suction and injection methods.
The method for connecting large diameter pipes as set forth in claim 14, wherein the fiber-reinforced plastic bonding panels are transparent to enable observation and inspection of internal coupling conditions or to determine whether bubbles are generated.
The method for connecting large diameter pipes as set forth in claim 14, wherein each of opposite ends of each of the large diameter pipes has a protrusion, and the protrusions of the large diameter pipes are coupled to each other by bolting or using a fiber bundle so as to increase a coupling strength between large diameter pipes.
A method for installing large diameter pipes in such a way that the large diameter pipes that are vertically connected to each other are vertically moved downwards from a platform of an installation ship or marine structure, the method comprising:

a heating and pressing band attachment operation of attaching a heating and pressing band to an outer circumferential surface of each junction between a plurality of large diameter pipes;

a hardening operation of applying heat and pressure to the heating and pressing band and hardening the junction between the large diameter pipes; and

a moving-down operation of tautly connecting a plurality of winches provided on the platform to the heating and pressing band using a plurality of wires so as to prevent deformation of the large diameter pipes and maintain a coupling strength between the large diameter pipes and vertically moving the large diameter pipes downwards.
The method for installing large diameter pipes as set forth in claim 17, wherein the heating and pressing band has a removable structure such that the heating and pressing band can be removably attached to the outer circumferential surface of the corresponding junction of the large diameter pipes.
The method for installing large diameter pipes as set forth in claim 18, wherein the heating and pressing band comprises a plurality of heating and pressing bands, wherein when a lower end of the large diameter pipes are moved to a predetermined depth while the large diameter pipes are longitudinally connected to each other, a lowermost heating and pressing band is removed from the large diameter pipes, is drawn upwards, and is attached to an uppermost junction of the large diameter pipes, whereby the large diameter pipes can be connected to each other using a predetermined number of heating and pressing bands without limiting a length of the large diameter pipes.