JPS6036517B2 - Parallel mooring cable with pre-corrosion protection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parallel line cable, and more particularly to a parallel line cable for mooring marine structures with a pre-corrosion protection coating.

In recent years, many offshore structures have been constructed, including those related to oil exploration.

Many of these offshore structures use piles driven into the seabed as foundations to support the structure; however, there are cases where the structure needs to be moved in a timely manner or when it is installed in deep water. , methods of fixing structures using mooring elements tend to be widely adopted. Until now, chains and stranded ropes have been mainly used as mooring elements.

However, since it is difficult to protect chains from corrosion, long-term durability cannot be expected. Therefore, in most applications requiring long-term durability, pre-corrosion-treated stranded ropes are being used as mooring elements. Types of stranded ropes include locked ropes, spiral ropes, and stranded ropes, but their elastic modulus is inferior to parallel cables conventionally used for bridges.
On the other hand, since the cross-sectional shape of parallel wire cables is greatly deformed when wound onto a reel, pre-corrosion protection is difficult, so they are not currently used as mooring elements for offshore structures. Parallel wire cables are generally made by bundling tens to hundreds of high-tensile steel wires having a diameter of 5 to 7 willow and having their surfaces subjected to anti-corrosion treatment, and fixing both ends thereof.

The length can be made from several meters to several thousand depending on the purpose of use. This parallel cable is often used as a cable for suspension bridges, and after the suspension bridge is erected, tension is applied to the cable, and once the cross-sectional shape of the cable no longer changes, scaffolding is installed along the cable to prevent corrosion. However, the present inventors have developed a pre-corrosion-proof parallel wire strand cable, designated as Special Iso-Sho No. 57-4761, which can omit the cable anti-corrosion work at the construction site and shorten the bridge construction period. It is proposed separately. Therefore, the present inventors continued their research and examined the technology of such pre-corrosion-proof parallel wire strand cables and whether or not they could be applied to mooring marine structures. Figures 1 and 2 show examples of how such mooring elements are used for marine structures. The structure 2 is supported by a buoyancy adjustment structure 4 below the sea surface 11, and the structure 4 is moored to the seabed 1 via a mooring cable 3.

The case shown in Fig. 2 is called a guide tower system, in which a superstructure 2 installed on the sea surface 11 is supported from the seabed 1 by a tower 5 that supports the superstructure.
The mooring element 3 prevents the upper structure 2 from falling over. As can be understood from these figures, the mooring element 3 is used with part or all of it submerged below the sea surface 11, and the environment in which it is used is highly corrosive.
Cables that are required to last for several decades naturally require some kind of anti-corrosion measure. Furthermore, unlike in the case of suspension bridges, it is impossible to apply anti-corrosion coating to the cables after they are installed.Therefore, the anti-corrosion coating of the cables is completed during the production process of parallel cables, and the cables are wound onto reels and transported to the installation site. Unless it can be transported and used, the advantages of parallel wire cables cannot be utilized as mooring elements.Parallel wire cables are different from stranded ropes, and due to their characteristics, they cannot be used when wound onto a reel. When a cable is bent, the cross-sectional shape of the cable inevitably changes.

If the curvature is reduced, the deformation rate can be reduced, but the deformation rate also increases because there is a restriction that the diameter of the roll must be as large as possible for transport. For this reason, even if pre-corrosion protection is applied in the same way as with stranded wire ropes, the corrosion protection layer is destroyed due to changes in the cross-sectional shape of the cable during reeling, so it has not been used as a mooring element. In view of the above points, the present invention solves these problems, and in order to enable parallel cables to be used as mooring elements for offshore structures, anti-corrosion coating is applied in a cable manufacturing factory.
It is possible to provide a pre-corrosion-proof parallel wire cable coated with a long-lasting anti-corrosion coating by selecting specific conditions so that the anti-corrosion coating layer is not destroyed even when wound on a reel. That is, the present invention has an effect of absorbing the deformation of the cross-sectional shape of the cable that occurs when the cable is bent after the band for restraining the cross-sectional shape of the cable is attached to the surface of the parallel wire cable in which the anti-rust material is densely filled between the strands of the cable. Parallel wire cable for mooring with pre-corrosion protection, characterized in that the inner layer is an elastic body having the same properties, and the outer layer is a coating made of a combination of a metal layer with a thickness of 40 mm to 5 mm and a plastic layer with a thickness of 20 mm to 8 mm. It is.

The present invention will be explained in detail below. The strands of the parallel wire cable used in the present invention are those coated with zinc or aluminum, or those coated with plastic on top of the plating.

This anti-corrosion treatment of the Qin wire is necessary so that even if the anti-corrosion coating layer is accidentally destroyed, the wire will not corrode and break in a short period of time. These strands are bundled to form a cable, but at this time the strands must be densely filled with a paste-like anti-corrosion material.

The anticorrosion material used here can be a semi-fluid substance such as grease or vetrolatum paste. This anti-corrosion material is important not only to protect the strands from corrosion but also to prevent damage to the anti-corrosion layer of cables submerged in seawater due to pressure due to water depth. The structure of the cable of the present invention is as follows:
As shown in Fig. 3, which shows an example of the cross-sectional shape of the cable, the cross-sectional shape of a parallel wire cable 6 made of strands densely filled with anti-corrosion material is shaped into a circular shape, and this cross-sectional shape is greatly distorted when the cable is bent. As shown in the side view of FIG. 4, cross-sectional shape restraining bands 0 are attached at predetermined intervals in the longitudinal direction in order to prevent this, and an elastic body is provided as an inner layer 7, and a metal layer 8 and a plastic layer are further formed as outer layers. 9 was formed to form an anticorrosive coating layer. In this case, the band can be made of metal or a high-strength non-metallic material. Moreover, various rubbers, plastics, and foams thereof can be used as the elastic body. However, mooring cables are subject to water pressure depending on the depth of the water in the ocean, so
A soft material such as the commonly used polyurethane foam is not suitable, and an elastic material having a relatively high density and a low hydraulic deformation rate must be selected. Furthermore, as the coating material for forming the outer layer, metals with excellent corrosion resistance without water permeability, such as aluminum, lead, and zinc stainless steel, and plastics with excellent corrosion resistance and durability, such as polyethylene, polyamide, polyurethane, vinyl chloride, and tetrafluoride, are used. Synthetic resins such as ethylene chloride, synthetic rubbers, etc. can be used.
In this case, the metal layer as the outer layer must have a skin thickness of 40 mm to 5 mm, and the plastic layer must have a side thickness of 20 mm to 8 mm. That is, the thickness of the metal layer needs to be at least 40 mm in order to prevent the formation of pinholes, and it is necessary to be 5 mm or less in view of the curvature of the coating layer. In addition, from the viewpoint of corrosion protection, it is unnecessary to use more than 5 skins, considering the cable's service life. Furthermore, considering the thickness of coating on both sides of a thin metal layer, 20 or more ridges are required for the plastic material. From the viewpoint of durability, it is sufficient for the thickness of the outermost layer to be 8 skins or less. Next, an example of the manufacturing method of the pre-corrosion-protected parallel wire cable for mooring offshore structures according to the present invention is as follows: First, Qin wires that have been subjected to a predetermined anti-corrosion treatment are gathered together and finished in a circular cross-sectional shape. . During this concentration, the anticorrosive material is supplied so as to be densely packed between the wires. In this case, a thin plastic sheath may be used to prevent the anticorrosion material from falling onto the floor from the surface of the cable after consolidation. Next, the amount of deformation of the cross-sectional shape of the parallel wire cable is estimated from the size structure of the parallel wire cable and the expected curvature of the cable, and bands for restraining the cross-sectional shape are attached at predetermined regular intervals. This installation interval is normally 0.
A range of 3 to 1.5 desks is appropriate. Next, an elastic body is coated on the surface of the parallel wire cable to form an inner layer.

The coating can be applied by wrapping a molded product or sheet-like product in a layer or multiple layers that matches the cross-sectional shape of the cable. Alternatively, after attaching the outer coating, the elastic body may be injected and cured. The primary purpose of the elastic body is to absorb changes in the cross-sectional shape when the parallel cable is bent, and to protect the outer anti-corrosion coating layer from destruction. Therefore, the thickness of the elastic body varies depending on the elastic modulus of the elastic body used, and the size configuration of the parallel cable,
The thickness must be determined depending on the spacing of the restraining bands and the curvature of the cable, but the appropriate thickness is usually about 5 to 30 m/m. This elastic body may be coated with a material that differs locally in the length direction of the parallel wire cable. The elastic body covers the parallel wire cable in a sealed state, and can be expected to be effective as an anti-corrosion coating. Next, the surface of the inner layer thus provided is further coated as an outer layer with a durable coating material having excellent resistance to corrosion and waterproofing properties, the main purpose of which is anticorrosion.

When covering the outer layer, it is important to form the outer layer so that there are no gaps between the outer layer and the inner layer. Therefore, the covering method is, for example, to split the covering material used as the outer layer into a split shape to have a predetermined inner diameter, and when it can be covered over the cable, push the elastic material of the inner layer a little, and glue the closing part of the split shape. , welded or mechanically joined. In addition to the above methods, the cable of the present invention may be manufactured by, for example, producing a heat-shrinkable tubular covering material with an outer diameter larger than the outer diameter of the inner layer, and inserting the cable coated with the inner layer into this tube. It is also possible to heat the heat-shrinkable tube to reduce it to a predetermined inner diameter and bring it into close contact with the outer surface of the inner layer.

Additionally, a plastic extrusion coating line may be used to coat the inner and outer layers sequentially. For the material composition and thickness of the outer layer, various coating materials are selected depending on the usage conditions of the mooring cable and the required service life, and the coating is made up of two or more layers. At least a durable plastic layer is provided as the outermost layer, and a water-impermeable metal layer is provided inside the durable plastic layer. The metal layer may be formed by coating both sides of a thin metal sheet with a plastic film, and at least one side of the film is made of a heat-fusible resin, and the plastic is fused and bonded. If a relatively thick layer is required, the metal layer may be coated continuously in the form of a corrugated tube to improve the bendability of the metal layer. Of course, the plastic layer can be configured not only as a single layer but also as multiple layers. Further, it is also effective for corrosion prevention to form a multilayer coating by alternately coating metal layers and plastic layers. Next, the effects of the present invention will be explained in more detail using examples.

Example 1 J in which vetrolatum-based antirust paste was densely filled between the wires
A parallel wire cable 100 consisting of 271 galvanized steel wires with 5 skins was developed in a straight line, and the cross-sectional shape was shaped into a circle.
Stainless steel cross-sectional shape restraining bands were attached at intervals of 40 skins.

Next, a betarolatum-based anticorrosive tape was wrapped around the cable surface to make the thickness approximately 1 side. On top of that, cover the entire length of the cable with a soft vinyl chloride sheath with a thickness of 0.3 skin.
The cable was sealed. And as an elastic body, the thickness is 1
The chloroprene rubber foam on the proboscis was covered with adhesive to form the inner layer. Next, an aluminum sheet having a thickness of 50 mm and coated with a polyamide resin of 30 mm on both sides was coated twice, and the resin layers were bonded by heat-sealing. Further, a heat-shrinkable polyethylene tube was used to form a double crosslinked polyethylene layer on the 2.5-thickness side to form a plastic layer to form an outer layer. The pre-corrosion-proof parallel wire cable prepared as described above was wound onto a reel having a drum diameter of 3.8 mm.

After being left in this condition for one month, the cable was placed vertically in the sea at a depth of 100 m, and after 6 months, it was recovered and the condition of the anti-corrosion coating layer and wire was examined, but no abnormality was found. Example 2 Aluminum-plated steel wire 169 with a thickness of 5 strands, with grease densely filled between the strands and covered with a PVC sheath of 0.3 willow thickness.
A parallel wire cable 100 consisting of a book is unfolded in a straight line,
The cross-sectional shape of the cable was shaped into a circle, and stainless steel bands were attached at intervals of 50 cm to restrain the cross-sectional shape of the cable.

Next, the SBR rubber on the 15-thickness side was covered to form an inner layer. Lead on the 1.5-thickness side was welded in a lap shape to cover it, a heat-shrinkable polyethylene tube was placed over this, and a cross-linked polyethylene layer of 3 cm thick was coated twice to form an outer layer. The pre-corrosion-proof parallel wire cable prepared as described above was wound onto a reel having a drum diameter of 3.4 mm.

After being left in this state for one month, the kite was placed vertically in the sea at a depth of 100 m, and after 6 months, it was recovered and the state of the anticorrosion coating layer and Qin line was examined, but no abnormality was found. Example 3 A parallel wire cable 100 consisting of 91 strands of 5-skin wire was galvanized with grease densely filled between the 3 strands and hermetically sealed with a polyamide resin sheath with a thickness of 0.2 strands. Steel pads were attached at intervals of 60c to constrain the cross section to be circular.

After winding it up onto a reel in this state, a 7/skin silicone rubber layer with a thickness of 7 is formed as the inner elastic body on an extrusion coating line, and then aluminum is extruded and coated on the 2-thickness side, and then as the outermost layer. A polyethylene layer having a thickness of 5 ribs was formed. The pre-corrosion-proof parallel cable made in this way was wound around a drum with a diameter of 4 mm, left for one month, and then
It was placed vertically in seawater on a desk, and after 6 months, it was recovered and the condition of the anti-corrosion coating layer and wires were examined, but no abnormalities were found. As described above, the present invention is a completely new pre-corrosion-protected parallel cable that can be used for mooring marine structures.

[Brief explanation of the drawing]

Figures 1 and 2 are views showing two examples of embodiments using mooring elements for marine structures, and Figure 3 is a front view showing an example of the cross-sectional shape of the parallel line cable with pre-corrosion protection of the present invention. The sectional view and FIG. 4 are side views showing an embodiment of the parallel wire cable subjected to pre-corrosion protection of the present invention. 1... Seabed, 2... Superstructure, 3.
... Mooring element, 4... Buoyancy adjustment structure, 5...
... Tower supporting the superstructure, 6... Parallel cable densely filled with anti-rust material, 7... Elastic layer,
8...Metal layer, 9...Plastic layer,
10... Cross-sectional shape restraint band, 11...
・Sea surface. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 After attaching a band for restraining the cross-sectional shape of the cable to the surface of the parallel wire cable with anti-rust material densely filled between the strands,
The inner layer is an elastic material that has the function of absorbing the cross-sectional deformation of the cable that occurs when the cable is bent, and the outer layer is a coating consisting of a combination of a metal layer with a thickness of 40 μm to 5 mm and a plastic layer with a thickness of 20 μm to 8 mm. Parallel cable for mooring with pre-corrosion protection.