Operation method applied to offshore anchor system tension verification

Abstract

The invention discloses an operation method applied to offshore anchor system tension verification, which comprises the following steps that: a work ship embeds a reaction anchor at a throwing position of the reaction anchor, and connects the reaction anchor chain to a positioning floating device; the working ship embeds the to-be-verified positioning anchor at the throwing position of the to-be-verified positioning anchor; connecting the positioning anchor chain from the stern of the working ship to a chain stopper with a tension measurement display component on the working ship; connecting a reaction anchor chain to a winch at the head of the working ship; the winch is tightened, and a propelling system of the working ship provides thrust towards the reaction anchor for the working ship; and verifying the anchor system tension of the to-be-verified positioning anchor according to the measured and displayed tension value of a tension measurement display component on the chain stopper. The method provided by the invention is more convenient to use and better in economical efficiency, and can complete the task of carrying out anchor system tension verification on a large-scale offshore floating fan foundation and a large-scale offshore platform.

Description

Technical Field

[0001] The invention relates to the technical field of ships, and in particular to an operation method for verifying the tension of offshore anchoring. Background Art

[0002] Offshore wind turbines are divided into fixed offshore wind turbines and floating wind turbines. The difference between fixed offshore wind turbines and floating wind turbines lies in their different wind turbine foundations. Fixed offshore wind turbine foundations are mainly suitable for water depths of 0 to 50m near the coast, including single pile foundations, jacket foundations, tripod foundations and gravity foundations, etc. Floating wind turbine foundations are generally used in sea areas with a seawater depth of greater than or equal to 50m, such as column foundations, tension leg foundations and semi-submersible foundations. Generally speaking, unlike fixed shallow water offshore wind turbines, which are installed on the offshore foundation by a dedicated wind turbine installation platform or crane ship at sea, floating wind turbines are already installed on the foundation at the onshore base.

[0003] Compared with fixed wind turbines, floating wind turbines are free from the limitation of water depth to a certain extent, which makes it easier to find better wind farms in the wider sea. In terms of scale, offshore floating wind turbines are easier to increase the scale of wind farms and are more economical.

[0004] The installation and positioning of floating wind turbines refers to effectively fixing floating wind turbines in offshore wind farms so that they can safely carry out wind power generation operations. The mooring and positioning system is crucial to ensure the normal power generation and even self-sustaining of floating wind turbines. Currently, the common floating wind turbine mooring systems mainly include catenary mooring and vertical tension leg mooring.

[0005] For column-type, semi-submersible and barge-type offshore floating wind turbines, catenary mooring is often used, and the mooring line is usually a steel chain structure. Steel chain has become the most widely used mooring material due to its low manufacturing cost, simple process and high strength. The pre-tension of the mooring line mainly depends on the suspended section of the anchor chain, and the restoring force of the anchor chain is mainly achieved by the change of the suspended section of the anchor chain; however, this mooring method has a long seabed lying section, so it occupies a larger seabed space, and the weight increases sharply with the increase of water depth.

[0006] The catenary mooring system is to fix the floating wind turbine foundation by the weight and curved shape of the steel chain. The lower section of the steel chain is located on the seabed and fixed to the seabed by supporting anchors to limit the movement of the platform. The characteristics of the catenary system are low installation cost and good economy, but the anchor tension verification is required to ensure the grip reliability of the anchor system.

[0007] For tension-leg offshore floating wind turbines, vertical tension-leg mooring is often used, and synthetic materials are often used for this type of mooring line. The tension mooring system is a system in which the floating wind turbine foundation and the anchor are tightened and fixed by steel chains or high-strength fibers to ensure the stability of the floating platform. The tension-leg platform balances the excess buoyancy of the floating wind turbine foundation upward through the vertical mooring tension, which is similar to a "tightening up and down" mechanism, so it has better platform vertical motion performance, but its installation process is more complicated. The characteristics of the tension mooring system are that it does not require anchor tension verification, but the installation cost is huge and the economy is poor.

[0008] Take the "Haiyou Guanlan", my country's first deep-sea floating wind turbine, for example. It is installed in an offshore oil field 136 kilometers offshore and 120 meters deep. The "Haiyou Guanlan" uses a three-way anchor positioning system, with three sets of anchors in each direction, a total of 9 152mm non-stop anchor chains and 9 suction anchors.

[0009] In order to ensure the reliability of the high holding power anchor, it is necessary to verify the tension of the offshore anchor system. The conventional tension verification method relies on the towing system of the anchor handling towing supply vessel (AHTS).

[0010] AHTS is mainly used for anchoring, towing and supplying, so it is also called anchor tug supply ship. The three-purpose work ship has its own mooring machine and can provide towing, anchoring and supply services for drilling operations of drilling platforms. In addition to the transportation function, the most important feature of this type of ship is that it is equipped with an anchoring and towing system.

[0011] In the prior art, when a three-purpose workboat is used to perform anchor tension verification operations, the positioning anchor that needs to be tension verified is mainly connected through the towing winch on the main deck, and the tension of the positioning anchor is verified through the thrust of the rear thruster of the three-purpose workboat. The tension of the positioning anchor will be displayed on the towing winch with tension display.

[0012] Since the verification load of the large holding anchor of the floating wind turbine mooring system is very large, usually exceeding 600t, and with the increase of the power generation of offshore floating wind turbines and the water depth of wind farms in the future, the verification load of the large holding anchor of the floating wind turbine mooring system will further increase, even exceeding 1000t. At present, the AHTS with the largest bollard pull in the world is 477t (the bollard pull is the tension value measured when the main engine is running at rated power and towed away from the dock or fixed point with a 100-meter-long towline when the ship is fully loaded, also known as the dock pull, the unit is t.). Since AHTS needs to perform many types of operations, the anchoring operation is only part of all its uses. Limited by the economic considerations of a single AHTS (higher bollard pull means that a larger power main engine is required), the bollard pull of AHTS cannot be increased indefinitely. Therefore, for smaller floating wind turbines, two AHTSs are currently required in parallel to complete the test operation (by connecting to the same towing lock). However, using two AHTS to verify the anchor tension at sea will greatly increase the economic cost and have more complicated operation steps. At the same time, using the towing lock to verify the tension, according to the parallelogram law of force synthesis, the tension of the towing lock on the anchor is less than the sum of the bollard towing forces of the two AHTS, but adding more AHTS means higher economic costs and more complicated operation procedures. Therefore, the operation process of using two or more AHTS is more complicated and the economic cost is very high.

[0013] For other offshore platforms, their foundations are similar to those of offshore floating wind turbines. They also need to be anchored and positioned in deep-water operating areas, and they also need to perform tension verification operations on offshore anchor systems.

[0014] The existing technology has the following defects: For the current smaller floating wind turbines, two AHTSs are also needed in parallel to complete the test operation. However, two AHTSs for offshore anchor tension verification means higher economic costs and more complicated operation steps. Adding more AHTSs means higher economic costs and more complicated operation processes. For larger floating wind turbine foundations or offshore platform foundations, there is currently no good method for offshore anchor tension verification. Summary of the invention

[0015] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide an operation method for verifying the tension of offshore anchors.

[0016] The present invention solves the above technical problems through the following technical solutions:

[0017] A method for verifying the tension of an offshore anchorage comprises the following steps:

[0018] Step 1: The working boat releases the reaction anchor and the reaction anchor chain at the casting position of the reaction anchor, buries the reaction anchor, and connects the reaction anchor chain to the positioning floating device;

[0019] Step 2: The workboat releases the positioning anchor to be verified and the anchor chain at the casting position of the positioning anchor to be verified, and buries the positioning anchor to be verified; the anchor chain of the positioning anchor is connected from the stern of the workboat to the chain stopper with a tension measurement and display component on the workboat;

[0020] Step 3, connecting the reaction anchor chain to the winch at the bow of the workboat;

[0021] Step 4, tighten the winch, and the propulsion system of the workboat provides the workboat with thrust in the direction of the reaction anchor;

[0022] Step 5: Verify the anchor tension of the positioning anchor to be verified according to the tension value displayed by the tension measurement display component on the chain stopper.

[0023] Furthermore, in step 1, the working vessel releases the reaction anchor and the reaction anchor chain through the tail towing winch on the working vessel at the casting position of the reaction anchor.

[0024] Furthermore, in step 1, after the reaction anchor is buried, the reaction anchor chain is tensioned by a workboat, and then the reaction anchor chain is connected to the positioning floating device.

[0025] Further, in step 1, the positioning floating device includes a positioning buoy and a positioning buoy cable, the positioning buoy cable is connected to the positioning buoy, and the reaction anchor chain is connected to the positioning buoy cable.

[0026] Furthermore, in step 2, the working vessel releases the positioning anchor to be verified and the anchor chain of the positioning anchor to be verified through the tail towing winch on the working vessel at the casting position of the positioning anchor to be verified.

[0027] Furthermore, in step 2, the chain stopper is arranged in the middle or middle rear part of the workboat.

[0028] Further, in step 3, after the reaction anchor chain is connected to the winch at the bow of the workboat, the bow of the workboat faces the reaction anchor, the stern of the workboat faces the positioning anchor to be verified, and the workboat is located between the reaction anchor and the positioning anchor to be verified.

[0029] Further, in step 4, the winch and the propulsion system provide a force from the stern toward the bow to the workboat.

[0030] Furthermore, step 4 also includes measuring the anchor tension of the positioning anchor to be verified through the tension measurement display component on the chain stopper.

[0031] Furthermore, the method further comprises step 6, after the anchor tension of the positioning anchor to be verified is verified, the reaction anchor chain and the positioning anchor chain are separated from the workboat respectively; and the reaction anchor and the reaction anchor chain are recovered.

[0032] The beneficial effects of the present invention are as follows: the method of the present invention is more convenient to use and more economical, and can accomplish the task of anchor tension verification of large offshore floating wind turbine foundations and large offshore platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a preferred embodiment of the present invention when a working vessel tightens the reaction anchor chain.

[0034] Figure 2 It is a schematic diagram of a preferred embodiment of the present invention when a reaction anchor chain is connected to a positioning floating device.

[0035] Figure 3 This is a schematic diagram of a preferred embodiment of the present invention when the positioning anchor to be verified is connected to a workboat through a positioning anchor chain.

[0036] Figure 4 This is a schematic diagram of a preferred embodiment of the present invention when a reaction anchor and a positioning anchor to be verified are simultaneously connected to a work vessel. DETAILED DESCRIPTION

[0037] A preferred embodiment is given below, and the present invention is described more clearly and completely in conjunction with the accompanying drawings.

[0038] An operating method for verifying the tension of an offshore anchorage comprises the following steps.

[0039] Step 1: The working boat releases the reaction anchor and the reaction anchor chain at the casting position of the reaction anchor, buries the reaction anchor, and connects the reaction anchor chain to the positioning floating device.

[0040] The working vessel is at the casting position of the reaction anchor and releases the reaction anchor and the reaction anchor chain through the stern towing winch on the working vessel.

[0041] After the reaction anchor is buried, the reaction anchor chain is tensioned by the workboat. Figure 1 As shown, after the reaction anchor 11 is buried, the working vessel 10 tightens the reaction anchor chain 12 .

[0042] Then connect the reaction anchor chain to the positioning floating device. Figure 2 As shown, the reaction anchor chain 12 is connected to the positioning floating device 13.

[0043] The positioning floating device comprises a positioning buoy and a positioning buoy cable, the positioning buoy cable is connected to the positioning buoy, and the reaction anchor chain is connected to the positioning buoy cable.

[0044] In this step, the reaction anchor is buried using a workboat and its tension state is ensured, and positioning is completed through a positioning buoy and a positioning buoy cable.

[0045] Step 2: The workboat releases the positioning anchor and the anchor chain to be verified at the casting position of the positioning anchor to be verified, and buries the positioning anchor to be verified; the anchor chain of the positioning anchor is connected from the stern of the workboat to the chain stopper with a tension measurement and display component on the workboat.

[0046] The working boat releases the positioning anchor to be verified and the anchor chain of the positioning anchor at the casting position of the positioning anchor to be verified through the tail towing winch on the working boat. The chain stopper is arranged in the middle or middle rear of the working boat.

[0047] like Figure 3 As shown, the positioning anchor 21 to be verified is connected to the chain stopper of the workboat 10 through the positioning anchor chain 22 .

[0048] Step 3, connect the reaction anchor chain to the winch at the bow of the workboat. After the reaction anchor chain is connected to the winch at the bow of the workboat, the bow of the workboat faces the reaction anchor, the stern of the workboat faces the positioning anchor to be verified, and the workboat is located between the reaction anchor and the positioning anchor to be verified.

[0049] like Figure 4 As shown, the work vessel 10 is located between the reaction anchor 11 and the positioning anchor 21 to be verified.

[0050] Step 4, tighten the winch, and the propulsion system of the workboat provides thrust to the workboat in the direction of the reaction anchor.

[0051] In this step, the winch and propulsion system provide force from the stern to the bow to the workboat.

[0052] This step also includes measuring the anchor tension of the positioning anchor to be verified by using the tension measurement display component on the chain stopper.

[0053] Step 5: Verify the anchor tension of the positioning anchor to be verified according to the tension value displayed by the tension measurement display component on the chain stopper.

[0054] Step 6, after the anchor tension of the positioning anchor to be verified is verified, the reaction anchor chain and the positioning anchor chain are separated from the workboat respectively; and the reaction anchor and the reaction anchor chain are recovered.

[0055] Through the above steps, the anchor tension verification of a floating wind turbine positioning anchor is completed.

[0056] Repeat the above steps to complete the anchor tension verification work for other floating wind turbine positioning anchors.

[0057] In this embodiment, the anchor verification process of a floating wind turbine positioning anchor is described. This technical solution is also applicable to other platforms or ships that require anchor tension verification.

[0058] The method of the present invention is more convenient to use and more economical, and can accomplish the task of anchor tension verification for large offshore floating wind turbine foundations and large offshore platforms.

[0059] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A method for verifying the tension of an offshore anchor, characterized in that: It includes the following steps: Step 1: The working boat releases the reaction anchor and the reaction anchor chain at the casting position of the reaction anchor, buries the reaction anchor, and connects the reaction anchor chain to the positioning floating device; Step 2: The workboat releases the positioning anchor to be verified and the anchor chain at the casting position of the positioning anchor to be verified, and buries the positioning anchor to be verified; the anchor chain of the positioning anchor is connected from the stern of the workboat to the chain stopper with a tension measurement and display component on the workboat; Step 3, connecting the reaction anchor chain to the winch at the bow of the workboat; Step 4, tighten the winch, and the propulsion system of the workboat provides the workboat with thrust in the direction of the reaction anchor; Step 5: Verify the anchor tension of the positioning anchor to be verified according to the tension value displayed by the tension measurement display component on the chain stopper.

2. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 1, the workboat is at the casting position of the reaction anchor, and releases the reaction anchor and the reaction anchor chain through the tail towing winch on the workboat.

3. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 1, after the reaction anchor is buried, the reaction anchor chain is tensioned by a workboat, and then the reaction anchor chain is connected to the positioning floating device.

4. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 1, the positioning floating device includes a positioning buoy and a positioning buoy cable, the positioning buoy cable is connected to the positioning buoy, and the reaction anchor chain is connected to the positioning buoy cable.

5. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 2, the workboat releases the positioning anchor to be verified and the anchor chain of the positioning anchor through the tail towing winch on the workboat at the casting position of the positioning anchor to be verified.

6. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 2, the chain stopper is arranged at the middle or middle rear part of the workboat.

7. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 3, after the reaction anchor chain is connected to the winch at the bow of the workboat, the bow of the workboat faces the reaction anchor, the stern of the workboat faces the positioning anchor to be verified, and the workboat is located between the reaction anchor and the positioning anchor to be verified.

8. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: In step 4, the winch and propulsion system provide force to the workboat from the stern toward the bow.

9. The method for verifying the tensile force of an offshore anchor as claimed in claim 7, characterized in that: Step 4 also includes measuring the anchor tension of the positioning anchor to be verified by using the tension measurement display component on the chain stopper.

10. The method for verifying the tensile force of an offshore anchor as claimed in claim 1, characterized in that: The method further comprises step 6, after the anchor tension of the positioning anchor to be verified is verified, the reaction anchor chain and the positioning anchor chain are separated from the workboat respectively; and the reaction anchor and the reaction anchor chain are recovered.

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