A method for inclining tests on heavy-lift vessels

Abstract

This invention relates to a method for inclining tests on heavy-lift vessels equipped with at least one crane. The method comprises the following steps: using the crane's boom as a movable weight, controlling the boom to rotate sequentially to several predetermined positions, and recording the heeling moment of the boom at each predetermined position, resulting in the heeling angle of the vessel, thus completing the inclining test. This method utilizes the crane's own weight and free left-right rotation to replace the traditional method of moving a heavy weight and ballast water, generating the moment required for the inclining test, thereby obtaining the vessel's center of gravity height using the heeling angle.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding, and in particular to a method for inclining tests on heavy-lift vessels. Background Technology

[0002] After a ship is built, an inclining test is conducted to determine its center of gravity height. The principle of the inclining test is to evenly distribute four sets of weights on the ship, forward, backward, left, and right. Moving these weights laterally generates a heeling moment, causing the ship to heel at a certain angle. To increase the reliability of the test, the inclining test is performed with the weights moved eight times. The results from the eight measurements are then weighted and averaged to obtain the final test center of gravity height. The steps for moving the weights are described below. Figure 1 . Figure 1 Black squares indicate the presence of heavy blocks, while blank squares indicate the absence of heavy blocks.

[0003] To improve the accuracy of tests, international regulations specify requirements for the heel angle produced during ship inclining tests. The movable weights used in the test should be sufficient to produce a heel angle of 1 to 4 degrees per side of the ship. This necessitates a large number of movable weights. For conventional ocean-going vessels of 10,000 tons or more, each set of weights requires tens of tons, resulting in 200 to 300 tons of fixed weights for the entire ship. This represents a considerable resource for shipyards; smaller shipyards may not even have these weights and lack the facilities for testing with movable weights. Temporary leasing would also incur significant transportation and rental costs for the shipyard.

[0004] During each step of the tilting test weight movement, this group of weights, weighing tens of tons, needs to be moved to either the port or starboard side. Each weight is not a single piece, but rather several pieces weighing approximately 10 tons each, stacked together to form a group. During the movement, the test personnel operate a shore crane, lifting one weight at a time to move the entire group to the next side. Each time a weight is placed, the shore crane can only lift it to its approximate position. The exact installation location on the ship requires multiple test personnel to manually climb and support it, which is not only time-consuming but also poses safety hazards. Therefore, moving each weight takes a considerable amount of time, and moving a group of weights takes even longer, often one to two hours.

[0005] The total experimental time, excluding the eight sets of weight movements, plus the preliminary experimental preparation and the readings after each set of weight movements, generally takes a whole day, but a large portion of the time is spent on the left-right movement of the weights. Reducing the weight movement time would greatly improve the overall efficiency of the experiment.

[0006] To shorten testing time, or for shipyards that do not meet the requirements for test weights, some projects use a method of adjusting ballast water on either side for inclination tests. The basic principle is to select a pair of ballast tanks on the ship. In the initial state (step 0), these tanks are filled halfway with water. From steps 1 to 8, the required ballast water is adjusted from one side of the ship to the other, replacing the port and starboard movement of the weight, to incline the ship to the desired heel angle. The amount of ballast water moved each time needs to be determined manually by testing personnel through depth measurements. While this method reduces testing time, the ship's ballast system is complex. When adjusting ballast water on either side, the water volume needs to reach the other side through multiple branch pipes and main pipes, often resulting in ballast water shortages. Secondly, the adjustment of ballast water is achieved by testing personnel operating the ship's ballast pumps, making it difficult to precisely lock the opening and closing timing, thus the amount of ballast water moved each time is not fixed. Furthermore, the depth measurements after each ballast water movement are done manually by testing personnel while the ship is in a state of heel and list, resulting in relatively large measurement errors. Overall, the testing method for moving ballast water has much lower testing accuracy.

[0007] Traditional moving weight testing methods require significant resources, resulting in high costs for shipyards. The port and starboard hoisting of the weights during the testing process is time-consuming, leading to low efficiency and safety risks for personnel. Moving ballast water testing methods lack sufficient accuracy, especially for small and medium-sized vessels, exhibiting substantial errors. Summary of the Invention

[0008] To address the aforementioned shortcomings and deficiencies, this invention provides a method for inclining tests on heavy-lift vessels. This method utilizes the left-right swinging of a crane to replace the left-right movement of weights or ballast water, thereby achieving the ship's heeling. This method reduces the need for shipyard resources, eliminates the need for any weights or ballast water, effectively lowering test costs; it also simplifies the test procedure, reduces test time, and improves inclining test efficiency; and it reduces the workload of test personnel while ensuring their safety.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for inclining test of a heavy-lift vessel, for a vessel equipped with at least one crane, includes the following steps: using the crane boom as a movable weight, controlling the crane boom to rotate sequentially to several predetermined positions, and recording the heeling moment of the boom at each predetermined position, resulting in a heeling angle of the vessel, to complete the inclining test.

[0011] A further improvement of this invention is that, for a predetermined position of the boom, the initial metacentric height of the ship is calculated based on the boom's heel moment, the ship's heel angle, and its displacement, and the expression is as follows:

[0012] High initial stability = Heeling moment / (Displacement * tan heel angle)

[0013] The initial metacentric height of the vessel under test is obtained by weighted averaging the initial metacentric heights measured at each predetermined position of the boom.

[0014] A further improvement of the present invention is that the number of cranes is two, both of which are located on one side of the ship.

[0015] A further improvement of the present invention is that the two cranes are referred to as Crane No. 1 and Crane No. 2, respectively; Crane No. 1 is located near the bow of the ship, and Crane No. 2 is located near the stern of the ship; the crane boom pointing towards the bow is position No. 1, pointing towards the starboard side is position No. 2, pointing towards the stern is position No. 3, and pointing towards the port side is position No. 4.

[0016] A further improvement of the present invention is that, when switching between predetermined positions, the position of the boom is adjusted by rotating the crane to simulate the multiple movement processes of the weight in a conventional tilting test.

[0017] A further improvement of the present invention is that: the two cranes are sequentially adjusted to the following nine predetermined positions, and the tilt angle is measured respectively:

[0018] For the designated position 0, crane number 1 is in position 1, and crane number 2 is in position 3;

[0019] For the designated position 1, crane number 1 is in position 2, and crane number 2 is in position 3;

[0020] For the designated position 2, crane number 1 is in position 2, and crane number 2 is in position 2;

[0021] For the designated position 3, crane number 1 is in position 2, and crane number 2 is in position 3;

[0022] For the designated position 4, crane number 1 is in position 1, and crane number 2 is in position 3;

[0023] For the designated position 5, crane number 1 is in position 4, and crane number 2 is in position 3;

[0024] For the designated position 6, crane number 1 is in position 4, and crane number 2 is in position 4;

[0025] For the designated position 7, crane number 1 is in position 4, and crane number 2 is in position 3;

[0026] For the designated position 8, crane number 1 is in position 1, and crane number 2 is in position 3.

[0027] A further improvement of the present invention is that each of the described cranes can suspend objects of the same weight.

[0028] Compared with existing technologies, this invention has the following advantages: It utilizes the weight of the crane itself and its free left-right rotation to replace the traditional method of moving weights and ballast water, generating the torque required for the inclination test, thereby obtaining the ship's center of gravity height using the ship's heel angle. This novel inclination test method eliminates the need for shipyards to prepare weights or ballast water, saving resources and reducing shipyard testing costs; by replacing the left-right movement of the weight with the rotation of the crane, the test time is significantly shortened, the test procedure is simplified, and the efficiency of the inclination test is improved; the crane is moved only by operators, eliminating the need to approach the test site to hold the weight, reducing the workload of test personnel while ensuring their safety. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a ship tilting test using a weight in the prior art;

[0030] Figure 2 A side view of a typical crane arrangement for a heavy-lift vessel;

[0031] Figure 3 A top view of a typical crane layout for a heavy-lift vessel;

[0032] Figure 4 This is a schematic diagram of the tilting test method in this invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] like Figure 1 As shown, an embodiment of the present invention provides a method for inclining tests on a heavy-lift vessel. This method is applicable to vessels equipped with at least one crane. In this embodiment, the vessel is equipped with two cranes, which are arranged along the port side of the vessel in the fore-and-aft direction.

[0035] Figure 2 The image shown is a side view of a typical crane arrangement on a heavy-lift vessel. Figure 3 The image shown is a top view of a typical crane arrangement on a heavy-lift vessel. Figure 3 The dashed circle represents the rotation range of the boom of crane 10. Cranes on heavy-lift vessels often have lifting capacities of several hundred tons. To lift even larger cargoes, crane 10 has a large lifting radius, reaching tens of meters; therefore, the boom itself is also very heavy. Figure 2Taking a certain type of heavy-lift vessel as an example, the vessel is equipped with two cranes 10, which are arranged on the port side of the vessel. Each crane has a maximum lifting capacity of 450 tons, a maximum lifting radius of 32m, and the crane boom 11 itself weighs about 100 tons.

[0036] Each crane 10's boom 11 rotates 90 degrees, equivalent to moving a weight equal to the weight of the boom 11 itself, with the moving distance being half the radius of the boom 11. These parameters of the crane 10 fully meet the requirements for conducting tilt tests according to standard procedures, replacing traditional moving weights. This approach simplifies the process while maintaining test accuracy and improving efficiency.

[0037] This embodiment provides a method for tilting tests on heavy-lift vessels. This method replaces the traditional method of moving heavy blocks or ballast water, using a crane to rotate and move the vessel to generate a tilting moment, thus achieving the purpose of tilting the ship. The flowchart of this tilting test method is shown below. Figure 4 .

[0038] The tilting test method for a heavy-lift vessel in this embodiment includes the following steps: using the boom of a crane as a movable heavy object, controlling the boom of the crane to rotate sequentially to several predetermined positions, and recording the tilting moment of the boom at each predetermined position, resulting in the tilting angle of the vessel, to complete the tilting test.

[0039] For a predetermined position of the boom, the initial metacentric height of the ship is calculated based on the boom's heel moment, the ship's heel angle, and its displacement. The expression is as follows:

[0040] High initial stability = Heeling moment / (Displacement * tan heel angle)

[0041] The heeling moment can be calculated based on the position of the crane boom and the ship's weight. Displacement is an inherent property of the ship. The height of the empty ship's center of gravity can be determined based on the initial metacentric height and other design parameters.

[0042] The initial metacentric height of the vessel under test is obtained by weighted averaging the initial metacentric heights measured at each predetermined position of the boom.

[0043] In this embodiment, the two cranes are referred to as Crane No. 1 and Crane No. 2, respectively. Crane No. 1 is located near the bow, and Crane No. 2 is located near the stern. The crane boom pointing towards the bow is position 1, towards the starboard side is position 2, towards the stern is position 3, and towards the port side is position 4. When switching between these predetermined positions, the position of the crane boom is adjusted by rotating the crane to simulate the multiple movements of the weight in a traditional tilting test.

[0044] During the test, the two cranes were sequentially adjusted to the following nine predetermined positions, and the tilt angle was measured at each position to calculate the initial stability height at that predetermined position. The nine predetermined positions are as follows:

[0045] For the designated position 0, crane number 1 is in position 1, and crane number 2 is in position 3; both cranes are in storage.

[0046] For predetermined position 1, crane number 1 is in position 2, and crane number 2 is in position 3. During the switch from predetermined position 0 to predetermined position 1, the boom of crane number 1 rotates 90° to the starboard side of the ship to enter position 2; crane number 2 remains stationary.

[0047] For predetermined position 2, crane number 1 is in position 2, and crane number 2 is in position 2; during the process of switching from predetermined position 1 to predetermined position 2, the boom of crane number 2 rotates 90° to the starboard side of the ship and enters position 2; crane number 2 remains stationary.

[0048] For predetermined position 3, crane number 1 is in position 2, and crane number 2 is in position 3 (same as predetermined position 1); during the process of switching from predetermined position 2 to predetermined position 3, the boom of crane number 2 rotates 90° toward the stern of the ship and enters position 3, and is placed longitudinally parallel to the hull on the port side of the ship; crane number 1 remains stationary.

[0049] For predetermined position 4, crane number 1 is in position 1, and crane number 2 is in position 3 (the same as predetermined position 0); during the process of switching from predetermined position 3 to predetermined position 4, the boom of crane number 1 rotates 90° toward the bow of the ship and enters position 1, and is parked on the port side of the ship with its longitudinal direction parallel to the hull; crane number 2 remains stationary.

[0050] For the predetermined position 5, crane number 1 is in position 4 and crane number 2 is in position 3; during the process of switching from predetermined position 4 to predetermined position 5, the boom of crane number 1 rotates 90° to the left of the ship and enters position 4; crane number 2 remains stationary.

[0051] For the predetermined position 6, crane number 1 is in position 4, and crane number 2 is in position 4; during the process of switching from predetermined position 5 to predetermined position 6, the boom of crane number 2 rotates 90° to the left of the ship and enters position 4; crane number 1 remains stationary.

[0052] For predetermined position 7, crane number 1 is in position 4, and crane number 2 is in position 3 (same as predetermined position 5); during the process of switching from predetermined position 6 to predetermined position 7, the boom of crane number 2 rotates 90° toward the stern of the ship and enters position 3, and is placed longitudinally parallel to the hull on the port side of the ship; crane number 1 remains stationary.

[0053] For predetermined position 8, crane number 1 is in position 1, and crane number 2 is in position 3 (the same as predetermined position 0). During the transition from predetermined position 7 to predetermined position 8, crane number 1's boom rotates 90° toward the bow of the ship, entering position 1, and is positioned longitudinally parallel to the hull on the port side of the ship; crane number 2 remains stationary.

[0054] During position switching, only one crane boom is rotated at a time. If the boom's own weight is insufficient, each crane can suspend an object of equal weight.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for inclining tests on heavy-lift vessels, for vessels equipped with at least one crane, characterized in that, The process includes the following steps: using the boom of a crane as a movable weight, controlling the boom of the crane to rotate sequentially to several predetermined positions, and recording the heeling moment of the boom at each predetermined position, which causes the ship to heel angle, in order to complete the tilting test. For a predetermined position of the boom, the initial metacentric height of the ship is calculated based on the boom's heel moment, the ship's heel angle, and its displacement. The expression is as follows: High initial stability = Heeling moment / (Displacement * tan heel angle) The initial metacentric height of the ship under test is obtained by weighted averaging the initial metacentric heights measured at each predetermined position of the boom. When switching between predetermined positions, the position of the boom is adjusted by rotating the crane to simulate the multiple movement processes of the weight in a traditional tilting test; The number of cranes is 2, both of which are installed on one side of the ship; The two cranes are referred to as Crane No. 1 and Crane No. 2; Crane No. 1 is located near the bow of the ship, and Crane No. 2 is located near the stern of the ship. The crane boom pointing towards the bow is position one, pointing towards the starboard side is position two, pointing towards the stern is position three, and pointing towards the port side is position four. Adjust the two cranes to the following nine predetermined positions in sequence, and measure the tilt angle of each position: For the designated position 0, crane number 1 is in position 1, and crane number 2 is in position 3; For the designated position 1, crane number 1 is in position 2, and crane number 2 is in position 3; For the designated position 2, crane number 1 is in position 2, and crane number 2 is in position 2; For the designated position 3, crane number 1 is in position 2, and crane number 2 is in position 3; For the designated position 4, crane number 1 is in position 1, and crane number 2 is in position 3; For the designated position 5, crane number 1 is in position 4, and crane number 2 is in position 3; For the designated position 6, crane number 1 is in position 4, and crane number 2 is in position 4; For the designated position 7, crane number 1 is in position 4, and crane number 2 is in position 3; For the designated position 8, crane number 1 is in position 1, and crane number 2 is in position 3.

2. The tilting test method for a heavy-lift vessel according to claim 1, characterized in that: Each of the aforementioned cranes can suspend objects of the same weight.

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