A method for conducting strength test of LNG ship bow ballast tank in dock

Abstract

The present invention relates to a method for conducting a strength test of the bow ballast tank of an LNG ship in a dock. The method comprises determining the loading and integrity status of half the ship; verifying the ship's floating state; selecting a test location in the dock; filling and draining the ballast tanks and dock, and submitting the strength test results of ballast tank No. 1. The present invention's method for conducting a strength test of the bow ballast tank of an LNG ship in a dock represents a technological breakthrough in completing strength tests of all cargo hold ballast tanks within an LNG dock, and has broad applicability.

Description

Technical Field

[0001] The present invention relates to the field of ship testing, and in particular to a method for carrying out a strength test of a bow ballast tank of an LNG ship in a dock. Background Art

[0002] Currently, large domestic LNG carriers have widely adopted a docked ballast tank strength test protocol. However, this in-dock strength test protocol remains unavailable for Ballast Tank No. 1, located near the bow of the vessel. This is because the No. 1 ballast tank has a large side plating profile, and the flat area of ​​the tank bottom is much smaller than that of other ballast tanks. This limits the number of piers that can be accommodated. If the same docked pier strength test protocol were used, the piers would not meet the required load-bearing capacity and would inevitably break. Even though the 4m draft of the plating provides a certain amount of buoyancy, the ballast tank's large profile limits the buoyancy of the water and is insufficient to meet the requirements of the pier strength test.

[0003] Comparative document CN112078746A discloses a method for conducting ballast tank strength tests in a dock, comprising the following steps: during the docking phase, filling the first batch of ballast tanks in the dock and half-ship with water in multiple stages until the first batch of ballast tanks is full; conducting strength tests on the first batch of ballast tanks; transferring the ballast water from the first batch of ballast tanks by gravity to the second batch of ballast tanks until the liquid levels in the two tanks are equal; filling the second batch of ballast tanks in the half-ship with water until the tanks are full, and conducting strength tests on the second batch of ballast tanks; and gradually draining the water in the half-ship and dock multiple times. This method in the comparative document brings the ballast tank strength test to the docking phase, accelerating the start of work on the cargo hold, shortening the ship's construction period, and improving construction efficiency. However, it does not disclose how to conduct strength tests on ballast tank No. 1, located near the bow of the ship. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a method for conducting a strength test of the bow ballast tank of an LNG ship in a dock, thereby shortening the ship construction period and improving the pre-installation efficiency in the dock.

[0005] To achieve the above object, the technical solutions of the present invention are as follows:

[0006] A method for conducting a strength test of a bow ballast tank of an LNG ship in a dock comprises the following steps:

[0007] Step 1: When the ship is half-built, check whether the loading status and integrity status of the half-ship meet the requirements;

[0008] Step 2: Check the ship's floating state using stability software;

[0009] Step 3: Select the test location in the dock, avoiding the dock area;

[0010] Step 4: Check the status of the dock and the ship;

[0011] Step 5: Add water to the left and right sides of the No. 1 ballast tank near the bow of the ship;

[0012] Step 6: Stop filling the dock when the water level reaches 3m above the outer plate, then add water to the No. 1 ballast tank and conduct a tightness check inside the tank;

[0013] Step 7: The dock continues to take on water until the ship floats and berths;

[0014] Step 8: After berthing, the dock is flooded again until the water level inside the dock is level with the river water, and the dock door is opened;

[0015] Step 9: Add water to the No. 1 ballast tank until it is full. Use the total station to monitor the ship's floating state, control the water addition speed in a timely manner, and adjust the ship's heel and trim;

[0016] Step 10: Submit the strength test results of ballast tank No. 1;

[0017] Step 11: Drain the No. 1 ballast tank and the No. 4 ballast tank near the stern of the ship in turn. Drain the dock to dry dock status, open the outer plate drain plugs, and empty the remaining water in all ballast tanks;

[0018] Step 12: Clean the dock bottom.

[0019] As a preferred technical solution, during the filling and drainage process, the ship's draft is always less than 6m.

[0020] As a preferred technical solution, in step 1, the integrity status of half the ship includes: welding of the cargo area is completed, the bow and stern have been brought on board, the main structure welding is completed, and the welding and tightness of the structure below the waterline are completed; the airtightness test submission of the No. 1 ballast tank is completed; ensure that the No. 1 ballast tank is clean and tidy to prevent garbage from clogging the pipelines and equipment during the strength test water transfer process; the single-side ballast pipe is connected and the valves are complete.

[0021] As a preferred technical solution, in step 2, the buoyancy of the ship is checked by the stability software. The checking method is: the weight of the ship is imported into the stability software, and the stability software automatically generates the three-dimensional center of gravity of the ship. The mass of ballast water is then added to the position of ballast tank No. 1 to obtain the center of gravity of the ship after pressurization. In the still water mode of the stability software, the buoyancy of the bow and stern is calculated.

[0022] As a preferred technical solution, in step 3, the method for avoiding the dock area in the test position is: checking the overlap between the flat bottom area of ​​the ship and the dock area to ensure that the overlap is zero, so as to determine the test position in the dock after the ship floats.

[0023] As a preferred technical solution, in step 4, the inspection contents include: shutting down the kinetic energy of the dock bottom; clearing the dock bottom, tying and fixing movable items on board; and final confirmation of the status of the outer plate before water ingress.

[0024] As a preferred technical solution, in step 7, when the ship is berthing, the ship is floated and dragged to the southeast corner of the dock, the ship's cable is tied to the east bank, the ship's outer plate is leaning against the target on the east bank dock wall, and the west bank cable is used to assist in ship positioning.

[0025] As a preferred technical solution, the dock door remains open during the entire floating process of the ship.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The method of the present invention for carrying out a strength test of the bow ballast tank of an LNG ship in a dock can carry out strength tests of all ballast tanks in the dock, and can advance all processes of the liquid cargo containment system of the four cargo tanks of the entire LNG ship by 3-4 months. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a half-ship loading mode for carrying out a ballast tank strength test of an LNG ship in a dock according to the present invention;

[0029] Figure 2 It is a schematic diagram of the ship position for carrying out the LNG ship ballast tank strength test in the dock according to the present invention.

[0030] In the figure: 1. Bow; 2. Stern; 3. Ballast tank No. 1; 4. Ballast tank No. 4; 5. Dock. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with specific embodiments:

[0032] like Figure 1 and Figure 2 As shown, a method for conducting a strength test of a bow ballast tank of an LNG ship in a dock comprises the following steps:

[0033] Step 1: When the ship construction reaches the half-ship stage, check whether the loading status and integrity status of the half-ship meet the requirements; the integrity status requirements of the half-ship include: the welding of the cargo area is completed, the bow 1 and stern 2 have been loaded on board, the main structure welding is completed, and the welding and tightness of the structure below the waterline are completed; the airtightness test submission of ballast tank 1 3 is completed; ensure that the interior of ballast tank 1 3 is clean and tidy to prevent garbage from clogging the pipelines and equipment during the strength test water transfer process; the single-side ballast pipe is connected and the valves are complete.

[0034] Step 2: Verify the vessel's floating state using stability software, known as NAPA. The calculation process involves importing the vessel's weight (including various information such as the weight of the structure, outfitting, welding, equipment, piping, and temporary tool kits) into the stability software. The stability software automatically generates the vessel's three-dimensional center of gravity. The mass of ballast water is then added to position 3 of ballast tank 1 to determine the vessel's center of gravity after ballast loading. Using the stability software's still water mode, the floating state of the bow 1 and stern 2 is calculated. The vessel's draft is required to be no greater than the objective limitation of the dock depth to prevent it from hitting the bottom.

[0035] Step 3: Select the test position in dock 5. The test position should avoid the dock area. To achieve this goal, it is necessary to check the overlap between the flat bottom area of ​​the ship and the dock layout area. The overlap is required to be zero, so as to determine the test position in dock 5 after the ship floats.

[0036] Step 4: Check the status of dock 5 and the vessel; shut down the kinetic energy of the dock bottom; clear the dock bottom and tie down movable items on board; make a final confirmation of the status of the outer plate before flooding.

[0037] Step 5: Add 2,000 tons of water to the left and right sides of the No. 1 ballast tank 3 near the bow 1 of the ship;

[0038] Step 6: Stop filling the dock 5 when the outer plate draft reaches 3m, then add water to the No. 1 ballast tank 3, filling the left side with water to 3000 tons and the right side with water to 2800 tons, and conduct an airtightness check inside the tank;

[0039] Step 7: Dock 5 continues to take on water until the ship floats. After the ship floats, it is towed to the southeast corner of Dock 5, avoiding the area where the dock piers were originally arranged. The ship is tied to the east bank with a cable, and the ship's outer plate is leaning against the target on the east bank dock wall. The west bank cable is used to assist in the ship's positioning.

[0040] Step 8: After berthing, dock 5 is flooded again until the water level in dock 5 is level with the river water, and the dock gate is opened; the water level in dock 5 is level with the river water, and the ship floats throughout the whole process with the rise and fall of the river water, and the dock gate remains open.

[0041] Step 9: Continue to add water to the left and right sides of the No. 1 ballast tank 3 until the tank is full. At the same time, add 3,500 tons of water to the left side of the No. 4 ballast tank 4 near the stern 2 and 3,300 tons of water to the right side. Use the total station to monitor the floating state of the ship, control the water addition speed in time, and adjust the ship's heel and trim.

[0042] Step 10: Submit the strength test results of No. 1 ballast tank 3;

[0043] Step 11: The drainage phase begins. First, drain the No. 1 ballast tank 3 to 5,000 tons on both sides. Then drain the No. 4 ballast tank 4 to 3,500 tons on the left and 3,300 tons on the right. Then drain the No. 1 ballast tank 3 to 4,000 tons on both sides. Then drain the No. 4 ballast tank 4 to 400 tons on both sides. Drain the No. 1 ballast tank 3 to 3,300 tons on the left and 3,100 tons on the right. Close the dock door, drain the dock 5, and lower the ship into the pier. Dock 5 drains until the outer plate draft is 3 meters, and then drains the No. 1 ballast tank 3 to 2,000 tons on both sides. Dock 5 is drained to the dry dock state. Open the outer plate drain plugs to drain the remaining water in all ballast tanks.

[0044] Step 12: Clean the dock bottom.

[0045] During the filling and drainage process, the ship's draft is always less than 6m.

[0046] This embodiment is only a further explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for conducting a strength test of a bow ballast tank of an LNG ship in a dock, characterized in that: The method comprises the following steps: Step 1: When the ship is half-built, check whether the loading status and integrity status of the half-ship meet the requirements; Step 2: Check the ship's floating state using stability software; Step 3: Select a test location in the dock, which avoids the dock area; Step 4: Check the status of the dock and the ship; Step 5: Add water to the left and right sides of the No. 1 ballast tank near the bow of the vessel; Step 6: Stop filling the dock with water when the water level reaches 3m above the outer plate, then add water to the No. 1 ballast tank to conduct a tightness check inside the tank; Step 7: The dock continues to take on water until the ship floats, and the ship berths; Step 8: After berthing, the dock is flooded again until the water level inside the dock is level with the river water, and the dock door is opened; Step 9: Add water to the No. 1 ballast tank until it is full, monitor the floating state of the ship by using a total station, control the water adding speed in time, and adjust the ship's heel and trim; Step 10: Submit the strength test results of the No. 1 ballast tank; Step 11: Drain the ballast tanks and the dock. Drain the dock to the dry dock state, open the outer plate drain plugs, and drain the remaining water in all ballast tanks; Step 12: Clean the dock bottom.

2. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: During the filling and drainage process, the draft of the ship is always less than 6m.

3. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: In step 1, the integrity status of half of the ship includes: welding of the cargo area is completed, the bow and stern have been put on board, the main structure welding is completed, and the welding and tightness of the structure below the waterline are completed; the airtightness test submission of the No. 1 ballast tank is completed; ensure that the No. 1 ballast tank is clean and tidy to prevent garbage from clogging the pipes and equipment during the strength test water transfer process; the single-side ballast pipe is connected and the valves are complete.

4. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: In step 2, the buoyancy of the ship is checked by using the stability software. The checking method is as follows: the weight of the ship is imported into the stability software, and the stability software automatically generates the three-dimensional center of gravity of the ship. The mass of the ballast water is then added to the position of the No. 1 ballast tank to obtain the center of gravity of the ship after being pressurized with water. In the still water mode of the stability software, the buoyancy of the bow and stern is calculated.

5. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: In step 3, the method for avoiding the dock area at the test position is: checking the overlap between the flat bottom area of ​​the ship and the dock area to ensure that the overlap is zero, so as to determine the test position of the ship in the dock after floating.

6. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: In step 4, the inspection contents include: shutting down the kinetic energy of the dock bottom; clearing the dock bottom, lashing and securing movable items on the ship; and final confirmation of the status of the outer plate before water ingress.

7. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: In step 7, when the ship is berthed, the ship is floated and towed to the southeast corner of the dock, the ship's cable is tied to the east bank, the ship's outer plate is leaning against the target on the east bank dock wall, and the west bank cable is used to assist in the positioning of the ship.

8. The method for conducting a strength test of a bow ballast tank of an LNG ship in a dock according to claim 1, characterized in that: The dock door remains open during the entire floating process of the vessel.

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