Method for measuring the post-weld capacity of a tank of a liquefied natural gas carrier using a total station

Abstract

This invention relates to a method for measuring the post-weld volume of liquefied natural gas (LNG) ship compartments using a total station. Measurement nodes are selected on the bow and stern transverse bulkheads. A tripod total station is placed inside the compartment, and a coordinate system is established to ensure that all measurement nodes on the bow and stern transverse bulkheads are visible. The coordinate system uses the bow-stern direction as the X-axis, a Y-axis perpendicular to the X-axis and horizontally positioned, and a Z-axis perpendicular to the X-axis and vertically positioned. Inspection lines are set on the longitudinal bulkheads parallel to the bow and stern transverse bulkheads, with the inspection lines at the same distance from the bow and stern transverse bulkheads. An angle is formed between the longitudinal bulkhead and the inner oblique side; reference nodes are set along the inspection lines from the angle, corresponding to the measurement nodes. This invention obtains the reference nodes by moving the measurement nodes along the X-axis, calculates the coordinates of the measurement nodes using the coordinates of the reference nodes, and inputs the coordinates of the measurement nodes into G3 software to obtain changes in the volume, thus solving the problem of not being able to directly obtain the coordinates of the measurement nodes.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding, and specifically to a method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station. Background Technology

[0002] After the welding of the liquefied natural gas (LNG) carrier is completed, the capacity of the compartments must be measured and analyzed. The control of the compartment capacity is an effective evaluation indicator of the ship's construction quality.

[0003] Existing technology, such as the invention patent with publication number CN107421482B, discloses a method for judging the compliance of LNG ship cargo hold capacity. This method uses a dedicated line-marking device to mark eight inflection points on the two transverse bulkheads of the ship's hold, determining eight measurement nodes. Reflective sheets are attached to these eight nodes, and the height and half-width values ​​of each node are measured using a total station. The average height and width of the transverse bulkheads are calculated and compared with the theoretical values ​​for the width and height of the transverse bulkheads to determine whether the LNG ship's cargo hold capacity is qualified. The problem with this method is that it is only applicable to measuring the cargo hold capacity of non-linear compartments. For linear compartments, this method is no longer suitable. With the advent of linear compartments, it is now necessary to measure the cargo hold capacity to verify the ship's construction quality.

[0004] However, due to the presence of modular scaffolding at the transverse bulkheads during measurement, it is impossible to measure the data of the bow and stern of the compartment. In addition, some compartments have a linear shape (such as compartment one), and the linear shape of the compartment changes in the bow and stern direction. Once a compartment has a linear shape, it is difficult to accurately measure the capacity of the compartment. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for measuring the post-weld capacity of liquefied natural gas (LNG) ship compartments using a total station, thereby achieving the purpose of measuring the compartment capacity with a linear orientation.

[0006] The technical objective of this invention is achieved through the following technical solution:

[0007] A method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station. The compartment includes a bow transverse bulkhead, a stern transverse bulkhead, longitudinal bulkheads, and an inner oblique section. Measurement nodes are selected on the bow and stern transverse bulkheads. A tripod total station is placed inside the compartment, and a coordinate system is established to ensure that all measurement nodes on the bow and stern transverse bulkheads are visible. The coordinate system uses the bow-stern direction as the X-axis, a Y-axis perpendicular to the X-axis and horizontally positioned, and a Z-axis perpendicular to the X-axis and vertically positioned. Inspection lines are set on the longitudinal bulkhead parallel to the bow and stern transverse bulkheads, with the inspection lines spaced a certain distance from the bow and stern transverse bulkheads. The compartments are spaced at equal distances; an angle is formed between the longitudinal bulkhead and the inner oblique side. Reference nodes are set along the inspection line from the angle, and each reference node corresponds to a measurement node. The distance from the reference node to the angle position is equal to the distance from the corresponding measurement node to the angle position. The X-axis coordinates of the measurement nodes are measured using a total station with a tripod. The three-dimensional coordinates of the reference nodes on the X, Y, and Z axes are measured using the total station with a tripod. The three-dimensional coordinates of the measurement nodes are calculated using the three-dimensional coordinates of the reference nodes. The calculated three-dimensional coordinates of the measurement nodes are input into the G3 software to obtain the cabin volume change.

[0008] Furthermore, the distances from the measuring nodes to the included angle are the same.

[0009] Furthermore, when selecting a reference node, an auxiliary template is made based on the distance between the measured node and the included angle. The auxiliary template has a first inclined plane and a second inclined plane corresponding to the included angle. The angle between the first inclined plane and the second inclined plane is equal to the size of the included angle. The distance between the end of the first inclined plane and the end of the second inclined plane and the intersection of the first inclined plane and the second inclined plane is equal to the distance between the measured node and the included angle.

[0010] Furthermore, the auxiliary template is also equipped with holding holes.

[0011] Furthermore, an arc-shaped opening is provided at the intersection of the first and second inclined planes.

[0012] Furthermore, the measurement nodes and reference nodes on the bow transverse bulkhead side are measured first; then the measurement nodes and reference nodes on the stern transverse bulkhead side are measured by means of a transfer station.

[0013] Compared with the prior art, the beneficial effects of the present invention are that the present invention obtains the coordinates of the measurement nodes that cannot be directly measured by reference nodes, and then obtains the changes in the tank volume of the liquefied natural gas ship compartment after welding by indirectly obtaining the coordinates of the measurement nodes, thus solving the problem that the measurement nodes cannot be directly measured; the method of this application solves the problem of how to conveniently and accurately determine the reference nodes when the compartment has a linear shape. Attached Figure Description

[0014] Figure 1This is a schematic diagram of the structure of the compartment near the bow transverse bulkhead in this invention.

[0015] Figure 2 This is a schematic diagram of the auxiliary template structure in this invention.

[0016] Figure 3 This is a diagram showing the usage status of the auxiliary template in this invention.

[0017] Figure 4 This is a schematic diagram of the distribution of measurement nodes on the bow transverse bulkhead in this invention.

[0018] Figure 5 This is a schematic diagram of the reference node and the corresponding measurement node in this invention.

[0019] In the diagram, 1. Longitudinal bulkhead; 2. Angle; 3. Bow transverse bulkhead; 4. 100MK inspection line; 5. Auxiliary template; 6. Handling hole; 7. First inclined plane; 8. Second inclined plane; 9. Arc-shaped opening; 10. Measurement node; 11. Inner inclined side. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0021] A method for measuring the post-weld volume of a liquefied natural gas (LNG) carrier compartment using a total station. The compartment includes a bow transverse bulkhead, a stern transverse bulkhead, longitudinal bulkheads, and an inner oblique section. Measurement nodes are selected on the bow and stern transverse bulkheads. A tripod total station is placed inside the compartment, and a coordinate system is established to ensure that all measurement nodes on the bow and stern transverse bulkheads are visible. The coordinate system uses the bow-stern direction as the X-axis, a Y-axis perpendicular to the X-axis and horizontally positioned, and a Z-axis perpendicular to the X-axis and vertically positioned. Inspection lines are set on the longitudinal bulkheads parallel to the bow and stern transverse bulkheads, with the inspection lines equidistant from the bow and stern transverse bulkheads. An angle is formed between the longitudinal bulkhead and the inner oblique side. Reference nodes are set along the inspection line from the angle, and each reference node corresponds to a measurement node. The distance of the reference node from the angle is equal to the distance of the corresponding measurement node from the angle, and the distances of the measurement nodes from the angle are the same. The X-axis coordinates of the measurement nodes are measured using a total station with a tripod. The three-dimensional coordinates of the reference nodes on the X, Y, and Z axes are measured using the total station with a tripod. The three-dimensional coordinates of the measurement nodes are calculated using the three-dimensional coordinates of the reference nodes. The calculated three-dimensional coordinates of the measurement nodes are then input into the G3 software to obtain the cabin volume change.

[0022] Because of the linear shape of the compartment, an auxiliary template is created based on the distance of the measured node from the included angle to facilitate the selection of reference nodes. The auxiliary template is as follows: Figure 2As shown, the auxiliary template 5 has a first inclined surface 7 and a second inclined surface 8 at the included angle 2. The included angle between the first inclined surface 7 and the second inclined surface 8 is equal to the included angle 2 of the longitudinal bulkhead. The distance from the end of the first inclined surface 7 and the end of the second inclined surface 8 to the intersection of the first inclined surface 7 and the second inclined surface 8 is equal to the distance between the measuring node 10 and the included angle 2. The auxiliary template is also provided with a holding hole 6 to facilitate the handheld use of the auxiliary template for drawing reference nodes. Due to the presence of the weld at the included angle, an arc-shaped opening 9 is provided at the intersection of the first inclined surface 7 and the second inclined surface 8 to facilitate the fit of the first inclined surface 7 and the second inclined surface 8 against the longitudinal bulkhead.

[0023] Taking the bow of a cabin as an example, one side of the bow of the cabin is as follows: Figure 1 As shown, longitudinal bulkheads 1 and inner diagonal sides 11 are alternately distributed, and longitudinal bulkhead 1 includes eight longitudinal bulkhead surfaces; eight measurement nodes 10 are selected on the bow transverse bulkhead 3, as follows. Figure 4 As shown, ensure that all measurement nodes 10 are visible when the total station on the tripod is placed on the cabin floor (the bottom longitudinal bulkhead); a 100MK inspection line 4 is drawn on the longitudinal bulkhead 1, and the distance of the 100MK inspection line 4 from the bow transverse bulkhead is 100mm; with the help of the auxiliary template 5, reference nodes are drawn on the longitudinal bulkhead 1 along the 100MK inspection line corresponding to the measurement nodes, and the distance of the reference node from the included angle is equal to the distance of the measurement node from the same included angle, such as... Figure 3 and Figure 5 As shown, in this embodiment, the distance of measurement node a from the included angle position is 200mm, and the corresponding distance of reference node b from the included angle position is also 200mm. The translation of the measurement node is accurately achieved through an auxiliary template, thereby ensuring the accuracy of the obtained reference node. For example, if the coordinates of measurement node a are (x1, y1, z1) and the coordinates of reference node b are (x2, y2, z2), then |x1-x2|=100, y1=y2, z1=z2. Thus, the coordinate values ​​of the measurement node can be calculated. Following this method, the coordinate values ​​of all measurement nodes on the bow transverse bulkhead are determined. After the measurement nodes and reference nodes on one side of the bow transverse bulkhead are measured according to the above method, the measurement nodes and reference nodes on the one side of the stern transverse bulkhead are measured by transferring to another station. After the measurement is completed, the obtained measurement node data is input into the G3 (EcoBlock G3) software. EcoBlock G3 is a 3D CAD-based software that can compare on-site segments with the corresponding design model and analyze deviation values.

[0024] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. Those skilled in the art can make non-inventive modifications to this embodiment as needed after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for measuring the post-weld hold capacity of a cargo tank of a liquefied natural gas carrier using a total station, characterized in that, The compartment includes a bow transverse bulkhead, a stern transverse bulkhead, a longitudinal bulkhead, and an inner oblique section. Measurement nodes are selected on the bow and stern transverse bulkheads respectively. A total station with a tripod is placed inside the compartment, and a coordinate system is established to ensure that all measurement nodes on the bow and stern transverse bulkheads are visible. The coordinate system has the bow-stern direction as the X-axis, a Y-axis perpendicular to the X-axis and horizontally set, and a Z-axis perpendicular to the X-axis and vertically set. Inspection lines are set on the longitudinal bulkhead parallel to the bow and stern transverse bulkheads, with the inspection lines equidistant from the bow and stern transverse bulkheads. Adjacent... An angle is formed between the longitudinal bulkheads. Reference nodes are set along the inspection line from the angle, and each reference node corresponds to a measurement node. The distance of the reference node from the angle is equal to the distance of the corresponding measurement node from the angle. The X-axis coordinate of the measurement node is measured using a total station with a tripod. The three-dimensional coordinates of the reference node on the X, Y, and Z axes are measured using the total station with a tripod. The three-dimensional coordinates of the measurement node are calculated using the three-dimensional coordinates of the reference node. The calculated three-dimensional coordinates of the measurement node are then input into the G3 software to obtain the cabin volume change.

2. The method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station according to claim 1, characterized in that, The distances from the measuring nodes to the included angle are the same.

3. The method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station according to claim 2, characterized in that, When selecting a reference node, an auxiliary template is made according to the distance of the measurement node from the included angle. The auxiliary template has a first inclined plane and a second inclined plane corresponding to the included angle. The angle between the first inclined plane and the second inclined plane is equal to the size of the included angle. The distance between the end of the first inclined plane and the end of the second inclined plane and the intersection of the first inclined plane and the second inclined plane is equal to the distance between the measurement node and the included angle.

4. The method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station according to claim 3, characterized in that, The auxiliary template is also provided with holding holes.

5. A method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station according to claim 3, characterized in that, An arc-shaped opening is provided at the intersection of the first inclined plane and the second inclined plane.

6. The method for measuring the post-weld volume of a liquefied natural gas (LNG) ship compartment using a total station according to claim 1, characterized in that, First, the measurement nodes and reference nodes on the bow transverse bulkhead side are measured; then, the measurement nodes and reference nodes on the stern transverse bulkhead side are measured by switching stations.

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