Pump tower base mounting and height measuring method

Abstract

The invention discloses a pump tower base mounting and height measuring method, and belongs to the field of ship building. The method for measuring the height of the pump tower base comprises the steps that a calculation expression used for calculating the pump tower base is determined according to the installation state of the pump tower base and a temporary box in the liquefied natural gas carrier, and measurement is conducted from the installation datum plane of the pump tower base to obtain a first parameter; and utilizing the first parameter, the second parameter and a preset third parameter to calculate and obtain the height of the pump tower base through a calculation expression, wherein the first parameter, the second parameter and the third parameter are all physical parameters associated with the installation state.

Description

Technical Field

[0001] The invention belongs to the field of shipbuilding, and in particular relates to a method for installing and measuring the height of a pump tower base. Background Art

[0002] Traditional energy sources such as coal and oil are prone to produce emissions such as sulfur dioxide and nitrogen oxides when used, which pollute the environment. The use of natural gas can greatly reduce pollutant emissions and improve the environment.

[0003] With rapid economic development, natural gas is becoming a mainstream energy source due to its high calorific value and low price. Consequently, demand for LNG (liquefied natural gas) vessels for transportation is increasing. Based on the type of containment system, some LNG carriers are classified into two types: the NO96 and the MARK III.

[0004] In the NO96 membrane tank, the pump tower, which functions as a pump-storage system, plays a crucial role. The Pump Tower Base Support (PTBS) at the bottom of the pump tower serves as a position limiter. The height of the pump tower base affects the connection between the pump tower and the primary and secondary membranes. Too high or too low will prevent the installation of the Invar membrane in that area.

[0005] Therefore, accurately and quickly obtaining the pump tower base height will help speed up work progress and improve work efficiency. Summary of the Invention

[0006] An example of the present invention provides a method for installing and measuring the height of a pump tower base.

[0007] The exemplary solution of the present invention is implemented as follows.

[0008] A method for measuring the height of a pump tower base, comprising:

[0009] According to the installation status of the pump tower foundation and temporary tank in the LNG carrier, the calculation expression for the pump tower foundation is determined:

[0010] Measure from the mounting datum surface of the pump tower base to obtain the first parameter:

[0011] Through the first parameter, get the second parameter: and

[0012] Using the first parameter, the second parameter, and the preset third parameter, the pump tower base height is calculated using the following expression:

[0013] The first parameter, the second parameter and the third parameter are all physical parameters associated with the installation state.

[0014] Optionally, the installation reference surface is determined as follows:

[0015] Created by dotting and dashing the designated surface of the cargo hold of a liquefied natural gas carrier.

[0016] Optionally, the calculation expression is H1+Dz=H2+Gap-H3;

[0017] Wherein, H1 is the height of the temporary box, Dz is the thickness of the wedge, which is used to raise the temporary box during installation, H2 is the height of the pump tower base, Gap is the thickness of the steel liner, and H3 is the welding shrinkage of the steel liner, which is used to connect to the pump tower base through welding;

[0018] The first parameter is H1, the second parameter is Dz, and the third parameter is Gap.

[0019] Optionally, the insulation box is supported on the installation reference surface by wedges, and the steel gasket is fixed to the installation reference surface.

[0020] Alternatively, Dz is the arithmetic mean of the thicknesses of the 12 wedges.

[0021] Optionally, the 12 wedges are distributed along the installation circle of the pump tower base according to 12 equally divided lines of the circumference of the installation circle.

[0022] Compared with the prior art, the method of the present invention can more quickly obtain the height of the pump tower base, so as to manufacture the pump tower base, thereby improving the manufacturing efficiency of the liquefied natural gas ship and shortening the construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a clearer explanation, the following briefly introduces the drawings required for the description.

[0024] Figure 1 The pump tower base and the pump pipe column in the specific embodiment of the present invention are matched and connected;

[0025] Figure 2 A flow chart of a method for determining the height of a pump tower base in a specific embodiment of the present invention;

[0026] Figure 3 A schematic diagram of determining the height of the pump tower base in a specific embodiment of the present invention;

[0027] Figure 4 This is a data diagram of Dz value in a specific embodiment of the present invention;

[0028] Figure 5 This is a diagram of an interface of a program for generating a CSV file in a specific embodiment of the present invention;

[0029] Figure 6This is a diagram illustrating the interface of GTT software for calculating gap values in a specific embodiment of the present invention;

[0030] Figure 7 A flow chart of a method for installing a pump tower base in the present invention is disclosed;

[0031] Figure 8 The following are physical pictures of three types of pump tower bases commonly used in the prior art. DETAILED DESCRIPTION

[0032] LNG membrane tank is mainly composed of prestressed concrete outer tank and membrane inner tank.

[0033] The membrane-type LNG carrier has multiple layers of special structures designed and installed on its inner wall, including a secondary insulation box, a secondary low-temperature resistant Invar steel membrane, a main insulation box, and a main low-temperature resistant Invar steel membrane.

[0034] The outer tank of the membrane type storage tank is composed of concrete vault, concrete tank wall and concrete support.

[0035] The outer tank consists of a 56-sided inner wall. All piping and instrumentation (pump column structure and insulation space monitoring system) are connected to the tank through the tank vault to ensure no penetration of the membrane. The pump column structure is fixed to the tank roof, with only the bottom portion being guided.

[0036] For bimetallic full-containment tanks, the pump column is directly welded to the inner tank wall using supports for securement. For membrane tanks, a pump tower structure is installed, with steel plates embedded in the pedestal and a pump tower base welded to secure the entire structure. All piping is connected to the tank roof. Because the inner wall of a membrane tank is made of membrane sheeting, which cannot be welded onto supports, a pump tower base is used to secure the pump column piping and other components.

[0037] The pump tower of an LNG ship is located at the rear bulkhead inside the liquid cargo tank. It is mainly composed of components such as filling pipes, unloading pipes, emergency pipes, struts and bases. It is a key component of the liquid cargo control system and is responsible for loading and unloading liquid tank cargo.

[0038] A pump tower is a vertically movable tripod mast that houses the main unloading pipeline and emergency pump well, supporting tank access ladders, other piping, and instrumentation. For some LNG membrane storage tanks, the pump tower structure primarily consists of three austenitic stainless steel pipes (two for the pump well and one for the liquid inlet), other piping, and a ladder platform.

[0039] The pump tower is suspended and installed in the liquid tank of the LNG carrier, with the top of the pump tower connected to the dome of the liquid tank. A casing is installed through the dome and the aluminum ceiling, and a pump tower base (guide mechanism) is installed at the bottom to support the load of the entire pump column.

[0040] The pump tower base support (PTBS) is installed in the membrane tank and connected to the embedded plate of the base. It plays the role of fixing the two pump pipes and the lower liquid inlet pipe. Figure 1 The structures of three common types of pump tower bases (NO96 type, MARKⅠⅠⅠ type, and GST type) are as follows: Figure 8 shown.

[0041] The pump tower base is a crucial component within the cargo tank. It secures the bottom of the pump tower in four directions: front, back, left, and right. It also serves as a guide for the pump tower as it slides up and down within the tank, allowing for thermal expansion and contraction. The pump tower is submerged in cryogenic liquefied natural gas (or ethane) for extended periods, and temperature fluctuations in the cargo tank during loading and unloading, or during maintenance, cause this expansion and contraction. The pump tower base also reduces friction during contraction, preventing damage to associated piping and equipment. The pump tower base itself consists of a central cylinder, a cone, and two side guides.

[0042] Due to the location and function of the pump tower base and the characteristics of the all-stainless steel material, the pump tower base has very high assembly requirements.

[0043] A method for installing a pump tower base is as follows:

[0044] 1. According to the hull markings, place four jacks at the four corners of the pump tower base (place the installation tooling on the jacks), and raise the jacks to the appropriate position.

[0045] 2. According to the marked lines, use the lifting equipment to slowly lower the pump tower base so that the secondary wing plates of the pump tower base fall evenly on the four jacks.

[0046] 3. Adjust the height of the oil pump, measure the height difference between the temporary insulation box and the secondary wing plate of the pump tower base, and adjust the height of the oil pump to ensure that the gap meets the requirements; at the same time, measure the height of the stern of the pump tower base from the surface of the reference wedge.

[0047] 4. Use a marker to evenly mark the designated distance between the lower opening of the pump tower base and the hull (clearance line);

[0048] 5. Remove the pump tower base and grind the bottom of the pump tower base according to the clearance line. After grinding, reinstall the pump tower base and adjust it into place to ensure that the gap between the bottom of the pump tower base and the bottom plate is 5-7mm. Measure the gap between the pump tower base and the hull and mark it on the base.

[0049] 6. Divide the stainless steel gasket into 8 sections and mark them. Place the 8 sections on the pre-marked circle and grind them to ensure the gap between them and the hull is less than 0.5mm.

[0050] 7. Install the 8 sections of stainless steel washers on the pump tower base according to the position on the hull, clamp them with pliers and adjust the gaskets according to the data marked on the pump tower base in advance and spot weld them. Spot weld only one point. When submitting, remove the outer ring of the gasket spot weld;

[0051] 8. Place the pump tower base with the stainless steel gasket installed directly on the installation position of the hull and adjust it into place, and check the gap between the stainless steel gasket and the hull;

[0052] 9. Lower the pump tower base again and adjust it into place (including the installation position and height position on the ship, there should be no jack at this time), recheck whether the stainless steel liner is tightly attached to the hull (the gap between the hull and the hull should not exceed 0.5mm), measure and record whether the distance between the stainless steel liner and the bottom of the pump tower base is less than 0.5mm. If the gap is too large, please grind it repeatedly until it meets the requirements.

[0053] Therefore, in the above process, a very important step is to determine the height of the pump tower base. Generally speaking, at this stage, the height of the pump tower base needs to be measured by laser marking inside the cabin to determine the base point.

[0054] Then, the base is ground and then installed and welded (referred to as welding).

[0055] After welding, the insulation box is professionally measured and installed with wedge values.

[0056] After that, the wedge value of the installation area is measured by the wedge value adjacent to the pump tower base to calculate the pump tower base height data.

[0057] However, in the above solution, because the pump tower base is installed on the C surface (bottom surface) of the ship's hold on level 0, the above work sequence must be from top to bottom, so measuring the pump tower height requires waiting for about 9 days, a total of 15 shifts. This leads to a series of problems.

[0058] Problem 1: Long waiting time.

[0059] Since each process is closely linked to each other, one must wait for the previous process to be completed before proceeding to the next one. Therefore, it takes a long time to measure the C-surface wedge block, and this professional labor force is idle for a long time.

[0060] Question 2: Impact on other professional work.

[0061] During the height measurement, other professionals need to use the elevator to transport materials and equipment. The measurement area is directly below the elevator. For safety reasons during the measurement, the elevator needs to be lowered to one floor and stopped from use, which will affect the normal transportation of materials and equipment by other professionals.

[0062] Furthermore, the pump tower base height was measured too late, resulting in a delay in the completion and transport of the pump tower base to the warehouse. When the pump tower base was being installed, the insulation box on the upper floor was being installed, and the elevator was stopped during the installation, which seriously delayed the return of the insulation box.

[0063] In view of this, in the present invention, the inventors propose a method to overcome the defects of the current pump tower base height measurement scheme, such as long initial waiting time, interference with other processes, and serious delay in the construction progress of LNG ships.

[0064] Accordingly, this method can effectively reduce the early waiting time, measure the height in advance and make the pump tower base in advance, so as to stagger the use of elevators by other professionals in the later stage and reduce the impact on the progress.

[0065] Specifically, the present application discloses a method for measuring the height of a pump tower base.

[0066] refer to Figure 2 , measurement methods include:

[0067] Step S101: Determine a calculation expression for calculating the pump tower foundation according to the installation status of the pump tower foundation and the temporary tank in the liquefied natural gas carrier:

[0068] Step S102: Measure from the installation reference plane of the pump tower base to obtain the first parameter:

[0069] Step S103: Obtain the second parameter through the first parameter: and

[0070] Step S104 uses the first parameter, the second parameter, and the preset third parameter to calculate the pump tower base height through a calculation expression: the first parameter, the second parameter, and the third parameter are all physical parameters associated with the installation state.

[0071] In step S101 , as a specific example, the calculation expression used in the method for measuring the height of the pump tower base is H1+Dz=H2+Gap-H3.

[0072] To facilitate the explanation of the above expression, please refer to Figure 3 .

[0073] Among them, H1 is the height of the temporary box, Dz is the thickness of the wedge, the wedge is used to raise the temporary box during installation, H2 is the height of the pump tower base, Gap is the thickness of the steel liner, H3 is the welding shrinkage of the steel liner, and the steel liner is used to connect the pump tower base by welding.

[0074] Accordingly, the first parameter mentioned above is H1, the second parameter is Dz, and the third parameter is Gap.

[0075] The calculation of the above expression is mainly based on the following considerations:

[0076] like Figure 3 As shown, the height of the rear panel of the left box (for example, which can be named as a temporary box) after the wedge block is placed is equal to the height of the rear panel of the right pump tower base after welding.

[0077] By establishing a corresponding relationship between the heights of the left and right sides, the height of the pump tower base can be calculated; that is, H2 = H1 + Dz - Gap + H3.

[0078] In step S102, the installation reference surface can be determined, for example, by marking a designated surface of the LNG carrier's cargo hold. This installation reference surface can be a theoretical reference surface. In practice, laser equipment can be used for measurement and marking. For example, a laser tracker can be used to establish a surface, followed by marking points using a dotting tool, and then connecting the lines using a marker.

[0079] After determining the installation datum, the insulation box can be installed. For example, wedges are used to support the insulation box on the installation datum. Accordingly, the steel pads used to weld the pump tower base are secured to the installation datum. The wedges can be made of Teflon and are used to adjust the gap between the box and the hull.

[0080] Then, the relevant data can be measured and obtained according to the calculation formula determined previously for subsequent calculations.

[0081] In particular, the actual hull structure is taken into account when calculating the height of the pump tower foundation.

[0082] Specifically, because the hull flatness varies around the pump tower base, the measured Dz value (i.e., the wedge thickness) is not a fixed value, and therefore the calculated pump tower base height H2 is not fixed. However, machining can only produce pump tower bases of fixed heights. Therefore, when manufacturing the pump tower base, a fixed Dz value can be compromised for the specific height of the base, and the corresponding pump tower base height can be calculated based on this fixed Dz value. Then, during the actual installation of the pump tower base, the Gap value is adjusted by grinding the steel liner to accommodate installation in different locations.

[0083] Specifically, fluctuations in the Dz value are accounted for by taking a compromise (e.g., calculating the arithmetic mean of multiple values) to determine the height of the pump tower base to be manufactured. During actual installation of the pump tower base, the steel liner can be polished to account for fluctuations in the Dz thickness. In some embodiments, the use of movable or fixed spacers on the pump tower base can be explored to reduce flatness requirements, facilitate leveling and fixing, and reduce polishing.

[0084] In addition to the arithmetic mean, the compromise value can also be obtained by other methods, such as the arithmetic mean, the harmonic mean and other types of averages.

[0085] Since it is necessary to consider different Dz values and take a compromise value (for example, an average value), different numbers of Dz values can be selected according to different examples. In the example of the present application, the Dz value can be selected as 12, so the number of wedges can be correspondingly selected as 12. In order to make the Dz values corresponding to these wedges more representative, thereby obtaining a more accurate, or more convenient to use, Dz value for the subsequent installation of the pump tower base, it is possible to choose to distribute these 12 wedges according to the 12 equally divided lines of the circumference of the installation circle of the pump tower base. That is, wedges arranged in the 12 equally divided line area of the installation circle of the pump tower base are selected.

[0086] As a more specific example, a method of measuring the height of a pump tower base may be disclosed as follows.

[0087] 1. Use the dotting and marking instrument to mark the C surface of layer 0 to generate a theoretical reference surface, and then measure the theoretical Dz value ( Figure 4 ).

[0088] Import the Dz.txt into the EXCEL calculation formula to generate a CSV file ( Figure 5 ), import into GTT software ( Figure 6 ), the gap value of the entire C surface is calculated, and the pump tower base area is selected as a reference.

[0089] 2. Place the theoretical value of the wedge in the pump tower base area and make minor adjustments based on site needs. Feedback to the insulation box department after adjustments, and the wedge value in that area will remain unchanged.

[0090] 3. Divide the pump tower base installation circle into 12 equal parts, and measure the wedge values at 12 positions based on the surrounding wedge values.

[0091] 4. Enter the 12 position wedge values into the calculation table to calculate the actual height of the pump tower base.

[0092] In summary, calculating the height of the pump tower base in the above way can achieve the following advantages:

[0093] 1. In the previous method, the pump tower base height was fixed, and the steel liner needed to be polished according to the actual situation during the on-site installation process, which was a lot of grinding work. Although the pump tower base height was later measured according to the on-site wedge block value to reduce the amount of steel liner grinding, it involved many previous processes and required a long waiting time.

[0094] The example method of this application uses software to calculate the wedge value of the corresponding area, which can save a lot of early waiting process. For example, the early waiting time of 9 days and 15 shifts can be shortened to 4 days and 7 shifts, greatly improving the work progress.

[0095] 2. By bringing forward the timeline for measuring the pump tower base's height, the production department has more time to manufacture the pump tower base, which helps ensure quality. Furthermore, earlier welding of the pump tower base reduces the impact of elevator downtime on other tasks and optimizes the work sequence.

[0096] As an example of the application of the above method, this application also discloses the application of the aforementioned method for measuring pump tower base height in pump tower base manufacturing. Specifically, LNG ship construction companies can use the above method to measure the required pump tower base height and then provide this data to the pump tower base manufacturer for customization.

[0097] As another application example, the present application also discloses a method for installing the base height of a pump tower.

[0098] See Figure 7 , the method comprising:

[0099] Step S201: providing a pump tower base having a given height, wherein the given height is determined by measuring the height of the pump tower base;

[0100] Step S202: grinding the steel liner, with different grinding amounts at different positions of the steel liner;

[0101] Step S203: Weld the pump tower base to the steel liner.

[0102] The grinding amount in step S202 may be configured such that the grinding amount at different positions is associated with the thickness of the wedge at different positions.

[0103] In step S203, the welding locations are polished and cleaned before welding. Before welding begins, multiple (e.g., 2-3) tack welds can be performed on the pump tower base to ensure there are no gaps between the pump tower base and the interior surface of the cargo hold. After welding, the welds are visually inspected, subjected to color flaw detection, and subjected to random tensile testing.

[0104] Before obtaining the height of the pump tower base, the installation position of the pump tower base can also be determined on site. For example, an existing method for determining the installation position of the pump tower base is as follows:

[0105] First, place the total station on the inner bottom plate of the hull inside the cargo tank.

[0106] Secondly, an xyz three-dimensional coordinate system is established with the plane of the hull bottom plate as the XY plane.

[0107] Then, adjust the total station to the tracking measurement mode and use the total station to determine and mark the installation position of the pump tower base.

[0108] Generally, the pump tower base is located below the pump tower at the rear of the cargo hold. A “sample punch” mark can be made on the frame on the inner bottom to facilitate the installation of the pump tower base.

[0109] The embodiments described above with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0110] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, one or more embodiments are described above with reference to the accompanying drawings. Throughout the text, like reference numerals are used to refer to like components. In the above description, for purposes of explanation, numerous specific details are set forth to provide a more thorough understanding of one or more embodiments.

[0111] In various cases, one or more embodiments may be practiced without these specific details, and the various embodiments may be incorporated into or referenced in conjunction with each other without inconsistency.

[0112] It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present invention described herein can be practiced in an order other than that illustrated or described herein.

[0113] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings. The above are only preferred embodiments of the present invention, but the scope of implementation of the present invention is not limited to what is shown in the drawings. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present invention.

Claims

1. A method for measuring the height of a pump tower base, characterized in that: include: According to the installation status of the pump tower foundation and temporary tank in the LNG carrier, the calculation expression for the pump tower foundation is determined: Measure from the mounting datum surface of the pump tower base to obtain the first parameter: By using the first parameter, the second parameter is obtained: and The pump tower base height is calculated using the first parameter, the second parameter, and the preset third parameter through the calculation expression: The first parameter, the second parameter and the third parameter are all physical parameters associated with the installation state.

2. The method for measuring the height of a pump tower base according to claim 1, wherein: The installation reference surface is determined as follows: Created by dotting and dashing the designated surface of the cargo hold of a liquefied natural gas carrier.

3. The method for measuring the height of a pump tower base according to claim 1, wherein: The calculation expression is H1+Dz=H2+Gap-H3; Wherein, H1 is the height of the temporary box, Dz is the thickness of the wedge, which is used to raise the temporary box during installation, H2 is the height of the pump tower base, Gap is the thickness of the steel liner, and H3 is the welding shrinkage of the steel liner, which is used to connect to the pump tower base through welding; The first parameter is H1, the second parameter is Dz, and the third parameter is Gap.

4. The method for measuring the height of a pump tower base according to claim 3, wherein: The temporary box is supported on the installation reference surface by the wedge block, and the steel liner is fixed to the installation reference surface.

5. The method for measuring the height of a pump tower base according to claim 3 or 4, characterized in that: Dz is the arithmetic mean of the thicknesses of the 12 wedges.

6. The method for measuring the height of a pump tower base according to claim 5, wherein: The 12 wedges are distributed along the installation circle of the pump tower base according to 12 equally divided lines of the circumference of the installation circle.

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