A method for pickling and passivation of LNG pump tower piping

Abstract

A method for pickling and passivation of LNG pump tower pipe system, the outer surface of the two ends of the stamping pipeline is provided with twisted wires, a circular fixing buckle is fixed at the root of the twisted wire, the stamping pipeline is provided with a high-pressure nozzle and a telescopic wheel in turn from the circular fixing buckle to the inside, the diameter of the passivation device is adjusted by the telescopic wheel, one end of the telescopic wheel is welded to the stamping pipeline, and the other end is fixed with a universal roller; a retractable passivation component is fixed in the middle of the stamping pipeline, and multiple passivation components are arranged at equal intervals along the circumference of the stamping pipeline, and multiple passivation components are provided with white steel grooves with notches facing outward, and the white steel grooves are filled with acid-resistant sponges. One end of the stamping pipeline is closed with a nut plug, and the other side is connected to high-pressure fresh water. The operator uses a rope to drag the device back and forth, and the passivation device moves in the pipe to thoroughly remove grease and dirt on the inner surface of the LNG pump tower pipe system. The invention has strong scalability, has the characteristics of efficient pickling and passivation ability, stable and durable structure, convenient and flexible operation, and excellent safety performance.

Description

Technical Field

[0001] The invention belongs to the field of ship construction and design, and in particular relates to a pickling passivation method for LNG pump tower pipe systems. Background Art

[0002] Stainless steel pipes are widely used in the fields of shipbuilding, aerospace, light industry and textiles due to their excellent corrosion resistance, high temperature oxidation resistance, good low temperature performance and excellent mechanical and processing properties. Especially in the shipbuilding industry, stainless steel pipes, as an excellent metal resistant to seawater corrosion, are increasingly widely used in the main parts of LNG carriers. The corrosion resistance of stainless steel mainly comes from the extremely thin (about 1nm) dense passivation film formed by its surface oxidation in the air. This passivation film can effectively prevent the further diffusion of corrosive factors such as oxygen and moisture to the surface of stainless steel, thereby achieving the effect of corrosion and rust prevention. However, the stainless steel passivation film formed by natural oxidation in the air has inevitable defects. At the same time, during the manufacturing process such as assembly and welding, the surface oxide film will be damaged, which greatly reduces the integrity of the passivation film. Therefore, in a strong corrosive environment such as the ocean, stainless steel pipes with defective or incomplete passivation films will still corrode.

[0003] The pump tower is a key component of LNG carriers, used for loading and unloading liquefied natural gas (LNG). Its construction is of great significance to the performance and safety of LNG carriers. The main structure of the pump tower is a stainless steel pipe system, which needs to be pickled and passivated as a whole after welding. The paste method is usually used inside and outside. However, due to the long pipeline, it is difficult for construction workers to apply it to all the inner surfaces of the pipe system, so it is particularly necessary to design a set of internal pickling and passivation equipment for the LNG pump tower pipe system.

[0004] LNG pump tower is a large device in LNG cargo tank. Its main function is to load, unload and transport liquefied natural gas. The manufacture of pump tower is one of the three core technologies for building LNG ships. This paper mainly studies the 175,000 cubic meter series LNG ship pump tower, which weighs 30 tons each and is made of 304L and 316L stainless steel. Pickling and passivation are required after assembly and welding. The pump tower is mainly composed of the main structure of the pump tower (triangular mast), the bottom plate structure and other accessories. The main dimensions of the main structure of the pump tower (triangular mast) are: 28m long * 5.2m wide * 5.2m high, mainly composed of emergency pump pipe, main discharge pipe No. 1, No. 2 and supporting inclined pipe.

[0005] The pickling and passivation process of stainless steel materials is usually divided into two stages: pickling and passivation. The pickling stage is to use acid to corrode a layer of about 10μm thick on the surface of the stainless steel material, so that the surface of the stainless steel material reaches a uniform balance and creates favorable conditions for the formation of a passivation film. The passivation stage uses a strong oxidant solution to quickly oxidize the surface of the stainless steel material after pickling, forming a uniform and dense oxide film to prevent the corrosion factor from diffusing to the surface of the stainless steel material.

[0006] There are many methods for pickling and passivation of stainless steel materials according to different processes and operations. Table 1 lists several commonly used methods for pickling and passivation of stainless steel materials and their applicable scopes.

[0007] method Scope of application Features Dipping method For parts that can be placed in pickling or passivation tanks Generally, pickling and passivation are performed in steps, and the acid solution can be reused; however, it is not suitable for large equipment due to the size limitation of the immersion tank. Brushing method Used for internal and external surfaces and local treatment of large equipment Manual operation, usually pickling and passivation step by step, the acid cannot be recycled, and the welds and other parts need to be brushed multiple times Ointment method Pipe systems used for on-site installation, especially suitable for pickling and passivation treatment of welding parts Manual operation, pickling and passivation can be done step by step, or two steps can be combined into one, the operation is simple and convenient Spray method Used for pickling and passivation on the construction site of the inner surface of large equipment The construction speed is fast, but a special spray gun and ring system are required. Round Robin Used for large equipment, manifold structures, such as heat exchangers, etc. The construction is convenient and the acid can be recycled, but a circulation system connecting pipes and pumps is required. Electrochemical method It can be used for parts and can also be used to treat the surface of on-site equipment by brush method. The technology is more complicated and requires a DC power supply or a constant potential instrument

[0008] Table 1

[0009] After the stainless steel pipe is welded, due to the long length of the pipe, considering the pipe size and on-site resource limitations, the paste method is the simplest and most economical choice. Paste pickling passivation is a process in which the prepared stainless steel pickling passivation paste is applied to the stainless steel surface, allowing it to react naturally until a passivation film is formed, and then the paste is washed off with clean water to obtain a passivation film. Summary of the invention

[0010] In order to solve the above problems, the present invention provides a method for pickling and passivation of LNG pump tower pipe system, aiming to achieve the purpose of combining the functions of pickling and passivation into one, and facilitating pickling and passivation. The technical solution adopted is:

[0011] A pickling and passivation method for LNG pump tower pipe system, the pickling and passivation device has a stainless steel stamping pipeline, the outer surfaces of both ends of the stamping pipeline are provided with twisted wires, a circular fixing buckle is fixed at the root of the twisted wire, the stamping pipeline is provided with a high-pressure nozzle and a telescopic wheel in sequence from the circular fixing buckle to the inside, and a passivation component is fixed in the middle of the stamping pipeline.

[0012] Multiple high-pressure nozzles are arranged at equal intervals along the circumference of the stamping pipeline. The telescopic wheel is composed of two sleeves and a round rod. Both ends of the round rod are twisted and connected with a sleeve to form the telescopic wheel. One end of the telescopic wheel is welded to the stamping pipeline, and the other end is fixed with a universal roller.

[0013] The passivation component includes a square white steel trough, which is placed upright with its notch facing outward. The white steel trough is bent as a whole to form an arc-shaped white steel trough. The notch of the white steel trough is filled with acid-resistant sponge. A first support plate is fixed on each side of the white steel trough, and a support rod is fixed on each upper and lower end of the first support plate. The support plate is twistedly connected to the support rod, and the other end of the support rod is twistedly connected to the second support plate. The second support plate is fixed on the stamping pipeline, the second support plate corresponds to the first support plate, and the two second support plates form an acute angle on the stamping pipeline.

[0014] A plurality of passivation components are arranged at equal intervals along the circumference of the stamping pipeline, and the arc-shaped white steel grooves of the plurality of passivation components enclose a circle.

[0015] The specific pickling passivation method is:

[0016] S1: Adjust the telescopic wheel of the pickling and passivation device and adjust its diameter to φ585 to achieve smooth operation of the pickling and passivation device on the inner surface of the LNG pump tower pipe system.

[0017] S2: One end of the punching pipeline of the pickling and passivation device is closed with a nut plug, and the other side is connected to high-pressure fresh water. The operator uses a rope to drag the device back and forth to thoroughly remove grease and dirt on the inner surface of the LNG pump tower pipe system.

[0018] S3: After cleaning, remove the high-pressure water pipe, connect the high-pressure air pipe, and blow dry the inner surface of the LNG pump tower pipe system.

[0019] S4: After the inner surface of the LNG pump tower piping is cleaned and completely dried, adjust the diameter of the passivation component to φ485, apply 3-5mm passivation paste to the outside of the acid-resistant sponge of the passivation component, and fine-tune the diameter of the passivation component to make the passivation paste tightly connected to the inner surface of the LNG pump tower piping. The operator gently pulls and slowly pulls the pickling passivation device, and repeats this operation many times to apply 3mm passivation paste to the inner surface of the LNG pump tower piping to form a dense oxide film. The passivation time is 20 minutes.

[0020] S5: After the pickling and passivation is completed, remove the acid-resistant sponge and connect high-pressure fresh water for flushing until the stainless steel surface on the inner surface of the LNG pump tower piping is neutral and there is no residual passivation paste.

[0021] S6: After high-pressure water flushing is completed, remove the high-pressure fresh water pipeline, connect the high-pressure air pipeline, drain all the moisture on the inner surface of the LNG pump tower pipeline, and finally ensure air drying.

[0022] The above-mentioned pickling and passivation method for LNG pump tower piping, further, in step 2, the pressure of the high-pressure fresh water needs to be greater than 0.4Mpa.

[0023] The above-mentioned pickling and passivation method for LNG pump tower piping, further, in step S5, the chloride ion content in the clean water used for flushing shall not exceed 25ppm.

[0024] The above-mentioned pickling and passivation method for LNG pump tower piping system further comprises the two second support plates forming an angle of 40°.

[0025] The above-mentioned pickling and passivation method for LNG pump tower piping, further, has a spacing between the high-pressure nozzle and the telescopic wheel of 75 mm.

[0026] The above-mentioned pickling and passivation method for LNG pump tower pipe system, further, the length of the punched pipeline is 1 meter and the diameter is φ33.4*4.55.

[0027] The above-mentioned pickling and passivation method for LNG pump tower pipe system further comprises 12 telescopic wheels arranged at equal intervals along the circumference of the stamping pipeline.

[0028] The above-mentioned pickling and passivation method for LNG pump tower piping system further comprises the following steps: the spacing between the high-pressure nozzle and the telescopic wheel is 120 mm.

[0029] The above-mentioned pickling and passivation method for LNG pump tower piping system further comprises 7 passivation components, and the 7 passivation components are arranged at equal intervals along the circumference of the stamping pipeline.

[0030] The above-mentioned pickling and passivation method for LNG pump tower pipe system, further, the pickling and passivation device is located inside the LNG pump tower pipe, at the junction of the universal roller and the inner wall of the pipe.

[0031] The LNG pump tower pipe system pickling and passivation device provided by the present invention has an exquisite design and powerful functions, showing many significant technical advantages:

[0032] 1. High-efficiency pickling and passivation capability: The device realizes high-efficiency pickling and passivation operation inside the stainless steel pipeline through carefully designed stamping pipelines, high-pressure nozzles and passivation components. This design ensures that the pickling and passivation process can fully and evenly cover the inner surface of the pipeline, thereby greatly improving the operation efficiency.

[0033] 2. Stable and durable structure: The stamping pipeline is made of high-quality SS316L stainless steel pipe, which has excellent corrosion resistance and strength, ensuring the stability and durability of the device in harsh environments. In addition, the connection method between the various components has also been carefully designed to ensure that the overall structure of the device is stable and reliable.

[0034] 3. Convenient and flexible operation: The design of the telescopic wheel allows the device to be easily dragged inside the pipeline, greatly reducing the labor intensity of the operator. At the same time, the height of the telescopic wheel can be adjusted to ensure the smooth movement of the roller on the inner surface of the pipeline. In addition, the height of the passivation component can also be adjusted by rotating the round steel rod to adapt to pipelines of different diameters, enhancing the flexibility of the device.

[0035] 4. Superior safety performance: The device adopts strict welding and flaw detection technology during the manufacturing process to ensure that the connection between components is firm and reliable, reducing the risk of leakage or breakage during use.

[0036] 5. Strong scalability: The pickling and passivation device provided by the present invention is not only suitable for LNG pump tower piping systems, but can also be improved and expanded according to actual needs and applied to other similar stainless steel piping systems. This scalability gives the device a wider application prospect and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the stamping pipeline structure with a high-pressure nozzle;

[0038] Figure 2 It is a schematic diagram of the structure of a stamping pipeline with a telescopic wheel;

[0039] Figure 3 It is a schematic diagram of the stamping pipeline structure with a passivation component;

[0040] Figure 4 It is a schematic diagram of the working status of the device;

[0041] Among them, 1-stamping pipeline, 2-high-pressure nozzle, 3-universal roller, 4-LNG pump tower pipe system, 5-casing, 6-fixing buckle, 7-round steel rod, 9-white steel trough, 10-first support plate, 11-second support plate, 12-support rod. DETAILED DESCRIPTION

[0042] The present invention will be further described in conjunction with the accompanying drawings.

[0043] The pickling and passivation device has a stainless steel stamping pipeline. The outer surfaces of both ends of the stamping pipeline are provided with twisted wires. A circular fixing buckle is fixed at the root of the twisted wire. The stamping pipeline is provided with a high-pressure nozzle and a telescopic wheel in sequence from the circular fixing buckle to the inside. A passivation component is fixed in the middle of the stamping pipeline.

[0044] 12 high-pressure nozzles are arranged at equal intervals along the circumference of the stamping pipeline. The telescopic wheel is composed of two sleeves and a round steel rod. Both ends of the round rod are connected with a sleeve by twisted wire to form the telescopic wheel. One end of the telescopic wheel is welded to the stamping pipeline, and a universal roller is fixed to the other end.

[0045] The passivation component includes a square white steel trough, which is placed upright with its notch facing outward. The white steel trough is bent as a whole to form an arc-shaped white steel trough. The notch of the white steel trough is filled with acid-resistant sponge. A first support plate is fixed on each side of the white steel trough, and a support rod is fixed at each upper and lower end of the first support plate. The support plate is twistedly connected to the support rod, and the other end of the support rod is twistedly connected to the second support plate. The second support plate is fixed on the stamping pipeline, the second support plate corresponds to the first support plate, and the two second support plates form a 40° angle on the stamping pipeline.

[0046] The seven passivation components are arranged at equal intervals along the circumference of the stamping pipeline, and the arc-shaped white steel grooves of the seven passivation components enclose a circle.

[0047] The stamping pipeline is the core component of the pickling and passivation device, which is mainly used for structural support and the delivery of high-pressure water and gas. The stamping pipeline is made of SS316L stainless steel pipe with a length of 1 meter and a diameter of φ33.4*4.55. The two ends of the wire are twisted with M30*1.5. The argon arc welding circular fixing buckle is 30mm near the twisted wire end. During the construction process, the operator drags the device.

[0048] The high-pressure nozzle is welded on the stamping pipeline, 75mm away from the circular fixing buckle. The high-pressure nozzle is made of SS316L stainless steel round steel bar with a size of φ3*8, and a φ1.5mm hole is drilled in the center of the nozzle. First, φ2 holes are evenly drilled on the outer wall of both sides of the stamping pipeline 75mm away from the circular fixing buckle, for a total of 12 holes. Then, the high-pressure nozzle is welded to the high-pressure pipe on both sides of the stamping pipeline using an argon arc welder. After welding, 100% PT flaw detection is performed to flush or dry the inner surface of the pipeline during work.

[0049] The telescopic wheel is welded on the stamping pipeline, located 120mm from the high-pressure nozzle. The telescopic wheel consists of two φ13.2*2.24*150 sleeves and φ12*290 round steel bars. The inner side of the sleeve is matched with the round steel bar twisted wire M10*1. A φ10 spherical universal roller is installed on the outermost side of the sleeve. All materials are SS316L stainless steel. First, 12 sleeves are welded on both sides of the stamping pipeline using a submerged arc welding machine at a distance of 120mm from the high-pressure nozzle as the telescopic wheel support. Then install the round steel bar in the sleeve, and install another sleeve on the outside as the leg adjustment device. Finally, install the universal roller on the outer sleeve to adjust the leg height to ensure that the roller moves smoothly on the inner surface.

[0050] The passivation component is welded at the center of the stamping pipeline. The size of the first support plate and the second support plate is 10*100*200, the size of the support rod is φ8*190, and the size of the white steel groove is 1*200*30. Drill a φ5 hole in the thickness direction of the second support plate, match the φ8*190 round steel rod with the second support plate twisted wire M6*1, and install another two first support plates at the other end of the φ8*190 round steel rod, which also needs to be matched with the twisted wire M6*1. Pay attention to the direction of the twisted wire so that the support plates can be extended and retracted at the same time when the round steel rod is rotated. Weld a 1*200*30 white steel groove at the position of the first support plate, and install an acid-resistant sponge on the groove. Rotate the round steel rod and adjust the height of the legs to ensure that the passivation paste can evenly cover the inner surface of the working pipeline during the application of the passivation paste. Example

[0051] A 175,000 cubic meter LNG ship pump tower weighs 30 tons and is made of 304L and 316L stainless steel. The pump pressure pipe is required to be pickled and passivated after welding.

[0052] 1.Safety work:

[0053] a. In view of the strong acidity and corrosiveness of the pickling passivation paste, construction workers must strictly follow the instructions, wear necessary labor protection supplies such as rubber gloves, rubber shoes, gas masks and protective glasses throughout the process, and ensure good ventilation;

[0054] b. During the construction process, it is strictly forbidden to have skin contact with the pickling passivation paste. If accidental contact occurs, rinse immediately with plenty of running water and go to the hospital for treatment;

[0055] c. The application of pickling passivation paste needs to be contained and stirred in acid-resistant plastic products. At the same time, the pickling passivation paste should be stored away from heat sources;

[0056] d. Waste and waste liquid generated during the construction process should be collected and handed over to qualified hazardous waste treatment units for treatment. It is strictly prohibited to discard or dispose of them improperly.

[0057] 2. Construction preparation:

[0058] a. Before starting construction, the following preparations need to be made:

[0059] b. All construction workers must receive training before taking up their posts;

[0060] c. Construction workers must wear personal protective equipment as required;

[0061] d. The flux and slag inclusions at the weld of stainless steel pipelines should be cleaned with stainless steel wire brushes, stainless steel shovels and other tools;

[0062] e. Ensure that there is sufficient running clean water on site.

[0063] 3. Pickling passivation:

[0064] a. Adjust the telescopic wheel of the pickling and passivation device and adjust its diameter to φ585 to achieve smooth operation of the pickling and passivation device on the inner surface of the emergency pump pipe.

[0065] b. Use a nut to close one end of the punching pipeline of the pickling and passivation device, and connect the other side to high-pressure fresh water. The pressure of the high-pressure water must be greater than 0.4Mpa. The operator uses a rope to drag the device back and forth to thoroughly remove grease, dirt, etc. on the inner surface of the emergency pump pipe.

[0066] c. After cleaning, remove the high-pressure water pipe, connect the high-pressure air pipe, and blow dry the inner surface of the emergency pump pipe.

[0067] d. After the inner surface of the emergency pump pipe is cleaned and completely dried, adjust the pickling support diameter to φ485. Fix an acid-resistant sponge with a thickness of 50 on the outside of the pickling support, and apply 3-5mm passivation paste on the outside of the sponge. Fine-tune the pickling support diameter so that the passivation paste is tightly connected to the inner surface of the emergency pump pipe. The operator gently pulls the pickling passivation device and repeats this operation many times to apply 3mm passivation paste on the inner surface of the emergency pump pipe to form a dense oxide film. The passivation time is 20 minutes.

[0068] e. After the pickling and passivation is completed, remove the sponge and connect high-pressure fresh water for flushing until the stainless steel surface on the inner surface of the emergency pump pipe is neutral and there is no residual passivation paste. Note that the chloride ion content in the clean water used for flushing should not exceed 25ppm to prevent chloride ions from corroding the passivation film.

[0069] f. After high-pressure water flushing is completed, remove the high-pressure fresh water pipeline, connect the high-pressure air pipeline, drain all the moisture on the inner surface of the emergency pump pipe, and finally ensure that it is air-dried.

[0070] 4.Quality inspection:

[0071] a. Appearance inspection: After the stainless steel pipeline is flushed and dried, a visual inspection is carried out. The inner surface of the emergency pump tube should be uniform silver-white, without obvious uneven color spots, and the passivation film should remain continuous and uniform.

[0072] b. Residual passivation paste inspection: After high-pressure clean water flushing, there should be no residual passivation paste on the inner surface of the emergency pump tube. Use pH test paper to test the surface pH. If the test result is neutral (pH=7), it means that the flushing is qualified and there is no residual passivation paste.

[0073] c. Blue spot detection: In the quality control process of pickling and passivation of emergency pump pipes, blue spot detection is a key step, which aims to accurately test the integrity of the passivation film. The operation method is: attach the soaked filter paper to the inner surface of the emergency pump pipe, and observe whether blue spots appear within 30 seconds. If blue spots appear, it means that there are ferrous ions on the surface of the pipeline that react with the solution to form blue precipitates, the passivation film is incomplete, the pickling and passivation are unqualified, and rework is required until no blue spots are produced. Blue spot detection should be carried out after the surface of the pipeline is basically dry. After the test is qualified, the surface solution should be rinsed with clean water, air-dried, and then subsequent coating construction can be carried out.

[0074] 5. Finished product protection

[0075] After the pickling and passivation are qualified, the emergency pump pipe must pay great attention to protective measures during the subsequent transportation and coating construction to prevent damage to the surface passivation film caused by bumps, scratches, etc. Example

[0076] A pickling and passivation device for LNG pump tower pipe system, which is used for pickling and passivation of the inner surface of the 175,000 cubic meter series LNG ship pump tower discharge pipe. The discharge pipe with a diameter of φ406*12 and a length of 28 meters and made of SS316L has been efficiently pickled and passivated.

[0077] Safety work, construction preparation, quality inspection, and finished product protection are consistent with those described in Example 1.

[0078] The specific pickling passivation method is as follows:

[0079] a. Use nuts to connect 2 sets of pickling and passivation devices to the stamping pipeline.

[0080] b. Adjust the telescopic wheel of the pickling and passivation device and adjust its diameter to φ380 to ensure that the device runs smoothly on the inner surface of the emergency pump pipe.

[0081] c. Use a nut to seal one end of the pressurized pipeline of a set of pickling and passivation equipment, and connect the other end to high-pressure fresh water. The pressure of high-pressure water should be greater than 0.4Mpa, and the operator should use a rope to drag the device back and forth to thoroughly remove grease, dirt, etc. on the inner surface of the discharge pipe.

[0082] d. After cleaning, remove the high-pressure water pipe, replace it with a high-pressure air pipe, and blow dry the inner surface of the emergency pump pipe.

[0083] e. After the inner surface of the emergency discharge pipe is cleaned and completely dried, adjust the pickling support diameter to φ280. Fix an acid-resistant sponge with a thickness of 50 on the outside of the pickling support, and apply 3-5mm passivation paste on the outside of the sponge. Fine-tune the pickling support diameter so that the passivation paste is tightly connected to the inner surface of the emergency pump pipe. The operator gently pulls the pickling passivation device and repeats this operation many times to apply 3mm passivation paste on the inner surface of the emergency pump pipe to form a dense oxide film. The passivation time is 20 minutes.

[0084] f. After the pickling and passivation is completed, remove the sponge and connect high-pressure fresh water for flushing until the stainless steel surface on the inner surface of the discharge pipe is neutral and there is no residual passivation paste. Note that the chloride ion content in the clean water used for flushing should not exceed 25ppm to prevent chloride ions from corroding the passivation film.

[0085] g. After high-pressure water flushing is completed, remove the high-pressure fresh water pipeline, connect the high-pressure air pipeline, drain all the moisture on the inner surface of the emergency pump pipe, and finally ensure that it is air-dried.

[0086] The present invention combines pickling and passivation in one by optimizing the design and function of each component, and the pickling and passivation device performs efficient pickling and passivation operations in stainless steel pipelines. Future research can further improve the performance of the platform and expand its application range.

Claims

1. A method for pickling and passivation of LNG pump tower piping, characterized in that: The pickling and passivation device has a stainless steel stamping pipeline. The outer surfaces of both ends of the stamping pipeline are provided with twisted wires. A round fixing buckle is fixed at the root of the twisted wire. The stamping pipeline is provided with a high-pressure nozzle and a telescopic wheel in sequence from the round fixing buckle to the inside. A passivation component is fixed in the middle of the stamping pipeline. Multiple high-pressure nozzles are arranged at equal intervals along the circumference of the stamping pipeline. The telescopic wheel is composed of two sleeves and a round steel rod. Both ends of the round rod are twisted and connected with a sleeve to form a telescopic wheel. One end of the telescopic wheel is welded to the stamping pipeline, and the other end is fixed with a universal roller. The passivation component includes a square white steel trough, which is placed upright with its notch facing outward, and the white steel trough is bent as a whole to form an arc-shaped white steel trough, and the notch of the white steel trough is filled with acid-resistant sponge, and a first support plate is fixed on each side of the white steel trough, and a support rod is fixed on each upper and lower ends of the first support plate, and the support plate is connected to the support rod by twisted wire, and the other end of the support rod is connected to the second support plate by twisted wire, and the second support plate is fixed on the stamping pipeline, and the second support plate corresponds to the first support plate, and the two second support plates form an acute angle on the stamping pipeline; A plurality of passivation components are arranged at equal intervals along the circumference of the stamping pipeline, and the arc-shaped white steel grooves of the plurality of passivation components enclose a circle; The specific pickling passivation method is: S1: Adjust the telescopic wheel of the pickling and passivation device to adjust its diameter to φ585 to achieve smooth operation of the pickling and passivation device on the inner surface of the LNG pump tower pipe system; S2: One end of the punching pipeline of the pickling and passivation device is closed with a nut plug, and the other side is connected to high-pressure fresh water. The operator uses a rope to drag the device back and forth to thoroughly remove grease and dirt on the inner surface of the LNG pump tower pipe system; S3: After cleaning, remove the high-pressure water pipe, connect the high-pressure air pipe, and blow dry the inner surface of the LNG pump tower pipe system; S4: After the inner surface of the LNG pump tower pipe system is cleaned and completely dried, adjust the diameter of the passivation component to φ485, apply 3-5mm passivation paste on the outside of the acid-resistant sponge of the passivation component, and fine-tune the diameter of the passivation component to make the passivation paste tightly connected to the inner surface of the LNG pump tower pipe system. The operator gently pulls and slowly pulls the pickling passivation device, repeats this operation many times, and applies 3mm passivation paste on the inner surface of the LNG pump tower pipe system to form a dense oxide film. The passivation time is 20 minutes; S5: After the pickling and passivation is completed, the acid-resistant sponge is removed and high-pressure fresh water is connected for flushing until the stainless steel surface on the inner surface of the LNG pump tower pipe system is neutral and there is no residual passivation paste; S6: After high-pressure water flushing is completed, remove the high-pressure fresh water pipeline, connect the high-pressure air pipeline, drain all the moisture on the inner surface of the LNG pump tower pipeline, and finally ensure air drying.

2. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: In step 2, the pressure of the high-pressure fresh water must be greater than 0.4Mpa.

3. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: In step S5, the chloride ion content in the clean water used for rinsing shall not exceed 25 ppm.

4. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: The two second support plates form an angle of 40°.

5. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: The distance between the high-pressure nozzle and the round fixing buckle is 75mm.

6. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: The length of the stamping pipeline is 1 meter and the diameter is φ33.4*4.

55.

7. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: The 12 telescopic wheels are arranged at equal intervals along the circumference of the stamping pipeline.

8. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: The distance between the high-pressure nozzle and the telescopic wheel is 120mm.

9. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: There are 7 passivation components, and the 7 passivation components are arranged at equal intervals along the circumference of the stamping pipeline.

10. A method for pickling and passivation of LNG pump tower piping according to claim 1, characterized in that: The pickling and passivation device is located inside the LNG pump tower pipe, where the universal roller connects to the inner wall of the pipe.

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