Multi-layer spray insulation structure of LNG liquid cargo containment system and construction method thereof

Abstract

The application discloses a multilayer spraying insulation structure of an LNG liquid cargo containment system and a construction method thereof. The structure comprises a prefabricated base component, three layers of sprayed polyurethane foam, two layers of crack arrest layers and a polyurea outer protective layer. The prefabricated plate is installed by welding bolts first, then the foam is sprayed layer by layer, the crack arrest layers are laid at 70mm and 190mm, and finally the polyurea is sprayed. Through the multilayer structure and the crack arrest layer design, the anti-cracking performance of the insulation system under the deep cooling condition is significantly enhanced, the thermal conductivity is as low as 0.023 W / (m*K), meanwhile, the construction efficiency is high, the protection performance is comprehensive, the quality is controllable and the like, and the application is suitable for the insulation construction of LNG ships and storage tanks.

Description

Technical Field

[0001] This invention relates to the field of liquefied natural gas storage and transportation technology, and more specifically, to a multi-layer sprayed insulation structure and its construction method for use in LNG ship or tank liquid cargo containment systems. Background Technology

[0002] Liquefied natural gas (LNG) is stored at temperatures as low as -162°C under normal pressure, which places extremely high demands on the insulation performance of the cargo containment system. The main objective of the insulation system is to reduce heat ingress to minimize evaporation, while protecting the hull structure in cryogenic conditions, preventing brittle fracture of the steel structure due to low temperatures, and reducing condensation and ice formation.

[0003] Existing LNG storage tank insulation technologies mainly fall into two categories: prefabricated insulation panel installation and on-site spraying insulation. While the prefabricated panel method offers quality control, it presents challenges in constructing on complex curved surfaces, resulting in numerous seams that lead to significant cold bridging and low material utilization. On-site spraying, although capable of creating a seamless insulation layer, is prone to cracking under cryogenic conditions due to temperature stress, and thickness control is difficult, especially when spraying vertical surfaces and the top, where sagging or uneven thickness can easily occur.

[0004] Furthermore, existing technologies lack systematic solutions for releasing internal stress in the insulation layer, blocking moisture, and providing external mechanical protection, resulting in limited service life of the insulation system and high maintenance frequency. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-layer sprayed insulation structure for LNG cargo containment systems and its construction method. This structure has excellent thermal insulation performance, crack resistance and construction efficiency, and can effectively extend the service life of ships.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a multi-layer sprayed insulation structure for an LNG cargo containment system, the structure comprising, from the inside out: The prefabricated base layer assembly includes multiple bolts welded to the surface of the tank, support members sleeved on the bolts, and prefabricated foam boards fixed to the support members by nuts and washers. The first layer of sprayed polyurethane foam, 20mm thick, completely covers the nut; The first crack-resistant layer is laid on the surface of the first sprayed polyurethane foam layer, located at a total thickness of 70mm. The second layer of sprayed polyurethane foam, with a thickness of 120mm, is sprayed on the surface of the first crack-resistant layer, making the total thickness reach 190mm. The second crack-resistant layer is laid on the surface of the second sprayed polyurethane foam layer; The third layer of sprayed polyurethane foam, with a thickness of 130mm, is sprayed on the surface of the second crack-resistant layer, bringing the total thickness to 320mm. The outer protective layer is a polyurea coating sprayed onto the surface of the third layer of sprayed polyurethane foam, with a thickness of 2±0.4mm.

[0007] Furthermore, the density of the prefabricated foam board is 40 kg / m³, the thermal conductivity of the sprayed polyurethane foam is ≤0.023 W / (m·K), and the closed-cell rate is ≥95%.

[0008] Furthermore, the bolt is an M8*80 bolt, and it must be welded perpendicular to the surface of the tank.

[0009] Furthermore, the crack-resistant layer is a glass fiber mesh or a polymer reinforcement layer, used to enhance the overall strength of the insulation system and prevent cracking under cryogenic conditions.

[0010] Furthermore, the outer protective layer is a black polyurea elastomer, which is elastic and has high strength, and is used to block moisture and resist mechanical impact.

[0011] Secondly, the present invention provides a construction method for a multi-layer sprayed insulation structure of an LNG cargo containment system, comprising the following steps: Step 1: Surface pretreatment and layout positioning: Sandblast the surface of the tank to ensure the paint is fully cured, clean the surface and submit for inspection; control the paint thickness to ≤100μm; according to the welding bolt point drawing, mark the positioning lines on the surface of the tank to determine the bolt positions.

[0012] Step 2: Welding bolts: According to the positioning marks, weld the M8*80 bolts vertically to the surface of the tank, ensuring the perpendicularity of the bolts to the surface of the tank.

[0013] Step 3, Precast Panel Installation: According to the welding bolt point drawing, the support is fitted onto the bolts and the bolts are centered; the precast foam board is placed on the support and fixed with nuts and washers, with the precast foam board in a free state between it and the tank body.

[0014] Step 4, First layer of sprayed foam construction: Use high-pressure spraying equipment to mix the polyhydroxy compound and isocyanate in proportion, and spray it through the spray gun under the set temperature and pressure; the spray thickness is 20mm, ensuring that the nut is completely covered; during the spraying process, keep the spray gun perpendicular to the spraying surface.

[0015] Step 5: Laying the first crack-stopping layer: When the insulation layer reaches a total thickness of 70mm, lay the first crack-stopping layer, which completely covers the surface of the first layer of sprayed foam.

[0016] Step 6: Apply the second layer of sprayed foam: Hold the spray gun at a 90-degree angle to the surface of the crack arrestor layer and spray polyurethane foam evenly to a thickness of 120mm, so that the total thickness reaches 190mm; avoid the formation of voids during the spraying process.

[0017] Step 7: Laying the second crack-resistant layer: When the insulation layer reaches a total thickness of 190mm, lay the second crack-resistant layer.

[0018] Step 8, Third layer of sprayed foam application: Keep the spray gun at a 90-degree angle to the surface of the crack arrestor layer and spray polyurethane foam evenly to a thickness of 130mm, so that the total thickness reaches 320mm; the final surface flatness is controlled within the range of -5mm to +30mm / square meter; all thickness and quality data are recorded to achieve traceability.

[0019] Step 9: Construction of the outer protective layer: A polyurea protective layer is sprayed onto the surface of the third layer of sprayed foam, with a thickness controlled at 2±0.4mm, forming an outer protective layer that is moisture-proof and resistant to mechanical impact.

[0020] Furthermore, the environmental requirements for the spray foam application are: relative humidity ≤75%, ambient temperature ≥10℃; the spraying machine transports materials through a pipeline of up to 90 meters, is continuously monitored during the spraying process, and automatically stops when a fault occurs.

[0021] Furthermore, the construction environment requirements for the polyurea protective layer are: relative humidity ≤80% and ambient temperature ≥10℃.

[0022] Furthermore, it also includes a foam thickness testing step: place a foam block of standard height on one side of the insulating foam, draw a horizontal straight line from the top of the foam block, and determine whether the thickness of the sprayed foam meets the requirements by measuring the height of the foam block and the distance from the horizontal line to the surface of the sprayed foam.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a multi-layer spraying structure, which is seamless and has a thermal conductivity as low as 0.023W / (m·K), which can effectively reduce heat entry and reduce LNG evaporation rate.

[0024] (2) By setting crack-stopping layers at 70mm and 190mm thickness positions, the present invention significantly enhances the overall strength of the insulation system under cryogenic conditions and effectively prevents cracking caused by temperature stress.

[0025] (3) The present invention adopts a combination of prefabricated plate and spraying. First, the bolt part is accurately positioned and protected by the prefabricated plate, and then the whole seamless insulation is achieved by multi-layer spraying. The material utilization rate and labor efficiency are high.

[0026] (4) The outer polyurea protective layer of the multi-layer sprayed insulation structure of the present invention has good elasticity and strength, which can effectively block water vapor from entering and resist mechanical impact. Furthermore, the surface skin can further enhance the strength of the system.

[0027] (5) The present invention ensures thickness uniformity through layer thickness control and standard block detection method; the whole process is recorded to achieve quality traceability.

[0028] (6) This invention is applicable to the insulation construction of various cryogenic storage facilities such as LNG ship cargo tanks and LNG storage tanks, and is especially suitable for high-requirement scenarios such as Type B independent cargo tanks. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the layered structure of the multilayer sprayed insulation structure of the present invention. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example

[0031] like Figure 1 As shown, this embodiment provides a multi-layer sprayed insulation structure and its construction method for an LNG cargo containment system, which is applied to the cargo tank of a 170,000 cubic meter LNG carrier.

[0032] The materials are prepared as follows: Polyurethane foam raw materials: polyhydroxy compounds (combined polyethers) and isocyanates (MDI), mixed using an automated high-pressure foaming machine; prefabricated foam boards: density 40kg / m³, dimensions prefabricated according to bolt locations; crack arresting layer: fiberglass mesh; outer protective layer: sprayed polyurea elastomer.

[0033] The multi-layer sprayed insulation structure of the LNG cargo containment system in this embodiment includes, from the inside out: The prefabricated base layer component includes multiple bolts welded to the surface of the tank, a support member 1 (high-density pad) sleeved outside the bolts, and a prefabricated foam board 3 fixed to the support member by nuts and washers 2.

[0034] The first layer of sprayed polyurethane foam 4, with a thickness of 20mm, completely covers the nut.

[0035] The first crack-resistant layer 5 is laid on the surface of the first sprayed polyurethane foam layer 4, located at a total thickness of 70mm.

[0036] The second layer of sprayed polyurethane foam 6, with a thickness of 120mm, is sprayed onto the surface of the first crack-resistant layer 5, bringing the total thickness to 190mm.

[0037] The second crack-resistant layer 7 is laid on the surface of the second sprayed polyurethane foam layer 6.

[0038] The third layer of sprayed polyurethane foam, 8, is 130mm thick and is sprayed onto the surface of the second crack-resistant layer, 7, bringing the total thickness to 320mm.

[0039] The outer protective layer 9 is a polyurea coating sprayed onto the surface of the third layer of sprayed polyurethane foam 8, with a thickness of 2±0.4mm.

[0040] The construction steps for the multi-layer sprayed insulation structure of the LNG cargo containment system in this embodiment are as follows: Step 1: Surface pretreatment: Sandblast the inner wall of the tank to remove rust to Sa2.5 grade, control the epoxy paint film thickness to 80-100μm, and clean the surface after complete curing and inspection.

[0041] Step 2, Layout and Bolt Welding: Lay out the layout lines on the surface of the tank according to the design drawings, and weld M8*80 bolts with a verticality deviation of ≤1°.

[0042] Step 3: Precast panel installation: Install the support components, ensuring the bolts are centered; place the precast foam board on the support components, tighten with M8 nuts and washers, controlling the torque to 15-20 N·m, ensuring the precast foam board is suspended from the tank.

[0043] Step 4, First coat spraying: Ambient temperature 18℃, relative humidity 65%, spraying pressure 12MPa, material temperature 35℃; the first coat thickness is 20mm, completely covering the nut.

[0044] Step 5, First crack-resistant layer: Lay fiberglass mesh at a total thickness of 70mm, with an overlap width of 50mm.

[0045] Step 6, Second coat spraying: The spray gun is perpendicular to the crack arrester layer, and the spray thickness is 120mm, with a total thickness of 190mm.

[0046] Step 7, Second crack-resistant layer: Lay a second layer of fiberglass mesh at a position of 190mm.

[0047] Step 8, Third layer spraying: Spraying thickness 130mm, total thickness 320mm; Flatness test: -3mm to +20mm / ㎡.

[0048] Step 9, Outer Protective Layer: Spray a 2.1mm layer of polyurea, ensuring a uniform appearance without pinholes.

[0049] The performance of this embodiment was tested as follows: thermal conductivity: 0.0228 W / (m·K); closed-cell ratio: 96%; compressive strength: 0.32MPa; water vapor transmission rate: <2.5ng / (Pa·s·m); after 10 simulated deep cryogenic cycles (-196℃←→room temperature), there was no cracking or delamination. Example

[0050] This embodiment is basically the same as embodiment 1, except that the crack-stopping layer uses polyester mesh cloth, and a surface finishing process is added after the third layer is sprayed. A special planing tool is used to treat the high points on the surface so that the flatness reaches -2mm to +15mm / ㎡.

[0051] Comparative Example 1 The installation method uses precast panels without multi-layer spraying. Results show that a significant cold bridging effect occurs at the joints, the overall thermal conductivity is 0.032 W / (m·K), and the construction period is extended by 30%.

[0052] Comparative Example 2 A single-layer, one-time spray coating was applied to a thickness of 320 mm without a crack-arresting layer. Results showed that during the cryogenic cycling test, multiple through-cracks appeared after the fifth cycle, resulting in a 40% decrease in insulation performance.

[0053] The thickness detection method of this invention is as follows: A foam block of standard height is placed on one side of the insulating foam. A horizontal straight line is drawn from the top of the foam block. By measuring the height of the foam block and the distance from the horizontal line to the surface of the sprayed foam, it is determined whether the sprayed foam meets the requirements. This method can quickly detect the thickness uniformity of large-area spraying, with a detection frequency of no less than 3 measuring points per 10㎡.

[0054] The quality control of this invention is as follows: continuous monitoring of the spraying process, automatic recording of pressure, temperature and flow parameters; random inspection of each layer thickness using an ultrasonic thickness gauge, with a sampling rate of ≥30%; detection of pinholes in the outer protective layer using an electric spark leak detector at a voltage of 5kV; and archiving of all records to achieve full-process traceability.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-layer sprayed insulation structure for an LNG cargo containment system, characterized in that: The structure, from the inside out, comprises: The prefabricated base layer assembly includes multiple bolts welded to the surface of the tank, support members sleeved on the bolts, and prefabricated foam boards fixed to the support members by nuts and washers. The first layer of sprayed polyurethane foam, 20mm thick, completely covers the nut; The first crack-resistant layer is laid on the surface of the first sprayed polyurethane foam layer, located at a total thickness of 70mm. The second layer of sprayed polyurethane foam, with a thickness of 120mm, is sprayed on the surface of the first crack-resistant layer, making the total thickness reach 190mm. The second crack-resistant layer is laid on the surface of the second sprayed polyurethane foam layer; The third layer of sprayed polyurethane foam, with a thickness of 130mm, is sprayed on the surface of the second crack-resistant layer, bringing the total thickness to 320mm. The outer protective layer is a polyurea coating sprayed onto the surface of the third layer of sprayed polyurethane foam, with a thickness of 2±0.4mm.

2. The multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 1, characterized in that: The prefabricated foam board has a density of 40 kg / m³, and the sprayed polyurethane foam has a thermal conductivity of ≤0.023 W / (m·K) and a closed-cell rate of ≥95%.

3. The multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 1, characterized in that: The crack-resistant layer is a glass fiber mesh or a polymer-reinforced layer.

4. A construction method for a multi-layer sprayed insulation structure of an LNG cargo containment system, characterized in that: Includes the following steps: Step 1: Surface pretreatment and layout positioning: Sandblast the surface of the tank to ensure the paint is fully cured, clean the surface and submit for inspection; control the paint thickness to ≤100μm; according to the welding bolt point drawing, mark the positioning lines on the surface of the tank to determine the bolt positions; Step 2: Welding bolts: According to the positioning marks, weld the M8*80 bolts vertically to the surface of the tank; Step 3, Precast Panel Installation: According to the welding bolt point drawing, the support is fitted onto the bolts and the bolts are centered; the precast foam board is placed on the support and fixed with nuts and washers, with the precast foam board in a free state between it and the tank body; Step 4, First layer of sprayed foam application: Using high-pressure spraying equipment, mix the polyhydroxy compound and isocyanate in the specified proportions, and spray them through a spray gun under the set temperature and pressure; the spray thickness is 20mm, ensuring that the nuts are completely covered; Step 5: Laying the first crack-stopping layer: When the insulation layer has been constructed to a total thickness of 70mm, lay the first crack-stopping layer, which completely covers the surface of the first layer of sprayed foam. Step 6, Second layer of sprayed foam application: Spray polyurethane foam evenly to a thickness of 120mm, making the total thickness 190mm; Step 7: Laying the second crack-resistant layer: When the insulation layer reaches a total thickness of 190mm, lay the second crack-resistant layer. Step 8, Third layer of sprayed foam construction: Spray polyurethane foam to a thickness of 130mm, making the total thickness 320mm; Step 9: Construction of the outer protective layer: Apply a polyurea protective layer to the surface of the third layer of sprayed foam, with a thickness controlled at 2±0.4mm, to form an outer protective layer that is moisture-proof and resistant to mechanical impact.

5. The construction method of the multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 4, characterized in that: The environmental requirements for the sprayed foam application are: relative humidity ≤75% and ambient temperature ≥10℃; the environmental requirements for the polyurea protective layer application are: relative humidity ≤80% and ambient temperature ≥10℃.

6. The construction method of the multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 4, characterized in that: The bolts are M8*80, and the perpendicularity deviation from the tank surface must be ≤1° during welding.

7. The construction method of the multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 4, characterized in that: During the fourth, sixth, and eighth steps of the spraying process, the spray gun is kept at a 90-degree angle perpendicular to the spraying surface.

8. The construction method of the multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 4, characterized in that: After the eighth step is completed, the final surface flatness is controlled within the range of -5mm to +30mm / square meter.

9. The construction method of the multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 4, characterized in that: It also includes a foam thickness testing step: place a foam block of standard height on one side of the insulating foam, draw a horizontal straight line from the top of the foam block, and determine whether the thickness of the sprayed foam meets the requirements by measuring the height of the foam block and the distance from the horizontal line to the surface of the sprayed foam.

10. The construction method of the multi-layer sprayed insulation structure of the LNG cargo containment system according to claim 4, characterized in that: The equipment is continuously monitored during the spraying process and automatically shuts down in case of malfunction; all thickness and quality data are recorded for traceability.

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