Cold insulation pipe elbow construction method, foaming agent generating device and device use method

Abstract

The application discloses a cold-preservation pipeline elbow construction method, a foaming agent generating device and a device using method, and comprises a gas conveying straight pipe for conveying LNG, a gas conveying elbow pipe, a protection straight pipe arranged outside the gas conveying straight pipe and a protection elbow pipe arranged outside the gas conveying elbow pipe, and the protection elbow pipe comprises a plurality of elbow metal protection layers, and the specific steps are as follows: first, the protection elbow pipe comprising the plurality of elbow metal protection layers is manufactured and assembled; then, the protection elbow pipe is holed through a hole opener; after the hole is arranged with an embedded rubber blocking plate, polyurethane black and white material mixed solution is injected; after the polyurethane black and white material mixed solution foaming is completed, a rivet is used to fix a metal disc at the hole. The application shortens the cold-preservation pipeline elbow cold-preservation construction period of the LNG gasification station. The application reduces the energy loss of the cold-preservation pipeline elbow cold-preservation position of the LNG gasification station, reduces the cold-preservation pipeline elbow cold-preservation layer main material cost of the LNG gasification station, and reduces the labor cost of the LNG gasification station.

Description

Technical Field

[0001] This invention relates to the field of LNG cold-insulated pipeline construction technology, and particularly to a construction method for cold-insulated pipeline elbows, a foaming agent generating device, and a method for using the device. Background Technology

[0002] With the widespread promotion and application of liquefied natural gas (LNG), LNG engineering construction projects are becoming increasingly common.

[0003] Since the temperature of LNG liquid is below -162℃, the process pipelines that are resistant to low temperatures are used for transportation during LNG storage. When transporting LNG fluid, the pressure of the medium inside the pipeline can reach more than 4.0MPa. As the receiving end of natural liquefied gas, the liquid phase and gas phase process pipelines of the LNG regasification station need to ensure the transportation environment and temperature of natural liquefied gas. Therefore, it has high requirements for its external structure and cold insulation effect.

[0004] In existing technologies, the specific construction process for multi-layer cold insulation of stainless steel process pipeline elbows in LNG terminals is as follows:

[0005] 1. Construction preparation → 2. Fabrication of polyurethane / foam glass tube shell → 3. Installation of polyurethane / foam glass tube shell → 4. Fixing with stainless steel straps → 5. Installation of polyurethane / foam glass tube shell → 6. Installation of polyurethane / foam glass tube shell → 7. Fixing with stainless steel straps → 8. Application of inner mastic moisture-proof layer → 9. Installation of fiberglass cloth reinforcement layer → 10. Application of outer mastic moisture-proof layer → 11. Fabrication and installation of metal protective layer → 12. Sealing with glass glue → 13. Inspection and acceptance.

[0006] However, the existing technical construction process is relatively cumbersome and complex, and the construction period is relatively long.

[0007] Firstly, although stainless steel strips were used for fixing twice, it was still impossible to ensure that there were gaps between the layers when installing polyurethane / foam glass tube shells in the multi-layered insulation structure. As a result, freezing and expansion occurred between the polyurethane / foam glass tube shell layers of the insulation layer at the elbow of the LNG gasification station during operation.

[0008] Secondly, the inner insulation layer of the two-layer polyurethane / foam glass pipe shell for the cold insulation of the elbow of the LNG gasification station's cold insulation pipeline needs to be made into shrimp-shaped blocks for splicing and installation, and then the seams need to be glued together with adhesive.

[0009] Moreover, each 360° section requires the fabrication of three polyurethane / foam glass tube shells before they can be spliced ​​and bonded together to form a complete circle.

[0010] In multi-layered polyurethane / foam glass tube shells, each layer needs to be manufactured in this way, which takes a relatively long time.

[0011] In the existing technology, the multi-layer insulation construction of stainless steel process pipeline elbows in LNG terminals requires a relatively long time. A team of two workers can only complete the installation of four such insulation elbows per day, which is inefficient.

[0012] Third, the use of screws or rivets for connection during the fabrication and installation of the metal protective layer can easily lead to incomplete sealing and energy loss later on. Finally, the fabrication process results in significant waste of the main polyurethane / foam glass tubing material.

[0013] Therefore, how to shorten the insulation period of the elbow of the LNG gasification station's cold insulation pipeline, save main materials, and reduce labor costs has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0014] In view of the above-mentioned deficiencies of the prior art, the present invention provides a construction method for cold-insulated pipeline elbows, a foaming agent generating device, and a method for using the device. The purpose is to shorten the cold-insulation period of cold-insulated pipeline elbows in LNG gasification stations, save main materials, and reduce labor costs.

[0015] To achieve the above objectives, the present invention discloses a method for constructing a cold-insulated pipeline bend, including a gas transmission straight pipe for transporting LNG, a gas transmission bend, and a protective straight pipe and a protective bend disposed outside the gas transmission straight pipe and the gas transmission bend, respectively.

[0016] The protective bend includes multiple bend metal protective layers, and the specific steps are as follows:

[0017] Step 1: Wrap aluminum foil around the outside of the gas delivery bend;

[0018] Step 2: Fabricate multiple metal protective layers for the elbows;

[0019] Step 3: Apply a first coat of mastic grease to the inner surface of the metal protective layer of each elbow;

[0020] Step 4: Before the first coat of horseshoe oil dries, attach fiberglass cloth as a reinforcing layer to the inner surface of the first coat of horseshoe oil.

[0021] Step 5: Apply a second coat of horseshoe oil immediately after each piece of the glued fiberglass cloth has dried;

[0022] Step 6: Install all the metal protective layers of the elbows in sequence to form the protective bend, set outside the gas transmission bend, and connect one end of the protective bend to the protective straight pipe;

[0023] Step 7: Secure the elbows by binding stainless steel straps between every two adjacent metal protective layers.

[0024] Step 8: Seal the space between every two adjacent elbow metal protective layers, and between the straight pipe section and the corresponding elbow metal protective layer, with glass glue;

[0025] Step 9: Use a hole opener to open a hole in the side wall of the metal protective layer of the bend closest to the middle position of the protective bend.

[0026] Step 10: Insert a built-in rubber plug into the protective bend through the opening;

[0027] Step 11: Inject a mixture of polyurethane black and white materials into the protective bend through the opening;

[0028] Step 12: Cover the opening with a metal disc and secure it with a spring clip;

[0029] Step 13: After the polyurethane black and white mixture is foamed, the built-in rubber stopper is pushed against the opening and the metal disc is pushed upward. Then, the metal disc and the built-in rubber stopper are fixed with rivets and sealed with glass sealant.

[0030] Step 15: Inspection and acceptance.

[0031] Preferably, the thickness of the aluminum foil is 0.1 mm.

[0032] Preferably, each application of the horseshoe oil should result in a smooth surface without bubbling.

[0033] Preferably, the fiberglass cloth is of type EWR200-100, with a thickness of 0.2 mm, a width of 20 cm, and a density of 210 g / m³. 2 ;

[0034] Each of the stainless steel strips is 10 mm wide;

[0035] The silicone sealant is 704 waterproof type, white paste, and has sun protection function;

[0036] The opening size is 5 cm;

[0037] The hole opener is a tungsten carbide drill bit DLX-T6, D=50mm type;

[0038] The polyurethane black and white mixture comprises polyurethane rigid foam polyether and polymeric MDI, and is a brownish-yellow viscous liquid. It is castable, with a milky whitening time of 3-10s, a fiber drawing time of 10-15s, a bulk density of 60kg / m3, a compressive strength of ≥100Kpa, a water absorption rate of ≤g / 100cm3, and a thermal conductivity of ≤0.025W / mk.

[0039] Preferably, the protective bend and the protective straight pipe are fixed together by rivets.

[0040] Preferably, the diameter of the metal disc is 2 cm larger than the diameter of the opening.

[0041] The present invention also provides a foaming agent generating device for the construction method of cold-insulated pipe elbows, wherein the generating device for injecting the polyurethane black and white material mixture includes an air compressor and a pressurized air storage tank thereof.

[0042] On the pressurized air storage tank, near both ends, the motor of the air compressor and a multi-row ball valve are respectively provided, and at the location where the multi-row ball valve is provided, there is a bracket with an openable baffle.

[0043] The multi-row ball valve is located below the bracket and includes multiple ball valves.

[0044] The bracket forms two storage spaces above the multi-row ball valve. The upper layer is equipped with a graduated, sealed, transparent mixing tank for black and white materials, as well as a stirrer. The lower layer is equipped with a black material tank and a white material tank.

[0045] Both the black material barrel and the white material barrel are equipped with proportional valves at their output ports.

[0046] The sealed transparent mixing tank for black and white materials is equipped with a discharge valve at its outlet.

[0047] The first and third ball valves of the multi-row ball valve are used to control the two air inlet booster pipes between the pressurized air storage tank and the black material barrel and the white material barrel, respectively, and the second ball valve is used to control the air inlet booster pipe between the pressurized air storage tank and the sealed transparent black and white material mixing tank.

[0048] Preferably, the pressurized air storage tank is provided with multiple wheels underneath, and the support frame is provided with a trolley handle on the side;

[0049] The motor is equipped with a metal protective cover.

[0050] The mixer is a rechargeable mixer.

[0051] This invention also provides a method for using the foaming agent generating device, wherein the working process of the device for generating the polyurethane black and white material mixture is as follows:

[0052] Step A: Start the air compressor;

[0053] Step B: After the pressure in the pressurized air storage tank stabilizes, open the first ball valve and the third ball valve to input pressurized air into the black material tank and the white material tank;

[0054] Step C: Open the proportional valves of the black material tank and the white material tank, adjust the output mixing ratio, and transport the polyurethane rigid foam polyether and polymeric MDI in the black material tank and the white material tank to the sealed transparent black and white material mixing tank.

[0055] Step D: Use the stirrer to stir the polyurethane rigid foam polyether and the polymeric MDI in the sealed transparent black and white material mixing tank, and at the same time open the second ball valve to pressurize the sealed transparent black and white material mixing tank by air intake.

[0056] Step E: After uniformly stirring using the stirrer, quickly open the discharge valve and input the polyurethane black and white mixture into the opening through the output pipe.

[0057] Preferably, the stirring time in step D does not exceed 5 seconds.

[0058] The beneficial effects of this invention are:

[0059] The application of this invention shortens the construction cycle of cold insulation for elbows in LNG gasification stations.

[0060] The application of this invention reduces energy loss at the cold insulation location of the elbow in the cold insulation pipeline of the LNG gasification station.

[0061] The application of this invention reduces the cost of the main material for the insulation layer of the elbow of the LNG gasification station's cold-insulated pipeline.

[0062] The application of this invention reduces the labor cost of cold insulation for elbows in LNG gasification stations.

[0063] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0064] Figure 1 A schematic diagram of the structure of the elbow portion of the cold insulation pipe in one embodiment of the present invention is shown.

[0065] Figure 2 This invention is shown Figure 1 Schematic diagram of the cross-sectional structure along the AA direction.

[0066] Figure 3 A schematic diagram of a foaming agent generating device is shown in one embodiment of the present invention. Detailed Implementation

[0067] Example: Figure 1 and Figure 2As shown, the construction method of the cold insulation pipeline elbow includes a gas transmission straight pipe 1 and a gas transmission elbow 2 for transporting LNG, as well as a protective straight pipe 3 set outside the gas transmission straight pipe 1 and a protective elbow 4 set outside the gas transmission elbow 2.

[0068] The protective bend 4 includes multiple bend metal protective layers 5, and the specific steps are as follows:

[0069] Step 1: Wrap aluminum foil 6 around the outside of the gas supply bend 2;

[0070] Step 2: Create multiple metal protective layers for elbows 5;

[0071] Step 3: Apply the first coat of horseshoe grease to the inner surface of the metal protective layer 5 of each bend;

[0072] Step 4: Before the first coat of horsehair oil dries, attach fiberglass cloth as a reinforcing layer to the inner surface of the surface after the first coat of horsehair oil has been applied.

[0073] Step 5: Apply a second coat of horseshoe oil immediately after each piece of fiberglass cloth has dried.

[0074] Step 6: Install all the metal protective layers 5 of the elbows into protective bends 4 in sequence, set them outside the gas transmission bends 2, and connect one end of the protective bends 4 to the protective straight pipes 3.

[0075] Step 7: Secure the metal protective layer 5 of each two adjacent bends by binding stainless steel straps 7 together.

[0076] Step 8: Seal the space between every two adjacent elbow metal protective layers 5, and between the straight pipe section and the corresponding elbow metal protective layer 5, with glass glue.

[0077] Step 9: Use a hole opener to make a hole 8 on the side wall of the metal protective layer 5 of the bend closest to the middle position of the protective bend 4.

[0078] Step 10: Insert the built-in rubber plug 9 into the protective bend 4 through the opening 8;

[0079] Step 11: Inject polyurethane black and white mixture 10 into the protective bend 4 through opening 8;

[0080] Step 12: Cover the opening 8 with a metal disc and secure it with a spring clip 26;

[0081] Step 13: After the polyurethane black and white mixture 10 is foamed, the built-in rubber plug 9 is pushed to the opening 8 and the metal disc is pushed upward. Then, the metal disc and the built-in rubber plug 9 are fixed with rivets and sealed with glass sealant.

[0082] Step 15: Inspection and acceptance.

[0083] The principle of this invention is as follows:

[0084] 1. The use of new polyurethane black and white materials for injection foaming avoids the problem of long construction time caused by the need to manufacture 3 polyurethane / foam glass shells for each 360° section of the inner and outer foam glass insulation layer of the LNG gasification station cold insulation pipeline elbows before splicing and bonding them into a circle.

[0085] 2. In this invention, stainless steel strips 7 are tied between every two adjacent metal protective layers 5 of the elbow for fixation, which avoids the problem of poor sealing and energy loss caused by the use of screws or rivets for drilling and connection in the production and installation of metal protective layers in the original construction method.

[0086] This invention uses a polyurethane black and white material mixture 10 for injection foaming, which results in a denser filling and reduces the loss of main materials.

[0087] In some embodiments, the thickness of the aluminum foil 6 is 0.1 mm.

[0088] In practical applications, the aluminum foil 6 can protect the gas delivery bend 2 and isolate it from the polyurethane black and white mixture 10 injected behind it, which facilitates later maintenance.

[0089] In some embodiments, each coat of horseshoe rosemary must be applied to a smooth surface without bubbling.

[0090] In practical applications, horseshoe oil is a commonly used material; it is a white paste with a density of 1.5-1.7 g / cm³. 3 Water absorption rate ≤ 1.0%; thickness according to specifications and client requirements.

[0091] In some embodiments, the fiberglass cloth is of type EWR200-100, with a thickness of 0.2 mm, a width of 20 cm, and a density of 210 g / m³. 2 ;

[0092] Each stainless steel strip 7 is 10mm wide;

[0093] The silicone sealant is 704 waterproof type, white paste, and has sun protection function;

[0094] The opening size is 5 cm;

[0095] The hole opener is a tungsten carbide drill bit DLX-T6, D=50mm type;

[0096] The polyurethane black and white mixture 10 includes polyurethane rigid foam combined with polyether and polymeric MDI. It is a brownish-yellow viscous liquid, castable, with a milky white time of 3-10s, a fiber drawing time of 10-15s, a density of 60kg / m3, a compressive strength of ≥100Kpa, a water absorption rate of ≤g / 100cm3, and a thermal conductivity of ≤0.025W / mk.

[0097] In some embodiments, the protective bend 4 and the protective straight pipe 3 are fixed together by rivets.

[0098] In some embodiments, the diameter of the metal disc is 2 cm larger than the diameter of the opening 8.

[0099] like Figure 3 As shown, the present invention also provides a foaming agent generating device for the construction method of cold-insulated pipe elbows. The generating device for injecting polyurethane black and white material mixture 10 includes an air compressor and a pressurized air storage tank 11.

[0100] On the pressurized air storage tank 11, near both ends, there are respectively an air compressor motor 12 and a multi-row ball valve 13, and at the location where the multi-row ball valve 13 is located, there is a bracket 14 with an openable baffle.

[0101] The multi-row ball valve 13 is located below the bracket 14 and includes multiple ball valves.

[0102] The bracket 14 forms two storage spaces above the multi-row ball valve 13. The upper layer is equipped with a graduated, sealed, transparent black and white material mixing tank 15 and a stirrer 16. The lower layer is equipped with a black material tank 17 and a white material tank 18.

[0103] Both the black material barrel 17 and the white material barrel 18 are equipped with proportional valves 19 at their output ports;

[0104] The outlet of the sealed transparent black and white material mixing tank 15 is equipped with a discharge valve 20;

[0105] The first and third ball valves of the multi-row ball valve 13 are used to control the two air inlet booster pipes 21 between the pressurized air storage tank 11 and the black material tank 17 and the white material tank 18, respectively. The second ball valve is used to control the air inlet booster pipe 21 between the pressurized air storage tank 11 and the sealed transparent black and white material mixing tank 15.

[0106] In some embodiments, the pressurized air tank 11 is provided with a plurality of wheels 22, and the support 14 is provided with a trolley handle 23 on the side;

[0107] The motor 12 is equipped with a metal protective cover 24;

[0108] The mixer 16 is a rechargeable mixer.

[0109] This invention also provides a method for using the foaming agent generating device. The working process of the device for generating the polyurethane black and white material mixture 10 is as follows:

[0110] Step A: Start the air compressor;

[0111] Step B: Once the pressure inside the pressurized air storage tank 11 is stable, open the first ball valve and the third ball valve to input pressurized air into the black material tank 17 and the white material tank 18.

[0112] Step C: Open the proportional valve 19 of the black material tank 17 and the white material tank 18, adjust the output mixing ratio, and transport the polyurethane rigid foam polyether and polymeric MDI in the black material tank 17 and the white material tank 18 to the sealed transparent black and white material mixing tank 15.

[0113] Step D: Use stirrer 16 to stir the polyurethane rigid foam polyether and polymeric MDI in the sealed transparent black and white material mixing tank 15, and at the same time open the second ball valve to pressurize the sealed transparent black and white material mixing tank 15.

[0114] Step E: After uniformly stirring with a mixer 16, quickly open the discharge valve 20 and input the polyurethane black and white mixture 10 into the opening 8 through the output pipe 25.

[0115] In some embodiments, the stirring time in step D does not exceed 5 seconds.

[0116] Taking the process unit area of ​​an LNG regasification station (receiving station) with two 150m3 storage tanks as an example, there are 82 cold insulation elbows with a pipe diameter of DN80 and a cold insulation thickness of 200mm.

[0117] According to the "Code for Design of Thermal Insulation Engineering for Industrial Equipment and Pipelines" GB50264-2011 and the calculation formula for cold insulation work in the quota:

[0118] Elbow insulation calculation formula:

[0119] V=π×(D+1.033δ)×1.5D×2π×1.033δ×N / B;

[0120] In the formula: D is the pipe diameter, δ is the insulation layer thickness, N is the number of elbows, and B is a fixed value: B=4 for 90° elbows; then:

[0121] V=3.14*(0.08+1.033*0.2*1.5*0.08*2*3.14*1.033*0.2*82 / 4=2.32(m3).

[0122] The required quantity of polyurethane / foam glass tubing for the cold insulation process pipeline elbows is 2.32 * 2 = 4.64 m. 3(Including losses), based on the current domestic Shandong Luyang manufacturer's price of 1700 yuan / m3 for polyurethane / foam glass pipe shells, the cost of polyurethane / foam glass pipe shells for cold insulation pipeline elbows is approximately 4.64 * 1700 = 7888 (yuan).

[0123] The new polyurethane black and white material is used for foaming. The unit price is 15 yuan / kg. 1 kg of polyurethane black and white material can foam 0.15 m3. The insulation work of 82 cold insulation elbows in the process unit area of ​​an LNG gasification station (receiving station) with two 150 m3 storage tanks is 2.32 m3. The total amount of polyurethane black and white material required is 2.32 / 0.15=15.47 (kg). The cost of purchasing 20 kg is 20*15=300 (yuan).

[0124] In summary, by adopting the new construction process, the cost of the main material for the cold insulation layer of the LNG gasification station's cold insulation pipeline elbow in the process unit area of ​​an LNG gasification station (receiving station) with two 150m3 storage tanks can be reduced by approximately 7888 yuan - 300 yuan = 7588 yuan.

[0125] With a scale of 2 150m 3 Taking the process unit area of ​​the LNG vaporization station (receiving station) of the storage tank as an example, there are 82 cold insulation elbows. The original construction process required a labor cost of approximately 82 / 4*400*2=16400 (yuan). After adopting the new construction method, the required labor cost is approximately 82 / 20*400*2=3280 (yuan). The labor cost is reduced by 16400 yuan - 3280 yuan = 13120 yuan.

[0126] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for constructing a cold-insulated pipeline elbow, comprising a straight gas pipeline (1) for transporting LNG, a gas elbow (2), and a protective straight pipeline (3) disposed outside the straight gas pipeline (1) and a protective elbow (4) disposed outside the gas elbow (2); characterized in that, The protective bend (4) includes multiple bend metal protective layers (5), and the specific steps are as follows: Step 1: Wrap aluminum foil (6) around the gas supply bend (2); The thickness of the aluminum foil (6) is 0.1 mm; Step 2: Fabricate multiple metal protective layers for the elbows (5); Step 3: Apply a first coat of horseshoe grease to the inner surface of the metal protective layer (5) of each elbow. Each application of the horseshoe rosemary should result in a smooth surface without any bubbling. Step 4: Before the first coat of horseshoe oil dries, attach fiberglass cloth as a reinforcing layer to the inner surface of the first coat of horseshoe oil. Step 5: Apply a second coat of horseshoe oil immediately after each piece of the glued fiberglass cloth has dried; Step 6: Install all the metal protective layers (5) of the elbows in sequence to form the protective bend (4), set outside the gas transmission bend (2), and connect one end of the protective bend (4) to the protective straight pipe (3); Step 7: Secure the elbow metal protective layer (5) by binding stainless steel strips (7) between each pair of adjacent elbow metal protective layers (5); Step 8: Seal with glass glue between every two adjacent elbow metal protective layers (5) and between the protective straight pipe (3) and the corresponding elbow metal protective layer (5); Step 9: Use a hole opener to open a hole (8) in the side wall of the metal protective layer (5) of the elbow closest to the middle position of the protective bend (4). Step 10: Insert the built-in rubber plug (9) into the protective bend (4) through the opening (8); Step 11: Inject polyurethane black and white mixture (10) into the protective bend (4) through the opening (8). Step 12: Cover the opening (8) with a metal disc and fix it with a spring clip (26); Step 13: After the polyurethane black and white mixture (10) has foamed, the built-in rubber plug (9) is pushed to the opening (8) and the metal disc is pushed upward. Then, the metal disc and the built-in rubber plug (9) are fixed with rivets and sealed with glass sealant. Step 14: Inspection and acceptance; The device for generating the polyurethane black and white mixture (10) includes an air compressor and a pressurized air tank (11). On the pressurized air tank (11), near both ends, the motor (12) of the air compressor and the multi-row ball valve (13) are respectively provided, and at the location where the multi-row ball valve (13) is provided, a bracket (14) with an openable baffle is provided. The multi-row ball valve (13) is located below the bracket (14) and includes multiple ball valves; The bracket (14) forms two storage spaces above the multi-row ball valve (13); The upper layer of the two storage spaces is equipped with a graduated, sealed, transparent mixing tank for black and white materials (15) and a stirrer (16), while the lower layer is equipped with a black material tank (17) and a white material tank (18). Both the black material barrel (17) and the white material barrel (18) are equipped with proportional valves (19) at their output ports. The outlet of the sealed transparent black and white material mixing tank (15) is equipped with a discharge valve (20). The first and third ball valves of the multi-row ball valve (13) are used to control the two air inlet booster pipes (21) between the pressurized air storage tank (11) and the black material barrel (17) and the white material barrel (18), respectively, and the second ball valve is used to control the air inlet booster pipe (21) between the pressurized air storage tank (11) and the sealed transparent black and white material mixing barrel (15). The operation process of the device for generating the polyurethane black and white material mixture (10) is as follows: Step A: Start the air compressor; Step B: After the pressure in the pressurized air storage tank (11) stabilizes, open the first ball valve and the third ball valve to input pressurized air into the black material tank (17) and the white material tank (18). Step C: Open the proportional valve (19) of the black material tank (17) and the white material tank (18), adjust the output mixing ratio, and transport the polyurethane rigid foam polyether and polymeric MDI in the black material tank (17) and the white material tank (18) to the sealed transparent black and white material mixing tank (15). Step D: Use the stirrer (16) to stir the polyurethane rigid foam polyether and the polymeric MDI in the sealed transparent black and white material mixing tank (15), and at the same time open the second ball valve to pressurize the sealed transparent black and white material mixing tank (15). Step E: After uniformly stirring using the stirrer (16), open the discharge valve (20) and input the polyurethane black and white mixture (10) into the opening (8) through the output pipe (25).

2. The construction method for cold-insulated pipe elbows as described in claim 1, characterized in that, The fiberglass cloth is of type EWR200-100, with a thickness of 0.2 mm, a width of 20 cm, and a density of 210 g / m³. 3 ; Each of the stainless steel strips (7) has a width of 10 mm; The silicone sealant is 704 waterproof type, white paste, and has sun protection function; The opening (8) is 5 cm in size; The hole opener is a tungsten carbide drill bit DLX-T6, D=50mm type; The polyurethane black and white mixture (10) comprises polyurethane rigid foam polyether and polymeric MDI, and is a brownish-yellow viscous liquid, castable, with a milky whitening time of 3-10s, a fiber drawing time of 10-15s, and a bulk density of 60kg / m³. 3 Compressive strength ≥100KPa, water absorption ≤100g / cm³ 3 Thermal conductivity ≦0.025W / mk.

3. The construction method for cold-insulated pipe elbows as described in claim 1, characterized in that, The protective bend (4) and the protective straight pipe (3) are fixed together by rivets.

4. The construction method for cold-insulated pipe elbows as described in claim 1, characterized in that, The diameter of the metal disc is 2 cm larger than the diameter of the opening (8).

5. The construction method for cold-insulated pipe elbows as described in claim 1, characterized in that, The pressurized air tank (11) is provided with multiple wheels (22) underneath, and the support (14) is provided with a trolley handle (23) on the side. The motor (12) is provided with a metal protective cover (24). The stirrer (16) is a rechargeable stirrer.

6. The construction method for cold-insulated pipe elbows according to claim 1, characterized in that, The stirring time in step D shall not exceed 5 seconds.

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