Pipeline construction method in air separation unit

Abstract

The present invention provides a pipeline construction method in an air separation device, which belongs to the technical field of air separation equipment, and includes the following steps: performing module division processing on the pipeline to obtain segmented pipelines; performing stress analysis on the hot pipeline and the cold pipeline on the segmented pipeline to determine the position offset between the cold pipeline and the hot pipeline corresponding to the segmented pipeline; determining the reserved gap between the hot pipeline and the pipeline support according to the position offset between the cold pipeline and the hot pipeline; after the equipment in the cold box is installed, the segmented pipeline is installed in the cold box according to the reserved gap between the hot pipeline corresponding to the segmented pipeline and the pipeline support to complete the pipeline construction in the air separation device. The present invention can solve the problems in the prior art that in order to adjust the cold deformation and compensation capacity of the pipeline under the low temperature state during the installation and construction of the air separation device, a bare cold test needs to be performed, which has high cost, long cycle, low installation efficiency and other problems.

Description

Technical Field

[0001] The present invention relates to the technical field of air separation equipment, and more specifically, to a pipeline construction method in an air separation device. Background Art

[0002] The air separation unit is a device that separates oxygen and nitrogen in the air under cryogenic conditions. Since the pipelines in the cold box of the air separation unit are installed at room temperature and operate under cryogenic conditions, the quality of the pipeline and bracket installation is very high, and a bare cold test inspection is required before starting.

[0003] The traditional bare cold test means that after the main air compressor is started normally, the compressed air is cooled by the air-water cooling tower precooling system, dried and activated by the molecular sieve purification system, and pressurized by the booster before entering the cold box; then the gas turbine expander is started to cool the equipment in the cold box. As all the equipment and pipelines in the cold box gradually cool down, the frost inside is observed by opening the cold box manhole. It is mainly used to check the cold deformation and compensation capacity of the pipeline under low temperature conditions, so as to compensate and adjust the cold deformation of the pipeline.

[0004] During the bare cold test, the air compressor, expander, etc. need to be started up again, and the scaffolding in the cold box cannot be removed. The operating electricity cost (steam cost) of the air compressor alone costs millions of yuan. The high cost and long cycle have become one of the constraints for the rapid installation and commissioning of air separation units. Therefore, it is urgent to develop a bare cold-free construction plan for large air separation units to solve the problems of long cycle and high energy and medium costs of traditional bare cold tests. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a pipeline construction method in an air separation unit to solve the problems in the prior art that during the installation and construction of the air separation unit, in order to adjust the cold deformation and compensation capacity of the pipeline under low temperature conditions, a bare cold test is required, which has high costs, long cycles, and low installation efficiency.

[0006] The pipeline construction method in an air separation device provided by the present invention comprises the following steps:

[0007] According to the single-line diagram of the pipeline in the cold box of the air separation unit, the pipeline is divided into modules to obtain segmented pipelines;

[0008] Performing stress analysis on the hot pipeline and the cold pipeline of the segmented pipeline to determine the position offset between the cold pipeline and the hot pipeline corresponding to the segmented pipeline;

[0009] Determining a reserved gap between the hot pipeline and the pipeline support according to a position offset between the cold pipeline and the hot pipeline;

[0010] After the equipment in the cold box is installed, the segmented pipelines in the cold box are installed according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline brackets to complete the pipeline construction in the air separation device.

[0011] In addition, a preferred solution is that the stress analysis of the hot pipeline and the cold pipeline on the segmented pipeline to determine the position offset between the cold pipeline and the hot pipeline corresponding to the segmented pipeline includes:

[0012] The state of the segmented pipeline when installed at room temperature is regarded as a hot pipeline, and the state of the segmented pipeline when in a cold environment of the cold box is regarded as a cold pipeline;

[0013] Based on the single-line diagram of the pipeline in the cold box of the air separation unit, and the average temperature and pressure in the cold box during the pipeline installation process, the stress analysis of the hot pipeline is performed to determine the position of the hot pipeline in the cold box; and based on the single-line diagram of the pipeline in the cold box of the air separation unit, the internal design temperature, design pressure and design flow of the cold box when the cold box is in operation, the stress analysis of the cold pipeline is performed to determine the position of the cold pipeline in the cold box;

[0014] Compare the offsets of the cold pipeline and the hot pipeline in four directions: up, down, left, and right.

[0015] In addition, a preferred solution is that determining the reserved gap between the hot pipeline and the pipeline support according to the position offset between the cold pipeline and the hot pipeline includes:

[0016] Taking the center of the cross section of the hot pipeline as the base point, the distances from the top, bottom, left and right points of the cross section of the cold pipeline to the base point are calculated respectively;

[0017] When the distance from the direction point to the base point is greater than the radius of the hot pipeline, the offset of the cold pipeline in the direction represented by the direction point is recorded as positive; when the distance from the direction point to the base point is less than or equal to the radius of the hot pipeline, the offset of the cold pipeline in the direction represented by the direction point is recorded as negative;

[0018] When the offset is positive, in the direction corresponding to the offset, the reserved gap between the hot pipeline and the pipeline support is the offset plus the thickness of the insulation pad; when the offset is negative, in the direction corresponding to the offset, the reserved gap between the hot pipeline and the pipeline support is 0; wherein the insulation pad is arranged on the pipeline support and corresponds to the positions of the four direction points of the hot pipeline: upper, lower, left and right.

[0019] In addition, a preferred solution is that the thermal insulation pad is a polytetrafluoroethylene pad with a thickness of 6-10 mm.

[0020] In addition, a preferred solution is that the thermal insulation pad is detachably fixed to the pipe support by means of stainless steel rivets; the end surface of the stainless steel rivet facing the hot pipe is a polished smooth end surface.

[0021] In addition, a preferred solution is that, during the installation of the segmented pipelines in the cold box according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline support, to complete the pipeline construction in the air separation unit,

[0022] Four stoppers are fully welded and fixed at the ends of the pipe support;

[0023] The four blocks correspond to the positions of four direction points of the hot pipeline respectively.

[0024] In addition, a preferred solution is that after installing the segmented pipelines in the cold box according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline support to complete the pipeline construction in the air separation device, it also includes:

[0025] The pipeline position of the pipeline in the air separation device, the gap size between the pipeline and the pipeline support, and the structural form of the pipeline are reviewed.

[0026] In addition, a preferred solution is that after installing the segmented pipelines in the cold box according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline support to complete the pipeline construction in the air separation device, it also includes:

[0027] The pipelines in the air separation unit are subjected to pipeline pressure test, cold box air tightness test, pipeline purging, cold box scaffolding removal, pearl sand filling in the cold box and oxygen output debugging.

[0028] In addition, a preferred solution is that when the pipelines in the air separation unit are pressure tested, the pressure test system is divided according to the pipeline medium in the cold box and the design pressure, and each system is isolated by adding a blind plate or closing a valve. The air inlet is the inlet of the existing pipeline or a temporary pipeline is added, and the pressure test medium is oil-free, dry air or nitrogen.

[0029] In addition, a preferred solution is that when purging the pipeline, oil-free dry air or nitrogen is used to purge the pipeline in sections.

[0030] It can be seen from the above technical scheme that the pipeline construction method in the air separation device provided by the present invention divides the pipeline into modules and performs stress analysis of the hot pipeline and the cold pipeline on the segmented pipeline to determine the offset of the cold pipeline relative to the hot pipeline. The reserved gap between the hot pipeline and the pipeline support is pre-designed based on the offset of the cold pipeline relative to the hot pipeline, so as to reserve the position offset space caused by the deformation of the cold pipeline when the segmented pipeline is installed in the cold box. There is no need to monitor and compensate for the cold deformation of the pipeline through bare cold experiments, which saves a lot of bare cold energy medium costs and bare cold commissioning period. The present invention has the advantages of safety, reliability, economy and high efficiency, and can ensure the safe and smooth operation of the air separation device.

[0031] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] By referring to the following description in conjunction with the accompanying drawings, and with a more complete understanding of the present invention, other objects and results of the present invention will become more apparent and easily understood.

[0033] Figure 1 is a flow chart of a pipeline construction method in an air separation unit according to an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the position offset between the cold pipeline and the hot pipeline according to an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of a reserved gap between a hot pipeline and a pipeline support according to an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of installation of segmented pipelines in a cold box according to an embodiment of the present invention;

[0037] Figure 5 is a schematic plan view of a thermal insulation pad according to an embodiment of the present invention;

[0038] Figure 6 Schematic diagram of fixing the thermal insulation pad and the pipe support according to an embodiment of the present invention.

[0039] In the attached drawings, 1-hot pipe, 2-cold pipe, 3-pipe support, 4-block, 5-insulation pad, 6-bolt hole, 7-stainless steel rivet.

[0040] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0041] In view of the above, in the prior art, during the installation and construction of an air separation unit, in order to adjust the cold deformation and compensation capacity of the pipeline under low temperature conditions, a bare cold test is required, which has the problems of high cost, long cycle, and low installation efficiency. A method and method for pipeline construction in an air separation unit are proposed.

[0042] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0043] In order to illustrate the pipeline construction method in the air separation device provided by the present invention, Figure 1 The flow chart of the pipeline construction method in an air separation unit according to an embodiment of the present invention is shown; Figure 2 The position offset structure between the cold pipeline and the hot pipeline according to an embodiment of the present invention is shown; Figure 3 The reserved gap between the hot pipeline and the pipeline support according to an embodiment of the present invention is shown; Figure 4 It shows the installation of segmented piping in a cold box according to an embodiment of the present invention; Figure 5 The planar structure of the heat insulating pad according to an embodiment of the present invention is shown; Figure 6 The figure shows the fixing of the heat insulating pad and the pipe support according to the embodiment of the present invention.

[0044] like Figures 1 to 6 As shown together, the pipeline construction method in the air separation device provided by the present invention comprises the following steps:

[0045] Step S1, according to the single-line diagram of the pipeline in the cold box of the air separation unit, the pipeline is divided into modules to obtain segmented pipelines;

[0046] Step S2, performing stress analysis on the hot pipeline 1 and the cold pipeline 2 of the segmented pipeline to determine the position offset between the cold pipeline 2 and the hot pipeline 1 corresponding to the segmented pipeline;

[0047] Step S3, determining a reserved gap between the hot pipeline 1 and the pipeline support 3 according to the position offset between the cold pipeline 2 and the hot pipeline 1;

[0048] Step S4: After the equipment in the cold box is installed, the segmented pipelines in the cold box are installed according to the reserved gap between the hot pipeline 1 and the pipeline support 3 corresponding to the segmented pipeline to complete the pipeline construction in the air separation unit.

[0049] Among them, in step 4, when the pipeline segments (modules) in the cold box are installed, the segmented pipelines and pipeline supports 3 can be prefabricated, but the prefabrication amount is preferably not more than 80% to avoid large cumulative errors and excessive pipeline stress, which will affect the installation of subsequent pipelines.

[0050] The pipeline is divided into modules, and stress analysis of the hot pipeline 1 and the cold pipeline 2 is performed on the segmented pipeline to determine the offset of the cold pipeline 2 relative to the hot pipeline 1. The reserved gap between the hot pipeline 1 and the pipeline support 3 is pre-designed based on the offset of the cold pipeline 2 relative to the hot pipeline 1, so as to reserve a position offset space caused by the deformation of the cold pipeline 2 when the segmented pipeline is installed in the cold box. There is no need to monitor and compensate for the cold deformation of the pipeline through a bare cold experiment, which saves a lot of bare cold energy medium costs and bare cold commissioning period. The present invention has the advantages of safety, reliability, economy and high efficiency, and can ensure the safe and stable operation of the air separation device.

[0051] As a preferred solution of the present invention, stress analysis of the hot pipeline 1 and the cold pipeline 2 is performed on the segmented pipeline to determine the position offset between the cold pipeline 2 and the hot pipeline 1 corresponding to the segmented pipeline, including:

[0052] The state of the segmented pipeline when installed at room temperature is referred to as hot pipeline 1, and the state of the segmented pipeline when working in a cold environment of a cold box is referred to as cold pipeline 2;

[0053] Based on the single-line diagram of the pipeline in the cold box of the air separation unit, and the average temperature and pressure in the cold box during the pipeline installation process, a stress analysis is performed on the hot pipeline 1 to determine the position of the hot pipeline 1 in the cold box; and based on the single-line diagram of the pipeline in the cold box of the air separation unit, and the internal design temperature, design pressure and design flow rate of the cold box when the cold box is working, a stress analysis is performed on the cold pipeline 2 to determine the position of the cold pipeline 2 in the cold box;

[0054] Compare the offsets of the cold pipe 2 and the hot pipe 1 in the four directions of up, down, left and right.

[0055] Specifically, the hot pipeline 1 in the present invention refers to the segmented pipeline when it is installed at room temperature; the cold pipeline 2 refers to the segmented pipeline when it is working in a cold state. According to the one-line diagram of the pipeline in the cold box of the air separation unit, the average temperature and pressure parameters in the cold box during the pipeline installation process, the stress analysis of the hot pipeline 1 can be performed to determine the appropriate position of the hot pipeline 1 in the cold box. According to the one-line diagram, the internal design temperature, design pressure and design flow parameters of the cold box when it is working, the stress analysis of the cold pipeline 2 can be performed to determine the position of the cold pipeline 2 in the cold box. The stress generated by the pipeline under the displacement load such as thermal expansion and contraction and additional displacement of the end points will cause uneven displacement of the pipeline in the cold box under different hot and cold working conditions. By comparing the cold and hot stress analysis, the offset of the cold pipeline 2 in the four directions of up, down, left and right compared with the hot pipeline 1 can be obtained, which are defined as the upper offset a, the left offset b, the right offset c and the lower offset d, respectively, as Figure 2 It should be noted that for the hot pipe 2 and the cold pipe, the four directions of top, bottom, left and right are the same.

[0056] As a preferred solution of the present invention, the reserved gap between the hot pipeline 1 and the pipeline support 3 is determined according to the position offset between the cold pipeline 2 and the hot pipeline 1, including:

[0057] Take the center of the cross section of the hot pipe 1 as the base point, and calculate the distances from the top, bottom, left, and right points of the cross section of the cold pipe 2 to the base point respectively;

[0058] When the distance from the direction point to the base point is greater than the radius of the hot pipe 1, the offset of the cold pipe 2 in the direction represented by the direction point is recorded as positive; when the distance from the direction point to the base point is less than or equal to the radius of the hot pipe 1, the offset of the cold pipe 2 in the direction represented by the direction point is recorded as negative;

[0059] When the offset is positive, the reserved gap between the hot pipe 1 and the pipe support 3 in the direction corresponding to the offset is the offset plus the thickness of the insulation pad 5; when the offset is negative, the reserved gap between the hot pipe 1 and the pipe support in the direction corresponding to the offset is 0; wherein the insulation pad 5 is arranged on the pipe support 3 and corresponds to the positions of the four direction points of the hot pipe 1, namely, the upper, lower, left and right directions.

[0060] Specifically, taking the center O of the cross section of the hot pipe 1 as the base point, when the distance from the upper direction point of the cold pipe 2 to the center O is greater than the radius of the hot pipe 1, the upper offset a is defined as positive, otherwise it is negative; and so on to determine the positive and negative relationship between the left offset b, the right offset c and the lower offset d. When the upper offset a is positive, the upper reserved installation gap a' is the value of a and the thickness value δ of the insulation pad 5; when the upper offset a is negative or 0, the upper reserved installation gap a' is 0; continue to determine the values ​​of the left reserved installation gap b', the right reserved installation gap c', and the lower reserved installation gap d' according to the above principles, such as Figure 3 shown.

[0061] As a preferred solution of the present invention, the thermal insulation pad 5 is a polytetrafluoroethylene pad with a thickness of 6-10 mm.

[0062] It should be noted that the thermal insulation pad 5 is preferably, but not limited to, a polytetrafluoroethylene pad, and the preferred value of the thickness thereof is 6-10 mm.

[0063] As a preferred solution of the present invention, the heat insulating pad 5 is detachably fixed to the pipe support 3 by stainless steel rivets 7;

[0064] The end surface of the stainless steel rivet 7 facing the hot pipeline 1 is a polished and smooth end surface.

[0065] Specifically, Figure 5 and Figure 6As shown, two bolt holes 6 can be opened on the insulation pad 5 and fixed to the pipe support 3 by stainless steel rivets 7, wherein the upper diameter of the bolt hole 6 is preferably 16 mm and the lower diameter is preferably 6-10 mm, and the contact surface between the end of the stainless steel rivet 7 and the hot pipe 1 needs to be polished smooth.

[0066] As a preferred solution of the present invention, during the installation of the segmented pipelines in the cold box according to the reserved gap between the hot pipeline 1 and the pipeline support 3 corresponding to the segmented pipelines, to complete the pipeline construction in the air separation unit,

[0067] Four stoppers 4 are fully welded and fixed at the ends of the pipe support 3;

[0068] The four blocks 4 correspond to the positions of four direction points of the hot pipeline 1 respectively.

[0069] Specifically, Figure 4 As shown, four blocks 4 are arranged on the pipe support 3 to prevent the pipe from shifting after installation, and the blocks 4 are fully welded to the pipe support 3 .

[0070] As a preferred solution of the present invention, after installing the segmented pipelines in the cold box according to the reserved gap between the hot pipeline 1 and the pipeline support 3 corresponding to the segmented pipeline to complete the pipeline construction in the air separation device, the present invention further includes:

[0071] Review the pipeline position of the pipeline in the air separation unit, the gap size between the pipeline and the pipeline support, and the structural form of the pipeline.

[0072] Specifically, after the installation of equipment and pipelines in the cold box is completed, a process inspection is required. The focus of the process inspection is the direction of the hot pipeline 1, the position and structure of the pipeline support 3, and the values ​​of the reserved installation gaps a', b', c', and d' in each direction of the hot pipeline 1. A list of problems is compiled based on the process inspection results, and the installation operators will make corrections one by one and continue to review until all process inspection items meet the requirements.

[0073] As a preferred solution of the present invention, after installing the segmented pipelines in the cold box according to the reserved gap between the hot pipeline 1 and the pipeline support 3 corresponding to the segmented pipeline to complete the pipeline construction in the air separation device, the present invention further includes:

[0074] The pipelines in the air separation unit are subjected to pipeline pressure test, cold box air tightness test, pipeline purging, cold box scaffolding removal, pearl sand filling in the cold box and oxygen output debugging.

[0075] As a preferred embodiment of the present invention, when the pipeline in the air separation unit is pressure tested, the pressure test system is divided according to the pipeline medium in the cold box and the design pressure, and each system is isolated by adding a blind plate or closing a valve. The air inlet is the inlet of the existing pipeline or a temporary pipeline is added, and the pressure test medium is oil-free, dry air or nitrogen.

[0076] As a preferred embodiment of the present invention, when purging the pipeline, oil-free dry air or nitrogen is used to purge the pipeline in sections.

[0077] Specifically, the pipeline media in the cold box include air, nitrogen, oxygen, argon, liquid argon, liquid nitrogen, liquid oxygen, oxygen-rich liquid, etc. The pressure test system can be divided according to the pipeline media in the cold box and the design pressure. The systems are isolated by adding blind plates or closing valves. The air inlet is the inlet of the existing pipeline or an additional temporary pipeline. The pressure test medium is oil-free, dry air or nitrogen.

[0078] After the pressure test of the pipeline in the cold box is completed, each system needs to be tested for leakage until the leakage meets the requirements while maintaining the design pressure for 4-8 hours. After the leakage test of each system of the pipeline in the cold box is passed, the partition blind plates and valves between the systems are removed, the equipment and pipelines in the cold box are connected into an integral system, inflated to 0.2MPa, and all pipelines, instrument points, and equipment are checked for air tightness; it is qualified only if there are no leaks after 3-4 rounds of repeated tests.

[0079] Use oil-free, dry air or nitrogen to purge the pipeline in sections. Before purging, disconnect the inlet and outlet pipes of the expander, remove all filter elements and flow meter orifice plates, and reinstall them in situ after purging. The purge pressure must not exceed the design pressure of the equipment or pipeline. Each system should be purged repeatedly until there is no rust, welding slag and other debris at the outlet.

[0080] After the pipelines in the cold box are purged, the scaffolding installed in the cold box is removed; during the scaffolding removal process, a dedicated person is required to supervise to prevent damage to the equipment and pipelines in the cold box.

[0081] After the scaffolding inside the cold box is removed, the holes in the cold box panel are closed and pearl sand is filled in the cold box; after a comprehensive cleaning and inspection, the pearl sand is gradually filled from the bottom to the top of the cold box, and the manhole is closed; the main cold box side and the pump box side are isolated with wire mesh, with a width of about 200-500mm on both sides, and filled with mineral wool to isolate the pump box and the main cold box; when the main cold box is filled with pearl sand, the pump box is not filled for the time being.

[0082] Start the air compressor, booster, gas turbine expander and other equipment. When the equipment temperature in the cold box drops to about -70℃, the operating personnel will isolate the pump box, cold-tighten the valve flange bolts in the pump box, and manually fill the pump box with pearlescent sand. When the expander runs stably and the pump box temperature stabilizes, continue to adjust the process parameters until the air separation unit produces oxygen.

[0083] Among them, the first-time pass rate of pipeline welding in the cold box can be controlled above 98% by optimizing welders and organizing excellent welders.

[0084] All safety valves on the pipelines must be removed and isolated with blind plates; except for the local pressure display points and non-detachable instrument points, other instrument unit points, flow orifice plates and filters must be disconnected or removed before the pipeline pressure test to prevent damage from foreign objects in the pipeline during the pressure test and discharge process.

[0085] The equipment inside the cold box is pressure tested together with the piping system with the same design pressure.

[0086] Temporary pipelines should be degreased and inspected for cleanliness.

[0087] The leakage test should be carried out within a range with a small temperature difference.

[0088] After the pipeline purge in the cold box is completed, restore the cryogenic pump, the filter element of the expander inlet and outlet pipelines and the inlet flange assembly, and conduct a single test of the gas turbine expander.

[0089] Pearlescent sand is filled by pumping with a filling machine.

[0090] It can be seen from the above specific implementation methods that the pipeline construction method in the air separation device provided by the present invention divides the pipeline into modules, and performs stress analysis of the hot pipeline and the cold pipeline on the segmented pipeline to determine the offset of the cold pipeline relative to the hot pipeline. Based on the offset of the cold pipeline relative to the hot pipeline, the reserved gap between the hot pipeline and the pipeline support is pre-designed to reserve position offset space caused by the deformation of the cold pipeline when the segmented pipeline is installed in the cold box. There is no need to monitor and compensate for the cold deformation of the pipeline through bare cold experiments, which saves a lot of bare cold energy medium costs and bare cold commissioning period. The present invention has the advantages of safety, reliability, economy and high efficiency, and can ensure the safe and stable operation of the air separation device.

[0091] As described above, the pipeline construction method in the air separation device proposed by the present invention is described by way of example with reference to the accompanying drawings. However, it should be understood by those skilled in the art that various improvements can be made to the pipeline construction method in the air separation device proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A method for constructing pipelines in an air separation unit, characterized in that: The steps include: According to the single-line diagram of the pipeline in the cold box of the air separation unit, the pipeline is divided into modules to obtain segmented pipelines; Performing stress analysis on the hot pipeline and the cold pipeline of the segmented pipeline to determine the position offset between the cold pipeline and the hot pipeline corresponding to the segmented pipeline; Determining a reserved gap between the hot pipeline and the pipeline support according to a position offset between the cold pipeline and the hot pipeline; After the equipment in the cold box is installed, the segmented pipelines in the cold box are installed according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline brackets to complete the pipeline construction in the air separation device.

2. The method for constructing pipelines in an air separation unit according to claim 1, characterized in that: The step of performing stress analysis on the hot pipeline and the cold pipeline of the segmented pipeline to determine the position offset between the cold pipeline and the hot pipeline corresponding to the segmented pipeline includes: The state of the segmented pipeline when installed at room temperature is regarded as a hot pipeline, and the state of the segmented pipeline when in a cold environment of the cold box is regarded as a cold pipeline; Based on the single-line diagram of the pipeline in the cold box of the air separation unit, and the average temperature and pressure in the cold box during the pipeline installation process, the stress analysis of the hot pipeline is performed to determine the position of the hot pipeline in the cold box; and based on the single-line diagram of the pipeline in the cold box of the air separation unit, the internal design temperature, design pressure and design flow of the cold box when the cold box is in operation, the stress analysis of the cold pipeline is performed to determine the position of the cold pipeline in the cold box; Compare the offsets of the cold pipeline and the hot pipeline in four directions: up, down, left, and right.

3. The method for constructing pipelines in an air separation unit according to claim 2, characterized in that: The step of determining a reserved gap between the hot pipeline and the pipeline support according to the position offset between the cold pipeline and the hot pipeline comprises: Taking the center of the cross section of the hot pipeline as the base point, the distances from the top, bottom, left and right points of the cross section of the cold pipeline to the base point are calculated respectively; When the distance from the direction point to the base point is greater than the radius of the hot pipeline, the offset of the cold pipeline in the direction represented by the direction point is recorded as positive; when the distance from the direction point to the base point is less than or equal to the radius of the hot pipeline, the offset of the cold pipeline in the direction represented by the direction point is recorded as negative; When the offset is positive, in the direction corresponding to the offset, the reserved gap between the hot pipeline and the pipeline support is the offset plus the thickness of the insulation pad; when the offset is negative, in the direction corresponding to the offset, the reserved gap between the hot pipeline and the pipeline support is 0; wherein the insulation pad is arranged on the pipeline support and corresponds to the positions of the four direction points of the hot pipeline: upper, lower, left and right.

4. The method for constructing pipelines in an air separation unit according to claim 3, characterized in that: The thermal insulation pad is a polytetrafluoroethylene pad with a thickness of 6-10 mm.

5. The method for constructing pipelines in an air separation unit according to claim 3, characterized in that: The thermal insulation pad is detachably fixed to the pipe support by stainless steel rivets; The end surface of the stainless steel rivet facing the hot pipeline is a polished and smooth end surface.

6. The method for constructing pipelines in an air separation unit according to claim 3, characterized in that: In the process of installing the segmented pipeline in the cold box according to the reserved gap between the hot pipeline corresponding to the segmented pipeline and the pipeline support to complete the pipeline construction in the air separation unit, Four stoppers are fully welded and fixed at the ends of the pipe support; The four blocks correspond to the positions of four direction points of the hot pipeline respectively.

7. The method for constructing pipelines in an air separation unit according to claim 1, characterized in that: After installing the segmented pipelines in the cold box according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline support to complete the pipeline construction in the air separation device, the method further includes: The pipeline position of the pipeline in the air separation device, the gap size between the pipeline and the pipeline support, and the structural form of the pipeline are reviewed.

8. The method for constructing pipelines in an air separation unit according to claim 1, characterized in that: After installing the segmented pipelines in the cold box according to the reserved gap between the hot pipelines corresponding to the segmented pipelines and the pipeline support to complete the pipeline construction in the air separation device, the method further includes: The pipelines in the air separation unit are subjected to pipeline pressure test, cold box air tightness test, pipeline purging, cold box scaffolding removal, pearl sand filling in the cold box and oxygen output debugging.

9. The method for constructing pipelines in an air separation unit according to claim 8, characterized in that: When the pipelines in the air separation unit are pressure tested, the pressure test system is divided according to the pipeline medium in the cold box and the design pressure. The systems are isolated by adding blind plates or closing valves. The air inlet is the inlet of the existing pipeline or a temporary pipeline is added. The pressure test medium is oil-free, dry air or nitrogen.

10. The method for constructing pipelines in an air separation unit according to claim 8, characterized in that: When purging the pipe, Use oil-free dry air or nitrogen to purge the pipeline in sections.

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