Pipeline mechanical state evaluation method
By establishing a complete mechanical calculation model for pipelines and using criteria for evaluation, the problem of discrepancies between mechanical analysis results and actual conditions in pipeline design was solved, achieving accurate evaluation of in-service pipelines and improving the accuracy of new pipeline designs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-03-17
- Publication Date
- 2026-03-31
AI Technical Summary
In existing technologies, the mechanical analysis results during pipeline design cannot reflect the actual situation, leading to safety hazards such as excessive pipeline stress and thrust, changes in drainage slope, and overload of rigid hangers. Furthermore, the design calculation model is too idealistic and the evaluation criteria are too simplistic.
By acquiring the pipeline's design parameters, actual operating information, and support performance curves, a complete mechanical calculation model is established. Accurate evaluation is then performed using stress, thrust, drainage slope, and rigid support load criteria to ensure the pipeline's mechanical safety.
It enables accurate mechanical condition assessment of in-service pipelines, avoids potential safety hazards, improves the calculation accuracy of new pipeline designs, and prevents unpredictable deviations from the intended state.
Smart Images
Figure CN114662234B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of power pipeline life evaluation, and relates to a pipeline mechanical state evaluation method. BACKGROUND
[0002] The safety of a power pipeline is of great importance, and once a problem occurs, unexpected consequences can be caused. To ensure the safe operation of the power pipeline within the design life, mechanical analysis including stress calculation must be performed on the pipeline in the design, and the pipeline must meet the requirements of relevant standards and specifications. In recent years, it is often found that the pipeline state line deviates greatly after installation or initial operation, and the performance of the support and hanger changes after operation, so that the pipeline rarely returns to the original position after each thermal cycle, which indicates that the mechanical analysis results made in the design of the pipeline can no longer reflect the actual mechanical state of the pipeline, and problems such as excessive pipeline stress, thrust, change of pipeline drainage slope and overload or even collapse of rigid hangers can be caused, which brings great hidden dangers to the safe operation. The reasons are that, on the one hand, the installation and operation of the pipeline are related, and on the other hand, the design calculation model of the pipeline is too idealized and the mechanical evaluation criterion is too simple. For the former, strict pipeline installation technology and improved operation level can be used to solve the problem, and for the latter, a mechanical state evaluation method reflecting the actual state of the pipeline needs to be proposed. SUMMARY
[0003] The application aims to overcome the shortcomings of the prior art, and provides a pipeline mechanical state evaluation method, which can accurately evaluate the mechanical state of the in-service pipeline and provide a reference for the accurate calculation of newly designed pipelines.
[0004] To achieve the above-mentioned purpose, the pipeline mechanical state evaluation method comprises the following steps:
[0005] 1) Obtain the design parameters of the pipeline and the actual operating temperature and pressure information of the pipeline, obtain the thermal insulation material parameters of the pipeline, and obtain the self-weight information of the pipeline, pipe fittings and valves;
[0006] 2) Obtain the performance measurement curves of each type of elastic support and hanger, and obtain the measured additional displacement of each end point of the pipeline;
[0007] 3) Establish a complete mechanical calculation model of the pipeline including the performance measurement curves of each elastic support, calculate the maximum stress, thrust, cold and hot state load and displacement data of each hanger point, and cold and hot state displacement data of important nodes of the pipeline according to the complete mechanical calculation model of the pipeline;
[0008] 4) Based on the maximum stress, thrust, cold and hot loads of each lifting point, and cold and hot displacement data of each lifting point and important nodes, the mechanical safety of the pipeline is assessed using stress criteria, thrust criteria, drainage slope criteria, rigid support load criteria, and sensitive small branch pipe criteria.
[0009] The stress and thrust criteria are that the stress and thrust of the pipeline meet the requirements of DL / T5366 Technical Specification for Stress Calculation of Steam and Water Pipelines in Power Plants.
[0010] The drainage slope criterion is that the slope obtained by dividing the height difference between the two ends of any horizontal pipe by the length of the horizontal pipe meets the requirements of GB 50764 Power Plant Power Pipeline Design Code.
[0011] The load criterion for rigid supports and hangers is that the cold and hot loads of the rigid supports and hangers do not exceed the allowable load of the rigid hangers calculated according to GB / T17116.1.
[0012] The criterion for sensitive branch pipes is that the cold and hot displacements at the branch pipes connected to the main pipeline are within a preset displacement range.
[0013] Additional displacements at each end of the pipeline are obtained through online or offline measurements in cold and hot conditions.
[0014] The measured performance curves of various elastic supports and dampers of the pipeline are obtained by online or offline measurement under cold and hot conditions.
[0015] The key nodes include the connection points of each branch pipe.
[0016] The present invention has the following beneficial effects:
[0017] In practical operation, the pipeline mechanical state assessment method described in this invention establishes a complete mechanical calculation model of the pipeline, including measured performance curves of various types of supports and hangers. Simultaneously, it utilizes stress criteria, thrust criteria, drainage slope criteria, rigid support and hanger load criteria, and sensitive small branch pipe criteria to assess the mechanical safety of the pipeline. This not only enables accurate assessment of the mechanical state of in-service pipelines, avoiding safety hazards caused by the pipeline's actual operating state failing to meet design requirements, but also improves the accuracy of mechanical calculations during new pipeline design, preventing unpredictable deviations from the pipeline's state line. Attached Figure Description
[0018] Figure 1 This is a structural diagram of Example 1. Detailed Implementation
[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.
[0020] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.
[0021] The pipeline mechanical condition assessment method of the present invention includes the following steps:
[0022] 1) Obtain the design parameters of the pipeline, as well as the actual operating temperature and pressure information of the pipeline, obtain the insulation material parameters of the pipeline, and obtain the self-weight information of the pipeline, fittings and valves;
[0023] 2) Obtain the measured performance curves of various types of elastic supports and dampers, and at the same time obtain the measured additional displacements at each end of the pipeline. Specifically, the additional displacements at each end of the pipeline are obtained by online or offline measurement in cold and hot conditions; the measured performance curves of each elastic support and damper of the pipeline are obtained by online or offline measurement in cold and hot conditions.
[0024] 3) Establish a complete mechanical calculation model of the pipeline including the measured performance curves of each elastic support and hanger, and calculate the maximum stress, thrust, cold and hot loads and displacement data of each hanging point and the cold and hot displacement data of important nodes based on the complete mechanical calculation model of the pipeline.
[0025] 4) Based on the maximum stress, thrust, cold and hot loads of each lifting point, and cold and hot displacement data of each lifting point and important nodes, the mechanical safety of the pipeline is assessed using stress criteria, thrust criteria, drainage slope criteria, rigid support load criteria, and sensitive small branch pipe criteria.
[0026] The key nodes include the connection points of each branch pipe.
[0027] The stress and thrust criteria are that the stress and thrust of the pipeline meet the requirements of DL / T5366 Technical Specification for Stress Calculation of Steam and Water Pipelines in Power Plants.
[0028] The drainage slope criterion is that the slope obtained by dividing the height difference between the two ends of any horizontal pipe by the length of the horizontal pipe meets the requirements of GB 50764 Power Plant Power Pipeline Design Code.
[0029] The load criterion for rigid supports and hangers is that the cold and hot loads of the rigid supports and hangers do not exceed the allowable load of the rigid hangers calculated according to GB / T17116.1.
[0030] The criterion for sensitive branch pipes is that the cold and hot displacements at the branch pipes connected to the main pipeline are within a preset displacement range.
[0031] Example 1
[0032] The specific process of this embodiment is as follows:
[0033] 1) To Figure 1 When conducting a mechanical condition assessment of the in-service high-temperature reheat steam pipeline, the design parameters of the high-temperature reheat steam pipeline and the actual operating temperature and pressure of the pipeline are collected first, and the self-weight data of the pipeline, fittings, valves and accessories are obtained.
[0034] 2) In the cold state, the performance curves of 9 sets of elastic supports and hangers were obtained by actual measurement, such as... Figure 1 The spring hangers and constant force hangers in the system read the actual additional displacement data (△X, △Y, △Z) at the endpoints by displacement measuring devices installed at the endpoints (A, B, C, D);
[0035] 3) Determine the location of each important node, such as Figure 1 As shown, the locations of important nodes include the locations of each support point, pipe fitting and valve connection point, and small branch pipe interface point (E, F, G). A complete mechanical calculation model of the pipeline is established, including the measured performance curves of various types of elastic supports and hangers, and stress calculation analysis is performed.
[0036] 4) The stress calculation for high-temperature reheat steam pipelines includes the range of axial stress and thermal expansion stress, which should respectively meet the following requirements:
[0037] When a pipeline is in operation, the sum of the axial stresses generated by internal pressure, its own weight, and other continuous external loads must not exceed the basic allowable stress of the steel at the design temperature.
[0038]
[0039] Where p is the internal pressure, MPa; D o D is the outer diameter of the pipe, in mm. i The pipe's inner diameter is in mm; M A W is the combined moment of the pipe's own weight and other continuous external loads acting on its cross-section, in N·mm; W is the pipe's section modulus, in mm. 3 ;[σ] t σ is the allowable stress of steel at the design temperature, in MPa; i is the stress enhancement factor; σ is the allowable stress of steel at the design temperature. L It is the sum of axial stresses caused by internal pressure, self-weight, and other continuous external loads, expressed in MPa.
[0040] The range of thermal expansion stress in a pipeline caused by thermal expansion, contraction, and other constrained displacements must satisfy the following calculation formula:
[0041] σ E =iM C / W≤f [1.2 [σ] 20 +0.2 [σ]t + ( [σ] t -σ L ) ] (2)
[0042] Among them, [σ] 20 M represents the allowable stress of the pipe steel at 20℃, in MPa; C The range of the combined torque caused by thermal expansion, calculated based on the full compensation value and the elastic modulus of steel at 20°C, is given in N·mm; σ E The range of thermal expansion stress is given by MPa, and f is the reduction factor for the range of thermal expansion stress.
[0043] Over the expected operating life of the power plant, the coefficient f is calculated based on the number of cycles N of the pipeline's full temperature cycle. When N ≤ 2500, f = 1; when N > 2500, f = 4.78N. -0.2 .
[0044] 5) The high-temperature reheat steam pipeline adopts the same cold-tightening ratio along the X, Y, and Z axes, and the thrust at each end to the connecting equipment should respectively meet the following requirements:
[0045] Under operating conditions, the thrust or torque exerted by the pipeline on the equipment or endpoint must satisfy the following calculation formula:
[0046]
[0047] In a cold state, the thrust or torque exerted by the pipeline on the equipment or endpoint must satisfy the following calculation formula:
[0048] R 20 =γR E (4)
[0049] or
[0050] when When the pipeline is in a cold state, the thrust or torque exerted on the equipment or end point is taken as the larger value in formulas (4) and (5) < [R]; when The thrust or torque exerted by the pipeline on the equipment or endpoint in a cold state is calculated according to equation (4), and R 20 <[R];
[0051] Among them, R t R represents the thrust or torque (N or N·mm) exerted on equipment or endpoints during the initial operating phase of the pipeline; 20 The thrust or torque (N or N·mm) exerted on equipment or endpoints during the initial cold state of pipeline operation; R represents the thrust or torque (N or N·mm) exerted on equipment or endpoints in a cold state after the pipeline has self-equilibrated its strain; EThe force or moment (N or N·mm) exerted by the endpoints on the pipeline is calculated based on the full compensation value and the elastic modulus of the steel at 20°C; γ is the cold-tightening ratio; E t E represents the elastic modulus of steel at the design temperature (GPa); 20 [R] represents the elastic modulus of steel at 20°C (GPa); [R] represents the permissible thrust or torque (N or N·mm) of the equipment or endpoint.
[0052] 6) After considering the calculated cold and hot displacement data, the slope obtained by dividing the height difference between the two ends of any horizontal pipe by the length of the horizontal pipe must satisfy i ≥ 0.005. Figure 1 The drainage slope of the medium- and high-temperature reheat steam pipeline is consistent with the airflow direction.
[0053] 7) Results of pipe stress calculation and analysis # 5. # 10. The cold and hot loads on rigid hangers shall not exceed the maximum allowable load of the installed rigid hanger assembly.
[0054] 8) Take the cold and hot displacements of the connection node between the pipeline and the small branch pipe as additional displacements at the endpoints, and estimate or calculate whether the additional displacements will affect the stress safety of the connected small branch pipe.
[0055] 9) If the above-mentioned pipe stress, thrust, drainage slope, rigid hanger load and small branch pipe are all qualified, the pipe mechanical state assessment can be confirmed as qualified. Otherwise, the treatment shall be carried out by changing the type or model of the support and hanger, adjusting the support and hanger, modifying the drainage pipe, etc., and a reassessment shall be carried out after the treatment.
Claims
1. A method for evaluating a mechanical state of a pipeline, characterized by, The method comprises the following steps: 1) obtaining the design parameters of the pipeline, the actual operating temperature and pressure information of the pipeline, the thermal insulation material parameters of the pipeline, and the self-weight information of the pipeline, pipe fittings, and valves; 2) obtaining the performance measurement curves of various types of elastic supports and hangers, and the measured additional displacements of the pipeline at each end point; 3) establishing a complete mechanical calculation model of the pipeline including the performance measurement curves of the elastic supports and hangers, and calculating the maximum stress, thrust, cold and hot state load and displacement data of each hanger point, and the cold and hot state displacement data of important nodes of the pipeline according to the complete mechanical calculation model of the pipeline; 4) evaluating the mechanical safety of the pipeline according to the maximum stress, thrust, cold and hot state load of each hanger point, the cold and hot state displacement data of each hanger point and important nodes, and the stress criterion, thrust criterion, drainage slope criterion, rigid support and hanger load criterion, and sensitive small branch pipe criterion; The stress calculation of the high-temperature reheat steam pipeline includes the axial stress and thermal expansion stress range, which should meet the following conditions respectively: The sum of the axial stresses generated by the internal pressure, self-weight and other continuous external loads of the pipeline in the working state should not be greater than the basic allowable stress of the steel material at the design temperature; b L = p ( - )+0.75iM A / W≤1.0 [σ] t (1) where p is the internal pressure, D o is the outside diameter of the pipe, D i is the inside diameter of the pipe, M A is the resultant moment of the dead weight and other constant external loads acting on the cross section of the pipe, W is the bending resistance coefficient of the cross section of the pipe, [σ] t is the allowable stress of the steel at the design temperature, i is the stress enhancement coefficient; б L is the sum of the axial stresses due to the internal pressure, the dead weight and other constant external loads; The thermal expansion stress range of the pipeline generated by thermal expansion, cold shrinkage and other displacement constraints should meet the following calculation formula: σ E = iM C / W≤f [1.2 [σ] 20 +0.2 [σ] t + ( [σ] t -σ L ) ](2) wherein [σ] 20 is the allowable stress of the pipe steel material at 20°C, MPa; M C is the range of resultant moments caused by thermal expansion calculated from the full compensation value and the elastic modulus of the steel material at 20°C; σ E is the thermal expansion stress range, and f is a reduction factor for the thermal expansion stress range; Within the expected operating life of the power plant, the coefficient f is calculated as a function of the number of full temperature cycles N of the pipe, f = 1 when N < 2500 and f = 4.78N when N > 2500 -0.2 ; 5) the same cold-tight ratio is adopted for the high-temperature reheat steam pipeline in the three directions of the coordinate axes X, Y and Z, and the thrust of each end point to the connecting equipment should meet the following conditions respectively: In the working state, the thrust or torque of the pipeline to the equipment or end point should meet the following calculation formula: （3） In the cold state, the thrust or torque of the pipeline to the equipment or end point should meet the following calculation formula: （4） or (5) When , the push or moment of the pipe on the equipment or end point in cold state takes the larger value of formula (4) and formula (5) ; when , the push or moment of the pipe on the equipment or end point in cold state is calculated according to formula (4), and ; Wherein, R t is the thrust or moment of the equipment or end point in the initial working state of the pipeline; R 20 is the thrust or moment of the equipment or end point in the cold state of the initial pipeline; is the thrust or moment of the equipment or end point in the cold state after the self-balancing of the pipeline strain; R E is the thermal expansion force or moment of the end point on the pipeline according to the full compensation value and the elastic modulus of the steel at 20°C; γ is the cold tight ratio; E t is the elastic modulus of the steel at the design temperature; E 20 is the elastic modulus of the steel at 20°C; is the allowable thrust or moment of the equipment or end point; 6) Slope i of the height difference between the two ends of any horizontal pipe divided by the length of the horizontal pipe after considering the calculated cold and hot state displacement data 、 ≥ 0.005; 7) The results of the pipe stress calculation analysis # 5、 # 10 The cold and hot state load of the rigid hanger shall not exceed the maximum allowable load of the installed rigid hanger assembly; 8) the cold and hot state displacements of the connection nodes of the pipeline and the small branch pipes are taken as the additional displacements of the end points, and it is estimated or calculated whether the additional displacements will cause the connected small branch pipes to be stressed safely.
2. The method of evaluating the mechanical state of a pipe according to claim 1, characterized by, The stress criterion and thrust criterion are that the stress and thrust of the pipeline meet the requirements of DL / T5366 Technical Code for Stress Calculation of Steam and Water Piping in Power Plants.
3. The method of evaluating the mechanical state of a pipe according to claim 1, characterized by, The drainage slope criterion is that the slope of the height difference between the two ends of any horizontal pipeline divided by the length of the horizontal pipeline meets the requirements of GB 50764 Code for Design of Power Piping in Power Plants.
4. The method of evaluating the mechanical state of a pipe according to Claim 1, wherein The rigid support and hanger load criterion is that the cold and hot state loads of the rigid support and hanger do not exceed the allowable load of the rigid hanger calculated according to GB / T 17116.
1.
5. The method of evaluating the mechanical state of a pipe according to Claim 1, wherein The sensitive small branch pipe criterion is that the cold and hot state displacements at the connection of the small branch pipe and the pipeline are within the preset displacement range.
6. The method of evaluating the mechanical state of a pipe according to Claim 1, wherein The additional displacements of the pipeline at each end point are obtained through cold and hot state online or cold state offline measurement.
7. The method of evaluating the mechanical state of a pipe according to Claim 1, wherein The performance measurement curves of the elastic supports and hangers and dampers of the pipeline are obtained through cold and hot state online or cold state offline measurement.