A method for designing a steel lining structure of a pressure pipeline end

Abstract

The application provides a steel lining structure design method for the end of a pressure pipeline, which combines the comprehensive calculation of the axial stress and the circumferential stress of the steel lining at the end of the pressure pipeline and comprises the following steps: step one, calculating the elongation of the steel lining; step two, calculating the proportion of the axial force of each thrust ring and determining the maximum proportion; step three, calculating the average compressive stress of the thrust ring on the surrounding concrete, the bending stress of the thrust ring, the longitudinal stress and the circumferential stress at the connection between the steel lining and the thrust ring according to the maximum proportion; step four, judging whether the design parameters meet the structural design requirements according to the calculation results obtained in steps one and three, and if not, adjusting the parameters that do not meet the requirements until the design parameters meet the structural design requirements; the method can reasonably determine the number of the thrust rings and the arrangement scheme of the multiple thrust rings, and at the same time, provide a theoretical calculation basis for the reasonable selection of the ball valve support pier and the expansion joint downstream of the ball valve, and effectively control the engineering cost.

Description

Technical Field

[0001] This invention relates to the field of steel lining design, and more particularly to a method for designing a steel lining structure at the end of a pressure pipeline. Background Technology

[0002] For steel lining design, the steel lining section at the end of the upstream water intake branch pipe of the plant is significantly different from the steel lining at other locations: because the steel lining section at the end of the branch pipe is close to the plant, it is usually designed as an exposed pipe. This steel lining section is connected to valves such as ball valves that control the water flow. When the valve is closed, in addition to the circumferential stress, the steel lining section will inevitably be subjected to axial stress due to the impact of the water flow, which will lead to axial deformation of the steel lining section. However, in the current design, the traditional circumferential stress calculation and safety verification are often performed solely based on the steel lining of other parts, resulting in insufficient safety margin of the steel lining, insufficient theoretical basis for the setting of ball valve supports and downstream expansion joints of ball valves, and unreasonable number of thrust rings and arrangement of multiple thrust rings. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a design method for the steel lining structure at the end of a pressure pipeline. This method can solve the problems of how to reasonably determine the number of thrust rings and the arrangement scheme of multiple thrust rings under the complex stress of the steel lining structure at the end of a pressure pipeline. At the same time, it provides a theoretical calculation basis for the reasonable selection of ball valve supports and downstream expansion joints of ball valves, and effectively controls the project cost while ensuring the safety of the project.

[0004] Therefore, the present invention adopts the following technical solution:

[0005] A design method for the steel lining structure at the end of a pressure pipeline, which combines the axial stress and circumferential stress of the steel lining at the end of the pressure pipeline through comprehensive calculation, includes the following steps:

[0006] Step 1: Calculate the elongation of the steel liner. ;

[0007] Step 2: Calculate the percentage of axial force experienced by each thrust ring. And determine the maximum percentage. ;

[0008] Step 3: Based on the maximum percentage Calculate the average compressive stress of the thrust ring on the surrounding concrete. Bending stress of the thrust ring Longitudinal stress at the connection between the steel liner and the thrust ring and circumferential stress ;

[0009] Step 4: Based on the calculation results obtained in Step 1 and Step 3, determine whether the design parameters meet the structural design requirements. If not, adjust the parameters accordingly until the design parameters meet the structural design requirements.

[0010] Based on the above technical solutions, the present invention may also employ the following further technical solutions, or combine these further technical solutions:

[0011] In step one, the elongation of the steel liner The calculation formula is as follows:

[0012] ;

[0013] in: , ;

[0014] in: : Maximum pressure value at the end of the steel lining under normal operating conditions (MPa);

[0015] Inner diameter of the steel lining, mm;

[0016] Axial force, kN;

[0017] Longitudinal stress of steel lining, MPa;

[0018] : Elastic modulus of steel lining;

[0019] : The distance from the last thrust ring to the ball valve position, in mm;

[0020] Poisson's ratio of steel;

[0021] Steel lining thickness, mm;

[0022] Elongation of steel liner This provides a theoretical basis for the selection and installation of the ball valve support 3 and the expansion joint 2.

[0023] In step two, the proportion of axial force experienced by each thrust ring is determined. The calculation formula is as follows:

[0024] ;

[0025] in: ;

[0026] Maximum proportion ;

[0027] in: The percentage of axial force experienced by each thrust ring;

[0028] The maximum percentage among all thrust rings;

[0029] : These represent the axial distances (in meters) between each thrust ring and the stiffening ring;

[0030] : The theoretical axial elongation of the steel liner at the corresponding position of each thrust ring, in meters.

[0031] In step three, the average compressive stress of the thrust ring on the surrounding concrete The calculation formula is as follows:

[0032] ;

[0033] in: : Thrust ring outer diameter, mm;

[0034] : Compressive strength of external backfill concrete, MPa;

[0035] like If the structural design requirements are not met, the outer diameter of the thrust ring should be increased. And perform verification until... It meets the structural design requirements.

[0036] In step three, the bending stress of the thrust ring The calculation formula is as follows:

[0037] ;

[0038] in: ;

[0039] in: : Thickness of the thrust ring, mm;

[0040] Unit bending moment at the connection between the thrust ring and the steel liner wall, kN·m / m;

[0041] Thrust ring height;

[0042] like If the structural design requirements are not met, the thickness of the thrust ring should be increased. Or reduce the height of the thrust ring And perform verification until... It meets the structural design requirements.

[0043] In step three, the longitudinal stress at the connection between the steel liner and the thrust ring... and circumferential stress The calculation formula is as follows:

[0044] ;

[0045] ;

[0046] in: : Maximum pressure value at the end of the steel lining under normal operating conditions (MPa);

[0047] Inner diameter of the steel lining, mm;

[0048] Steel lining thickness, mm;

[0049] : The unit bending moment of the steel lining wall at the connection between the thrust ring wall and the steel lining wall.

[0050] Longitudinal stress Circumferential stress The bending stress of the steel should not exceed the allowable bending stress of the steel lining. .

[0051] In step three, based on the longitudinal stress and circumferential stress The Mises stress is calculated using the following formula:

[0052] ;

[0053] If Mises stress The allowable bending stress of the steel is greater than that of the steel lining. Then increase the thickness of the steel lining. And perform verification until... It meets the structural design requirements.

[0054] Compared with the prior art, the present invention has the following advantages and beneficial effects: for the complex stress of the steel lining structure at the end of the pressure pipeline, it can reasonably determine the number of thrust rings and the arrangement scheme of multiple thrust rings, and at the same time provide theoretical calculation basis for the reasonable selection of ball valve support and downstream expansion joint of ball valve, effectively controlling the project cost while ensuring the safety of the project. Attached Figure Description

[0055] Figure 1 This is a longitudinal cross-sectional view of the steel lining structure at the end of the pressure pipeline of the present invention.

[0056] Figure 2 This is a schematic diagram showing the axial distance between each thrust ring and the stiffening ring in this invention. Detailed Implementation

[0057] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote elements with the same or similar functions throughout. However, it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0058] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0059] This invention provides a design method for the steel lining structure at the end of a pressure pipeline, which combines the axial stress and circumferential stress of the steel lining at the end of the pressure pipeline through comprehensive calculation, and includes the following steps:

[0060] Step 1: Calculate the elongation of steel liner 4. ;

[0061] Step 2: Calculate the percentage of axial force on each thrust ring 6. And determine the maximum percentage. ;

[0062] Step 3: Based on the maximum percentage Calculate the average compressive stress of thrust ring 6 on the surrounding concrete. Bending stress of the thrust ring Longitudinal stress at the connection between steel liner 4 and thrust ring 6 and circumferential stress ;

[0063] Step 4: Based on the calculation results obtained in Step 1 and Step 3, determine whether the design parameters meet the structural design requirements. If not, adjust the parameters accordingly until the design parameters meet the structural design requirements.

[0064] like Figure 1 As shown, the steel liner 4 is located at the end of the pressure pipeline. One end of the steel liner 4 is welded to the ball valve 1. The other end of the ball valve 1 is equipped with an expansion joint 2. The lower end of the ball valve 1 is equipped with a ball valve support 3. A pad 5 is provided between the outer wall of the steel liner 4 and the surrounding concrete. The thrust ring 6 and the stiffening ring 7 are respectively welded to the outer wall of the steel liner 4 and fixed in the surrounding concrete. Multiple thrust rings 6 are located between the thrust ring 6 and the ball valve 1.

[0065] 1. The theoretical judgment steps are as follows:

[0066] a. Based on the thickness of the steel lining, use the maximum pressure head at the end of the steel lining to calculate the axial force and the elongation of the steel lining, i.e., the maximum displacement. The elongation should take into account the influence of circumferential stress.

[0067] b. Based on the longitudinal displacement of the steel lining end, propose the displacement requirements of the ball valve (or other types of valves), and the electromechanical design should consider suitable ball valve supports and select suitable downstream expansion joints for the ball valve;

[0068] c. For axial force, the force on the thrust ring at the upstream position of the steel liner is given, and for multiple thrust rings, the force on each thrust ring is reasonably derived.

[0069] d. Perform stress calculations for each thrust ring to verify whether the stress is within the allowable stress range, and complete the stress verification of the entire end steel pipe section of the water diversion branch.

[0070] 2. Detailed theoretical analysis and formula judgment

[0071] This section introduces the theory that was derived and adopted.

[0072] 1) Calculate the axial force of the steel liner.

[0073] When the ball valve (or other valve) at the end of the steel liner is closed, the steel liner will be subjected to an axial water thrust, the magnitude of which is represented by F as follows:

[0074] ,

[0075] in:

[0076] : Maximum pressure value at the end of the steel lining under normal working conditions (MPa) (water hammer condition is considered normal working condition);

[0077] Inner diameter of the steel lining, mm;

[0078] Axial force, kN.

[0079] 2) Calculate the elongation at the end of the steel liner.

[0080] Considering that the axial force is entirely borne by the steel lining, resulting in longitudinal displacement of the steel lining downstream of the thrust ring, and neglecting the skin friction of the contact concrete on the steel lining, the calculation formula can be referenced as follows:

[0081] ,

[0082] ,

[0083] in:

[0084] Longitudinal stress of steel lining, MPa;

[0085] The elastic modulus of the steel lining is typically taken as 2.06 × 10⁵ N / mm².

[0086] : The distance from the last thrust ring to the ball valve position, in mm;

[0087] Poisson's ratio of steel;

[0088] : Steel lining thickness, mm.

[0089] 3) Derivation of the force ratio of the thrust ring

[0090] If multiple thrust rings exist (usually because a single thrust ring is too thick or the number of rings is insufficient), the axial force needs to be distributed among the multiple thrust rings. However, how to distribute the axial force is a problem that needs to be solved. Considering that force and deformation are positively correlated, the force ratio of each thrust ring can be calculated using the following formula. The deformation of each thrust ring at the distance from the stiffening ring needs to be calculated. The deformation is the same as the calculation formula in Section 2), except that L is replaced with Li:

[0091] ,

[0092] in:

[0093] : These represent the distances (in meters) from the first to the last thrust ring to the front stiffening ring;

[0094] : The theoretical axial elongation of each thrust ring position without considering the constraints of the surrounding concrete, in meters.

[0095] From the distance ratio, the force ratio of each thrust ring can be obtained:

[0096] ,

[0097] ,

[0098] in:

[0099] The percentage of axial force experienced by each thrust ring;

[0100] The maximum percentage of all thrust rings.

[0101] The maximum value of the stress ratio is used for the thrust ring stress calculation, or the calculation and analysis are performed separately for each thrust ring. Considering that the thrust ring accounts for a small proportion of the total engineering volume, the maximum value ratio is usually used as the basis for the calculation.

[0102] 4) Thrust ring under stress

[0103] a) Calculate the concrete stress

[0104] Since the thrust ring is subjected to axial force, which will eventually be transmitted to the concrete, it is important to ensure that the concrete is not crushed. The following formula can be considered:

[0105]

[0106] in:

[0107] : Average compressive stress of the thrust ring on the surrounding concrete, MPa;

[0108] : Thrust ring outer diameter, mm;

[0109] : 28-day compressive strength of external backfill concrete, MPa.

[0110] b) Bending stress of the thrust ring

[0111] The thrust ring is subjected to axial force, which exerts a bending moment on the steel pipe wall in the opposite direction. The unit bending moment at the bottom of the thrust ring with height H can be calculated using the following formula:

[0112]

[0113] in:

[0114] Unit bending moment at the connection between the thrust ring and the steel pipe wall, kN·m / m;

[0115] Thrust ring height.

[0116] The bending stress in the thrust ring is as follows:

[0117]

[0118] in:

[0119] : Bending stress at the thrust ring connection, MPa;

[0120] : Thickness of the thrust ring, mm.

[0121] c) Longitudinal stress at the connection between the pressure steel pipe and the thrust ring

[0122] Due to the complete constraint of the backfill concrete, movement is restricted. Therefore, the longitudinal stress on the outer wall of the pressure steel pipe at the connection with the thrust ring can be obtained by the following formula:

[0123]

[0124] in:

[0125] Part One This refers to the longitudinal stress caused by internal pressure when the valve is closed;

[0126] Part Two The stress in the formula refers to the circumferential stress caused by the internal pressure acting on the steel pipe wall, taking into account the effect of Poisson's ratio.

[0127] Part Three The formula refers to the bending stress of the water intake pipe wall at the connection between the annular thrust ring wall and the water intake pipe wall, where Its formula differs from that for the bending stress in the thrust ring. It is the circumferential bending stress at the connection between the annular pipe and the pressure pipe wall.

[0128] d) Circumferential stress

[0129] The circumferential stress is calculated as follows:

[0130]

[0131] in:

[0132] Longitudinal stress in the wall of the water diversion steel pipe;

[0133] Circumferential stress in the wall of the water diversion steel pipe;

[0134] Allowable bending stress in steel.

[0135] e) Mises stress

[0136] Considering the combination of biaxial stresses, the Mises stress can be used for verification, as shown in the following formula:

[0137]

[0138] 5) Summary

[0139] The elongation at the end of the steel lining provides a theoretical basis for selecting suitable movable ball valve supports and downstream expansion joints. Furthermore, the calculation of the thrust ring's stress ratio is neither overly conservative nor overly risky. This comprehensive analysis of the final concrete stress and the stress on the steel pipe and thrust ring, among other steel structures, includes… , , The stresses meet the requirements of the steel's tensile strength, ensuring the completeness of the overall structural theory and structural safety.

[0140] It should be noted that the above experiments must be conducted according to scientific methods, and the final values ​​of each group should be the average.

[0141] Based on the description and accompanying drawings of this invention, those skilled in the art can readily manufacture or use the steel lining structure design method for the end of a pressure pipeline according to this invention, and can achieve the positive effects described in this invention.

[0142] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "installed," "set," "equipped with," "connected," "linked," and "sleeve" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral construction; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two mechanisms, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0143] In the description of this invention, it should be understood that the terms "one end," "the other end," "outer side," "inner side," "horizontal," "end," "length," "outer end," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The terms "first" and "second" are also used only for the sake of brevity in description and do not indicate or imply relative importance.

[0144] Furthermore, in practicing the claims of this invention, those skilled in the art can understand and influence variations to the disclosed embodiments through a study of the drawings, the disclosure, and the appended claims. Additionally, in the claims and description, words such as "comprising" and "containing" do not exclude other elements or steps, and non-plural nouns do not exclude their plural forms.

[0145] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the present invention are covered by the scope of the claims of the present invention, and will not be listed here.

Claims

1. A design method for a steel lining structure at the end of a pressure pipeline, characterized in that, The comprehensive calculation of axial and circumferential stresses of the steel lining (4) at the end of the pressure pipeline includes the following steps: Step 1: Calculate the elongation of the steel liner (4). ; Step 2: Calculate the proportion of axial force on each thrust ring (6). And determine the maximum percentage. ; Step 3: Based on the maximum percentage Calculate the average compressive stress of the thrust ring (6) on the surrounding concrete. Bending stress of the thrust ring Longitudinal stress at the connection between the steel liner (4) and the thrust ring (6) and circumferential stress ; Step 4: Based on the calculation results obtained in Step 1 and Step 3, determine whether the design parameters meet the structural design requirements. If not, adjust the parameters accordingly until the design parameters meet the structural design requirements.

2. The design method for the steel lining structure at the end of a pressure pipeline as described in claim 1, characterized in that, In step one, the elongation of the steel liner (4) The calculation formula is as follows: ； in: , ; in: : Maximum pressure at the end of the steel lining under normal operating conditions (MPa); : Inner diameter of steel lining (4), mm; Axial force, kN; Longitudinal stress of steel lining (4), MPa; : Steel lining (4) Elastic modulus; :The distance from the last thrust ring to the ball valve position of the steel liner (4), mm; Poisson's ratio of steel; : Steel lining (4) thickness, mm; Elongation of steel liner (4) This provides a theoretical basis for the selection and setting of ball valve support (3) and expansion joint (2).

3. The design method for the steel lining structure at the end of a pressure pipeline as described in claim 1, characterized in that, In step two, the proportion of axial force on each thrust ring (6) The calculation formula is as follows: ； in: ; Maximum proportion ; in: The percentage of axial force experienced by each thrust ring (6); The maximum percentage among all thrust rings (6); : These represent the axial distances (m) between each thrust ring (6) and the stiffening ring; :The theoretical axial elongation of the steel lining at the corresponding position of each thrust ring (6), in meters.

4. The design method for the steel lining structure at the end of a pressure pipeline as described in claim 1, characterized in that, In step three, the average compressive stress of the thrust ring (6) on the surrounding concrete The calculation formula is as follows: ； in: : Thrust ring (6) outer diameter, mm; : Compressive strength of external backfill concrete, MPa; like If the structural design requirements are not met, the outer diameter of the thrust ring (6) should be increased. And perform verification until... It meets the structural design requirements.

5. The design method for the steel lining structure at the end of a pressure pipeline as described in claim 1, characterized in that, In step three, the bending stress of the thrust ring The calculation formula is as follows: ； in: ; in: : Thickness of thrust ring (6), mm; : The unit bending moment at the connection between the thrust ring (6) and the steel lining (4) pipe wall, kN·m / m; : Thrust ring (6) height; like If the structural design requirements are not met, the thickness of the thrust ring (6) should be increased. Or reduce the height of the thrust ring And perform verification until... It meets the structural design requirements.

6. The design method for the steel lining structure at the end of a pressure pipeline as described in claim 1, characterized in that, In step three, the longitudinal stress at the connection between the steel liner (4) and the thrust ring (6) and circumferential stress The calculation formula is as follows: ； ； in: : Maximum pressure value at the end of the steel lining under normal operating conditions (MPa); : Inner diameter of steel lining (4), mm; : Steel lining (4) thickness, mm; : Thrust ring (6) Steel lining at the connection between pipe wall and steel lining (4) Unit bending moment of pipe wall.

7. The design method for a steel lining structure at the end of a pressure pipeline as described in claim 6, characterized in that, Longitudinal stress Circumferential stress The allowable bending stress of the steel should not exceed that of the steel lining (4). .

8. The design method for the steel lining structure at the end of a pressure pipeline as described in claim 7, characterized in that, In step three, based on the longitudinal stress and circumferential stress The Mises stress is calculated using the following formula: ； If Mises stress The allowable bending stress of the steel is greater than that of the steel lining (4). Then increase the thickness of the steel lining (4). And perform verification until... It meets the structural design requirements.

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