A design method for the socket thickness of a socket-and-spigot pipe

Abstract

The present invention discloses a design method for the thickness of the socket of a socket-and-spigot pipe, comprising: step S1: selecting multiple places on the inner wall of the socket where stress is easily concentrated, and the selection principle is: if the wall thickness of each selected place is designed to meet the stress strength requirement, then each place of the socket meets the wall thickness requirement; step S2: determining the minimum wall thickness of each selected place in step S1, and the determination principle is: when the material of the socket and the material of the pipe body are the same, the stress of each selected place is not greater than the stress of the inner wall of the pipe body; when the material of the socket and the material of the pipe body are different, the ratio of the stress of each selected place to the yield strength of the socket material is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the pipe body material. The present invention can obtain the minimum wall thickness size of several key parts of the socket through theoretical analysis and calculation, saves materials, and reduces the production, manufacturing and transportation costs of the pipe. The design method is theoretical calculation, low cost and high efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of pipe design, and in particular relates to a method for designing the thickness of a socket of a socket-and-spigot type pipe. Background Art

[0002] Most of the water pipes in the water supply and drainage systems for life and production are socket-and-spigot pipes, with a socket at one end and a spigot at the other. During installation, the spigot of one pipe is inserted into the socket of another pipe and sealed with a seal, thus achieving the connection of each pipe in the pipe network. Figure 1 In the figure, M is the spigot and F is the socket. The socket F is shaped like a trumpet and has different outer diameters at different locations. In order to save materials and reduce the production, manufacturing and transportation costs of pipes, it is best to make the thickness of the socket F at each location minimum or close to the minimum while meeting the use strength. Summary of the invention

[0003] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a design method for the socket thickness of a socket-type pipe. The minimum wall thickness dimensions of several key parts of the socket can be obtained through theoretical analysis and calculation, so that the minimum wall thickness of each part of the socket can be designed. The wall thickness of the processed socket is minimum or close to the minimum, which saves materials and reduces the production, manufacturing and transportation costs of the pipe. The method for designing the minimum wall thickness is theoretical calculation, which has low cost and high efficiency, and provides strong support for experiments and pipe design.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for designing the thickness of a socket of a socket-and-spigot pipe comprises the following steps:

[0006] Step S1: Select multiple locations on the inner wall of the socket where stress is likely to concentrate. The selection principle is: if the wall thickness of each selected location is designed to meet the stress strength requirement, then the wall thickness of each location of the socket designed according to the outer wall design requirement meets the strength requirement;

[0007] Step S2: Determine the minimum wall thickness of each selected location in step S1 to obtain the outer wall of each selected location. The determination principle is: when the material of the socket and the material of the pipe body are the same, the stress at each selected location is not greater than the stress of the inner wall of the pipe body; when the material of the socket and the material of the pipe body are different, the ratio of the stress at each selected location to the yield strength of the socket material is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the pipe body material.

[0008] As a further improvement of the above technical solution:

[0009] The design method further comprises step S3: connecting the outer walls at various selected locations in sequence to obtain the shape of the outer wall of the socket and the thickness at various locations.

[0010] For the same base pipe, along the direction from the socket to the spigot, the inner wall of the socket includes a first step, a second step, a third step, a fourth step, and a fifth step arranged in sequence, one end of the inner wall of the pipe body is a sixth step, the chamfer at the connection between the fourth step and the fifth step is a first chamfer, the chamfer at the connection between the fifth step and the sixth step is a second chamfer, the chamfer at the connection between the second step and the third step is a third chamfer, the chamfer at the connection between the first step and the second step is a fourth chamfer, and the chamfer at the connection between the third step and the fourth step is a fifth chamfer.

[0011] In step S1, the selected locations on the inner wall of the socket where stress is likely to concentrate are the first chamfer, the second chamfer and the third chamfer.

[0012] In step S2, the minimum wall thickness of each selected point in step S1 is calculated by using the stress calculation formula.

[0013] In step S2, the socket is regarded as a pressure vessel including at least two coaxially connected pressure vessels with conical inner walls and at least one annular reinforcement ring installed on the inner wall of the pressure vessel.

[0014] When the material of the socket is the same as that of the pipe body, the stress calculation formula is: ,in, is the hoop stress of the pipe body, is the hoop stress at the selected location.

[0015] When the material of the socket is different from that of the pipe body, the stress calculation formula is: ,in, is the hoop stress of the pipe body, is the hoop stress at the selected location, Q0 is the yield strength of the pipe body material, and Q1 is the yield strength of the socket material.

[0016] , , where D0 is the outer diameter of the base tube, D is the diameter of the selected location, p is the pressure of the fluid in the base tube, S is the thickness of the base tube, S0 is the wall thickness of the selected location, and α is the semi-cone angle of the cone at the selected location.

[0017] When selecting the location where the sealing ring will be installed, .

[0018] The beneficial effects of the present invention are as follows: the minimum wall thickness dimensions of several key parts of the socket can be obtained through theoretical analysis and calculation, so that the minimum wall thickness of each part of the socket can be designed, and the wall thickness of the processed socket is minimum or close to minimum, which saves materials and reduces the production, manufacturing and transportation costs of pipes. The method for designing the minimum wall thickness is theoretical calculation, which has low cost and high efficiency, and provides strong support for experiments and pipe design. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the socket and the spigot connection of the present invention Figure 1 ;

[0020] Figure 2 Schematic diagram of the socket and the spigot connection of the present invention Figure 2 . DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0022] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0023] Embodiment 1

[0024] A design method for the thickness of the socket of a spigot-and-socket pipe, wherein the inner wall shape of the socket F of the pipe is in accordance with the inner wall shape specified in the group standard "Spigot-and-socket Flexible Joint Anti-corrosion Steel Pipe for Water Supply and Drainage" (T / CISA 108-2021) and GB / T 13295-2008, such as Figure 1As shown. The inner wall of the socket F is stepped. For the same base pipe, along the direction from the socket F to the spigot M, the inner wall of the socket F includes the first step 1, the second step 2, the third step 3, the fourth step 4, and the fifth step 5 arranged in sequence. One end of the inner wall of the pipe body is the sixth step 6, and the corresponding inner diameters are: D2, D1, (D3-2F0), D3, D4, (D0-2S), among which the inner diameters of the sixth step 6, the first step 1, the fifth step 5, the third step 3, the fourth step 4, and the second step 2 increase in sequence, that is: (D0-2S) < D2 < D4 < (D3-2F0) < D3 < D1. The lengths of the first step 1, the second step 2, the third step 3, the fourth step 4, and the fifth step 5 are respectively: T3, T4, T5, (T2-T4-T5), (T1-T2-T3), that is, T1 is the sum of the lengths of the first step 1, the second step 2, the third step 3, the fourth step 4, and the fifth step 5, and T2 is the sum of the lengths of the second step 2, the third step 3, and the fourth step 4. The lengths refer to the dimensions of the corresponding parts in the axial direction of the base pipe. S is the wall thickness of the pipe body, and F0 is the height of the third step 3 protruding from the fourth step 4, and F0 ≥ 0. The connection of each step is processed with chamfers, wherein the chamfer at the connection of the fourth step 4 and the fifth step 5 is the first chamfer R1, the chamfer at the connection of the fifth step 5 and the sixth step 6 is the second chamfer R2, the chamfer at the connection of the second step 2 and the third step 3 is the third chamfer R3, the chamfer at the connection of the first step 1 and the second step 2 is the fourth chamfer R4, and the chamfer at the connection of the third step 3 and the fourth step 4 is the fifth chamfer R5. Wherein, D0 is the outer diameter of the base pipe of the pipe. The base pipe refers to the pipe in the factory setting, and the base pipe is not installed with a reinforcement ring, and no secondary processing such as a composite process is performed. The base pipe includes a socket F, a pipe body and a socket M connected in sequence. The pipe body can be divided into two parts, namely a main body and a transition part, and the transition part is used for the transition connection between the main body and the socket F, that is, the socket F, the transition part, the main body and the socket M are connected in sequence. The inner wall surface of the pipe body is a cylindrical surface, that is, the inner diameter of the transition part is equal to the inner diameter of the main body. The main body is cylindrical, and the outer wall of the transition part is a conical surface. In other words, the thickness of the main body is uniform or substantially uniform, and the thickness of the transition part gradually decreases along the direction from the socket F to the spigot M. The outer diameter of the pipe body refers to the outer diameter of the main body, the outer diameter of the base pipe is the outer diameter of the pipe body, and the thickness of the pipe body refers to the thickness of the main body. Figure 1 In the figure, X is the length of the chamfer at the end of the socket M along the axial direction, Y is the height of the chamfer at the end of the socket M (i.e. the radial dimension), DE is the outer diameter of the socket M, and T6 is the length of the socket M.

[0025] Since the dimensions of the inner wall of the socket F are fully given by the relevant standards, it is necessary to design some key dimensions of the outer wall on this basis, in order to save costs such as materials while meeting strength requirements.

[0026] Based on the above structure, the purpose of this scheme is to design the thickness of the socket F so that the thickness is minimum or close to minimum while meeting the use strength, so as to reduce the production, manufacturing and transportation costs of the pipe.

[0027] The design method comprises the following steps:

[0028] Step S1: Select multiple locations on the inner wall of the socket F where stress is likely to concentrate. The selection principle is: if the wall thickness of these locations meets the stress strength requirements, then the wall thickness of each location of the socket F meets the strength requirements.

[0029] Step S2: Determine the minimum wall thickness of each selected location in step S1, and obtain the outer wall of each selected location. The determination principle is: when the material of the socket F is the same as the material of the pipe body, the stress at each selected location is not greater than the stress of the inner wall of the pipe body; when the material of the socket F is different from the material of the pipe body, the ratio of the stress at each selected location to the yield strength of the socket F material is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the pipe body material.

[0030] Step S3: Connect the selected outer walls in sequence to obtain the outer wall shape and thickness of the socket F at various locations.

[0031] In step S1, based on material mechanics knowledge and experience, several locations on the inner wall of the socket F where stress is most likely to be concentrated are selected as the first chamfer R1, the second chamfer R2, and the third chamfer R3. The analysis is as follows:

[0032] For the inner wall of the stepped socket F, according to mechanical knowledge, the stress concentration point is located at the connection between adjacent steps, that is, at each chamfer. Since the socket F is a trumpet-like shape, the outer diameter of the socket F tends to decrease from the socket F to the spigot M of the same base pipe.

[0033] Based on the above conditions, since the inner diameter at the fourth chamfer R4 is equal to the inner diameter at the third chamfer R3, both are equal to D1, the wall thickness at the fourth chamfer R4 must be greater than the wall thickness at the third chamfer R3 to meet the requirement that the socket F is quasi-trumpet-shaped. Therefore, as long as the wall thickness at the third chamfer R3 meets the stress strength requirement, the wall thickness at the fourth chamfer R4 must meet the strength requirement. Similarly, the inner diameter at the fifth chamfer R5 is equal to the inner diameter at the first chamfer R1, both are D3, so the wall thickness at the fifth chamfer R5 must be greater than the wall thickness at the first chamfer R1 to meet the requirement that the socket F is quasi-trumpet-shaped. Therefore, as long as the wall thickness at the first chamfer R1 meets the stress strength requirement, the wall thickness at the fifth chamfer R5 must meet the strength requirement. Therefore, the stress concentration points finally selected are the first chamfer R1, the second chamfer R2, and the third chamfer R3. In other words, in this scheme, the analysis area of ​​the socket F is the area between the third chamfer R3 and the second chamfer R2.

[0034] In step S2, the minimum wall thickness of each location selected in step S1 is calculated by the stress calculation formula. The specific method is as follows: the analysis area of ​​the socket F is regarded as consisting of at least two coaxial pressure vessels with conical inner walls connected end to end and several internal reinforcement rings, and the reinforcement rings are connected to the inner wall of the pressure vessel. In other words, the analysis area of ​​the socket F is regarded as consisting of at least two conical pressure vessels and several internal reinforcement rings. At this time, as long as the corresponding conical pressure vessel meets the strength requirements, the socket F will definitely meet the strength requirements, such as Figure 1 and 2 shown.

[0035] For a thin-walled cylindrical pressure vessel, its wall thickness is S, its diameter is D0, and its internal pressure is p. From material mechanics, we can get the axial stress σ of the pressure vessel wall: 轴 and hoop stress σ 环 They are as follows:

[0036] (1)

[0037] (2)

[0038] The hoop stress σ 环 That is, the circumferential stress, wherein the diameter D0 is half of the sum of the outer diameter and the inner diameter of the cylinder, or the inner diameter of the cylinder, or the outer diameter of the cylinder.

[0039] Similarly, for a thin-walled conical pressure vessel, when the wall thickness is S and the internal pressure is p, the stress σ in the axial direction of the vessel wall at the diameter D is 轴 and hoop stress σ 环 They are:

[0040] (3)

[0041] (4)

[0042] in α It is the semi-cone angle of the conical pressure vessel, that is, half of the opening angle. In other words, in the section passing through the central axis of the cone, the angle between the cone wall and the central axis is the semi-cone angle. Wherein, the diameter D is half of the sum of the outer diameter and the inner diameter of the corresponding part of the cone, or the inner diameter of the corresponding part, or the outer diameter of the corresponding part.

[0043] From the above, in this embodiment, the analysis area of ​​the socket F includes two coaxially connected conical pressure vessels plus several internal reinforcement rings. The two coaxially connected conical pressure vessels are respectively a first cone and a second cone, which share the same central axis with the socket F, wherein the first chamfer R1 and the second chamfer R2 are located on the inner wall of the first cone, as shown in FIG. Figure 1The dotted line between the first chamfer R1 and the second chamfer R2 is the inner wall section of the first cone. The first chamfer R1 and the third chamfer R3 are located on the inner wall of the second cone. Figure 1 The dotted line between the first chamfer R1 and the third chamfer R3 is the inner wall section of the second cone. For the area between the first chamfer R1 and the second chamfer R2, the portion between the inner wall of the first cone and the outer wall of the socket F is the entire side wall of the first cone, and the portion between the inner wall of the first cone and the inner wall of the socket F is an annular reinforcement ring j. Similarly, for the area between the first chamfer R1 and the third chamfer R3, the portion between the inner wall of the second cone and the outer wall of the socket F is the entire side wall of the second cone, and the portion between the inner wall of the second cone and the inner wall of the socket F is another annular reinforcement ring.

[0044] exist Figure 1 In the cross section shown, the angle between the straight line passing through the first chamfer R1 and the second chamfer R2 and the axis of the tube is the semi-cone angle of the first cone, set as α1. The angle between the straight line passing through the first chamfer R1 and the third chamfer R3 and the axis of the tube is the semi-cone angle of the second cone, set as α2.

[0045] but:

[0046] (5)

[0047] (6)

[0048] Generally, the material of the socket is consistent with that of the pipe body, and the pipe body meets the strength requirements. To make the socket meet the strength requirements, the hoop stress at the first chamfer R1 Not greater than the hoop stress of the pipe body , hoop stress at the second chamfer R2 Not greater than the hoop stress of the pipe body , Hoop stress at the third chamfer R3 Not greater than the hoop stress of the pipe body , that is:

[0049] (7)

[0050] (8)

[0051] (9)

[0052] Then we have:

[0053] (10)

[0054] (11)

[0055] (12)

[0056] in, S 1. S 2. S 3 are the wall thicknesses at the first chamfer R1, the second chamfer R2, and the third chamfer R3, respectively, and we get:

[0057] (13)

[0058] (14)

[0059] (15)

[0060] Since there is a sealing ring z at the third chamfer R3, in order to achieve sealing, the pressure of the sealing ring z on the socket F must be greater than the pressure p of the fluid in the pipe. According to existing research, the average pressure of the sealing ring z on the inner wall of the socket F is generally 1.4 times the fluid pressure. It can be obtained from formulas (3) and (4) that the stress is proportional to the pressure and inversely proportional to the wall thickness. When the pressure increases to 1.4 times, in order to keep the stress unchanged, the wall thickness should be increased to 1.4 times at the same time. Then formula (15) is corrected to:

[0061] (16)

[0062] So we have:

[0063] (17)

[0064] (18)

[0065] (19)

[0066] Among them, S 1m , S 2m , S 3m They are the minimum wall thickness at the first chamfer R1, the second chamfer R2, and the third chamfer R3 respectively.

[0067] From above, Figure 2 As shown, the minimum outer diameter at the second chamfer R2 d 1. Minimum outer diameter at the first chamfer R1 d 2 , the minimum outer diameter at the third chamfer R3 d 3 are as follows:

[0068] (20)

[0069] (twenty one)

[0070] (twenty two)

[0071] The following example is used to calculate the wall thickness parameters of the socket F.

[0072] In this embodiment, the material of the pipe body and the socket F is Q235.

[0073] Table 1 is the socket size parameter table for the nominal pipe diameters of 600mm and 1200mm at a pressure of 3MPa as specified in the relevant standards:

[0074] Table 1 Dimensional parameters of sockets with nominal pipe diameters of 600 mm and 1200 mm as specified in relevant standards

[0075]

[0076] Based on this scheme, the wall thickness dimensions of the two sockets F in Table 1 are calculated and shown in Table 2.

[0077] Table 2 Wall thickness, outer diameter and semi-cone angle of two sockets

[0078]

[0079] In step S3, the outer diameter of the end surface of the socket F only needs to be larger than the outer diameter at the third chamfer R3, and the specific value can be flexibly selected.

[0080] Embodiment 2

[0081] Different from the first embodiment, the material of the socket F in this embodiment is different from the material of the pipe body. Assume that the yield strength of the pipe body material is Q0, and the yield strength of the material used for the socket F is Q1.

[0082] Similarly, in order for the socket F to meet the strength requirements, the stress at the first chamfer R1, the second chamfer R2, and the third chamfer R3 and the stress on the inner wall of the pipe body should satisfy:

[0083] (twenty three)

[0084] (twenty four)

[0085] (25)

[0086] Then we have:

[0087] (26)

[0088] (27)

[0089] (28)

[0090] Similarly, considering the influence of the sealing ring at the third chamfer R3, the wall thickness of each chamfer is:

[0091] (29)

[0092] (30)

[0093] (31)

[0094] Therefore, the minimum wall thickness at the first chamfer R1, the second chamfer R2, and the third chamfer R3 are as follows:

[0095] (32)

[0096] (33)

[0097] (34)

[0098] Minimum diameter at the second chamfer R2 d 1. Minimum diameter at the first chamfer R1 d 2 , the minimum diameter at the third chamfer R3 d 3 are as follows:

[0099] (35)

[0100] (36)

[0101] (37)

[0102] Finally, it is necessary to explain here that the above embodiments are only used to further illustrate the technical solution of the present invention in detail and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above content of the present invention all fall within the scope of protection of the present invention.

Claims

1. A method for designing the thickness of the socket of a socket-and-spigot pipe, characterized in that: The steps include: Step S1: Select multiple locations on the inner wall of the socket (F) where stress is likely to be concentrated. The selection principle is: if the wall thickness of each selected location is designed to meet the stress strength requirement, then the wall thickness of each location of the socket (F) meets the strength requirement; Step S2: Determine the minimum wall thickness of each selected location in step S1, and obtain the outer wall of each selected location. The determination principle is: when the material of the socket (F) is the same as the material of the pipe body, the stress at each selected location is not greater than the stress of the inner wall of the pipe body; when the material of the socket (F) is different from the material of the pipe body, the ratio of the stress at each selected location to the yield strength of the socket (F) material is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the pipe body material. The minimum wall thickness of each location selected in step S1 is calculated by the stress calculation formula.

2. The design method according to claim 1, characterized in that: The design method further comprises step S3: connecting the outer walls of the selected locations in sequence to obtain the shape of the outer wall of the socket (F) and the thickness of the outer wall at each location.

3. The design method according to claim 1 or 2, characterized in that: For the same base pipe, along the direction from the socket (F) to the spigot (M), the inner wall of the socket (F) comprises a first step (1), a second step (2), a third step (3), a fourth step (4), and a fifth step (5) arranged in sequence, one end of the inner wall of the pipe body is a sixth step (6), the chamfer at the connection between the fourth step (4) and the fifth step (5) is a first chamfer (R1), the chamfer at the connection between the fifth step (5) and the sixth step (6) is a second chamfer (R2), the chamfer at the connection between the second step (2) and the third step (3) is a third chamfer (R3), the chamfer at the connection between the first step (1) and the second step (2) is a fourth chamfer (R4), and the chamfer at the connection between the third step (3) and the fourth step (4) is a fifth chamfer (R5).

4. The design method according to claim 3, characterized in that: In step S1, the selected locations on the inner wall of the socket (F) where stress is likely to concentrate are the first chamfer (R1), the second chamfer (R2) and the third chamfer (R3).

5. The design method according to claim 1 or 4, characterized in that: In step S2, the minimum wall thickness of each selected point in step S1 is calculated by using the stress calculation formula.

6. The design method according to claim 5, characterized in that: In step S2, the socket (F) is regarded as a pressure vessel comprising at least two coaxially connected pressure vessels with conical inner walls and at least one annular reinforcement ring installed on the inner wall of the pressure vessel.

7. The design method according to claim 6, characterized in that: When the material of the socket (F) is the same as that of the pipe body, the stress calculation formula is: ,in, is the hoop stress of the pipe body, is the hoop stress at the selected location.

8. The design method according to claim 6, characterized in that: When the material of the socket (F) is different from that of the pipe body, the stress calculation formula is: ,in, is the hoop stress of the pipe body, is the hoop stress at the selected location, Q0 is the yield strength of the pipe body material, and Q1 is the yield strength of the material used for the socket (F).

9. The design method according to claim 7 or 8, characterized in that: , , where D0 is the outer diameter of the base tube, D is the diameter of the selected location, p is the pressure of the fluid in the base tube, S is the thickness of the base tube, S0 is the wall thickness of the selected location, and α is the semi-cone angle of the cone at the selected location.

10. The design method according to claim 9, characterized in that: When selecting the location where the sealing ring will be installed, .

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