RU2111404C1 - Method of manufacture of unit for connecting metal pipes - Google Patents

Abstract

FIELD: manufacture of electrically insulating, compensating and other inserts from composite materials for protection of pipe lines against corrosion, vibration for oil and gas lines, heating systems, aggressive media transport pipe lines, etc. SUBSTANCE: method includes manufacture of two metal tips with beads on their outer surfaces, fitting these tips on mandrel coaxially and at spaced relation to reach other and laying beads on them for embracing the other and lateral surfaces which are opposite to adjacent ends of tips of longitudinal and/or spiral layers of reinforcing dielectric, for example, glass fibres impregnated with polymer binder. Longitudinal and/or spiral layers are laid at varying tension increasing with distance between outer surfaces of tips and/or angle of reinforcing decreasing in the same direction. EFFECT: enhanced efficiency. 2 dwg

Description

 The invention relates to the field of manufacture of pipes, namely, nodes of their connection, and can be used in the manufacture of electrical insulating compensation and other inserts from composite materials to protect against corrosion, vibration, compensation of temperature movements in oil and gas pipelines, heating networks, lines of transportation of aggressive media etc.

 A known method of manufacturing metal pipes [1], including the manufacture of two metal endings with collars on the outer surfaces, installing the endings on the mandrel coaxially with each other, laying reinforcing non-metallic filler, such as glass fibers impregnated with a polymer binder, with the coverage of the collars.

 This method cannot be applied in pipelines operating at high pressures, because when they are used at the fiberglass-shoulder edges, high ones arise that exceed the tensile strength of fiberglass plastic. The increase in the surface area of the collar, bordering fiberglass, in turn leads to high bending stresses in its body, and also does not allow the use of a rational method of manufacturing the tip: welding of rolled profiles to the outer surface of the pipe, because profile rolling is limited in height (12 mm for a pipe with a radius of 350 mm).

 Closest to the technical nature of the claimed is a method of manufacturing a node for the connection of metal pipes [2].

 The method includes the manufacture of two metal tips with the formation on the outer surface of each of them at least two shoulders, the installation of blanks on the mandrel coaxially with a gap to each other and laying on them with the shoulders of the longitudinal and / or spiral layers unidirectionally reinforcing dielectric, for example glass fibers impregnated polymer binder.

 This method allows you to slightly increase the level of the working pressure of the manufactured joint nodes due to a decrease in the level of contact stresses due to an increase in the contact area of fiberglass-material collar due to an increase in the number of the latter at a given building height.

However, the method does not allow the use of such connection nodes in high pressure pipelines, for example gas pipelines (P _y = 5.0 - 9.0 MPa), because the increase in quantity has a limitation arising from the exponential law of the distribution of longitudinal stresses and strains in the longitudinal and spiral layers of fiberglass, covering the shoulders. This is explained by the fact that as the shoulders move away from the ends of the workpieces, the longitudinal loads in the layers are measured from N _max and tend to 0, therefore, an increase in the number of shoulders over 4-5 does not make sense due to the small influence on the working pressure.

 The inventive method allows to increase the level of the working pressure of the manufactured connection node due to the redistribution of the load between the longitudinal layers and the creation of uniform stresses and strains in them. This is achieved by the fact that in the known method of manufacturing a node for connecting metal pipes, including the manufacture of two metal ends with the formation on the outer surface of each of them at least two shoulders, the installation of the ends coaxially with a gap between them and laying on them with the coverage of the outer and side surfaces opposite to the adjacent ends of the workpiece collars of the longitudinal and / or spiral layers of a reinforcing dielectric, for example glass fibers impregnated with a polymer binder, the longitudinal and / or spiral layers are laid with a variable that increases as the distance from the outer surfaces of the tips is increased by the tension and / or modulus of elasticity of the unidirectional material and / or decreases in the same direction the reinforcement angle.

 Laying the longitudinal and / or spiral layers of a unidirectional reinforcing dielectric with a variable that increases with tension as the distance from the outer surfaces of the endings increases, makes it possible to redistribute the loads and make stresses even during loading during operation due to the creation of a rational level of initial technological stresses in each layer.

 Laying the longitudinal and / or spiral layers of a reinforcing unidirectional dielectric with a variable that increases as the elastic modulus of the unidirectional material moves away from the outer surfaces of the tips also makes it possible to redistribute the loads and make the stresses even when loading the joint during operation by using different materials in each or group of adjacent differing in modulus of elasticity in the direction of reinforcement.

 Laying of spiral layers with a variable, decreasing as the angle of reinforcement decreases from the outer surfaces of the tips, also allows you to redistribute the load, make the stress even when loading the joint during operation by creating the required axial stiffness in each layer.

 In all cases, less rigid layers cover the collars adjacent to the ends of the workpieces facing each other, and more rigid layers cover collars located at a maximum distance from these ends. This allows you to provide a time-based connection of all longitudinal and / or spiral layers in the work with the full implementation of the strength characteristics.

 In FIG. 1 shows a General view in section of the connection of metal pipes on the mandrel in the context; in FIG. 2 - graphs of the distribution of stresses along the longitudinal and / or spiral layers.

 The method is as follows. Two metal ends 1 and 2 are made by welding trapezoidal metal profiles 3, 4, 5 and 6, 7, 8 sealed to pipes rolled under their outer radius. Material of pipes and profiles 3 GOST 10705-91. On the outer surface of the blanks 1, 2, annular grooves 9 and 10 are machined and sealing rings 11, 12 are installed. Then, the ends 1, 2 are mounted coaxially on the mandrel 13, maintaining a gap 6 between their adjacent ends 14 and 15. After that, a gap 6, space between adjacent to the adjacent ends 14, 15 of the endings, install a preformed sealing element 16 of rubber 51-2058 TU 105180-88. Then the mandrel with the tips is installed in the machine brand SNP-2 and lay the winding longitudinal and / or spiral layer 17 with the coverage of the outer and side, opposite ends 14, 15, collars 3, 6 of the tips 1, 2, respectively. After that - the space between the side surfaces of the shoulders 3, 4 and 6, 7.

 Then, laying is carried out by winding the longitudinal and / or spiral layer 20 with the coverage of the outer and lateral, opposite ends 14, 15 of the shoulders 18, 19, respectively. Then the spaces between the side surfaces of the shoulders 4, 5 and 7, 8 are filled with end layers 21 and 22, respectively. Then, laying is carried out by winding a spiral or longitudinal layer 23, after which the final external profile of the connection unit by winding the annular layers 24 is formed.

In all cases, the unidirectional reinforcing filler of layers 17, 18, 19, 20, 21, 22, 23, 24 is impregnated in the process of passing the net tract of the SNP-2 machine with a polymer binder ETFM TU 1-596-36-82. After the formation of the outer surface of the node, the polymerization of this binder is carried out in a known manner:
- raising the temperature in the furnace to 90 ^o C for 2.5 ^+0.5 hours;
- exposure at 90 ± 5 ^o C for 3 ^+0.5 hours;
- temperature rise to 120 ^o C for 1.5 ^+0.5 hours;
- exposure at 120 ± 5 ^o C for 4 ^+0.5 hours;
- rise in temperature to 150 ^o C for 1.5 ^+0.5 hours;
- exposure at 150 ± 5 ^o C for 6 ^+0.5 hours;
- temperature rise to 170 ^o C for 1 ^+0.5 hours;
- exposure at 170 ± 5 ^o C for 8 ^+0.5 hours;
- cooling to a temperature of 70 ^o C with the furnace doors closed, further cooling is free.

 In the annular layers 18, 19, 21, 22 in all cases, the fiberglass RVMN TU 6-05-241-404-84 is used as a reinforcing material. Technological tension, reinforcement angles and materials (elastic modulus) of the longitudinal or spiral layers 17, 20, 23 may be different. The options are listed below.

Option 1. Layers 17, 20, 23 - longitudinal (reinforcement angle 0 ^o ) based on fiberglass RVMN TU 6-05-241-404-84; layers 17, 20, 23 are stacked with a variable that increases with distance from the outer surface of the tip by tension.

 Option 2. Layers 17, 20, 23 - spiral based on fiberglass RVMN TU 6-05-241-404-84; these layers are laid by winding with equal tension for each layer, but with a variable, decreasing as the distance from the outer surface of the tips of the reinforcement angle.

Option 3. Layers 17, 20, 23 are longitudinal, they are laid with constant technological tension, and layer 17 is made on the basis of fiberglass RVMN TU 6-05-241-404-84 (elastic modulus 5 • 10 ⁴ MPa), layer 23 - based on the Organos harness TU 6-06-31-581-87 (elastic modulus 11.5 • 10 ⁴ MPa), layers 20 based on the SVM organic harness TU 6-06-31-502-85 (elastic modulus 9 • 10 ⁴ MPa). In other words, when laying, the elastic modulus of the unidirectional material increases with distance from the outer surface of the tips.

 The proposed method produced three nodes of the connection of metal pipes, which were used as electrically insulating, which are elements of the cathodic protection of a high-pressure main gas pipeline. The inserts differed in the values of the technological tension and the laying angles of the longitudinal or spiral layers. In addition, reinforcing dielectrics with different elastic moduli were used for these layers.

Technical characteristics of the connection node:
Conditional pressure, MPa - 7.5
Nominal pass, mm - 700
Length, mm - 1200
Weight, kg - 700
Electrical resistance, MΩ - 5.0
Ending material - Steel Art. 3
Binders - ETFM TU 1-596-36-82
The material of the annular layers - RVMN TU 6-05-241-404-84
First, three pairs of metal embedded elements 1, 2 were made for all variants by welding three rolled trapezoidal profiles 3, 4, 5 and 6, 7, 8 to the outer surface of the pipes, respectively. The profiles were rolled under the outer radius (mm) of the pipes. Annular grooves 9, 10 were cut with a depth of 10 mm. Then, for each variant, three sealing elements 16 and three pairs of sealing rings (D = 11 mm) 11, 12 were molded from rubber 51-2058 TU 105180-88. After that, in all cases, the sealing element 16 and the ends 1, 2 with the sealing rings 11, 12 located in the grooves 9, 10 were installed on the mandrel of the workshop manufacture 13. Endings 1, 2 were mounted coaxially on the mandrel 13, withstanding between adjacent ends 14, 15 clearance σ = 12 mm, selected from the condition for providing electrical resistance R 5 MOhm. The connection node No. 1 was made according to embodiment 1, with the first longitudinal layer being laid with a tension of 5 kg / tourniquet, the second longitudinal layer - 6 kg / tourniquet, and the third - 7 kg / tourniquet.

The connection node N 2 was made in accordance with option 2, while the first layer was laid with an angle of reinforcement of 15 ^o , the second layer - 10 ^o and the third - 5 ^o . The connection node N 3 was made in accordance with option 3.

 After forming the outer surface of the connection node, the product was placed in an aerodynamic furnace and the polymerization mode was carried out according to the mode indicated above. After the regime, the mandrel was removed and pneumatic tests were carried out for tightness and hydraulic tests until destruction. All nodes showed the required tightness at a design pressure of 20.0 MPa. The nodes of the joints were destroyed at the following pressures: 21.2; 20.5; 23.4 MPa - the first, second and third options, respectively.

 When designing by calculation, the axial stresses arising in the longitudinal and / or spiral layers 17, 20, 23 were determined for the prototype method and three options for implementing the proposed method. The calculation results are shown in FIG. 2. Here, curve 25 belongs to the prototype method, curves 26, 27, 28 - options 1, 2, 3 of the proposed method, respectively. The diagram shows that all three options allow you to redistribute the loads between the layers and make the stresses uniform, and most importantly reduce them, which allows you to increase the working pressure, if necessary, or reduce the amount of material at a given working pressure.

 From the requirements for the connection node, determined by the operating conditions of the pipeline, as well as the capabilities of a particular production depends on the correct choice of implementation of the proposed method. So, option 1 has a high bearing capacity, rather cheaper, but it can be implemented only on machines where there is a device for longitudinal laying. Option 2 can be implemented on any spiral winding machine, but the deviation of the reinforcement angle from the meridian somewhat reduces the bearing capacity. Option 3 has the maximum load-bearing capacity due to the use of stronger and tougher materials, but this, as well as the time taken to readjust the nettract when replacing the material, leads to an increase in price, which is justified when using such connection nodes on the most critical and stressed sections of pipelines.

Claims (1)

 A method of manufacturing a node for connecting metal pipes, including the manufacture of two metal endings with the formation on the outer surface of each of them at least two shoulders, installing the ends coaxially with a gap to each other on the mandrel and laying on them with the outer and side surfaces of the shoulders opposite the adjacent ends of the ends longitudinal and / or spiral layers of a reinforcing dielectric, for example glass fibers, impregnated with a polymer binder, characterized in that the longitudinal and / or spiral layers are laid with AC line, increasing with increasing distance from the outer surfaces endings tension and / or elasticity modulus unidirectional material, and / or decreasing in the same direction as reinforcing angle.

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