Pipeline repair welding heat exchange simulation device and simulation method

Abstract

The application belongs to the technical field of pipeline repair, and provides a pipeline repair welding heat exchange simulation device and a simulation method, wherein the device comprises a pipeline, a B-type sleeve, a compressed air bottle and a liquid nitrogen bottle; the pipeline is sealed at both ends, one end of which is provided with a thermometer, and the other end is connected with the compressed air bottle and the liquid nitrogen bottle through an air pipe; the B-type sleeve is welded on the surface of the pipeline, and the welding position is an in-service welding seam; the compressed air bottle is used for introducing air into the pipeline; and the liquid nitrogen bottle is used for introducing nitrogen into the pipeline. The device of the application introduces mixed cooling medium into the pipeline by using the compressed air bottle and the liquid nitrogen bottle, so that a temperature difference can be generated between the inner wall and the outer wall of the pipeline, thereby effectively simulating the actual working condition of the pipeline, providing a simulation device for studying the hardening condition of the pipeline, and making the test condition reach or even exceed the same construction site condition, thereby providing hardware support for the research on the pipeline repair technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pipeline repair, and particularly relates to a pipeline repair welding heat exchange simulation device and a simulation method. BACKGROUND

[0002] In-service welding repair refers to a kind of welding repair of a pipeline under the condition of no stop of conveying, which guarantees the continuous operation of the pipeline and is an environmentally friendly, economical and efficient repair mode, and has a broad development prospect. The welding of an in-service pipeline system mainly has two problems. One is to avoid "burning through", that is, the rupture caused by the arc burn of a pipeline wall. The other is hydrogen-induced cracking, which is mainly caused by the acceleration of the heat dissipation of the pipeline wall by the flowing medium in the pipeline, so that the cooling speed of the welding is increased. The generation of hydrogen-induced cracking should meet three conditions at the same time: the oxygen content in the weld, the hardening tendency of the welded joint and the restraint stress borne by the welded joint. If one of the conditions is not met, hydrogen-induced cracking can be avoided. When the welding of an in-service pipeline system is performed, the use of a low-hydrogen electrode or a low-hydrogen welding process method, and a method for reducing the formation of hardened structure (when low-hydrogen level cannot be guaranteed) can effectively avoid hydrogen-induced cracking. At the same time, after experiencing the complex thermal cycle process of rapid non-uniform heating and cooling of welding, the performance of the welding pool, especially the heat-affected zone (HAZ) of welding, often seriously mismatches the performance of the pipeline itself, which causes the problem of service safety and reliability. In order to avoid hydrogen-induced cracking, the most commonly used method is to use sufficient heat input to overcome the influence of the flowing medium.

[0003] At present, the method of preheating or tempering bead deposition sequence can also reduce the generation of hydrogen-induced cracking, but when the welding of certain in-service pipeline systems is performed, due to the heat dissipation of the conveying medium, it is difficult to preheat. There are various methods for predicting heat input, including computer simulation thermal analysis to predict the heat input required in the welding production, but it cannot replace the welding procedure qualification. The influence law of different flowing medium cooling environments in the pipeline and different welding processes on the comprehensive performance of the in-service welding of the pipeline is studied, but due to the great danger of actual oil and gas pipeline in-service welding and the high cost of the test, it is necessary to simulate the in-service welding environment in the laboratory for research and evaluation, and the water is mostly used as the flowing medium for the in-service welding research in the international. API 1104 and GB / T 31032 Appendix stipulate that "when the welding test joint is tested, the test pipe is filled with water, and the heat condition when the water flows through the test section is the same as or more severe than the construction site", but there are some problems in the implementation process of the method, such as the limited volume of the pipe cavity, the un-timely control of the water flow velocity at the inlet and outlet of the device, and the like, which can cause the delayed heat dissipation of the test section, and it is difficult to achieve the same construction site conditions. SUMMARY

[0004] In order to solve at least one problem in the background art, the present application proposes a pipeline repair welding heat exchange simulation device and a simulation method.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A pipeline repair welding heat exchange simulation device, comprising a pipeline, a B-type sleeve, a compressed air bottle and a liquid nitrogen bottle.

[0007] The pipeline is sealed at both ends, one end of which is provided with a thermometer, and the other end is connected to the compressed air bottle and the liquid nitrogen bottle through an air pipe.

[0008] The B-type sleeve is welded to the surface of the pipeline, and the welding position is an in-service welding seam.

[0009] The compressed air bottle is used to introduce air into the pipeline.

[0010] The liquid nitrogen bottle is used to introduce nitrogen into the pipeline.

[0011] Preferably, the compressed air bottle and the liquid nitrogen bottle are respectively connected with gas delivery pipes, one end of the two gas delivery pipes is connected with a converging gas pipe, and the converging gas pipe is connected with the pipeline.

[0012] Preferably, a valve is installed on the gas delivery pipe.

[0013] Preferably, a flow meter is installed on the converging gas pipe.

[0014] A simulation method for the above-mentioned pipeline repair welding heat exchange simulation device, comprising the following steps:

[0015] Controlling the opening of the valve to introduce the cooling medium into the pipeline;

[0016] Welding the pipeline and the B-type sleeve;

[0017] Calculating the temperature change of the pipeline with wall thickness.

[0018] Preferably, controlling the opening of the valve to introduce the cooling medium into the pipeline comprises the following steps:

[0019] Adjusting the input temperature of the cooling medium;

[0020] Adjusting the flow of the cooling medium.

[0021] Preferably, the cooling medium is air or nitrogen or a mixture of air and nitrogen.

[0022] Preferably, the input temperature is:

[0023] T=(v1xT1+v2xT2) / (v1+v2);

[0024] In the formula, T is the input temperature, v1 is the air flow rate, T1 is the nitrogen temperature, v2 is the nitrogen flow rate, and T2 is the nitrogen temperature.

[0025] The flow rate of the cooling medium is the total amount of the cooling medium entering the pipeline per unit time, which is equal to the product of the flow rate of the cooling medium and the unit time.

[0026] Preferably, the temperature change of the pipeline with wall thickness is calculated, including the following steps:

[0027] Obtain the temperature of the inner wall of the pipeline;

[0028] Obtain the temperature of the outer wall of the pipeline;

[0029] Calculate the heat conduction temperature at any wall thickness of the pipeline based on the temperature of the inner wall and the temperature of the outer wall of the pipeline.

[0030] Preferably, the heat conduction temperature at any wall thickness of the pipeline satisfies:

[0031]

[0032] In the formula, T h is the heat conduction temperature with a wall thickness of h; T 外 is the outer wall temperature of the pipeline; T 内 is the inner wall temperature of the pipeline, which is equal to the temperature of the cooling medium; A1 and A2 are conversion coefficients; and X is the direction of heat flow.

[0033] The beneficial effects of the present application are:

[0034] 1. The device of the present application uses compressed air bottles and liquid nitrogen bottles to introduce mixed cooling medium into the pipeline, which can generate a temperature difference between the inner wall and the outer wall of the pipeline, thereby effectively simulating the actual working condition of the pipeline, providing a simulation device for studying the hardening condition of the pipeline, and making the test conditions reach or even exceed the same construction site conditions, thereby providing hardware support for the research of pipeline repair technology.

[0035] 2. The present application provides a method for simulating the heat exchange of in-service pipeline repair welding, which adjusts the temperature and flow rate of the cooling medium in the pipeline to control the temperature gradient attenuation in the wall thickness direction of the pipeline at the welding position, so as to realize the supercooling degree of the welding temperature near the welding pool close to the actual working condition or more severe. The present application overcomes the problem of delayed heat dissipation of the test section in the original method, and can effectively carry away a large amount of heat through the temperature and flow rate control of the cooling medium, so as to quickly and flexibly control the temperature of the test section and meet the actual non-stop transportation working condition.

[0036] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The purposes and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description and appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0038] Figure 1 A structural schematic diagram of a pipeline repair welding heat exchange simulation device of the present application is shown.

[0039] Figure 2 A schematic diagram of a welding molten pool of the present application is shown.

[0040] Figure 3 A schematic diagram of the temperature field distribution of the pipeline wall thickness direction of the welding position of the present application is shown.

[0041] In the figure: 1, pipeline; 2, B-type sleeve; 3, in-service welding weld; 4, thermometer; 5, compressed air bottle; 6, liquid nitrogen bottle; 7, valve; 8, flowmeter; 9, welding torch tip; 10, welding molten pool; 11, coarse grain zone; 12, fine grain zone. DETAILED DESCRIPTION

[0042] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0043] Embodiment one

[0044] A pipeline repair welding heat exchange simulation device, such as Figure 1As shown, it comprises a pipeline 1, a B-type sleeve 2, a compressed air bottle 5 and a liquid nitrogen bottle 6. The pipeline 1 is sealed at both ends, one end of which is provided with a thermometer 4, and the other end is connected with the compressed air bottle 5 and the liquid nitrogen bottle 6 through a gas pipe. The B-type sleeve 2 is welded on the surface of the pipeline 1, and the welding position is a welding seam 3 in service. The compressed air bottle 5 is used to introduce air into the pipeline 1, and the liquid nitrogen bottle 6 is used to introduce nitrogen into the pipeline 1. In addition, the compressed air bottle 5 and the liquid nitrogen bottle 6 are respectively connected with gas delivery pipes, one end of the two gas delivery pipes is connected with a converging pipe, the converging pipe is communicated with the pipeline 1, and the two gas delivery pipes are respectively provided with a valve 7, so that the flow of the cooling medium can be controlled. A flow meter 8 is also arranged on the converging pipe, so that the flow of the cooling medium through the converging pipe per unit time can be calculated.

[0045] It should be noted that, Figure 1 For the implementation diagram of Example 1, in some specific implementation processes, the valve 7 can be an electromagnetic valve, so as to more accurately control the opening of the valve 7. In addition, in the Figure 1 cooling medium is mainly provided by the compressed air bottle 5 and the liquid nitrogen bottle 6, which can deliver compressed low-temperature air and low-temperature nitrogen gas vaporized from liquid nitrogen, so as to ensure that the temperature inside the pipeline 1 is lower than the temperature generated by the external welding, and heat exchange is realized. Of course, in some specific implementation processes, the cooling medium is not limited to compressed air and liquid nitrogen, for example, liquid water, dry ice and other cooling media can also be added, and the specific cooling medium should be determined according to actual needs.

[0046] It should be further pointed out that the thermometer 4 is arranged at one end of the pipeline 1, and the purpose is to detect the problem of the cooling medium in the pipeline 1, and the temperature of the cooling medium can be considered as the same as the temperature of the inner wall of the pipeline 1.

[0047] Further, as shown in the accompanying Figure 2 When repairing the outer wall of the pipeline 1 by welding, the heat generated by the welding torch tip 9 causes the welding pool 10 to appear on the outer wall of the pipeline 1, and the coarse grain zone 11 and the fine grain zone 12 caused by welding heat input will appear around the welding pool 10. Generally, the large temperature gradient existing in the outer surface layer of the welding position will cause the appearance of quenched structure near the welding pool 10, and then the hydrogen-induced cracking phenomenon will appear, and the delayed cracking problem will exist in the weld toe position. In order to effectively simulate the quenched cracking problem of the pipeline 1, the device of Example 1 is proposed.

[0048] Example Two

[0049] Based on the device of Example One, a simulation method is proposed, which comprises the following steps:

[0050] S1: control the opening of the valve 7, and introduce the cooling medium into the pipeline 1, wherein the cooling medium is air or nitrogen or a mixture of air and nitrogen; S2: weld the pipeline 1 and the B-type sleeve 2; S3: calculate the temperature change of the pipeline 1 with the wall thickness.

[0051] Further, in S1, the following steps are included:

[0052] S101: adjust the input temperature of the cooling medium, wherein the input temperature is:

[0053] T=(v1×T1+v2×T2) / (v1+v2); (1)

[0054] In the formula, T is the input temperature, v1 is the air flow rate, T1 is the nitrogen temperature, v2 is the nitrogen flow rate, and T2 is the nitrogen temperature.

[0055] S102: adjust the flow of the cooling medium, wherein the flow of the cooling medium is the total amount of the cooling medium entering the pipeline 1 per unit time, which is equal to the product of the flow rate of the cooling medium and the unit time.

[0056] It should be noted that the pipeline 1 of the present application will change the heat conductivity, thereby forming different temperature gradients, according to Fourier's law, the definition formula of the heat conductivity is:

[0057] q=-λ(dt / dx); (2)

[0058] Wherein, x is the heat flow direction, q is the heat flow density, that is, the heat transferred per unit time in the heat direction; dt / dx is the temperature gradient in the heat flow direction; λ is the thermal conductivity, the thermal conductivity of different substances is different, and the thermal conductivity of the same substance will change due to the different state parameters, and the thermal conductivity is generally regarded as a function of temperature.

[0059] Further, in S3, the following steps are included:

[0060] S301: obtain the temperature of the inner wall of the pipeline 1; S302: obtain the temperature of the outer wall of the pipeline 1; S303: calculate the heat conduction temperature at any wall thickness of the pipeline 1 based on the temperature of the inner wall and the temperature of the outer wall of the pipeline 1.

[0061] Further, the heat conduction temperature at any wall thickness of the pipeline 1 satisfies:

[0062]

[0063] In the formula, T h is the heat conduction temperature at the wall thickness h; T 外 is the outer wall temperature of the pipeline 1; and T 内Tin is the inner wall temperature of the pipeline 1, which is equal to the temperature of the cooling medium; A1 and A2 are conversion coefficients, wherein A1 is 0.055℃ / mm, and A2 is 0.256℃ / mm 2 x is the direction of heat flow, i.e. the wall thickness direction.

[0064] It should be noted that in Example Two, the device of the present application at least includes the following control modes:

[0065] Mode One

[0066] The low-temperature air in the compressed air bottle 5 is introduced into the pipeline 1, the opening of the valve 7 is controlled, the valve 7 corresponding to the liquid nitrogen bottle 6 is closed, and then the heat exchange effect of the low-temperature air on the pipeline 1 is calculated.

[0067] Mode Two

[0068] The nitrogen in the liquid nitrogen bottle 6 is introduced into the pipeline 1, the opening of the valve 7 is controlled, the valve 7 corresponding to the compressed air bottle 5 is closed, and then the heat exchange effect of the nitrogen on the pipeline 1 is calculated.

[0069] Mode Three

[0070] The nitrogen and the low-temperature air are introduced into the pipeline 1 at the same time, the opening of the valve 7 is controlled, and then the heat exchange effect of the mixed gas on the pipeline 1 is calculated.

[0071] Mode Four

[0072] Both of the valves 7 are closed, and then the heat exchange effect of the normal-temperature air on the pipeline 1 is calculated.

[0073] Mode Five

[0074] The cooling medium in the compressed air bottle 5 or the liquid nitrogen bottle 6 is replaced by water, and then the heat exchange effect of the water on the pipeline 1 is tested separately.

[0075] As Figure 3As shown in the figure, wherein straight line A represents the temperature gradient of the empty welded pipeline 1 along the wall thickness direction (from the outer wall to the inner wall), the outer wall temperature of the pipeline 1 during the in-service welding process remains unchanged due to the continuous welding heat input. In the conventional welding evaluation method, there is no medium in the pipeline 1, and the inner wall cooling temperature of the pipeline 1 is the ambient temperature. In general, the temperature change of the pipeline 1 in the wall thickness direction is nearly linear. Curve B represents the temperature gradient of the in-service welded pipeline 1 along the wall thickness direction. The temperature change is caused by the heat dissipation of the inner wall due to the flow of the conveying medium. Due to the flow of the medium in the in-service welded pipeline 1, the inner wall cooling temperature of the pipeline 1 is the conveying medium temperature. Different medium temperatures and medium flow rates can sharply take away a large amount of heat, causing the temperature change of the pipeline 1 along the wall thickness direction to be nonlinear attenuation. The temperature attenuation of the fusion zone (the depth range from the outer surface is 0-5mm) of the welding position is more serious, and the conventional test device method is difficult to simulate the similar temperature attenuation method. Curve C represents the welding temperature gradient of the pipeline 1 along the wall thickness direction of the device of the present application. The main reason for the heat dissipation of the inner wall is the cooling environment. By controlling the flow of the mixed gas, the device continuously inputs a large amount of cooling medium temperature control, reduces the temperature of the inner wall of the pipeline 1, and further realizes the supercooling requirement of the fusion zone of the in-service welding position. The heat exchange effect of curve B is more obvious, which can better simulate the hardening condition of the pipeline 1, and provide data support for the repair technology of the pipeline 1.

[0076] Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalent ones. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A pipe repair welding heat exchange simulation apparatus, characterized by, The pipeline (1), the B type sleeve (2), the compressed air bottle (5) and the liquid nitrogen bottle (6) are included. The pipeline (1) is sealed at both ends, one end of which is provided with a thermometer (4), and the other end is connected with the compressed air bottle (5) and the liquid nitrogen bottle (6) through a gas pipe. The B type sleeve (2) is welded on the surface of the pipeline (1), and the welding position is the in-service welding seam (3). The compressed air bottle (5) is used to introduce air into the pipeline (1). The liquid nitrogen bottle (6) is used to introduce nitrogen into the pipeline (1). The compressed air bottle (5) and the liquid nitrogen bottle (6) are respectively connected with a gas conveying pipe, one end of the two gas conveying pipes is connected with a converging gas pipe, the converging gas pipe is communicated with the pipeline (1), and the gas conveying pipe is provided with a valve (7). The pipeline repair welding heat exchange simulation device is used for: Introducing low-temperature air in the compressed air bottle (5) into the pipeline (1), controlling the opening of the valve (7), closing the valve (7) corresponding to the liquid nitrogen bottle (6) at the same time, and then calculating the heat exchange effect of the low-temperature air on the pipeline (1); Or, introducing nitrogen in the liquid nitrogen bottle (6) into the pipeline (1), controlling the opening of the valve (7), closing the valve (7) corresponding to the compressed air bottle (5) at the same time, and then calculating the heat exchange effect of the nitrogen on the pipeline (1); Or, introducing nitrogen and low-temperature air into the pipeline (1) at the same time, controlling the opening of the valve (7), and then calculating the heat exchange effect of the mixed gas on the pipeline (1); Or, both valves (7) are closed, and then the heat exchange effect of the normal temperature air on the pipeline (1) is calculated; Or, the cooling medium in the compressed air bottle (5) or the liquid nitrogen bottle (6) is replaced by water, and then the heat exchange effect of the water on the pipeline (1) is tested alone; The heat conduction temperature of the pipeline (1) at any wall thickness position meets: ； wherein T is the temperature of the outer wall of the pipe (1) ; T h is the temperature of the inner wall of the pipe (1), which is equal to the temperature of the cooling medium; and 外 is the temperature of the outer wall of the pipe (1) ; T 内 is the temperature of the inner wall of the pipe (1), which is equal to the temperature of the cooling medium; and A 1 and A 2 are conversion factors, wherein A1 is taken as 0.055 °C / mm and A2 is taken as 0.256 °C / mm 2 ; X is the direction of heat flow.

2. A pipe repair welding heat exchange simulation apparatus according to claim 1, wherein A flow meter (8) is installed on the converging gas pipe.

3. A simulation method characterized by, A pipeline repair welding heat exchange simulation device for claim 1 or 2, comprising the following steps: Controlling the opening of the valve (7) and introducing the cooling medium into the pipeline (1); Welding the pipeline (1) and the B type sleeve (2); Calculating the temperature change of the pipeline (1) with the wall thickness.

4. The simulation method of claim 3, wherein, Controlling the opening of the valve (7) and introducing the cooling medium into the pipeline (1), comprising the following steps: Adjusting the input temperature of the cooling medium; Adjusting the flow of the cooling medium.

5. The simulation method of claim 4, wherein, The cooling medium is air or nitrogen or a mixture of air and nitrogen.

6. The simulation method of claim 5, wherein, The input temperature is: T=(v1×T1+v2×T2) / (v1+v2); In the formula, T is the input temperature, v1 is the air flow rate, T1 is the nitrogen temperature, v2 is the nitrogen flow rate, and T2 is the nitrogen temperature; The flow of the cooling medium is the total amount of the cooling medium entering the pipeline (1) per unit time, which is equal to the product of the flow rate of the cooling medium and the unit time.

7. The simulation method of claim 3, wherein, Calculating the temperature change of the pipeline (1) with the wall thickness, comprising the following steps: Obtaining the temperature of the inner wall of the pipeline (1); Obtaining the temperature of the outer wall of the pipeline (1); Based on the temperature of the inner wall and the outer wall of the pipeline (1), the heat conduction temperature of the pipeline (1) at any wall thickness position is calculated.

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