Water-cooling construction method for welding TP321 thick-wall high-pressure pipeline

Abstract

The invention discloses a TP321 thick-wall high-pressure pipeline welding water-cooling construction method. A lathe beveling machine is used for manufacturing a V + U-shaped groove; after the welded junctions are assembled, welding seams are manually bottomed for 2-3 times, and the welding seams are hoisted to an automatic welding machine tool after being qualified; during welding seam filling, the water gun sprays clean water, in the pipeline rotating welding process, clean water is continuously sprayed to the welding seam on the inner wall of the pipeline and a heat affected area, water flows and circulates to take away heat so as to accelerate inter-channel temperature reduction, and continuous welding operation is achieved. The clean water is continuously sprayed on the inner wall of the pipeline, the cooling speed of the inter-channel temperature is increased in a water cooling mode, the continuous welding operation capacity is improved, and the welding efficiency is improved. On the basis, the procedure of spraying the clean water is optimized, and the welding quality of the TP321 thick-wall high-pressure pipeline is improved.

Description

Technical Field

[0001] The invention relates to a welding construction method, in particular to a TP321 thick-wall high-pressure pipeline welding water-cooling construction method. Background Art

[0002] In recent years, the construction scale of modern petrochemical plants has been continuously expanded. With the continuous research and development of new processes and new materials, the production capacity has become higher and higher, and the corresponding equipment, process pipelines and other systems need to withstand higher and higher pressure. Taking the catalytic 1# 3.2 million tons / year wax oil hydroprocessing unit of the second phase of the Zhejiang Petrochemical 40 million tons / year refining and chemical integration project as an example, its system characteristics are high temperature and high pressure. The process pipeline system uses a large number of thick-walled high-pressure pipes, and the materials are A312 TP321, A335 P11, and A106.Gr.B. Among them, the A312 TP321 pipeline system has a maximum specification of DN700*68.27mm, a system operating pressure of 14.2MPa, an operating temperature of 400℃, a design pressure of 15.75MPa, a test pressure of 28.19MPa, and the medium is high-temperature and high-pressure circulating hydrogen and oil and gas.

[0003] When welding A312 TP321 pipes, the temperature between passes needs to be controlled. Therefore, the welding speed needs to be controlled during the welding process, and welding should be stopped when necessary. The conventional welding method is to weld one pass and wait for the temperature between passes to cool naturally to below 120°C before welding the next pass. This welding method takes a long time, resulting in increased costs and extended construction period. Summary of the invention

[0004] The purpose of the present invention is to provide a TP321 thick-walled high-pressure pipeline welding water-cooling construction method to increase the continuous welding operation time and improve the welding efficiency.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A TP321 thick-wall high-pressure pipeline welding water-cooling construction method, comprising: Step 1: Use a lathe beveling machine to make a V+U-shaped bevel; Step 2: After the weld joints are matched, the weld is manually primed 2 to 3 times, and after passing the test, it is hoisted to the automatic welding machine; Step three: When the weld is filled, clean water is sprayed from a water gun. During the pipeline rotation welding process, clean water is continuously sprayed on the weld and heat-affected area on the inner wall of the pipeline. The water flow circulation takes away the heat to accelerate the temperature drop between passes and realize continuous welding operation.

[0006] As a preferred embodiment of the present invention, in step 2, PT testing is performed after primer application.

[0007] As a preferred embodiment of the present invention, in step three, when spraying clean water, a temperature measuring gun and a temperature measuring device provided by the machine tool are used to record the temperature between channels.

[0008] As a preferred embodiment of the present invention, in step three, during the welding process, the interlayer temperature is controlled below 120°C.

[0009] As a preferred embodiment of the present invention, in step three, the chloride ion content in the sprayed clean water is ≤50 mg / L.

[0010] As a preferred embodiment of the present invention, in step three, the temperature of the sprayed clean water is controlled at 10°C-40°C.

[0011] As a preferred embodiment of the present invention, the clean water injection procedure is: Time: 0-7min, flow rate: 40L / min; time 7-14min, flow rate: 38L / min; time: 14-21min, flow rate: 35L / min; time: 21-28min, flow rate: 30L / min; when the time exceeds 30min, the flow rate is maintained at 25L / min.

[0012] As a preferred embodiment of the present invention, in step three, the welding parameters are: welding current is 160-200A, and welding arc voltage is 17-30V.

[0013] The present invention uses a continuous spraying of clean water on the inner wall of the pipeline, and the water cooling method accelerates the cooling speed of the interpass temperature, improves the continuous welding operation capability, and improves the welding efficiency. On this basis, the present invention optimizes the procedure of spraying clean water and improves the welding quality of TP321 thick-walled high-pressure pipelines. DETAILED DESCRIPTION

[0014] TP321 steel has low thermal conductivity and large linear expansion coefficient. Under local heating conditions, the high temperature stays for a long time at the hydrogen pipeline welding joint, and the weld metal and the near weld are subjected to high tensile stress and strain at high temperature. It is more difficult to dissipate heat when the wall thickness is large. During the welding process, if the interpass temperature is too high and the welding current is large, the tendency to form cracks is more obvious. The conventional welding method is to weld one pass of the weld and wait for the interpass temperature to cool naturally to below 120°C before welding the next pass. This welding method takes too long.

[0015] Based on this, this embodiment provides a TP321 thick-walled high-pressure pipeline welding water cooling construction method. The overall concept of this method is to accelerate the temperature reduction between passes by continuously spraying clean water on the inner wall of the pipeline and using water cooling.

[0016] The design pressure of the TP321 thick-walled high-pressure process system involved in this embodiment is greater than 10MPa. After the pipes and pipe fittings enter the site, they are tested for size, metal element analysis and 100% of the pipe surface. Using a φ168.3*36mm pipe section as a test piece, the weld metal thickness can be covered to 72mm, which is greater than 68.27mm, meeting the requirements of NB / T47014-2011 "Welding Process Assessment for Pressure Equipment".

[0017] The above-mentioned TP321 thick-walled high-pressure pipeline welding water cooling construction method includes: Step 1: Use a lathe beveling machine to make a V+U-shaped bevel.

[0018] V-shaped groove only needs single-sided welding, which is suitable for manual priming of welds. U-shaped groove is generally suitable for thicker weldments, which can reduce the cross-sectional area of ​​the groove (narrow gap groove is smaller), thereby reducing the filling amount of welding materials, reducing welding time, and lowering the overall cost. Using V+U-shaped groove improves economy and conforms to the welding method of mechanical automation.

[0019] Step 2: After the weld joints are matched, the weld is manually primed 2 to 3 times, and after passing the test, it is hoisted to the automatic welding machine.

[0020] After primer laying, PT testing is carried out. After the weld is primed, it is tested once. When the thickness is filled to about 25mm, non-destructive testing is carried out again. After passing the test, the weld is filled to ensure the qualified rate of the weld.

[0021] Step three: When the weld is filled, clean water is sprayed from a water gun. During the pipeline rotation welding process, clean water is continuously sprayed on the weld and heat-affected area on the inner wall of the pipeline. The water flow circulation takes away the heat to accelerate the temperature drop between passes and realize continuous welding operation.

[0022] Prepare materials and equipment such as water pumps, hoses, buckets, plastic film, clean water, etc. The plastic film covers the inside of the bucket to isolate the clean water and the bucket. The water pump is placed in the bucket and connected to the hose. A flow valve is set on the hose to control the flow rate.

[0023] The chloride ion content of the sprayed clean water described in this embodiment is ≤50 mg / L, so as to prevent the chloride ions in the water from exceeding the standard and corroding the stainless steel pipes and causing damage to the pipes.

[0024] When spraying clean water, use a temperature gun and the machine tool's own temperature measuring device to record the temperature between passes. During welding, the interlayer temperature is controlled below 120°C.

[0025] The temperature of the sprayed clean water is controlled at 10℃-40℃. The diameter of the hose nozzle is 18mm. During the construction of this method, the spraying procedure was optimized. We found that using different flow rates in different time periods can further improve the welding quality compared with a constant flow rate.

[0026] The preferred injection program of this embodiment is: time: 0-7min, flow rate: 40L / min; time 7-14min, flow rate: 38L / min; time: 14-21min, flow rate: 35L / min; time: 21-28min, flow rate: 30L / min; when the time exceeds 30min, the flow rate is maintained at 25L / min.

[0027] Compared with the constant flow rate injection method, the results are as follows:

[0028] In summary, the construction method of the present invention can not only ensure continuous operation, quality, construction period and cost, but also save energy and protect the environment, and reduce waste of resources and environmental pollution.

[0029] Under the condition of ensuring good penetration and fusion, it is advisable to adopt low current, short arc, fast welding speed and multi-layer and multi-pass process. The welding parameters are: welding current is 160~200A, and welding arc voltage is 17~30V.

[0030] During the welding process, the Fn value of the weld layer is monitored using a ferrite detector, and the ferrite value of the weld is required to be controlled between 3Fn and 8Fn.

[0031] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various deformations and changes. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A TP321 thick-walled high-pressure pipeline welding water-cooling construction method, characterized in that: include: Step 1: Use a lathe beveling machine to make a V+U-shaped bevel; Step 2: After the weld joints are matched, the weld is manually primed 2 to 3 times, and after passing the test, it is hoisted to the automatic welding machine; Step three: When the weld is filled, clean water is sprayed from a water gun. During the pipeline rotation welding process, clean water is continuously sprayed on the weld and heat-affected area on the inner wall of the pipeline. The water flow circulation takes away the heat to accelerate the temperature drop between passes and realize continuous welding operation.

2. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 1 is characterized in that: In step 2, PT testing is performed after primer application.

3. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 1 or 2, characterized in that: In step three, when spraying clean water, use a temperature gun and the machine tool's own temperature measuring device to record the inter-pass temperature.

4. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 3 is characterized in that: In step 3, during welding, the interlayer temperature is controlled below 120°C.

5. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 1 or 4, characterized in that: In step 3, the chloride ion content in the sprayed clean water is ≤50mg / L.

6. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 5 is characterized in that: In step 3, the temperature of the sprayed clean water is controlled at 10°C-40°C.

7. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 1 or 6, characterized in that: The clean water injection procedure is: Time: 0-7min, flow rate: 40L / min; time 7-14min, flow rate: 38L / min; time: 14-21min, flow rate: 35L / min; time: 21-28min, flow rate: 30L / min; when the time exceeds 30min, the flow rate is maintained at 25L / min.

8. The TP321 thick-walled high-pressure pipeline welding water-cooling construction method according to claim 7 is characterized in that: In step three, the welding parameters are: welding current is 160-200A, and welding arc voltage is 17-30V.

Images