The problem of not needing socket welding for small pipes
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In a small project, when we were making pipe materials, the wall thickness of small pipes under DN50 was about SCH40, basically around 3mm. We originally wanted to use socket welding, but Party A objected, saying that they had always used butt welding, and even the grassroots employees had never heard of the word socket welding. So, does such a thin pipe need to be beveled during welding? Is the welding quality guaranteed? The branch pipe connections on large pipelines naturally do not use single socket pipe clamps (SHC, SHCB) and half pipe joints (HALF COUPLING). As for the branch pipe stand, some people have never heard of it. Some people say that the branch pipe stand is like a tumor, which is ugly and they are unwilling to use it. They recommend open hole welding. How should we choose to be reasonable, safe, reliable and compliant? Of course, this project is relatively mild overall, with low pressure and temperature below 200°C. Most of the media are medium to low hazards, and some media are highly hazardous. However, SH recommends considering quasi-extreme media.
For small pipes below DN50, the wall thickness is generally around 3mm. The welding method at this time will indeed have a certain impact on the performance of the pipe. In response to your question, I will answer it from the following aspects:: 1. Is beveling required during welding?: For such thin pipes, beveling is generally not required. The purpose of beveling is to increase the stress area of the weld and reduce the stress concentration of the weld. However, for such small pipes, due to the small wall thickness, direct butt welding can ensure its performance. 2. How to ensure welding quality: Quality assurance mainly relies on welding process control and post-welding inspection. First, a reasonable welding process needs to be formulated, including the setting of welding parameters, the arrangement of welding sequences, etc. Then after the welding is completed, the weld quality is checked through various non-destructive testing (such as radiographic flaw detection, ultrasonic flaw detection, etc.). 3. Branch pipe connection method on large pipelines: For branch pipe connections on large pipelines, single-socket pipe hoops, half-pipe joints and branch pipe stands are all available. Which one to choose mainly depends on the use environment and usage requirements. Open-hole welding is also a common branch pipe connection method. Its advantages are simple structure, convenient production, and suitable for various pipeline systems. However, the quality of open-hole welding is more difficult to guarantee than other connection methods, requiring more detailed process control and strict inspection. 4. How to choose a reasonable, safe and reliable pipeline connection method: A good connection method should be able to meet the design requirements while simplifying the production process and reducing costs. It needs to be comprehensively selected according to the specific use environment, pipeline material, process conditions and other factors. For your project, since the temperature and pressure are relatively low, ordinary steel pipe welding should be sufficient. If there are highly hazardous media, a higher level of connection may be required, such as using corrosion-resistant materials and increasing interface sealing. .
Direct opening welding of pressure pipe branches requires opening reinforcement calculations, while tees or branch pipes do not require calculations.
This post was last edited by Liushuiyunshine on 2023-10-19 11:38. Some provisions of GB 50316-2000 Industrial Metal Pipe Design Specifications (2008 Edition). Note that the half-pipe joint here refers to a single-socket pipe clamp (SHCB) with a groove. However, in the grade tables of several design institutes that can be collected on the Internet, there is no mention of the need for a groove when using a single-socket pipe clamp. This matches the SH3410-96 version.
The main reason is that Party A does not know what the branch pipe station does. Just explain it clearly patiently. If the explanation is not clear, write a contact sheet or construction instructions to inform them. There is no problem if the wall thickness of the direct opening is below 1.0mpa. Another main reason is that the owners have been doing this without any problems, so what they think is right is actually wrong.
This post was last edited by Liushuiyunshine on 2023-10-19 15:19 https://bbs.hcbbs.com/thread-488699-1-1.html zhonglanqiudui said : Half Coupling, a single-head pipe hoop with a flat bottom, Boss, a welded pipe platform with a flat bottom and a beveled bottom, OLET, a branch pipe platform with a saddle-shaped bottom. However, I personally think that Half Coupling is different from Boss. You cannot simply think that Boss is a Half Coupling with a gap. There are still some problems. For example, their sizes are different. Take CL3000# DN25 socket welded pipe fittings as an example.: The thickness C of the Half Coupling is 5.0, and it is equipped with a pipe with an outer diameter B of 34.1. The height E is 29, and the socket depth J is 13. The thickness of the Boss is 5.0, and it is equipped with a pipe with an outer diameter B of 34.1. The height F is 35, and the socket depth J is 16. A certain petrochemical project said: 4.2.4 Selection of strengthening nozzle (BOSS): When the diameter of the branch pipe is DN ≤ 40 and the standard tee cannot be used, a reinforced nozzle should be used. When the diameter of the main pipe is DN ≥ 125, a flat-bottom reinforced nozzle (BFS) should be used. ； When the diameter of the main pipe is DN ≤ 100, the arc-bottom reinforced reinforced nozzle (BRS) should be used. 4.2.4 Selection of reinforced pipe joints (OLET): When the branch pipe diameter is 50 ≤ DN ≤ 200 and the standard tee cannot be used, reinforced pipe joints should be used for connection.
English original version, compared to 50316, BOSS is a half-pipe joint, and COUPLET is a plug-in branch pipe table.
This is not necessary. . . Just available
This post was last edited by Liushuiyunshine on 2023-10-24 11:45 * * * * * * * * * Example 3 Edition Song Keke P138. Teacher Song’s suggestions are more pertinent and very practical. Due to the different degree of standardization of pipe fittings in various countries, the connection methods of branch pipes and the selection of pipe fittings are also different. Under normal circumstances, branch pipe connections mostly use formed branch pipe connectors, welded outlet connectors, and branch pipes directly welded to the main pipe. @ The selection of branch pipe connectors is mainly based on the flange pressure level or nominal pressure that has been determined in the pipeline grade. Generally speaking, when the nominal pressure of the flange is not greater than PN2.5 (Class 150), the branch pipe is directly welded to the main pipe; when the nominal pressure is not less than PN4.0 (Class 300), the butt welding tee, welded branch pipe stand, socket welding or threaded connection tee, socket welding or threaded pipe branch table are selected in the order according to the nominal diameter of the main pipe and branch pipe.
Safety is no small matter, and Party A will send out a contact sheet if they don’t listen.