Why can’t the ordinary or thickened wall thickness of welded steel pipes meet the requirements of its pipe fitting standards?
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1 According to GB3091-2015 "Welded Steel Pipes for Low-Pressure Fluid Transport", the wall thickness of the pipe is based on ordinary wall thickness or thickened wall thickness, as shown in the table below. For example, the ordinary wall thickness of DN50 welded steel pipe is 3.8mm； Thickened wall thickness is 4.5mm ； Of course, this standard also allows the production of other wall thicknesses, but I estimate that the market mainly only supplies pipes with these two wall thickness series. 2 According to Table 13 of GB20801.3 "Pressure Piping Specification Industrial Pipes Part 3 Design and Calculation", welded pipe connections can use threaded connection pipe fittings of GB/T 14383 "Forged Socket Welds and Threaded Pipe Fittings and" and GB/T32294 "Forged Socket Welds and Welded Unions". 3 However, in GB/T 14383-2021 and GB/T32294-2015, the pipes connected to these pipe fittings (elbows, tees, unions, etc.) are required to have certain thickness requirements. For example, DN50 pipes are required to be 5.54mm and reach Sch80. 4 Why is this? When using GB3091 welded steel pipe, how to choose the pipe wall thickness?
The normal wall thickness and thickened wall thickness of welded steel pipes are set to meet different application requirements. When choosing the wall thickness of steel pipes, you need to consider the following aspects:: 1. Operating environment and fluid pressure: According to the use environment and the working pressure of the fluid, select the appropriate wall thickness to ensure the safe operation of the pipeline. 2. Strength requirements: According to the requirements of the usage scenario, select the appropriate wall thickness to meet the required strength and pressure resistance. 3. Economical: Steel pipes with larger wall thickness can provide higher strength and pressure resistance, but will also increase the cost accordingly. Therefore, it is necessary to comprehensively consider economy and safety to select the most appropriate wall thickness. As for why the market mainly supplies pipes with ordinary wall thickness and thickened wall thickness, there may be the following reasons: 1. Ordinary wall thickness and thickened wall thickness are commonly used wall thicknesses specified in the GB3091 standard, and are suitable for most low-pressure fluid transportation application scenarios. 2. Market demand is concentrated on steel pipes with ordinary wall thickness and thickened wall thickness, and suppliers will be more inclined to produce and supply pipes with these two commonly used specifications. In summary, the wall thickness of welded steel pipes should be evaluated based on actual usage scenarios and needs, and factors such as safety, strength requirements, and economy should be comprehensively considered. .
If it is a finished welded steel pipe, the manufacturer will produce it according to the required specifications. There is no such thing as "the market probably only supplies pipes of these two wall thickness series" as you think.
In addition, we generally select models from regular series because these series are used by many people and are easy for manufacturers to prepare materials and produce. They may even have some inventory, so the supply will be faster. This does not mean that special specifications cannot be purchased in the market.
According to Table 12 of GB20801.3-2020, GC2 threaded connection DN50 carbon steel pipe wall thickness Sch40 (wall thickness 4mm).
The steel pipe sizes in Appendix A of GB/T14383 are only recommended. . Not mandatory.
The recommended pipe wall thickness in GB3091-2015 "Welded Steel Pipes for Low-Pressure Fluid Transport" is as follows：
This post was last edited by Fuguifang on 2023-9-12 18:12. You can refer to the pipeline grade table of the project's craft room.； GB/T14383 Table 2 also says "it can be thicker or thinner than what is shown in Table 2". Low-pressure fluid welded pipes have been used, and the pressure and medium risks are not high. In fact, they are thickened pipes in 3091
The person who asks the question sets a trap, and the person who replies jumps into it. The nature of low-pressure fluid welded steel pipes is first limited. The pressure is ≤1.6MPaG. Most of them are used in non-toxic and harmless media such as water and compressed air. Do you dare to use them in high-pressure systems and hazardous chemical media? Within the scope of application of this type of pipe, these two wall thicknesses are sufficient. Pressure pipeline is a general term, and the thickness needs to be calculated. In this case, if you dare to use low-pressure fluid to weld the pipe, you will be punished.
He was talking about threaded pipe fittings for welded pipes. The wall thickness does not meet the wall thickness requirements for threaded pipe fittings. He did not say that 3091 should be used when using high-pressure hazardous media.
3358755[/attachimg You can look at the relevant regulations of 14383. Thin steel pipes can be used, but it is not prohibited, as long as the thickness of the steel pipe meets the design requirements.