Are there any standard specifications for the wall thickness of pipe fittings in pipeline design?
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In design, the selection of material for pipes can generally be determined by following relevant specifications, taking into account common types of pipes available. For example, for DN150 pipes, seamless steel pipes with dimensions 159X4.5 are used. However, components such as elbows and tees are subjected to frequent stress, so it is necessary to thicken them appropriately. Since GB/T12459-2005 only specifies the nominal diameter of these components, I would like to ask: are there any clear regulations or calculation methods for determining the wall thickness of components used in pipes of a certain specification?
For the calculation of pipe fitting thickness, the formulas provided in the \"Code for Design of Gas Pipeline Engineering\" GB50251-2003 can be used, and then the corresponding thickness can be determined by referring to GB/T12459-2005.
References can be selected based on the recommendations for piping components in Chapter 4 of the Handbook for Design of Petrochemical Pipeline Installation
In design, the selection of material for pipes can typically be determined using relevant standards. Calculation 1: (Design pressure/Allowable stress) x 1000 = Wall thickness grade. Calculation 2: For pressure vessels, GB150 provides formulas for calculation based on internal pressure, as stated on page P26. Calculation 3: ASME B31.3 offers formulas for calculating the thickness of straight pipes or elbows (304.1 for straight pipes, 304.2 for elbows). Based on these calculations, the result is rounded to the commonly used wall thickness grades. For example, if the calculated wall thickness for a DN80 pipe is 1.5 mm with a corrosion allowance of 1 mm, then a pipe of size 89x4 or DN80-Sch20 can be used (Sch is the code for the wall thickness grade)
Based on my long-term experience in working with designers from design institutes, it is generally sufficient to make the selection based on experience. For example, for a pipeline with dimensions of Φ159×4.5, the wall thickness of the elbows or tees can be chosen as Φ159×5 or Φ159×6, that is, 2 mm greater than the wall thickness of the pipeline
What was said upstairs isn’t entirely correct; the methods for selecting the wall thickness of pipes made from different materials vary. For non-metallic pipes, you can choose the appropriate thickness based on the design nominal pressure and the relevant pipe standards. For metal pipes, you can do some calculations and then choose a standard thickness that is close to the result; however, it’s not necessarily easy for the owner to find a pipe with exactly that wall thickness
SCH is merely a wall thickness grade for seamless steel pipes connected to fittings, and it is listed in the appendix of GB/T12459-2005. However, the choice is still often based on experience at present; the calculated wall thickness of the pipe is around 3 mm, so a pipe wall thickness of 159X4.5 is selected, while for the fittings, STD values from SCH are used, resulting in a thickness of 159X7.11. But I wonder if there are more standardized methods for selection.
Experience values are all for reference only; there are no specific standards, and they can be found in many design books
If it is for steel pipes, you can refer to the Series for the Selection of Seamless and Welded Steel Pipes for Chemical Piping, HG20553-93
The question raised by the original poster is worth discussing. I have also been puzzled by the calculations regarding the wall thickness of fittings specified in the \"Code for Design of Gas Pipeline Engineering\" GB50251-2003; however, no such requirements are mentioned in other documents. Should we proceed with the calculations according to the provisions in GB50251-2003?