May I ask if there are any requirements regarding the outer diameter of the pipeline?
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Is that the wall thickness? After all, there are different types of oil, and after discussing it with colleagues all day today, we still haven’t reached any conclusion
Each medium requires a specific type of pipe; each pressure rating demands a corresponding wall thickness, and every pipe diameter has a minimum size – all of these values need to be calculated!
Due to different process requirements regarding temperature, pressure, and flow rate, pipes vary in inner diameter, wall thickness, and outer diameter. However, there are safety requirements: the wall thickness of the pipeline must not be less than a certain value. The parameters vary depending on the material, so it cannot be generalized.
Steel pipes: They have a specific DN; their outer diameter is usually constant, while the wall thickness varies – depending on temperature, pressure, and corrosion allowance.
In our country, seamless pipes are currently available in two series: metric and imperial. The metric series refers to those with a smaller outer diameter, while the imperial series has a larger outer diameter. For example, for a metric pipe with DN50, the outer diameter is 57 mm; for DN100, the outer diameter is 108 mm； The outer diameter for British standard DN50 is 60.3 mm, while that for DN100 is 114.3 mm. However, for large-diameter seamless pipes, the outer diameter of metric (small outer diameter) pipes is larger than that of imperial (large outer diameter) pipes; for example, for DN400, the outer diameter of metric pipes is 426 mm, while that of imperial pipes is 406.4 mm. When selecting fittings and flanges, they must be compatible with each other. For example, when it comes to flanges, European series should be used for male pipes, while American series are suitable for imperial pipes. For seamless pipes of the same diameter, the outer diameter remains unchanged regardless of the wall thickness; otherwise, the fittings and flanges cannot be fitted together properly.
What was said upstairs is already very clear; I’m just emphasizing it. What we usually refer to as the size of a pipe is actually its nominal diameter in millimeters, that is, what is known as DN ； When the diameter of the pipe is specified, that refers to the pipe’s size in inches. This is related to the metric and imperial systems mentioned earlier: the metric system refers to the smaller outer diameter, while the imperial system refers to the larger outer diameter. The outer diameter of the pipe usually remains constant, but the wall thickness varies – depending on temperature, pressure, and the required corrosion resistance.
The inner diameter of the pipeline doesn’t matter; as for the thickness, it is certainly related to the operating conditions during production (pressure, temperature), the material of the pipeline, the specific environment (whether it is buried underground), corrosion requirements, and the medium being transported. Additionally, design institutes have relevant standards, and in order to ensure safety, they may choose to design the pipeline with a thicker wall. It’s probably just these connections