Why must the industrial pipeline instrument interfaces under high temperature, high pressure, and vibration be at least DN20?
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According to Article 8.1.18.3 of GB 50316-2000 (2008 edition), the Code for Design of Industrial Metal Piping, for pipelines with a design pressure greater than 6.3 MPa, or a design temperature greater than 425°C, or those that are subject to vibration, it is specified that the nominal diameter of the instrument connections shall not be less than 20 mm. What is its purpose?
After reviewing the explanatory text, it is noted that ASME B31.3 is referenced, but the reason for this approach is not explained.
This is Baidu AI’s answer. Do everyone agree with it? I don’t know where it was copied from, and I can’t find any evidence.
The purpose is to ensure the stability and safety of the pipeline system. Larger interfaces can reduce stress concentration caused by high pressure, high temperature, or vibration, preventing damage to pipes and instruments and ensuring the accuracy of measurements as well as the reliable operation of the system. At the same time, interfaces with a larger diameter help reduce resistance and improve fluid transfer efficiency. .
Isn’t it the case that the smaller the aperture of the opening made in the main pipe, the less the reduction in the strength of the main pipe? I know that if the openings are too large, additional reinforcement is needed.
Indeed, the smaller the opening, the less impact it has on the strength of the main pipeline. However, in high-temperature, high-pressure, and vibrating environments, smaller interfaces may increase the flow rate of the fluid, thereby exacerbating local wear, corrosion, or erosion, and may also cause stress concentration, increasing the risk of leakage. Therefore, the requirement in the specifications that the instrument interface should be no smaller than DN20 is aimed at balancing pipe strength and safety, measurement accuracy, and ease of maintenance. At the same time, larger interfaces also facilitate the installation and maintenance of instruments. .