How exactly should the requirement in instrument design that the materials used should be of at least the same quality as those used for the pipes be understood?
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How exactly should the requirement in instrument design that the materials used should be of at least the same quality as those used for the pipes be understood? It’s quite clear how to rank materials among themselves; for example, 316 > 304 > CS. Sometimes, other materials are used for pipes; for example, 15CrMoG is used for steam pipelines. The manufacturers of E+H vortex flowmeters state that 316 is suitable for use under conditions of 250 degrees and 5.5 MPa. So how should we understand the differences between 316 and 15CrMoG?
The statement in instrument design that \"the material used should be no inferior to that of the pipeline\" means that the material of the instrument should meet at least the same material performance standards as those of the pipeline. This is mainly to ensure the compatibility, corrosion resistance, and safety of the entire system. Comparisons between materials are usually based on factors such as corrosion resistance, strength, and temperature tolerance. For example, 316 contains more nickel and molybdenum than 304, and therefore has better corrosion resistance ； 15CrMoG is an alloy steel that possesses excellent high-temperature and oxidation resistance, making it suitable for use in high-temperature and high-pressure conditions. If 15CrMoG is used for the pipeline, it indicates that high requirements are placed on the material’s temperature and pressure resistance in such applications. Although 316 does not belong to alloy steel, manufacturers of E+H vortex flowmeters have confirmed that it is safe to use 316 under conditions of 250 degrees and 5.5 MPa. This indicates that, under these specific conditions, the performance of 316 meets the requirements, and it can be considered equivalent to or better than 15CrMoG. However, under other more severe conditions (such as higher temperatures or more complex chemical environments), 316 may no longer be suitable, and it becomes necessary to consider using 15CrMoG or higher-grade materials. Therefore, when interpreting that \"the material used should be no inferior to that of the pipeline,\" it is necessary to take into account all operating conditions as well as the specific properties of the materials, to ensure that the selected materials can safely and effectively function in the actual application environment. In case of doubt, it is very helpful to consult the suggestions of the material supplier or seek advice from a professional engineer. .
Perhaps they are worried about unstable connections at the flange joints; the properties of the material decline when it is heated. Since the material of your instrumentation is superior to that of the pipes, the risks in this regard are certainly lower.
The various properties of 316 are superior to those of 15Cr; you can find out by asking those specializing in materials