Regarding the material selection for instrument flanges
Thread Content
Stainless steel is often chosen as the material for instruments. Flange-connected instruments, such as thermometers, are installed on carbon steel pipes of the same pressure rating. Flange material 304 is selected, as it can withstand the operating temperatures and pressures specified by the process. But it cannot withstand the design temperature and pressure of the pipeline. Is it necessary to raise the flange grade by one level? Or simply choose a carbon steel flange. I saw the instruments from other design firms on site; the instruments installed on their carbon steel pipes were also made of 304 material, with a pressure rating matching that of the pipes, and the same problem existed there as well. Should the design temperature and pressure of the pipes or equipment be taken into account when selecting materials for instruments?
The material is selected based on considerations such as temperature resistance, pressure resistance, corrosion resistance, and wear resistance
The material used for instruments must not be inferior to the requirements for pipeline equipment materials.
I have now increased the pressure rating of all the flanges on the belt drives by one level, which is sufficient to meet the design temperature and pressure requirements of the pipes.
This post was last edited by hfrs on 2017-6-14 at 21:06. Regarding thermometers, it’s really strange to choose 304 material; you must be referring to a fake design institute. Reputable design institutes either choose 316 or 321; they never choose 304.
I checked the flange standards; at the same temperature, the pressure resistance of 321 and 316 is slightly higher than that of 304. But it still cannot meet the design pressure of the pipeline. For example, he has a pipe with a pressure class of PN16, with a design pressure of 1.25 Mpa and a design temperature of 184°C. According to the table, when the temperature exceeds 150°C, the design pressure is not met; therefore, the flange grade must be increased to PN 25.
I checked the flange standards; at the same temperature, the pressure resistance of 321 and 316 is slightly higher than that of 304. But it still cannot meet the design pressure of the pipeline. For example, he has a pipe with a pressure class of PN16, with a design pressure of 1.25 Mpa and a design temperature of 184°C. According to the table, when the temperature exceeds 150°C, the design pressure is not met; therefore, the flange grade must be increased to PN 25.