Pipeline material issues
Thread Content
Could any netizen help us? The steel material used for the pipes in our methanol shift unit is OCR18NI9; the operating temperature is 400 degrees, with a pressure of 39 KG/CM2. The medium involved is shift gas (acidic gas). Is this material suitable for use? Can 12CRMOV be used? This post was last edited by YANHONGQUN on 2009-4-20 16:54.]
Why isn’t Haiyou following? :call:
The original poster didn’t clarify what kind of acid it is Generally speaking, in acidic media, 0Cr18Ni9 cannot be used; instead, appropriate tubing materials, whether metallic or non-metallic, must be selected depending on the type of acid.
Could the conditions be more detailed? However, given the conditions, using 304 is indeed very dangerous
I’ve seen materials for a methanol project as well; it involves acidic gases, with a pressure of 0.3 MPa and a temperature of 170 degrees, and the material chosen is 316
12CrMoV is likely to be an alloy steel with high strength, but it is probably not resistant to acid corrosion; it is recommended to use at least 0Cr18NI9.
The components of acidic gases are H2S and CO2. According to other manufacturing units, 304 steel is prone to hydrogen embrittlement, which results in small cracks in the pipes. I don’t know what material would be good? 12CRMV performs well in high-temperature environments; some data also indicate its suitability for acidic gas environments. If I’m not sure, I seek advice from experts.
0Cr18Ni9 is 304, a common type of stainless steel. Its acid resistance is somewhat poor. At least 316 or 321 should be used (312 may also work; I’m not sure), and it needs to contain Mo in order to resist intergranular corrosion. 12Cr1MoV is used in high-temperature conditions, but its primary function is to resist high-temperature creep, rather than providing corrosion resistance. It is not recommended to use it.
Acid-resistant: Use PVC pipes. It is said that there are now PVC pipes that can withstand high temperatures, but more corrugated expansion joints will be needed.