Pipeline material selection
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Hello, experts. I would like to ask what kind of material is suitable for pipes used in transporting methanol, acetaldehyde, benzene, and ammonia solution? I checked online, and only those materials that are not suitable were mentioned, but there was no specific answer. Anyone who has worked with or seen such materials could please give some advice. Thank you!
It should be noted here that benzene belongs to GC1; try to avoid using 8163 type tubes, and 9948 type tubes are recommended.
So, is it to choose carbon steel or alloy steel? Won’t any of these media use stainless steel?
Carbon steel works fine with all four of these media. Provided that impurities are not a concern or similar cleanliness requirements apply to the manufacturing process, stainless steel is probably not necessary.
I saw a table online regarding the selection of various chemical fluid materials, and it said the same thing; but should benzene be listed separately? Some people say to use PP.. Have you designed these media before? Impurities are definitely present to some extent; I still don’t know the specific components and concentrations of those impurities
Here, the ammonia is separated into different types: 304SS is used for dilute ammonia, while 20# steel is used for concentrated ammonia and liquid ammonia. Everything else is the same as what was mentioned on the upper floors
Your answer is great. I just received the detailed specifications today; both formaldehyde and acetaldehyde are in aqueous solution, with concentrations of around 37%. After checking their properties, it seems that stainless steel is necessary for handling these substances, as the aqueous solutions can cause corrosion. The equipment provided by the manufacturer is also made of stainless steel. Generally, the material used for pipes should be of a higher grade than that used for the equipment. As for benzene, 20# 9948 material can be used. However, for gaskets and fasteners, wound gaskets with good sealing properties should be chosen. As for ammonia water, I’ll wait until I have more details about its composition first. I’m extremely grateful to you:handshake
Is stainless steel actually used for dilute ammonia solutions? Do you understand the specific principle?
Here, dilute ammonia solution (6%) causes more corrosion than concentrated ammonia or liquid ammonia. In the past, carbon steel was used; the pressure was similar, but flanges would thin out easily at the areas where the diameter changed. That’s why we now use 304SS. For concentrated ammonia, we use fluid pipes with a corrosion allowance of 3 mm, and so far no corrosion has occurred. We measure the wall thickness every year.
:$You’re welcome! I’ll take the chance to learn it too*. The simplest way to determine the size of a pipe is to refer to the equipment it is connected to; generally, the required size should be at least that level. ;P
For methanol, carbon steel of grade 20#8163 is sufficient; for higher pressures, 9948 grade steel can be used. For acetaldehyde, 304 standard steel with grade 14976 is appropriate, as it is acidic and prone to polymerization and discoloration – carbon steel cannot be used when the concentration of heavy components is high. For benzene, 20# carbon steel, i.e., 8163 grade, is sufficient; for higher pressures, 9948 grade steel can be used. For ammonia water, 20# carbon steel, or 8163 grade, is adequate; for higher pressures, 9948 grade steel can be used. Of course, the higher the grade, the better, but economic considerations also need to be taken into account