The primary distinction between 304 and 316 stainless steel pipe is that 316 comprises 2%-3% molybdenum and 304 has no molybdenum. The “moly” is added to enhance the corrosion resistance to chlorides (like sea water). So, while 316 stainless steel pipe is generally thought-about extra corrosion resistant than 304, depending on the nature of the corrosive media the corrosion rates of 304 and 316 could possibly be comparable.
Generally, SS 304/304L is assumed to be corrosion-resistant material. But once we come to Piping Specs with SS 304/304L MOC, its worth is taken as 0.063 inches — similar for SS316/316L . Please explain.
We have a plant that produces fertilizer. If you have any questions pertaining to the place and how to use steel pipe price, you can speak to us at our internet site. In one section we mix 40% phosphoric acid and steel pipe price 98% sulfuric acid together in a ratio of 75-80 : 25-20 phosphoric acid:sulfuric acid. After that the mixture is cooled to a temperature of 80 degrees C. What’s the very best material of construction for transfer piping? The existing materials, 304 stainless steel pipe, reveals issues on the welds.
From a supplies of development perspective, this is a tricky mixture to deal with, especially at 80 degrees C and better. Phosphoric acid is much less corrosive than sulfuric acid. Pure phosphoric acid has no oxidizing energy but industrial phosphoric acid incorporates impurities resembling fluorides and chlorides that can significantly increase its corrosivity. The corrosivity of sulfuric acid is determined by many factors together with temperature, focus, the presence of oxidizing or lowering impurities, velocity effects, and solids in suspension.
It’s usually not wise to pick supplies of construction for sulfuric acid handling gear based mostly solely on revealed corrosion data since corrosion by sulfuric acid is a complex phenomenon. Small differences in impurities, velocity, or concentration can significantly impact the corrosion charge. Halides usually increase corrosion whereas aeration or the presence of oxidizing agents usually will increase the corrosion price of non-ferrous supplies and reduces the corrosion rates of stainless steel pipe alloys. I strongly recommend laboratory corrosion research be run on your specific stream as a part of your materials of building choice process.
I have a large storage tank of 93% sulfuric acid. I am having extreme corrosion of the top of the 4-inch carbon steel outlet pipe. I’m considering of replacing the outlet pipe with Schedule one hundred twenty carbon steel pipe. Is there any extra resistant materials, insert, or coating you might advocate for elevated life?
Carbon steels are solely acceptable for 93% sulfuric acid when fluid velocity is low (< 3 ft/sec). For 4-inch diameter piping or less with velocities up to 5.9 ft/sec, 316L stainless steel pipe is a good choice. For velocities higher than 5.9 ft/sec, alloy tube 20Cb-3 (UNS N08020) has been used successfully. For additional information, consult NACE Recommended Practice RP-0391 “Materials for the Handling and Storage of Commercial Concentrated (90 to 100%) Sulfuric Acid at Ambient Temperatures.”
In your question, you mentioned you’re experiencing issues with 304 stainless steel pipe at the welds. If that is the case, you may consider shifting to 304L stainless steel pipe. Low carbon variations of austenitic Stainless steel seamless pipe like 304L are designed to eradicate issues associated with carbide precipitation and chromium depletion at welds. If 304L doesn’t work, try steadily transferring up to a higher alloy. Possible candidate materials in order of generally rising corrosion resistance are: 316L stainless steel pipe, 20-kind alloys like 20Cb-3, higher chromium Fe-Ni-Mo alloys like Alloy 31, and nickel-base molybdenum-chromium alloys like C-276.