What’s The Difference Between 304 And 316 Stainless Steel Pipe
The primary difference between 304 and 316 stainless steel pipe is that 316 accommodates 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 mostly thought of extra corrosion resistant than 304, depending on the nature of the corrosive media the corrosion rates of 304 and 316 could possibly be related.
Generally, SS 304/304L is assumed to be corrosion-resistant materials. But after we come to Piping Specs with SS 304/304L MOC, its value is taken as 0.063 inches — same for SS316/316L . Please clarify.
We have now a plant that produces fertilizer. In one part we mix 40% phosphoric acid and 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 levels C. What’s the very best materials of development for transfer piping? The present material, 304 stainless steel pipe, reveals issues on the welds.
From a materials of building perspective, that is a difficult mixture to deal with, especially at 80 degrees C and higher. Phosphoric acid is less corrosive than sulfuric acid. Pure phosphoric acid has no oxidizing power however industrial phosphoric acid contains impurities resembling fluorides and chlorides that can significantly increase its corrosivity. The corrosivity of sulfuric acid will depend on many elements including temperature, focus, the presence of oxidizing or decreasing impurities, velocity effects, and solids in suspension.
It’s usually not sensible to pick out materials of development for sulfuric acid handling gear primarily based solely on printed corrosion data since corrosion by sulfuric acid is a complex phenomenon. Small differences in impurities, velocity, or focus can considerably impression the corrosion charge. Halides typically enhance corrosion whereas aeration or the presence of oxidizing agents usually increases the corrosion charge of non-ferrous materials and reduces the corrosion rates of stainless steel pipe alloys. I strongly advocate laboratory corrosion research be run on your specific stream as part of your materials of building choice course of.
I have a big storage tank of 93% sulfuric acid. I am having extreme corrosion of the top of the 4-inch carbon steel outlet pipe. I am pondering of replacing the outlet pipe with Schedule 120 carbon steel pipe. Is there any extra resistant materials, insert, or coating you could possibly suggest 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 tubing pipe is a good choice. For velocities higher than 5.9 ft/sec, Alloy 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 query, you stated you are experiencing problems with 304 stainless steel pipe at the welds. If that is the case, you might consider moving to 304L stainless steel pipe. Low carbon variations of austenitic Stainless steel seamless pipe like 304L are designed to get rid of problems related to carbide precipitation and chromium depletion at welds. If 304L would not work, Seamless steel tube Price strive regularly moving as much as the next alloy. If you have any issues concerning wherever and how to use seamless steel tube price, you can make contact with us at our own webpage. Possible candidate materials in order of usually rising corrosion resistance are: 316L stainless steel pipe, 20-kind alloys like 20Cb-3, increased chromium Fe-Ni-Mo alloys like Alloy 31, and nickel-base molybdenum-chromium alloys like C-276.
