You should tell what is the meterial, NORSOK M650-M is cert for stainless steel and duplex & super duplex ss,etc AD2000 cert is for pressure vessel equipment,what is TR2000?
duplex 2205 is very common used in industrial applications now days ,and you can find out of duplex 2205 stock very easy as 316L, but the price is a little higher than 316L, actually there is nearly no stock of 316 grade in worldwide market, reminder they are different grades between 316 and 316L.
1.ASTM A249 and A269 do not restrict their scope to round tubing, but they are implicitly designed and applied to round tubing in practice.
2.Yes, round tubing produced to A249/A269 could be formed or drawn into square tubing, but it risks compromising weld quality and wouldn’t strictly conform...
If your HVAC system handles just freshwater and mild conditions, 304 is sufficient and cheaper than 316. if water quality is variable (e.g., contains salts) or longevity is critical, 316 is the better grade. Avoid 303 for water-contact parts—it’s better suited for dry, machined components.
