kevlar49
Materials
- Jun 1, 2006
- 287
Does anyone have experience with Polythionic Acid Stress Corrosion Cracking (PASCC) in bolted/removable Type 304 reactor internals (e.g. tray floor, scale trap, etc) in a hydroprocessing reactor operating between 750 and 800°F if the reactor is not soda ash washed?
All pressure-retaining components are either Type 347 (shell overlay) and welded components are Type 321 (e.g. beams). All removable/bolted internals are Type 304 (non-L grade to the best of my knowledge; don't know if they are annealed). The reactor typically operates between 750 and 800 F which is borderline sensitization threshold for the Type 304.
We have traditionally soda ash washed, but I am debating whether that is truly necessary. I suspect that the type 304, since it is not welded, will be less likely to SCC. I suspect that only the bolting is at risk of cracking. We can save time and money if we do not need to soda ash wash. An internal memo stated that we did not need to soda ash until after 800 F. I am thinking that we can probably tolerate up to 850 F and anneal the type 304 components if they need to be replaced if necessary. Any thoughts?
All pressure-retaining components are either Type 347 (shell overlay) and welded components are Type 321 (e.g. beams). All removable/bolted internals are Type 304 (non-L grade to the best of my knowledge; don't know if they are annealed). The reactor typically operates between 750 and 800 F which is borderline sensitization threshold for the Type 304.
We have traditionally soda ash washed, but I am debating whether that is truly necessary. I suspect that the type 304, since it is not welded, will be less likely to SCC. I suspect that only the bolting is at risk of cracking. We can save time and money if we do not need to soda ash wash. An internal memo stated that we did not need to soda ash until after 800 F. I am thinking that we can probably tolerate up to 850 F and anneal the type 304 components if they need to be replaced if necessary. Any thoughts?
