Q: We need a custom bolt for securing a 304SS flange to a pressure vessel located in a submerged DI water pit. We have a few concerns/requirements. First, we need to ensure that galling and corrosion do not prevent us from removing the bolts during service events (between 1 and 5 years apart). Second, we’ll need a bolt with a yield strength of at least 45ksi.
A: We certainly could help you with this. First, regarding the material, I would consider the Duplex or Super Duplex Stainless Steel bolts. These will offer good corrosion resistance in a submerged environment. Both materials offer an adequate yield strength for your application: approximately 80ksi yield. Super Duplex 2507 bolts will offer you slightly better corrosion resistance and higher tensile strength (125ksi) compared to Duplex 2205 bolts (110ksi UTS).
I’m not sure if there are contamination concerns with the DI water but you also might want to utilize a Moly-disulphide anti-galling lube. This will help ensure minimal galling. If you want to go to the next level with galling protection we could silver plate the threads as well.