There is nothing that I'm aware of that prohibits SW connections in NACE MR0175/ISO 15156. However, the welds would need to meet the welding requirements of the standard including hardness.
It can be difficult to achieve the required hardness values and I'm aware of one project where there were significant in service problems that resulted from the SW on SW flanges (small bore).
I would specify that a minimum 2 pass hardness qualified weld procedure be used. In addition, some people specify that the welders must be specifically qualified for fillet welds - that qualification completed on groove welds is not acceptable as qualification for fillet welds.
Correct. There is nothing in ISO 15156:2009 that forbids socket welds. Aversion to socket welds in H2S service is usually based on putting a difficult to make and inspect weld directly into contact with the fluid. Socket welds can also create a flow disturbance issue in services such as amine gas sweetening.
Thanks at the moment for your help. Is clear that the SW connection is not the best solution for this application, in any case there is not a specific statement on NACE MR0175/ISO 15156 that forbids the use of this type of connection.
