PetroStreet

With introduction of Appendix M, should the specifications to perform duplex stainless steel welding be revised especially when in highly corrosive environments like urea /carbamate?
Any thoughts of inclusion of some of the very useful information specified within this Appendix?

With this introduction of Appendix M, the requirements mentioned under welding procedure qualifications M-500 are required to be met, wherever the required corrosion resistance and other properties are expected. That is the classical application which you mentioned, Urea & Carbamate. The classes which have been mentioned in this Appendix M are required to be followed as-is when qualifying the welding procedure.
I would stringly agree that this Appendix M must be mentioned when specifying welding procedure qualification both for in-house applications and wherever necessary to be done through external parties.

The major issues when welding duplex stainless steels are the following:
1. Target ferrite %
2. Maximum heat input
3. Cooling rate

While we perform the welding procedure qualification for duplex stainless steels, it is required to use the same class of duplex stainless steel which is actually intended to be used when in operation.
The variables are required to be closely applied & monitored to have the intended performance once the qualified WPS is used for production welds.
Austenitic formation is critical to the corrosion-resistant & toughness performance while in service and this is exactly what Appendix M has been applied to achieve. Presence of N2 is critical and matching fillers are required to suitably address that.

It is recommended to apply this to the case you have mentioned.

While we prepare the specifications to engage the Contractor, this Appendix has now been mentioned as a reference to be followed.
Do you think for welding of duplex stainless steels, any other reference should also be valuable.