What is the bridle /standpipe design and material code?

[Eng.Mohaned]

Dears,

I am looking for some guidance on modifying a vessel (3 phase seperator) to add a new level bridle.
My question is, does the design and material for the bridle/standpipe follow asmeb31. 3 or the design code for the vessel (asme VIII Division 1)??

 

[mk3223]

As the bridle/standpipe fabricated after the first nozzle of rat vessel, it can be designed per B31.3. Typically, it is grouped to the vessel trim piping.