Use of plateswelded to pipe as end cap for hydrotesting

Hi All,
I have a unique situation. we have spools that needs to be hydrotested.The end of the spool is golden welded to the final location. These spools are 24" dia SS material.To hydrotest this (test pressure is 1500 kpa) spool normally,we require flanges or end caps which needs to be cut after testing. But can we use plates welded into pipes as end caps and test? This will solve many problems of sourcing correct size of caps or flanges which is very costly.I want to raise a Technical query to the client whether they accept this. Can we use cs plates welded to SS pipes using 309 rod ,and after hydrotesting cut this cs part away and Golden weld.

Can anyone give me code reference too.

Thanks in advance.
Deepu Varghese