Exchangers tube inspection is an added cost and it is applied only when risk based inspection asks for that.
For selection of appropriate NDE methods, you can refer to Section 1 of API 586.

What are the successful stories of performing non-intrusive in-operation inspection of internal non-metallic coating for piping?
Please support with recognized publications, if any.

What are the typical safety checks which should ideally be made when performing a welding job at site, being a critical work activity.
Provided, gas checks are made supported through permit management system.

ben,
What is the reference of this 8% limit?

Attached

A recommendation if someone is interested in this title by Arthur C. Reardon.
Easy to understand.
Excellent introduction to metallurgy for mechanical and inspection engineers.
Best for beginners and intermediate engineers.

Yes, corrosion inhibitors should be considered as one of the primary mitigation methods for carbonic acid corrosion—but not automatically in every system. Whether they are necessary depends on the process conditions, materials of construction, and whether other mitigation measures alone can achieve ...

It has now been identified that the failure was caused due missing supporting system for the socket weld as it was carrying a load of a valve on the downstream end.
Gussets system is one recommended to be welded now and yes we are identifying other such cases as well system wide.

Yes that is what we have initiated now and looking for the leads.

In addition to what has already been mentioned, shielding gas composition is important as well as that is directly connected to the weld quality. Argon is the one used for GTAW, although the addition of approximately 2–3% nitrogen is recommended as nitrogen promotes austenite reformation during weld ...