davelamps
1) How many years of service HRSG would be completing before you commence inspection?
2) For any Boiler, you must concentrate on conditions of tubes. I suggest, in addition to tube wall thickness, you should consider RFET (Remote Field Electromagnetic Testing) to establish a base line data for future refrence.
3) Also replica of tube surface sample must be picked up for metallographical exmaination of microsturture of tubes. (Include sample from tubes of each sections ie.e Evaporator, superheater etc.)
4)A thorough visual examination of all zones in HRSG will make a good base for future.
5) Take relevant pictures.
6) Include chimney / stack in your inspection plan.
7) Random thickness measurement on tubes, steam and water drums will form a good base for future.
8) Refractory inspection is a vital component.
9) Finally a hydro test @ 1.3 times of Design pressure will be an ulitmate to cehck the integrity.
10) For more info, please refer API 510, inspection of pressure vessels.