Regarding the National Board Inspection Code, you'll find plenty of information on:
www.nationalboard.com
which is the site of the National Board of Boiler and Pressure Vessels Inspectors.
Attention, though, it's information on what it contains, what are its purposes, what it's useful for etc. I doubt very seriously that you'll be able to download it for free.
Giovanni S. Crisi
Sao Paulo - Brazil