ditto Duwe6. API-653 IS the procedure and it is really one of the best How-To-Evaluate/Fix-It standards compared to other industries. It is very concise too and there is no fluff to skim over in that book. If anything API-653 is the Cliffs Notes to tank engineering and there are no Cliffs Notes to the Cliffs Notes. btw, i'm not flaming you here. i just want to emphasize the point since you might be making a career out of it. start with API-653, then API-650, then API-2000, then....
a good starting point is to understand everything on the out-of-service inspection checklist at the back of API-653.