Scope, References, and Organization/Personnel Qualifications
What API 510 governs
API 510 is the owner/user's in-service inspection code for pressure vessels. It picks up where construction codes stop: it covers inspection, examination, testing, repair, alteration, and rerating of vessels after they enter service, plus the pressure-relieving devices that protect them. Its scope reaches vessels built to ASME BPVC Section VIII Divisions 1, 2, and 3, and - when the owner/user elects - older vessels built to earlier or other recognized codes (pre-1956 ASME, API-ASME). It is not a construction code (that is Section VIII), not a piping code (API 570), not a tank code (API 653), and not a fitness-for-service method (API 579-1/ASME FFS-1).
Who may inspect
The "inspector" is an API Authorized Pressure Vessel Inspector - certified by examination under the API 510 program - working for the owner/user or an authorized inspection agency. The owner/user owns the program: it must designate inspection responsibilities, keep records (design data, service history, thickness surveys, repairs, PRD test results), set intervals, and approve repairs and reratings. Where a Jurisdiction regulates the vessel, the jurisdictional authorized inspector may also be involved.
Traps
Questions like to blur code boundaries - a "repair" question that is really answered by ASME Section IX (welding) or Section V (NDE) rather than by API 510 itself. Another trap: assuming a certified NDE technician or a mechanical engineer automatically qualifies as the inspector.
Rule of thumb
If the question is about why an activity happens (program, records, intervals, approvals), cite API 510; if it is about how (procedure qualification, NDE technique, design thickness), cite the referenced code.