Inspection
API 510, 570 and 653 Inspection Intervals: How They Set the Shutdown Window
API 510 limits internal or on-stream vessel inspection to the lesser of half the remaining life or 10 years, with external visual inspection at the lesser of 5 years or that interval. API 570 sets piping intervals by consequence class, and API 653 sets tank internal intervals from measured corrosion. The earliest due date among in-scope equipment, unless risk-based inspection supports a longer interval, drives the turnaround date.
How MaintWiz helps: The MaintWiz shutdown module carries this work as work packages with checklists, readings and photos, permits and readiness gates, so the result stays with the work order.
By Jai Balachandran · Technical review: Murali Nerur Pasupathy · Published · Last reviewed
What MaintWiz adds:Critical path and floatReadiness gatesPermits and isolationsChecklists with readings
Interval rules
What do the three codes say about inspection intervals?
Maximum intervals as summarised in public guides; confirm the current edition before you rely on a number.
| Code | Equipment | Interval rule (maximum) | Source |
|---|---|---|---|
| API 510 | Pressure vessel, internal or on-stream | Lesser of half the remaining life or 10 years | Reliamag guide |
| API 510 | Pressure vessel, external visual | Lesser of 5 years or the internal interval | Reliamag guide |
| API 570 | Piping class 1 (thickness / external visual) | 5 years / 5 years | Reliamag guide |
| API 570 | Piping class 2 (thickness / external visual) | 10 years / 5 years | Reliamag guide |
| API 570 | Piping class 3 (thickness / external visual) | 10 years / 10 years | Reliamag guide |
| API 653 | Tank, formal external inspection | 5 years or less, by shell corrosion rate | Reliamag guide |
| API 653 | Tank, internal (bottom) | 10-year baseline, then by corrosion rate; ceiling 20 years, or 30 with a release prevention barrier | Reliamag guide |
OSHA's process safety management rule sets no fixed interval: inspection and test frequency must follow manufacturer recommendations and good engineering practice, and be more frequent if experience shows it is needed.
Shutdown window
How do the intervals set the shutdown window?
The earliest internal inspection due among the equipment that needs the stop is the latest date the window can open.
- Build a due-date list of every vessel, piping circuit and tank that needs internal access, with its last inspection date and its interval.
- Sort by earliest due date: that equipment limits how late the shutdown can start.
- Check whether risk-based inspection (API RP 580) supports a longer interval where the code allows it; the support must be documented.
- Shorter intervals follow from shorter remaining life, higher consequence class, higher corrosion rates, corrosion under insulation and low tank floor thickness.
- Group the due items into one window where possible, and plan the access, cleaning and inspection time for each.
- Put the inspection jobs in the scope before the scope freeze so the findings work can be planned.
FAQ
Frequently asked questions
Do API 510, 570 and 653 set the turnaround date?
They set maximum inspection intervals. The earliest due internal inspection among in-scope equipment limits how late a window can open, so the shortest interval usually drives the date, unless risk-based inspection supports a longer one.
What is the API 510 internal inspection interval?
Per public summaries, the lesser of half the remaining life or 10 years. Confirm against the current edition.
Can risk-based inspection extend an interval?
Public summaries say a documented risk-based inspection under API RP 580 can support different intervals where the code permits.
What shortens an inspection interval?
Shorter remaining life, higher corrosion rates, higher piping consequence class, corrosion under insulation and, for tanks, low floor thickness.
Does OSHA set inspection intervals?
OSHA's process safety rule sets no fixed interval; it requires frequency consistent with manufacturer recommendations and good engineering practice.
Sources
Sources
Public trade guides and the OSHA rule, read on 30 October 2026; the API standards themselves are paywalled and were not read.
- Reliable, API 510, 570 and 653 inspection intervals: vessels, piping and tanks
- OSHA, 29 CFR 1910.119 Process safety management of highly hazardous chemicals
- Falcon Inspection and Services, API 510 remaining life
- Arveng Training and Engineering, Frequency of pressure vessel inspections according to API 510
Plan this work in the shutdown module
Book a demo and bring your next shutdown scope. We will show how the work, the permits and the results sit in one plan.