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    API 570 Piping Inspection Record: Thickness, Corrosion Rate and Remaining Life

    An in-service inspection record for one piping circuit: the thickness readings at each condition monitoring location (CML), the long-term and short-term corrosion rates and remaining life worked out from them, the next inspection dates, the external visual inspection, and the recommendations that come out of it. It follows the method API 570 sets out, without reproducing the code.

    At every thickness or external visual inspection of the circuit, on the intervals its piping class and remaining life set, and after a process upset, a change of service or a leak.

    Legal basis checked 26 October 2026

    Distillation columns and pipework at a process plant

    What is in the template

    Circuit data

    • Material specification
    • Nominal size and schedule
    • Nominal thickness (mm)
    • Corrosion allowance (mm)
    • Design pressure and temperature
    • Operating pressure and temperature
    • Insulation and coating
    • Year installed
    • Previous inspection: date and type
    • Damage mechanisms expected

    CML thickness readings

    Columns: CML · Component, location and method · t initial (mm) · t previous (mm, date) · t actual (mm) · t required (mm) · LTCR (mm/y) · STCR (mm/y) · Remaining life (y) · 9 rows per page

    Long-term corrosion rate LTCR = (t initial - t actual) / years between those readings. Short-term rate STCR = (t previous - t actual) / years between those readings. Remaining life = (t actual - t required) / the governing rate, normally the higher of the two unless the inspector records why the other reflects current operation better. t required is the greater of the pressure-design and the structural minimum thickness. A reading at or below t required is evaluated (repair, replacement, rerating or fitness for service) before the circuit stays in service.

    Inspection intervals

    • Governing corrosion rate (mm/y) and why it was chosen
    • Lowest remaining life in the circuit (years) and its CML
    • Next thickness inspection due (the lesser of half the remaining life and the class maximum)
    • Next external visual inspection due (class maximum)
    • Changes in service or operating limits since the last inspection

    Maximum intervals by piping class, as published summaries of the 5th edition give them: Class 1, 5 years for thickness and 5 for external visual; Class 2, 10 and 5; Class 3, 10 and 10; Class 4, set by the owner. Check them against your copy of API 570 and your inspection plan.

    External visual inspection

    Columns: Check · OK / Defect / N/A · Finding and photo reference

    • Coating and paint condition
    • Insulation and jacketing: damage, gaps and wet areas where corrosion under insulation is likely
    • Supports: pipe sitting on its shoes, corrosion at contact points, hangers and springs set
    • Small-bore connections and vents: bracing and signs of vibration
    • Leaks at flanges, valves, fittings and threaded joints
    • Misalignment, sagging or signs of unusual movement
    • Injection and mix points
    • Deadlegs
    • Soil-to-air and concrete-to-air interfaces
    • Bolting complete, fully engaged and not corroded
    • Temporary repairs and clamps identified, recorded and within their approved life
    • Pressure-relief devices in place and within their test date

    Recommendations and deferrals

    Columns: Recommendation · Priority · Owner · Due date · Deferral: reason, review and approver · Closed: date and evidence · 6 rows per page

    The 5th edition of API 570 (2024) added the review of inspection repair recommendations and guidance on deferring their due dates. Record every deferral with its reason, the review behind it and who approved it.

    Sign-off

    • Inspector: name and certification
    • Inspection supervisor or competent person: name and signature
    • Date
    • Report reference

    How to fill it in

    1. 1Fill in the circuit data once and carry it forward; confirm the piping class and the damage mechanisms at every inspection.
    2. 2Take each CML reading at the same marked spot as last time, and enter the baseline, previous and current readings with their dates.
    3. 3Work out the long-term and short-term corrosion rates and the remaining life for each CML, or use the free corrosion rate calculator; the lowest remaining life in the circuit governs.
    4. 4Set the next thickness inspection at the lesser of half the remaining life and the class maximum, and the next external visual at the class maximum.
    5. 5Walk the line for the external visual checks, photograph every finding, and turn each one into a recommendation with an owner and a due date.

    A general template, not legal advice. Check it against the Act, the regulations and the codes of practice that apply to your site, and against your own safety management system. In South Africa, regulation 11(1)(e) of the Pressure Equipment Regulations, 2009 requires piping and pipelines to be inspected and tested in accordance with the relevant in-service standard (for process piping this is usually API 570), with intervals set by risk-based inspection where the standard sets none, and requires Category II and higher piping to be inspected by a competent person; regulation 14(1) requires the user to keep a record of all inspections, tests, modifications and repairs, open to an inspector. API 570, Piping Inspection Code, 5th edition (February 2024), is published by the American Petroleum Institute. This record follows its method without reproducing it and cites no clause numbers, so check the intervals and limits against your copy.

    Legal basis checked on against: Pressure Equipment Regulations, 2009 (GN R734 of 15 July 2009), regulations 11(1)(e) and 14(1).

    Convert this template into a digital form

    Run it on an Android phone with no signal, attach photos as evidence, and every failed item raises an issue with an owner and a due date.

    Start the trial from here and this template is waiting in your workspace as a ready-made form.

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    The same record in Inspecable

    On paper the register is only as current as the last person who updated it. In Inspecable the same record keeps going:

    Do it in InspecableAsset registerThe longer readWhat the Pressure Equipment Regulations require you to record

    Questions

    How do you calculate corrosion rate and remaining life for piping?

    Long-term rate = (initial thickness - current thickness) / years between them; short-term rate = (previous - current) / years between them. Remaining life = (current thickness - required thickness) / the governing rate, usually the higher of the two. The free corrosion rate calculator on this site works it out per CML.

    How often must piping be inspected under API 570?

    The next thickness inspection is due at half the remaining life or the class maximum, whichever comes first. Published summaries of the 5th edition give class maximums of 5 years (Class 1) and 10 years (Classes 2 and 3) for thickness, and 5, 5 and 10 years for external visual inspection. The owner sets Class 4.

    Does API 570 apply in South Africa?

    Not by name. The Pressure Equipment Regulations, 2009 require piping to be inspected to the relevant in-service standard (regulation 11(1)(e)), and for process piping that is usually API 570. Where the standard sets no interval, a risk-based inspection applying sound engineering practice sets it.

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