What is API 570?
API 570 ("Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems") governs metallic process piping after it has entered service — how it is inspected, how its condition is rated, and under what conditions it may be repaired or altered. It is the piping counterpart of API 653 for storage tanks and API 510 for pressure vessels: the construction code (typically ASME B31.3 for process piping) builds the system; API 570 manages its life.
For a maintenance or reliability team, the code matters for a concrete reason: when an inspection finds wall loss, API 570 is the framework within which "run, repair, or replace" gets decided — and it constrains which repair methods are on the table.
Service classes: not all piping is watched equally
API 570 classifies piping by the consequence of a failure, and the class drives how much inspection attention a circuit receives. In broad terms:
| Class | Consequence profile | Typical examples |
|---|---|---|
| Class 1 | Highest — failure could cause immediate emergency | Flammable services that may auto-refrigerate or flash, streams over hydrocarbon flash points near sensitive areas, hydrogen sulfide services |
| Class 2 | Significant — most process piping not in Class 1 or 3 | On-site hydrocarbon and chemical process lines |
| Class 3 | Lower — flammable but slow to vaporize, or hazardous but remote | Product lines to storage, off-site distillate piping |
| Class 4 (optional) | Lowest — non-flammable, non-toxic | Utility water, steam condensate, air |
Recent editions add the optional Class 4. The exact interval and extent of inspection for each class come from the code edition, the calculated corrosion rate and the remaining-life assessment — numbers your authorized inspector derives for your circuits, not values to copy from a blog. The principle to retain: the class decides how often someone looks, and the corrosion rate decides how long you have.
CMLs: where the code actually measures
API 570 monitors piping through condition monitoring locations (CMLs) — designated points where thickness and condition are tracked over time. Their placement is risk-informed: injection points, elbows and tees where turbulence accelerates loss, dead legs where stagnant fluid concentrates attack, soil-to-air interfaces on buried lines, and points under supports where moisture sits.
Two failure patterns deserve particular respect because they routinely surprise plants: dead legs, which can corrode at many times the rate of the flowing circuit they branch from, and corrosion under pipe supports and at soil-to-air interfaces, invisible until the line is lifted or excavated. If your CML plan has none in these locations, the plan is measuring where the pipe is healthiest.
When the reading comes back low: the repair pathways
A low thickness reading triggers the remaining-life calculation, and if the answer is unfavorable, API 570 frames the repair conversation. The main pathways:
| Pathway | What it involves | When it fits |
|---|---|---|
| Re-rating | Recalculating the circuit for reduced conditions | When operating conditions can permanently drop |
| Welded repair (patch, weld overlay, replacement spool) | Hot work, qualified welders and procedures, often isolation and gas-freeing | Generalized loss, high-consequence circuits, permanent restoration to original rating |
| Mechanical clamp / enclosure | Engineered fitting containing the defect | Temporary containment, leak box on live line, pending turnaround |
| Engineered composite repair | Designed per ASME PCC-2 / ISO 24817, no hot work | Localized external loss or reinforcement where the defect, service and engineering assessment allow — see cold bonding vs welding |
The composite option deserves the same discipline here as everywhere: API 570 and the governing construction code frame the acceptance, the owner-user's inspection organization and authorized inspector sign off, and the repair carries a design basis, qualified installers and documentation. "Temporary or permanent" is a property of the engineering case and its acceptance — not of the material.
What the owner-user side must hold up
API 570 places the inspection program in the hands of the owner-user: records of thickness history by CML, calculated corrosion rates, inspection intervals justified by remaining life, and a documented trail for every repair and alteration. In practice, the file quality decides how smooth the next inspection is. A repair — welded or composite — that lacks its design basis, procedure and acceptance records gets treated exactly as you would expect: as a finding.
FAQ
Does API 570 apply to my plant in Canada? Applicability depends on the owner, the jurisdiction and contractual requirements — many Canadian operators adopt API 570 as their in-service piping practice alongside provincial pressure-equipment regulations. Confirm with your jurisdiction and your inspection authority rather than assuming either way.
Can a composite repair be permanent under API 570? It can be accepted with a defined design life when the defect type, the engineering assessment and the owner and inspector acceptance support it. The lifetime comes from the qualified design — not from the word "permanent" in a brochure.
What is a dead leg and why does it matter? A section with no or intermittent flow — bypasses, drains, spare pump suctions. Stagnation concentrates water, solids and bacteria, so corrosion rates there routinely exceed the flowing circuit's. API 570 expects them to be identified and monitored specifically.
Who can perform repairs on API 570 piping? Repair organizations working under the owner-user's program: welded repairs by qualified welders to qualified procedures, composite repairs by installers qualified on the engineered system used — in both cases with the authorized inspector's involvement.
How is API 570 different from ASME B31.3? B31.3 is the construction code — it governs design and fabrication of new piping. API 570 takes over once the system is in service. A repair must satisfy the in-service code while respecting the original construction code's intent.
Piping repairs during your next shutdown window
Induscoat Canada performs engineered composite and cold-bonding repairs on process piping — external corrosion reinforcement, soil-to-air interface protection, and pipe coating — with the design basis and documentation your inspector will ask for. Send the inspection report and CML data through our request a quote page; we respond within 24 business hours.
Hicham M, P Eng, PMP
Engineer and project manager (PMP) at Induscoat Canada. Over 16 years of experience in industrial coatings, composite repairs and wear protection on mining, energy and petrochemical sites in Canada and internationally.