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API 510, 570, and 653: Pressure Vessel, Piping, and Storage Tank Inspection Standards

NDTAPIPressure VesselPipelineStorage Tank

Three API standards come up regularly for NDT and inspection companies working in petrochemical, refinery, chemical plant, and energy sectors: API 510 for pressure vessels, API 570 for piping, and API 653 for storage tanks. These codes define which inspection methods to apply, how often, and how — so that equipment can continue operating safely.

API 510: Pressure Vessel Inspection Code

API 510 covers the inspection, repair, alteration, and re-rating of in-service pressure vessels that cannot be taken permanently out of service. It governs periodic inspections during the operating life of the vessel, not initial manufacturing inspection.

Scope

  • Pressure vessels in refineries and chemical plants
  • Vessels at risk under operating conditions (temperature, pressure, process fluid)

Key Requirements

Internal Inspection: Vessels under API 510 are inspected internally at intervals that depend on the risk assessment. The code permits RBI (Risk-Based Inspection); this allows inspection intervals to be extended for low-risk equipment.

External Inspection: Vessel exteriors — including insulation and support systems — are examined at shorter intervals.

Thickness Measurement: UT (ultrasonic) measures wall thickness; corrosion rate is calculated from the data and remaining life is estimated.

Inspector: API 510 inspections are conducted by or under the supervision of an API 510 Authorized Pressure Vessel Inspector.

API 570: Piping Inspection Code

API 570 covers the inspection of in-service process piping systems in refineries, chemical plants, and petrochemical facilities. It provides a systematic framework for managing corrosion, erosion, and fatigue damage during operation.

Scope

  • Process piping carrying pressurized fluids
  • Offshore pipelines are largely excluded

Key Requirements

Inspection Classes: API 570 classifies piping by risk level (Class 1, 2, 3). Class 1 lines carrying high-hazard fluids are inspected more frequently.

UT Thickness Measurement: Point or scan-based UT measurements determine corrosion rate. Measurement locations are recorded and compared with previous readings.

CML (Corrosion Monitoring Locations): CML positions are defined for each piping circuit; regular measurements at those points feed trend analysis.

Inspector: Conducted by an API 570 Authorized Piping Inspector.

API 653: Aboveground Storage Tank Inspection Standard

API 653 covers the inspection, repair, alteration, and reconstruction of in-service aboveground steel storage tanks — crude oil, petroleum products, chemicals — built to API 650 or API 12C.

Scope

  • Cylindrical, flat-bottomed steel storage tanks
  • Refineries, terminals, and storage facilities

Key Requirements

Floor Inspection: After the tank is cleaned and emptied, floor plates are scanned by UT or MFL (magnetic flux leakage). Corrosion, pitting, and wall thinning are identified.

Shell Thickness Measurement: UT measurements of tank shell; calculated minimum thickness must exceed the minimum allowable.

Roof Inspection: Internal or external assessment depending on operating pressure.

External Inspection: Walkdown survey with thickness readings from the outside.

Inspector: Conducted by an API 653 Authorized Storage Tank Inspector.

Integration with RBI

All three codes support Risk-Based Inspection (RBI). In RBI:

  • Damage mechanisms (corrosion, cracking, erosion) are identified for each piece of equipment
  • Probability and consequence of failure are calculated to establish risk level
  • Inspection resources are allocated in proportion to risk

This lets you extend intervals on low-risk equipment while focusing attention where it matters.

Records Management and NDT Software

All inspections under API 510/570/653 require comprehensive record keeping:

  • Equipment history (manufacture, prior inspections, repairs)
  • Individual inspection report and measurement data per inspection
  • CML list and historical thickness trend
  • Remaining life calculation and next inspection date

For a handful of vessels this is manageable in spreadsheets. At facilities with dozens or hundreds of equipment items, a centralized software system becomes necessary.

ceres-ndt handles work order management, UT thickness tracking, CML records, and reporting for equipment under API 510/570/653 — on one platform. Get in touch.

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