1.2 Inspector Roles, Responsibilities & Certification Requirements

API 653 Aboveground Storage Tank Inspector Exam

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1 Chapter 1: API 653 Scope, Inspector Certification & Roles

1.1 Scope of API 653, Tank Types & Construction Standards 1.2 Inspector Roles, Responsibilities & Certification Requirements 1.3 Inspection Planning, Safety, Confined Space Entry & Preparation

2 Chapter 2: Tank Shell & Roof Components Inspection

2.1 Fixed Roof Types, Structural Supports & Inspection Practices 2.2 Floating Roofs, Seals, Drainage & Operational Issues 2.3 Shell Courses, Welds, Attachments & Wind Girders 2.4 Tank Appurtenances, Nozzles, Manways & Piping Connections

3 Chapter 3: Tank Bottom & Foundation Inspection

3.1 Tank Bottom Types, Annular Plates & Internal Bottom Inspection 3.2 Foundation Types (Concrete Ringwall, Earth, Asphalt) & Inspection 3.3 Leak Detection Systems, Secondary Containment & Under-Tank Monitoring

4 Chapter 4: Corrosion & Damage Mechanisms in Storage Tanks

4.1 Atmospheric Corrosion, Condensation & External Deterioration 4.2 Corrosion Under Insulation (CUI) & Piping/Nozzle Interfaces 4.3 Soil-Side Corrosion, Under-Bottom Pitting & Microbiologically Induced Corrosion (MIC) 4.4 Product-Side Deterioration: Chemical Attack, Ethanol SCC, Concentration Cell & Sulfuric Acid Corrosion

5 Chapter 5: Materials, Toughness & Brittle Fracture Prevention

5.1 Tank Steels, Material Specifications & Historic Standards 5.2 Brittle Fracture Assessment: Figure 5.1 Decision Tree & Exemption Curves (API 653 Section 5) 5.3 Charpy V-Notch Impact Testing & Minimum Design Metal Temperature (MDMT)

6 Chapter 6: Cathodic Protection & Interior Linings

6.1 Cathodic Protection Principles & Systems for Tank Bottoms (API RP 651) 6.2 CP Criteria, Surveys, Potential Measurements & Interference (API RP 651) 6.3 Tank Bottom Interior Linings, Surface Prep & Inspection (API RP 652)

7 Chapter 7: Corrosion Rates, Remaining Life & Inspection Intervals

7.1 Determining Corrosion Rates (Short-Term vs. Long-Term) 7.2 Remaining Life Calculations & Limiting Components 7.3 Establishing In-Service & Out-of-Service Inspection Intervals (API 653 Section 6)

8 Chapter 8: Tank Shell Minimum Thickness Evaluation

8.1 Shell Minimum Thickness Calculations (tmin for Hydrostatic & Operating Levels) 8.2 One-Foot Method, Variable Design Point & Reconstructed-Tank Shell Thickness 8.3 Joint Efficiency (E) Selection, Missing Data & Radiography Factors 8.4 Evaluation of Pitting, Localized Thin Areas (LTA) & Critical Length (L)

9 Chapter 9: Bottom Plate & Annular Ring Thickness Evaluation

9.1 Minimum Bottom Thickness Formulations (MRT, MRTbottom, MRTlinear) 9.2 Annular Plate Evaluation, Stress Criteria & Critical Zones 9.3 Bottom Pitting Evaluation & Remaining Thickness Before Next Inspection

10 Chapter 10: Tank Repairs & Alterations Standards

10.1 Classification: Repair vs. Alteration vs. Reconstruction (API 653 Section 9) 10.2 Shell Plate Replacement, Lapped Patch Plates & Insert Plates 10.3 Shell Penetrations, Door Sheets & Nozzle Additions 10.4 Hot Tapping Requirements, Limitations & Pre-Engineering (API 653 Section 9.15 & API Publ 2201)

11 Chapter 11: Welding Procedures, Qualifications & Quality Control

11.1 Welding Procedure Specification (WPS) & Procedure Qualification Record (PQR) per ASME IX 11.2 Welder Performance Qualification (WPQ) & Continuity per ASME IX 11.3 Essential, Non-Essential & Supplementary Essential Variables 11.4 Preheating, Post-Weld Heat Treatment (PWHT) & Weld Flaw Remediation

12 Chapter 12: Nondestructive Examination (NDE) Methods

12.1 Visual Examination (VT) & Magnetic Particle Testing (MT) per ASME V 12.2 Liquid Penetrant (PT) & Ultrasonic Thickness Measurement (ASME V Article 6 & SE-797) 12.3 Radiographic Testing (RT): Acceptance Criteria, Film Interpretation & ASME V/API 650

13 Chapter 13: Hydrostatic Testing & Post-Repair Examination

13.1 Hydrostatic Test Triggers, Exemption Criteria & Major Alterations (API 653 Section 12.3) 13.2 Leak Testing: Vacuum Box, Tracer Gas, Diesel & Air Pressure Tests 13.3 NDE Examination Requirements for Shell, Bottom, Roof & Nozzle Welds (API 653 Section 12.1)

14 Chapter 14: Relief Devices, Tank Settlement & Nameplate Records

14.1 Pressure & Vacuum Relief Devices, Venting Principles (API RP 576 & API 2000) 14.2 Tank Settlement Types: Uniform, Tilt, Out-of-Plane & Edge Settlement (API 653 Annex B) 14.3 Evaluating Settlement Limits, Cosine Curve Analysis & Remedial Action 14.4 Tank Marking, Nameplates, Inspection Reports & Recordkeeping (API 653 Section 13)

1.2 Inspector Roles, Responsibilities & Certification Requirements

Key Takeaways Explain This Topic AI

The API 653 Authorized Inspector holds exclusive non-delegable authority to perform visual examinations, evaluate NDE findings, assess structural fitness, and sign inspection reports.

The API 653 exam is 170 questions - 140 scored plus 30 unscored pretest items - split into a 110-question closed-book portion of 2 hours 45 minutes and a 60-question open-book portion of 3 hours 45 minutes, within a 7.5-hour total sitting.

Candidate eligibility to sit for the API 653 exam scales according to education: 1 year of AST experience for engineering degrees, 2 years for technical associate degrees, 3 years for high school graduates, and 5 years for candidates without formal credentials.

Inspectors maintain certification through 3-year recertification cycles requiring a minimum 20% AST inspection engagement and 24 CPD hours, plus a 25-question open-book web quiz every 6 years.

The Owner-User holds ultimate accountability for tank safety, inspection frequencies, QA/QC systems, and recordkeeping, while API 653 recognizes four categories of Authorized Inspection Agency: owner-user inspection teams, jurisdictional bodies, independent agencies recognized by a jurisdiction, and third-party inspection contractors.

Last updated: September 2026

The API 653 Authorized Inspector: Definition and Authority

In the API 653 Section 3 definitions, an Authorized Inspector is defined as an individual who has satisfied the certification requirements established by the API Individual Certification Program (ICP) . The Authorized Inspector acts as the technical arbiter of tank mechanical integrity, executing on-site visual assessments, directing non-destructive examinations, calculating corrosion rates, and verifying that all repairs, alterations, and reconstruction projects conform strictly to API 653 and owner-user specifications.

Non-Delegable Authority vs. NDE Examiners

A critical distinction exists between an Authorized Inspector and an NDE Examiner :

Authorized Inspector (AI) : Must be certified under API 653. The AI holds sole statutory and code responsibility for reviewing inspection records, performing external and internal visual inspections, determining minimum acceptable thicknesses ( t m i n t_{min} t min ​ ), approving repairs, witnessing or verifying hydrostatic testing, and certifying the final inspection report authorizing return to service. These core evaluative tasks cannot be delegated.

NDE Examiner : An individual certified under the employer’s written practice conforming to ASNT SNT-TC-1A or CP-189 (in methods such as Ultrasonic Testing [UT], Magnetic Flux Leakage [MFL], Radiographic Testing [RT], Magnetic Particle Testing [MT], or Liquid Penetrant Testing [PT]). Examiners may collect thickness readings, scan tank floors, or radiograph weld seams, but the Authorized Inspector must review, interpret, and formally accept all NDE findings.

Exam Format: Two Parts, Two Different Study Strategies

The API 653 certification exam is a 170-question computer-based test, of which 140 are scored and 30 are unscored pretest items seeded for future exams. The sitting is split into two parts that test genuinely different skills, and the Body of Knowledge is explicit about why:

Portion Questions Time What it tests

Closed book 110 2 hr 45 min Everyday working knowledge of API 653 and the reference documents — the material an inspector carries in their head

Open book 60 3 hr 45 min Detailed information the inspector is expected to be able to find in the documents but would not normally commit to memory

Total 170 7.5 hr (including tutorial and lunch break)

Three consequences for how you prepare:

Memorize the closed-book layer deliberately. Corrosion rate, remaining life, remaining corrosion allowance, and inspection interval formulas and the rules for setting intervals may all appear closed book, so drill them until they are automatic.

Practice navigation, not recall, for the open-book layer. Tab the tables and figures you will be sent to — API 653 Tables 4.1, 4.2, 4.3, 4.4, and 4.5; Figures 4.1, 4.2, 5.1, 5.2, 9.1 through 9.5; Annex B Figures B.1 through B.13; and the API 650 opening figures and tables. Speed of lookup is the scored skill.

Only the listed editions count. Questions come solely from the publications in the Body of Knowledge at the editions named on the matching Publications Effectivity Sheet , and only the sections listed there are available during the open-book portion. Some jurisdictions still operate under older editions codified in state law; the exam does not.

Choose the best answer from the options provided — API notes that most ICP items are single-answer multiple choice, with alternative item types being introduced.

Education and Experience Qualification Pathways

To ensure candidate inspectors possess the necessary engineering foundation and hands-on competence, API 653 Annex D specifies strict eligibility criteria to sit for the computerized, 170-question ICP examination. The required years of documented experience in aboveground storage tank activities vary inversely with the candidate's formal education level: +-------------------------------------------------------------------------+

• | API 653 ICP QUALIFICATION PATHWAYS |
• +---------------------------------------+---------------------------------+
• | Formal Educational Credential | Required Documented Experience |
• +---------------------------------------+---------------------------------+
• | Bachelor of Science in Engineering or | 1 Year of AST design, repair, |
• | Engineering Technology | operation, or inspection |
• +---------------------------------------+---------------------------------+
• | 2-Year Associate Degree or Technical | 2 Years of AST design, repair, |
• | Certification in Engineering/NDT | operation, or inspection |
• +---------------------------------------+---------------------------------+
• | High School Diploma or Equivalent | 3 Years of AST design, repair, |
• | (GED) | operation, or inspection |
• +---------------------------------------+---------------------------------+
• | No Formal Educational Credential | 5 Years of documented AST |
• | | design, construction, repair, |
• | | operation, or inspection |
• | | (>= 1 year in inspection) |
• +---------------------------------------+---------------------------------+

Documented experience must reflect direct involvement with aboveground atmospheric storage tanks in petroleum refineries, chemical processing plants, pipeline terminals, or marine shipping facilities. Two further conditions from the API ICP application rules are easy to overlook:

The qualifying experience must have been gained within the last 10 years , while employed by or under contract with an authorized inspection agency.

For the 2-year, 3-year, and 5-year pathways, at least one of those years must be in inspection (the remainder may be design, construction, repair, or operation).

API also recognizes technical military service as an education substitute: 3 or more years of technical military service maps to the 1-year experience pathway, and 2 years of technical military service maps to the 2-year pathway.

Recertification Cycle and Professional Development

Achieving initial certification is not a lifetime credential. API 653 certificates expire every three years , requiring active maintenance and continuing competency verification:

The 3-Year Recertification Term

Every three years, the certified inspector must submit a formal application demonstrating:

Active Practice Verification : The inspector must document that at least 20% of their professional time over the preceding three-year certification term was actively spent performing, supervising, or directing API 653 storage tank inspection activities.

Continuing Professional Development (CPD) : API 510, API 570, and API 653 certificants must complete 24 CPD hours per 3-year recertification cycle , earned through continuing education, industry conference attendance, training courses, and verified inspection assignments.

The 6-Year Web Quiz Requirement

Every six years (coinciding with every second three-year renewal cycle), active practice verification alone is insufficient. The inspector must also:

Successfully take and pass the online recertification web quiz .

The web quiz is an open-book, timed examination of 25 questions with a 4-hour limit , administered online through API’s ICP portal. It focuses specifically on code revisions, addenda, and technical modifications published across the referenced API and ASME publications during the prior six years.

The quiz and the recertification application open 90 days before the expiration date and remain available through a 90-day grace period after it. If an inspector fails to apply or fails the web quiz by the end of that grace period, the certification is terminated. Reinstatement requires reapplying and passing the full 170-question computerized proctored examination.

Organizational Roles and Division of Responsibilities

API 653 delineates an operational framework involving four primary entities: the Owner-User, the Authorized Inspection Agency, the Authorized Inspector, and the Repair Organization. +-------------------------------------------------------------------------+

• | API 653 GOVERNANCE HIERARCHY |
• | |
• | +-----------------------+ |
• | | OWNER-USER | |
• | | (Ultimate Compliance, | |
• | | Intervals, Records) | |
• | +-----------+-----------+ |
• | | |
• | v |
• | +---------------------+---------------------+ |
• | | | |
• | v v |
• | +-----------------------+ +-----------------------+ |
• | | AUTHORIZED INSPECTION | | REPAIR ORGANIZATION | |
• | | AGENCY (AIA) | | (WPS, Welder Qual, | |
• | | (QA/QC Supervision) | | Workmanship, MTRs) | |
• | +-----------+-----------+ +-----------+-----------+ |
• | | | |
• | v | |
• | +-----------------------+ | |
• | | AUTHORIZED INSPECTOR |<------------------------------+ |
• | | (Visual, Calculations,| Witnesses NDE, Reviews WPS/PQR, |
• | | Report Sign-Off) | Authorizes Return to Service |
• | +-----------------------+ |
• +-------------------------------------------------------------------------+
• 1. The Owner-User Organization

The owner-user is the organization that owns or operates aboveground storage tanks. Under API 653 Section 4 and Section 6, the owner-user carries ultimate responsibility for:

Maintaining an updated, documented Quality Assurance / Quality Control (QA/QC) inspection system.

Creating and archiving permanent tank records throughout the operating life of the equipment (construction drawings, baseline thicknesses, repair dossiers, settlement logs, and product service history).

Establishing formal inspection frequencies and out-of-service intervals in accordance with API 653 limits or Risk-Based Inspection (RBI) standards (API RP 580/581).

Approving engineering calculations, down-rating decisions, and major repair or alteration designs prior to field execution.

2. Authorized Inspection Agency (AIA)

The API 653 Section 3 definitions define an authorized inspection agency as any one of the following four distinct entities:

Category 1 : The inspection organization of an owner-user who maintains an internal inspection department dedicated to its own operating facilities.

Category 2 : An inspection organization of a jurisdiction (state, municipal, or regional government entity enforcing boiler and pressure vessel/tank safety laws).

Category 3 : An independent inspection organization licensed or recognized by the jurisdiction in which the storage tank is operated.

Category 4 : An independent inspection organization operating under direct contract to the owner-user, providing certified third-party inspection services.

3. The Repair Organization

A repair organization (defined in the API 653 Section 3 definitions) is any contractor or owner-user maintenance force executing repairs or alterations. The repair organization is strictly responsible for:

Providing materials, certified Mill Test Reports (MTRs), and components that conform to API 650/653 material specifications.

Establishing and maintaining qualified Welding Procedure Specifications (WPS) supported by verified Procedure Qualification Records (PQR) conforming to ASME Section IX and API 650.

Ensuring all welders and welding operators hold valid Welder Performance Qualifications (WPQ) and maintain continuity logs per ASME Section IX.

Executing all cutting, fitting, preheating, welding, and post-weld heat treatment in strict compliance with the approved repair scope and API 653 requirements.

Comparison Matrix: Duties Across Organizations

The following matrix summarizes the jurisdictional division of responsibilities under API 653:

Organizational Entity Code Definition Core Prerequisites Primary Responsibilities Deliverables Produced

Owner-User Operating entity owning the tank assets Owns/operates facility; maintains QA/QC system Retains ultimate accountability; sets inspection intervals; archives asset dossiers Inspection policies, RBI assessments, archived asset records

Authorized Inspector Certified under API ICP to inspect ASTs API 653 certification + active practice & web quiz Performs visual exams; reviews NDE; calculates t m i n t_{min} t min ​ & remaining life; signs reports Signed inspection reports, remaining life calculations, repair authorizations

Authorized Inspection Agency (AIA) 1 of 4 defined categories (owner-user, state, licensed, contractor) Accredited organization with certified inspectors Employs/supervises inspectors; enforces quality standards; verifies code adherence Certified inspection agency audit records, NDE quality oversight dossiers

Repair Organization Contractor or owner-user maintenance crew Qualified to ASME Section IX and API 650/653 Executes repairs/alterations; provides qualified welders & procedures; maintains QC Welder continuity logs, WPS/PQRs, MTR material certificates, post-repair QC packages