What are you expected to know for the exam?

Before answering this question, we need to know how API 653 Publication Effectivity Sheet (documents identified by API ICP to study for the exam) and Body of Knowledge (what you expected to know for the exam) is selected by API.

API; first identifies a general job description for API 653 inspector. In order to carry the job description assigned to you as an authorized inspector, you are expected to have certain knowledge and experience.

If we categorize API inspectors into 3 levels:

• Apprentice
• Basic Inspector (This is the level you are being examined against)
• Supervising Inspector

Fact: API exam is based on a wide range of topics but the good news is that many exam questions are based on very basic inspection rules. Hence, lots of questions from vocabulary and scope, Organization and Certification Requirements, Types and Definitions of Maintenance Inspections.

Fact: API exam does not want to verify whether the inspector has memorized the standards and RPs, on the other hand, the exam tries to verify whether you have understood the concepts and rules to be able to apply it on various scenarios.

The knowledge type of question comes from understanding standards and recommended practices (Open book questions that you are not expected to remember but should know where to find a particular piece of information, how to interpret and use them for answering a question) while the practical or closed book type of questions come from experience or everyday knowledge that you expected to know by heart.

For API 653 Storage Tank Inspector Exam, we have the publication effectivity sheet which tells us that as an Inspector, we should know about:

API Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction. This is a standard and tells us about dos and don’ts.

Note: Standards are legally enforceable, mandatory sets of regulations, rules, and minimum requirements for safety and design, usually established by government bodies. Standards are voluntary, consensus-based, detailed technical guidelines and procedures often developed by organizations to ensure quality and consistency, which may become mandatory if cited within a code.

API 653 is based on API Standard 650, Welded Tanks for Oil Storage. While API 650 used for construction of the tank, API 653 is used for operation and maintenance.

API 653 Standard should be read in conjunction with API Recommended Practice 575, Inspection Practices for Atmospheric and Low-Pressure Storage Tanks. You can find many similarities between them, especially the vocabulary.

API Recommended Practice 575, Inspection Practices for Atmospheric and Low-Pressure Storage Tanks is a guide or best practice and tell you how to inspect the tanks. This is the document that you mostly use during your day to day inspection activities.

Fact: Definite exam question: Study API 653 and API 575 vocabulary very carefully.  Lots of basic questions come in the exam.

Every Storage Tank involves welding and NDT.

For welding you should know about welding methods and processes (API Recommended Practice 577, Welding Processes, Inspection, and Metallurgy) as well as WPS, PQR and WPQ and hence ASME Section IX, Qualification Standard for Welding, Brazing, and Fusing Procedures.

You should know about popular NDT methods (VT, MT, PT, RT, UT) and ASME Section V tell you about how a procedures is written, how often NDT equipment should be calibrated and what should be the qualification of NDT inspectors (cross referenced to ASNT SNT TC 1A).

Storage Tank always comes with flanges and hence you should know about B16.5, Pipe Flanges and Flanged Fittings.

You should also know about popular corrosion modes and damage and deterioration mechanism for Storage Tank and hence the selective parts of API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry.

You should know about pressure relieving devices that any Storage Tank has to vent off during emergency and hence API Recommended Practice 576, Inspection of Pressure-relieving Devices.

You should know about protection of storage tanks against corrosion and hence API Recommended Practice 651, Cathodic Protection of Aboveground Petroleum Storage Tanks.

Storage tanks are normally internally coated or cladded and hence you should know about API Recommended Practice 652, Lining of Aboveground Petroleum Storage Tank Bottoms

Let’s look at what type of exam question you should expect from another perspective

API 653 Body of Knowledge not only tells us about the type of questions to expect but also hints at some potential questions:

Fact: API Authorized Aboveground Storage Tank Inspectors must have a broad knowledge base relating to tank inspection and repair of aboveground storage tanks.

Fact: Only inspection parts of standards and recommended practices shall be used for exam questions.

You should know about Corrosion Rate and Inspection Intervals. Metal Loss (including corrosion averaging – API 653, Section 4) is definitely an exam question (Open book).

The exam consists of two parts.

The closed-book part tests the candidate on knowledge and tasks requiring everyday working familiarity of API 653 and the applicable reference documents. You shall not have access to Standards and RPs during closed book so you should know the answer by heart.

The open-book portion of the exam requires the use of more detailed information that the inspector is expected to be able to find in the documents but would not normally commit to memory.

During the exam, applicants will be expected to choose the best answer from the options provided (multi choice exams) although recently API introduced some 4-5 drag and drop type of questions.

 API 653

Fact: Definite closed book questions from these API 653 standards sections:

1. a) Metal Loss (including corrosion averaging – (API 653, Section 4)
2. b) Corrosion Rates
3. c) Remaining Life
4. d) Remaining Corrosion Allowance
5. e) Inspection Interval (API 653, Section 6)

Note: Corrosion Rates & Inspection Interval also brought in API 575, 7.1 & 7.2.

The joint efficiency, “E”, of a tank weld is brought in  Joint Types (API 653 Section 4, Table 4.2)

Type and extent of radiography performed is brought in (API 653, Table 4.2, Section 12; API 650, Section 8.1, Figure 8.1).

The sizes and spacing of welds for shell openings is brought in API 650, Tables 5.6a, 5.6b, 5.7a, 5.7b, 5.9a, 5.9b.

The minimum and maximum allowable thickness is brought in Section 4 of API 653.

Hot Tapping requirements are brought in (API 653, 9.15).

The minimum spacing between an existing nozzle and a new hot tap nozzle is brought in (API 653, 9.15.3).

Edge Settlement is brought in (API 653 Annex B.2.3, Figure B.6).

The number of survey points for determining tank settlement is brought in (API 653, 12.5.2, Annex B, Figure B.1, Figure B.2).

Tank design metal temperature is brought in (API 650, 3.8, 4.2.10 & Figure 4.2).

Material Group Number for a plate is brought in (API 650, Tables 4.4a and 4.4b).

To check if impact testing is required is brought in (API 650, Figure 4.1a and 4.1b)

To check if impact test values are acceptable; is brought in (API 650, Table 4.5a and 4.5b)

 “S”, allowable stress calculation is brought in (API 653, 4.3.3.1 & 4.3.4.1)

“E”, Joint efficiency calculation is brought in (API 653, 4.3.3.1, 4.3.4.1 & Tables 4.2 & 4.3)

“H”, liquid height calculation is brought in (API 653, 4.3.3.1 & 4.3.4.1)

Calculate minimum acceptable thickness calculation is brought in (API 653, 4.3.3.1 & 4.3.4.1)

Thickness calculation for continued service is brought in (API 653, 4.3.3.1 & 4.3.4.1)

“Sd”, allowable stress calculation for design condition is brought in (API 650, Tables 5.2a and 5.2b, and API 653, 8.4.2)

“St”, allowable stress for hydrostatic test condition calculation is brought in (API 650, Tables 5.2a and 5.2b, and API 653, 8.4.3)

“td”, design shell thickness calculation is brought in (API 650, 5.6.3.2, for tanks of 200-ft. (61 m) diameter and smaller)

“tt”, hydrostatic test shell thickness calculation is brought in (API 650, 5.6.3.2)

Select “t2”, minimum thickness exclusive of pits for a corroded area (API 653, 4.3.2.1.a & Figure 4.1)

Calculation for “L”, critical length for a corroded area is brought in (API 653, 4.3.2.1.b & Figure 4.1)

Calculation for “t1”, average thickness for a corroded area is brought in (API 653, 4.3.2.1.c, 4.3.2.1.d, Figure 4.1)

“tmin” for the corroded area “H”, height and “E”, joint efficiency will be based on corroded area (API 653, 4.3.3.1)

Calculate if tmin is acceptable (API 653, 4.3.3.1.a & 4.3.3.1.b)

Calculate maximum acceptable pit depth (API 653, 4.3.2.2.a)

Determine the maximum length of pits in any 8 in. (200 mm) vertical length (API 653, 4.3.2.2.b & Figure 4.2)

Calculate “MRT”, bottom minimum remaining thickness at the next inspection. (API 653, 4.4.5.1)

The inspector should be able to determine the minimum dimensions for a replacement plate. (API 653, Figure 9.1)

Per API 653, 9.3 the inspector should be able to determine:

1. a) The minimum thickness
2. b) The minimum weld size
3. c) The allowable size of the patch plate

API 650 and API 653: General welding requirements

General rules for welding in API 650, Section 9,

1. a) typical joints and definitions
2. b) weld sizes
3. c) restrictions on joints
4. d) maximum allowable reinforcement
5. e) inspection requirements

General rules for welding in API 653, Section 11.

ASME IX

Inspector should know about:

• Weld Procedure Specification (WPS)
• Procedure Qualification Record (PQR)
• Welder Performance Qualification (WPQ)
•  Essential and non-essential variables. (Supplementary essential variables in case of PWHT)
• Number and type of mechanical tests for PQR, and acceptable results
• Welder is qualified in terms of weld thickness and welding position.

Fact: Definite exam question: PQR and WPQ must be certified by signing and dating.

ASME Section V, Non-destructive Examination

You should know about NDT examiner qualification, instrument calibration and what comes in a typical NDT procedure and report for RT, MT, PT and UT (thickness measurement only) methods.

General Practical Knowledge (Closed book)

• Organization and API 653 Certification Requirements.
• Types and Definitions of Maintenance Inspections.
• Storage Tank Materials and Fabrication Problems.
• Welding on Storage Tank.
• General Knowledge of NDT Methods.
• Pressure Relief Devices.
• Maintenance Inspection Safety Practices.
• Inspection Records and Reports.
• Difference between Repair and Alteration.
• Rerating Storage Tank.
• Pressure-Temperature Ratings

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