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10/11 Page 1 BODY OF KNOWLEDGE CERTIFICATION EXAMINATION October 2009 (Replaces November 2008) API Authorized Aboveground Storage Tank Inspectors must have a broad knowledge base relating to tank inspection and repair of aboveground storage tanks.
The API Aboveground Storage Tank Inspector Certification examination is designed to identify individuals who have satisfied the minimum qualifications specified in API Standard 653, Tank Inspection, Repair, Alteration, and RThe examination consists of two parts.
The closed book part tests the candidate on knowledge and tasks requiring everyday working knowledge of API Standard 653 reference documents.
The open book portion of the examination requires the use of more detailed information that the inspector is expected to be able to find in the documents, but would not normally be committed to memory.A.API Publications API Recommended Practice 571ms Affecting Equipment in Refining Industry API Recommended Practice 577API Standard 650API Recommended Practice 651Cathodic Protection of Aboveground Petroleum Storage API Standard 653B.ASME Publications American Society of Mechanical Engineers (ASME)Boiler & Pressure Vessel Code, Nondestructive Examination ng Qualifications Note: Refer to the Publications Effectivity Sheet in the application package for a list of which editions, addenda, and supplements of the reference publications are effective for your exam. 10/11 Page 2 CALCULATIONS & TABULAR
EVALUATIONS FOR EVALUATING THICKNESS MEASUREMENTS, WELD SIZES, AND TANK INTEGRITY (NOTE: Paragraph references for all formulas and calculations listed here should be checked for accuracy to the edition, addenda, or supplement for the examination you plan to take per the Publication Effectivity Sheet in the API Examination Application.) NOTE:
Candidates are expected to be able to understand SI units (metric system) and the US customary units
(inches, feet, PSI, etc.) and to use both system questions will be oriented toward existing tanks, not new tanks.
API Authorized AST Inspectors should be able to check and perform calculations included in the following categories: 1.CORROSION RATES AND INSPECTION INThe Inspector should be able to take inspection data and determine the internal and external inspection intervals.These calculations could be in either the open book or closed book portion of the exam.
The Inspector must be able to calculate: Metal Loss (including corrosion averaging - API-653, Section 4) Corrosion Rates
= the thickness, in inches (millimeters), recorded at the time of inspection for a given location or component.
minimumminimum allowable thickness, in inches (millimeters), for a given location or component.Corrosion rate
= t between
= the thickness, in inches (millimeters), recorded at the same location as t actua measured during a previous inspection.The formulas for performing the above calculations and rules for setting the inspection intervals may be "closed-book" during the exam.
The inspector should also be able to compensate for the corrosion allowance.
(Add or subtract based on requirements from the exam problem.) 2.
JOINT EFFICIENCIES The inspector must be able to determine the joint efficiency, "E", of a tank weld.
Inspector should be able to determine: Joint Types (API-653 Section 4, Table 4-2) Type and extent of radiography performed (API 653, Table 4-2, Section 12; API 650, Section 8.1, Figure Joint efficiency by reading API-653, Table 4-2 10/11 Page 3 Determining joint efficiency may be part of a minimum thickness or maximum fill height problem since joint efficiency, "E", is used in the formulas for determining required thickness.(API-653, 22.214.171.124) 3.
MAXIMUM FILL HEIGHT (HYDROSTATIC TESTING) The inspector should be able to determine the maximum liquid height for a tank.
To determine the height, the min formula in API-653 is rearranged as follows.
This formula will be provided in the exam.
The inspector is NOT expected to derive this formula by using transposition.a. Calculate the minimum allowable thickness per Section 4 of API 653 or the maximum fill height in the localized corroded area per: SEtCalculate the minimum allowable thickness per Section 4 of API 653 or the maximum fill height for an entire shell course per:
WELD SIZES FOR SHELL & ROOF OPENINGS The inspector should be familiar with determining the sizes and spacing of welds for shell openings to the extent of being able to use the information in the following Figures and Tables: API-650, API-650, Tables
5-9 API-653, Figures 9-1, 9-2, 9-3A, 9-3B The Inspector should be familiar with the Hot Tapping requirements.(API-653, Paragraph 9
.14) The inspector should be able to calculate the minimum spacing between an existing nozzle and a new hot tap nozzle.
(API-653 Paragraph 9.14.3) 6.
SETTLEMENT EVALUATION The Inspector should be able to calculate the maximum allowed settlement for the following: Edge Settlement (API-653 Appendix B.2.3, fig.B-5) Bottom Settlement Near the Tank Shell (API-653, Appendix B.2.4, Figures B-6, B-7, B-9 B-10, B-11, B-Localized Bottom Settlement Remote from the Tank Shell (API-653, B.2.5, Fig.B-8) 7.
NUMBER OF SETTLEMENT POINTS The inspector should be able to calculate the number of survey points for determining tank settlement.
IMPACT TESTING 10/11 Page 4 The inspector should understand the importance of tank materials having adequate toughness.
MbIn the near future, API will publish an appendix toThe background on the development of the new appendix.Why and how did it comThe scope of the document as defined by the Process Industry Practices group.x.Where do the rules comWhcomponents are included? A design example to illustrate application of the design proWhsign rules fornal pressure originated with the of numerous petroleum and chemical comappendix to API Standard 650.
Anpermission.This document, togetherrting point in formulating and be considered adequate for externcolumn, PIP asked that rules be s greater than this amount.
The PIP request was dated April 15, 1998.The effort point.The specific Scope of We API Standard 650 for external pressure design.Uniform partial vacuum not to exceed one pound per square inch gage and partial submergence in near-static liquids shall be considered.Closed tanks having both supported and steel construction shall be consideed.Limitationmamum configuration size and my be imposed for specific geometries, mactices (PIP) efforts to harmonize specification requirements for storage tanks among min addition to vacuum processing lf.ronmental reglations oftetings for equipment which might see such service.
There meappendix are derived from several well-known documents, including: Guide to Stability Design Criteria f WeASME Boiler & Pressure Vessel Code, Section VIII, Divising Standard.However, closer sferences in som equations.These felly related to nomesafety factors, for example, to make the equA brief summary of the technical baasLoading Conditions and Combinations: The appendix will prescribe rules ffo and will include rules for combining that specified pressuA recently approved change to API 650 will prescribe rules for load itions and load comude these rules in a cenajowith API 650s level of risk of tank failure.LikewiseThus, starting with a speified designre+Pe+0.4(Lr or S), where DL = Dead Load.And the toc loading in accordance with load escribed The appendix includes, in both SI and US Customary Units, the equations necessarfor both conical and dome roofs thickness of shell and intermediate cirrential stiffefeIn addition, guidance on bottom evaluation, but escriptive equ foer-supported s.For relatively low specified ective, the necessary equations are availabreferences.For mor supported dome roofs mpared to self-supporting roofs.
might look like.The appendix sign example that illusion of the design equations for a 75 foot diameter Thbut moderate to small by petroleum industry standards.
a vacuum of 0.6 psig, and that the
prescribed in the appeRoof Thickness = 0.529 in 75 ft DIA.
48 ft r this example tank to withstand the specified vacuum loading within safably and the shell needs to be thickenfened with four intermediate circumfeOn a tank as large as this one, it was necessary to the dome roof and increase the thickness beyond the limits of lap-welding.The thickness of the entire shell was increased to the mnimum thicknessss as well.This allows the most cost-eff special importance to the PIP group x was the case wnt, or secondary containment area pty of liquid.Such an occurrence tends to uplift the bottom of the tank and to impose hydrostatic pressure against the outside of the shell.Norally, the amount of liquid, usually primarily water, that collects is not sufficient to the tank, but the height of water can be significant enough to balloon the bottom of the tank.This is trated in the fincluding such components as the com, tank anchorage, and attached or bottom fittings such as sums.
Onthod commonly used to mitigate thrisk of damage in this eent is to maintain a mmuto want to balloon.The appendix provides the e this minimum liquid level.Power of External Pressure: maessure is similar, whether the damby wind pressure or by negative internal g less extreme than negative internal pressure because wind is time.
Of course there are exceptions to both of thtimes the damage done can ired by simly pulling out thdents.In other caseshell mterial has yielded and is ed, replacement of some material is necessIn extreme cases, as shown in Photo 3, the dam so extreme that the tank my not be salvageable.
ge mechanism for vacuum loading is similar to that fthat the preventative measures in the design for vacuum loading are similar to those for wind loading, feners to increasof the shell.Tank Damaged by NegTank Damaged by Tornado Winds Tank Damaged Beyond Repair by Vacuum.
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