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API 653 Intro 2024 Questions & Answers
| 100% Correct | Verified
What does API 653 cover? - ✔✔Steel storage tanks built to API 650 and its predecessor API 126. Provides minimum requirements for maintaining integrity of such tanks after they have been placed in service and addresses inspection, repair, alterations, relocation, and reconstruction. What is the scope of API 653 limited to? - ✔✔scope is limited to tank foundation, bottom, shell, structure, roof, attached appurtenances, and nozzles to the face of the first flange, first threaded joint, or first welding in connection. What shall govern if there is a conflict between API 653 and API 126? - ✔✔API 653 shall govern for tanks that have been put in service. Can the principles of API 653 be applied to tanks not built using the specifications of API 650? - ✔✔Yes, storage tank owners/operators, based on the consideration of specific construction and operating details, may apply this standard to any steel tank constructed in accordance with a tank specification. What organizations is API 653 intended to be used by? - ✔✔Organizations that maintain or have access to engineering and inspection personnel technically trained and experienced in tank design, fabrication, repair, construction, and inspection. Since API 653 does not contain rules or guidelines to cover all the varied conditions which may occur in an existing tank, what shall the level of integrity be equal to if no design and construction details of a tank are given and are not available in the as-built standard? - ✔✔details that will provide a level of integrity equal to the level provided by the current edition of API 650 must be used. Who has the ultimate responsibility for complying with the standards of AI 653? - ✔✔Owner/Operator What governs if API 653 presents a direct or implied conflict with a jurisdictional regulation? - ✔✔The regulation will govern, unless the requirement from API 653 is more stringent.
What API standards shall be used to develop safe work procedures? - ✔✔API standard 2015 and API 2217A and shall include safeguards for personnel health and safety, prevention of accidental fires and explosions, and prevention of property damage. Define- Break Over Point - ✔✔The area on a tank bottom where settlement begins. Define- Candidate Tank - ✔✔The tank(s) for which corrosion rates are not known Define- Control Tank - ✔✔the tank(s) for which corrosion rates and service history are known. Define- Critical Zone - ✔✔The portion of tank bottom or annular plate within 3" of the inside edge of the shell, measured radially inward. Define- Insert Plate - ✔✔A steel plate that replaced part of a shell plate with a nominal thickness no more than 1/8" greater than the nominal thickness of the adjoining material. When an insert plate is equal to the full height of a shell ring, it is considered to be a shell plate. Define- Major Alteration/or Major Repair - ✔✔An alteration or repair that includes the following: a) installing a shell penetration larger than NPS 12 beneath the liquid level b) installing a bottom penetration within 12" of the tank shell c) removing and replacing or adding a a shell plate beneath the liquid level where the longest dimension of the replacement plate exceeds 12" d) removing or replacing annular late material where the longest dimension of the replacement plate exceeds 12" e) complete or partial (more than 1/2 of the weld thickness) removal and replacement of more than 12" of vertical weld joining shell plates or radial weld joining the annular plate. f) installing new bottom plate (note: installation of a partition of a new bottom as described in 12.3.3.3 is not defined as a major repair) g) removing and replacing part of the weld attaching the shell to bottom, or to the annulaer plate ring, in excess of the amounts listed in 12.3.2.5.1a h) jacking a tank shell
Where are the guidance for the repair of floating roof found? - ✔✔Guidance for the repair of floating roof shall be based on the criteria of API 650, Annex A for external floating roofs, and Annex H for internal floating roofs. However, upgrading to meet this standard is not mandatory. What requirements shall be considered when performing a change in service to the internal pressure? - ✔✔All requirements of API 650, Annex F, shall be considered in the evaluation and subsequent alterations to the tank roof and roof to shell junction. What evaluation shall be performed for an external pressure change in service? - ✔✔As applicable, the roof support system (if any) and the roof to shell junction shall be evaluated for the effects of a design partial vacuum. The criteria outlined in API 650, Annex V shall be used. What shall be considered when performing a change in service to operation at elevated temperature? - ✔✔All requirements of API 650, Annex M, shall be considered before changing the service of a tank to operation above 200F What requirements shall be met before a change in service to operation at a lower temperature? - ✔✔The requirements of the current applicable standard for the lower temperature shall be met. Who shall conduct evaluations on a tank shell and what considerations shall the analysis include? - ✔✔Evaluation of existing tank shell shall be conducted by a storage tank engineer and shall include an analysis of the shell for the intended design conditions, based on existing shell thickness and material. The analysis shall take into consideration all anticipated loading conditions and combinations, including pressure due to fluid static head, internal and external pressure, wind loads, seismic loads, nozzle loads, settlement, and attachment loads. Where are the methods for determining the minimum shell thickness suitable for continued operation given? - ✔✔API 653, Sec. 4.3.2, 4.3.3, and 4.3. If the requirements of API 653 4.3.3 (welded) or 4.3.4 (riveted) cannot be satisfied, what actions shall be performed? - ✔✔the corroded or damaged areas shall be repaired, or the allowable liquid level of the tank reduces, or tank retired. the allowable liquid level for the continued use of the tank may be established by using the equations for a minimum acceptable thickness ( see 4.3.3.1 and 4.3.4.1) and
solving for H. The actual thickness, as determined by inspection, minus the corrosion allowance shall be used to establish the liquid level limit. The maximum design liquid level shall not be exceeded. How shall the controlling thickness in each shell course when there are areas of corrosion of considerable size be determined? - ✔✔Thickness shall be averaged in accordance with the following: A) For each area, the authorized inspector shall determine the minimum thickness, t2,, at any point in the corroded area, excluding widely scattered pitting (see 4.3.2.2) B) calculate the critical length, L. L= 3.7√Dt2, but not more than 40" C) The authorized inspector shall visually or otherwise decide which vertical plane(s) in the area likely to be the most affected by corrosion. Profile measurements shall be taken along each vertical plane for a distance of L. In the plane(s), determine the lowest average thickness, t2, averaged over a length of L, using at least 5 equally spaced measurements over length L. D) see API 653 4.3.3.1 for minimum permitted values for t1 and t2. The additional loads in 4.3.3.5 shall also be considered. E) the criteria for continued operation is as follows: 1)the value of t, shall be greater or equal to tmin (see 4.3.3 or 4.3.4), subject to verification of all other loading's listed in 4.3.3.5.
- the value of t2 shall be greater than or equal to 60% of tmin.
- any corrosion allowance required for service until the time of the next inspection shall be added to tmin and 60% of tmin. When can widely scattered pitting be ignored in determining actual thickness? - ✔✔Widely scattered pitting may be ignores provided that no pit depth results in the remaining shell thickness being < .5tmin- Corrosion Allowance and or the sum of dimensions along any vertical line does not exceed 2" in an 8" length. Where in API 653 will you find the minimum thickness calculation for welded tank shell? - ✔✔API 653, Sec. 4.3. What is the largest diameter tank allowed to calculate minimum thickness for welded tank shell using equations given in API 653, Sec. 4.3.3? - ✔✔200ft
What is the required evaluation and/or repair action for undercut of shell butt welds? - ✔✔If from original construction, undercut shall not require repair if the tank has been hydro tested or will not undergo a change in service. What is the required evaluation and/or repair action for weld corrosion on shell welds? - ✔✔shall be repaired if the corrosion pit cavity bottom is below the surface of the adjacent shell plate. What is the required evaluation and/or repair action for shell to bottom weld corrosion? - ✔✔Shall be repaired if the remaining fillet weld is less than the required weld size. What is the required evaluation and/or repair action on fillet weld size on existing nozzles? - ✔✔Shall be evaluated according to the original standard of construction. What is the required evaluation and/or repair action for surface defects, such as arc strikes? - ✔✔shall be acceptable if the tank has been hydro tested or will not undergo a change of service. What is considered operation at elevated temperatures and what evaluation shall be performed? - ✔✔operation at elevated temperatures (above 200f, below 500f) shall be evaluated for suitability of service. Where are tank bottom leak detection systems and testing methods listed? - ✔✔API 575 Where are Cathodic protection systems covered? - ✔✔API 651 Where are applied linings and coatings for internal surfaces of thank bottoms covered? - ✔✔API 652 What are RPBs? - ✔✔Release Prevention Barriers are barriers placed in the bottom of or under a tank to prevent the escape of released material and containing or channeling released material for leak detection.
What NDE is commonly used to examine tank bottoms? - ✔✔Magnetic Flux Leakage tools are commonly used, along with UTT to examine tank bottoms. UTT is used to confirm and further quantify data obtained by MFL examination. Where is the equation to determine the minimum thickness for tank bottom found? - ✔✔API 653, Sec 4.4. What actions shall be performed if minimum bottom thickness at the end of the in-service period of operation are calculated to be less than the tmin given in Table 4.4, or less than the tmin given by RBI? - ✔✔The bottom shall be lined, repaired, replaced, or the interval to the next inspection shortened. Unless a stress analysis is performed, what shall be the tmin for bottom plate in the critical zone? - ✔✔tmin for bottom plate in the critical zone shall be the smaller of 1/2 the original plate thickness ( not including corrosion allowance) of 50% of tmin of lower shell course per 4.3.3.1 but not less than .1". Isolated pitting will not appreciably affect the strength of the plate. Can the treatment of bottom plate pitting by non welded repairs be used to increase RTic for calculating MRT? - ✔✔no What thickness shall the projection of bottom plate beyond the shell, as measured at the toe of the outside bottom to shell weld, be less than? How far beyond the shell to bottom plate weld shall the bottom plate project past? - ✔✔Bottom plate shall not be less than .1" thick, and must project past shell to bottom weld at least 3/8" Where is the minimum thickness for annular plate ring described? - ✔✔Minimum thickness for annular plate thickness shall not be less than the thickness given in API 653, Table 4. When shall routine in-service inspections be performed? Who performs them? - ✔✔routine in-service inspections shall be performed not exceeding 1 month apart. Inspection may be performed by an employee of the owner/operator and does not have to be the authorized inspector. When shall external inspections of tank be performed? Who performs them? - ✔✔shall be performed by authorized inspector at least every 5 years or RCA/4N years (Remaining Corrosion Allowance, N= shell corrosion rate)
