API 653 Study Guide Questions with Correct Answers

API 653 Study Guide Questions with Correct Answers API publications necessarily address problems of what type? - Answer-Problems of a general nature. (Special notes section) API Standard 653 covers in service steel tanks built to what standards? - Answer-This standard covers steel storage tanks built to API 650 and its predecessor API 12C. (1.1.1) What API Standard always governs for tanks that have been placed in service? - Answer-In the case of apparent conflicts between the requirements of this standard and API 650 or its predecessor API 12C, API 653 shall govern for tanks that have been placed in service. (1.1.2) API Standard 653 employs the design principles of what standard? - Answer-This standard employs the principles of API 650. (1.1.3) When design and construction details are not given and are not available in the standard to which the in service tank was originally constructed, then details that will provide a level of integrity equal to the level provided by the current edition of which standard must be used? - Answer-The current edition of API 650 must be used. (1.1.5) Who has the ultimate responsability for complying with the provisions of API653? - Answer-The owner/operator. (1.2) The inspector agency of the jurisdiction in which the above ground is storage tank is operated is called what? - Answer-Authorized inspection agency (3.3) An employee of an authorized inspection agency certified as an AST inspector per API 653 Appendix D, is known as what? - Answer-Authorized inspector (3.4) What is the total metal loss divided by the period of time over which the metal loss occurred? - Answer-Corrosion rate (3.9) What is the definition of a "repair" to a tank? - Answer-Work necessary to maintain or restore a tank to a condition suitable for safe operation. (3.24) What must be done when the results of a tank inspection show that a change has occurred from the original physical condition of that tank? - Answer-An evaluation shall be made to determine its suitability for continued use. (4.1.1) What must be done when the cone roof tank roof plates corrode to an average thickness of less than 0.09" in any 100 in^2 area? - Answer-Shall be repaired or replaced. (4.2.1.2) What section of API 653 must be considered when changing the service of a tank to operation at temperatures above 200F? - Answer-All requirements of API 650, Appendix M. (4.2.4.3) What form of corrosion does not normally represent a significant threat to the overall structural integrity of the tank shell unless it is present in a severe and numerous form? - Answer-Pitting (4.3.1.3) When can widley scattered pits inside the tank shell be ignored? - Answer-Provided that: a) no pit depth results in the remaining shell thickness being less than one-half the minimum acceptable tank shell thickness exclusive of the corrosion allowance; and b) the sum of their dimensions along any vertical line does not exceed 2 in. in an 8-in. length (see Figure 4.2). (4.3.2.2). A tank of a single butt-weld with a back-up bar construction, built to an unknownstandard in 1940 is inspected. Corrosion is general and an evaluation of the tank's minimum thickness is required. What joint factor would you use? - Answer-E = 0.85. (Table 4.2) What can foundation settlement cause to appear in the shell of an AST? - Answer-Shell distortions. (4.3.5.2, 4.3.5.3) Unless a stress analysis is performed what is the minimum bottom plate thickness in the critical zone of the tank bottom? - Answer-the smaller of one-half the original bottom plate thickness or 50 % of tmin of the lower shell course, but not less than 0.1 in. (4.4.5.4) An AST operating at 250F is evaluated for continuing service. The inspector checks the tank records and finds that the tank was originally built of ASTM A516 gr60. What allowable stress should the inspector use in evaluation the minimum thicknesses of the tank's shell? - Answer-32,000 * 0.80 = 25,600 (4.3.10.1.1a or Table 4.1) A six year old storage tank is inspected. The tank has a diameter of 125 feet and its maximum liquid level height is 40 feet. The tank was constructed of ASTM A283 gr C steel. The product stored in the tank has a specific gravity of 0.85. What is the Tmin for the lower shell course plate? - Answer-Tmin = (2.6*H*D*G)/(S*E) = (2.6*40*125*0.85)/(23600*1) = (11050)/(23600) = 0.468" (4.3.3.1) An AST that has a diameter of 121ft and a height of 40ft (five 8ft courses).Its bottom shell course has a thickness of 0.55" and a corrosion allowance of 0.1". The tank is built from ASTM A283 gr C CS. It has a joint eff of 0.85. The tank is to be hydrostatically tested. Determine the hydrostatic test height. Round to nearest 100th of a ft. - Answer- Ht = ((St*E*Tmin)/(2.6D)) + 1 = ((26,000*0.85*0.55)/(2.6*121)) +1 = (12155/314.6)+1 = 39.64ft (4.3.3.2) What is the risk of brittle facture failure in continued service after a tank has demosntrated the ability to whitstand the combined effects of maximum liquid level (highest stress) and lowest operating temperature without failing... great, minimal or average? - Answer-Minimal (5.2.2) Using Fig 5-2 of API 653, determine the lowest temperature that a tank constructed from CS of unknown thoughness may be used if its maximum shell thickness is 0.75" - Answer-55F (Table 5-2) The external condtion of storage tanks shall be monitored by close visual inspection from the ground on a routine basis. The inspection can be done by owner/operator personnel, and can be done by other Authorized inspector. The interval of such inspections shall not exceed how many months? - Answer-The interval of such inspections shall be consistent with conditions at the particular site, but shall not exceed one month. (6.3.1.2) External ultrasonic thickness measurements of the shell, when used and when the corrosion rate is not known, are taken at intervals not to exceed how many years? - Answer-When the corrosion rate is not known, the maximum interval shall be five years. (6.3.3.2)