API 653:2001 pdf download

API 653:2001 pdf download.Tank Inspection, Repair, Alteration,and Reconstruction.
4.1 GENERAL
4.1.1 When the results of a tank inspection show that a change has occurred from the original physical condition of that tank, an evaluation shall be made to determine its suitability for continued use.
4.1.2 This section provides an evaluation of the suitability of an existing tank for continued service, or for a change of service, or when making decisions involving repairs, alterations, dismantling, relocating, or reconstructing an existing tank.
4.1.3 The following list of flictors for consideration is not all-inclusive for all situations, nor is it intended to be a substitute for the engineering analysis and judgements required for each situation:
a. Internal corrosion due to the product stored or water bottoms.
b. External corrosion due to environmental exposure.
c. Stress levels and allowable stress levels.
d. Properties of the stored product such as specific gravity, temperature, and corrosivity.
e. Metal design temperatures at the service location of the tank.
f. External roof live load, wind, and seismic loadings.
g. Tank foundation, soil, and settlement conditions.
h. Chemical analysis and mechanical properties of the materials of construction.
i. Distortions of the existing tank.
j. Operating conditions such as filling/emptying rates and frequency.
4.2 TANK ROOF EVALUATION
4.2.1 General
4.2.1.1 The structural integrity of the roof and roof support system shall be verified.
4.2.1.2 Roof plates corroded to an average thickness of less than 0.09 in. in any 100 in.2 area or roof plates with any holes through the roof plate shall be repaired or replaced.
4.2.2 Fixed Roofs
Roof support members (rafters, girders, columns, and bases) shall be inspected for soundness by a method acceptable to the responsible inspector; distorted (such as out-ofplumb columns), corroded, and damaged members shall be evaluated and repaired or replaced if necessary. Particular attention must be given to the possibility of severe internal corrosion of pipe columns (corrosion may not be evidenced by external visual inspection).
4.2.3 Floating Roofs
4.2.3.1 Areas of roof plates and pontoons exhibiting cracks or punctures shall be repaired or the affected sections replaced. Holes through roof plates shall be repaired or replaced.
4.2.3.2 Areas that are pitted shall be evaluated to determine the likelihood of through-pitting occurring prior to the next scheduled internal inspection, if so, the affected areas shall be repaired or replaced.
4.2.3.3 Roof support systems, perimeter seal systems, appurtenances such as a roof rolling ladder, anti-rotation devices, water drain systems, and venting systems shall be evaluated for needed repairs or replacements.
4.2.3.4 Guidance for the evaluation of existing floating roofs shall be based on the criteria of API Std 650, Appendix C, for external floating roofs, and Appendix H for internal floating roofs. However, upgrading to meet this standard is not mandatoiy.
4.2.4 Change of Service
4.2.4.1 Internal Pressure
All requirements of the applicable standard (for example, API Std 650, Appendix F) shall be considered in the evaluation and subsequent modifications to the tank roof and roof- to-shell junction.
4.2.4.2 External Pressure
As applicable, the roof support structure (if any), and the
roof-to-shell junction shall be evaluated for the effects of a
design partial vacuum. The criteria outlined in API Std 620
shall be used.
4.2.4.3 Operation at Elevated Temperature
All requirements of API Std 650, Appendix M, shall be considered before changing the service of a tank to operation at temperatures above 200°F.
4.2.4.4 Operation at Lower Temperature Than Original Design
if the operating temperature is changed to a lower temperature than the original design., the requirements of the applicable standard or API Std 650 for the lower temperature shall be met.