API RP 579
|Publication Date:||1 January 2000|
The methods and procedures in this recommended practice are intended to supplement and augment the requirements in API 510, API 570 and API 653.
The assessment procedures in this recommended practice can be used for fitness-for-service assessments and/or re rating of components designed and constructed to the following codes:
• ASME B&PV Code, Section VIII, Division 1
• ASME B&PV Code, Section VIII, Division 2
• ASME B&PV Code, Section 1
• ASME B31.3 Piping Code
• ASME B31.1 Piping Code
• API 650
• API 620
The assessment procedures in this recommended practice may also be applied to pressure containing equipment constructed to other recognized codes and standards, including international and internal corporate standards. This recommended practice has broad application since the assessment procedures are based on allowable stress methods and plastic collapse loads for non-crack-like flaws, and FAD-based strategies for crack-like flaws (see Section 2, paragraph 2.4.2).
The user is advised to first review the validation discussion of Appendix H when the procedures of this recommended practice are applied to pressure containing equipment not constructed to the codes listed in paragraph 1.2.2. The information in Appendix H, along with a knowledge of the of differences in design codes, should enable the user to factor, scale, or adjust the acceptance limits of this recommended practice such that equivalent FFS in-service margins can be attained for equipment not constructed to these codes. When evaluating other codes and standards the following attributes of the ASME and API design codes should be considered:
• Material specifications
• Upper and/or lower temperature limits for specific materials
• Material strength properties and the design allowable stress basis
• Material fracture toughness requirements
• Design rules for shell sections
• Design rules for shell discontinuities such as nozzles and conical transitions
• Design requirements for cyclic loads
• Design requirements for operation in the creep range
• Weld joint efficiency or quality factors
• Fabrication details and quality of workmanship
• Inspection requirements, particularly for welded joints
As an alternative, users may elect to correlate the pressure-containing component's material specification to an equivalent ASME or API listed material specification to determine an associated allowable stress. This approach provides an entry point into the ASME or API codes (refer also to Appendix A) where in the pressure-containing component is reconciled or generally made equivalent to the design bases assumed for this recommended practice. Hence general equivalence is established and the user may then apply the acceptance limits of these fitness for service procedures unaltered. Equivalent ASME and ASTM material specific at ions provide a satisfactory means for initiating a reconciliation between the ASME and API design codes and other codes and standards. However, the user is cautioned to also consider the effects of fabrication and inspection requirements on the design basis (e.g., joint efficiency with respect to minimum thickness sizing).
The Fitness-For-Service assessment procedures in this recommended practice cover both the present integrity of the component given a current state of damage and the projected remaining life. Assessment techniques are included to evaluate flaws including: general and localized corrosion, widespread and localized pitting, blisters and laminations, weld misalignment and shell distortions, and crack-like flaws including environmental cracking. In addition, evaluation techniques are provided for condition assessment of equipment including resistance to brittle fracture, long-term creep damage, and fire damage.
Analytical procedures, material properties including environmental effects, NDE guidelines and documentation requirements are included in the fitness-for-service assessment procedures in this document. In addition, both qualitative and quantitative guidance for establishing remaining life and in-service margins for continued operation of equipment are provided in regards to future operating conditions and environmental compatibility.
The Fitness-For-Service assessment procedures in this recommended practice cover situations involving flaws commonly encountered in the refining and petrochemical industry in pressure vessels, piping and tank age. The procedures are not intended to provide a definitive guide line for every possible situation that maybe encountered. However, flexibility is provided to the user in the form of an advanced assessment level to handle uncommon situations that may require a more detailed analysis.
The methods and procedures in this recommended practice can also be used in conjunction with the National Board Inspection Code (NBIC) to the extent currently permitted by that document and local regulations.