API RP 579-2000 pdf free download
API RP 579-2000 pdf free download.Fitness-for-Service.
8.1 General Fitness-For-Service ( FFS ) assessment procedures for pressurized components with geometric irregularities are provided in this section. The geometric irregularities covered include weld misalignment and shell distortions including out-of-roundness, bulges and dents. A flow chart for the evaluation procedure of equipment with a geometric irregularity is shown in Figure 8.1. 8.2 Applicability And Limitations Of The Procedure 8.2.1 The procedures in this section can be used to assess geometric irregularities associated with weld misalignment and shell distortions in components made up of flat plates; cylindrical, conical, and spherical shells; and formed heads. These types of flaws will be referred to as geometric irregularities in this section and are defined in the following paragraphs. In general, if the current geometry of the component is such that the original fabrication tolerances are satisfied, an assessment is typically not required. Exceptions include components subject to cyclic service and components which have a localized geometric irregularity such as a dent. 8.2.1.1 Weld Misalignment – Categories covered include centerline offset, angular (peaking), and a combination of centerline offset and angular misalignment of butt weld joints in flat plates, cylindrical shells and spherical shells (see Figures 8.2 through 8.6). 8.2.1.2 Shell Distortion – Categories of shell distortion are defined as follows: a. General Shell Distortion – A deviation of a shell from an ideal or perfect geometry which occurs in either the meridional or circumferential directions. This type of distortion is characterized by significant shape variation of the shell (multiple local curvatures) and typically requires an assessment based on a numerical analysis method. Flat spots on a shell are also classified as general shell distortion.
b. Out-of-roundness – A deviation of the cross-section of a cylindrical shell and pipe bend from an ideally circular geometry. The out-of-roundness for a cylinder is assumed to be constant in the longitudinal direction (see Figure 8.7 and paragraph 8.2.3.2.g for a discussion of limitations), and either global (oval shape) or arbitrarily shaped in the circumferential direction. The out-of-roundness of a pipe elbow is assumed to be global (oval shape) in the mid-elbow region with an ovality at the end equal to 50% of the mid-elbow value. c. Bulge – An inward or outward deviation of a cross-section of a shell member from an ideally circular geometry which can be characterized by a local radius (see Figures 8.8 and 8.9). The local bulge geometry may be either spherical or cylindrical. Flat spots (infinite radius of curvature) are not considered as a bulge, and are classified as general shell distortion. Note that if the bulge is associated with a blister, then the analysis procedures in Section 7 should be utilized for the assessment. d. Dent – An inward or outward deviation of a cross-section of a shell member from an ideally circular geometry which is characterized by a small local radius or notch (see Figure 8.10). 8.2.2 Calculation methods are provided to rerate the component if the acceptance criteria in this section are not satisfied. For pressurized components (pressure vessels and piping) the calculation methods can be used to find a reduced maximum allowable working pressure (MAWP) and/or coincident temperature. For tank components( shell courses) the calculation methods can be used to determine a reduced maximum fill height (MFH).
8.2.3 Specific details pertaining to the applicability and limitations of each of the assessment procedures are discussed below. 8.2.3.1 Level 1 assessment procedures are based on the criteria in the original construction code. In some cases, these criteria are not completely defined by the original construction code and are dependent on the original design specification of the owner-user. In addition, the Level 1 Assessment procedures should not be used if the component is in cyclic service. A screening procedure to determine if a component is in cyclic service is provided in Appendix B, paragraph B.5.4. 8.2.3.2 The Level 2 assessment procedures in this section only apply if all of the following conditions are satisfied: a. The geometric irregularity is due to weld misalignment, shell out-of-roundness (general or arbitrary), a bulge, or a dent (see paragraph 8.2.1.2). b. The original design criteria were in accordance with Section 2, paragraph 2.2.2. c. The component is not operating in the creep range (see Section 4, paragraph 4.2.3.1.b). d. The component geometry is one of the following: · Flat plate · Pressure vessel cylindrical and conical shell sections · Spherical pressure vessels and storage tanks · Formed heads including spherical, elliptical, and torispherical shapes · Straight sections of piping systems · Elbows or pipe bends which do not have structural attachments · Shell courses of atmospheric storage tanks
