• Author / Uploaded
• Charlie Chong

• Categories
• Tensión (Mecánica)
• Fractura
• Mecánica de fractura
• Esfera
• Refinería de petróleo

Citation preview

API 579: a comprehensive fitness-for-service guide Ted L. Anderson•·*, David A. Osageb 'Smtcluml Reliabilil)• Teclmolgy, 1898 S Flmirort Cotm. Sui1e 235, Boulder. CO 80301. USA 'M & M Engineering, Sltaker fleiglm. OH. USA Received 4

Augus12000; revised II Decemher 2000; accep1ed 13 Decemher 2000

Abstract This an iclc presents an overv iew of the rcccmly published Amc1ican Pctroleumlnstitutc (API) Recommended Pwctice 579, which covers fitness-for-service assessmem of pressure equi pmem in petrochemical and other industries. Although API 579 covers a wide range of flaws and damage mechanisms, including local metal loss, pitting coiTosion, blisters, weld misal ignmem. and fi re damage, the emphasis of the present arricle is on the assessment of crack-like llaws. The API 579 p rocerlure for evaluating c.-acks incorporates a fai lm·e assessment diagram (FAD) methodology very similar to that in other documents. such as the British Energy R6 approach and the BS 7910 method. The API document contains 1m extensive compendium of K solutions, including a number of new cases generated specifically for AP1579. In the initial release of the document. API bas adopterl ex isting reference stress solutions fo.r the calcul.ation of L, in the FAD procerlure. In a future release, however, API plans to replace these solutions with values based on a more rational definition of reference stress. These revised reference stress solutions will incorporate the effect of weld mismatch. In addition to the Appendices of K and reference stress solutions, API 579 includes awendices that provide guidance on esti mating fracture toughness and we ld residual stress distributions. Over the next few years these appemUces will be enhanced with advances in technology. Recently, API has entered into discussions with the American Society of Mechanica l Engineers (ASME) to convert API 579 into a joint APIIASME fitness-for-service guide. © 2001 PubJishcd by Elsevier Science Ltd. Keywords: American Petroleum Institute; Pai lun:: assessment diagram; f:o"Jaw assessment: J'}itness for service; Fracture toughness; Rcfcn::m:c Slress; Residual

stress; Stress imcosity fac1or

1. Background Ex isting US design codes and smndards for pressurized equipment provi de ru.les for the design, fabrication, inspection and testing of new pressure vessels. piping systems. and storage tanks. These code-s do not address the fact that equipment degrades whi le in -service and deficiencies due to degradation or from original fabrication may be found during subsequent inspections. Fitness-for-service (FFS) assessmentS are quantitative engi neering eva.luations, which are performed to demonstrate the structural integrity of an in-service component containing a flaw or damage. The American Perro.leum Institute (APT) Recommended Practice 579 [ l] has been developed to provide guidance for conducting FFS assessments of flaws commonly encountered in the refining and petrochemica l industry which occur in pressure vessels, piping, and tankage. However, the assessment procedures can also be applied to flaws encountered in other industries such as the pu lp and paper industry, " Com:spondingaulhor. Tel.: +1 -303-415-1475; fa.: +J-303-415-1847. E-mail address: [email protected] (T.L. Anderson).

0308-0 161/001$ - see fron1 mauer © 2001 Published by Elsevier Science Lrd. Pll: S0308-0161(01l000 18-7

fossil fuel util ity industry, and nuclear industry . The guideli nes provided in API 579 can be used to make run-repairreplace decisions to ensure that pressurized equipment contain.ing flaws that has been ident ified during an inspection can continue to be operated safe.ly. API 579 is intended to supplement and augment the requirements in APT 510 [2], APT 570 [3], and API 653 [4): to ensure safety of plant personnel and the publ ic whi le older equipment continues to operate; 10 provide technicall y sound FFS assessment procedures: to e nsure that di:fferent serv ice providers furnish consistent remaining life predictions; and to help optimize maintenance and operation of e)(iSiing facilities to maintain avai.l ability of older plants and enhance long-tenn economic viabili ty. In addition. API 579 will also be used in conjunction with API 580 Recommended Practice For Risk-Based Inspection [5] that is being developed to provide guidel ines for risk asse-ssment, and prioritization for inspection and m ai ntenance planning for pressure-containing equ ipment. The initial impetus to develop an FFS standard that cou ld be referenced from the API inspection codes was provided by a Joint Industry Project (JlP) administered by the

954

T.L Anderson. D.A. Osag' /lntenuuiOiwl Journal of Presmre Vessels and Piping 77 (2000) 953- 963

Material Properties Council (MPC). The driving force behind this development was p lant safety. The methodology provided for in this document, together with the appropriate API inspection code, had to ensure that equipment integrity cou ld be safely maintained when operating equipment with flaws or damage, and could also be used to demonstrate compUaoce with US Occupational Safery and Health Administmtion (OSHA) 19 10 Process Safety Management (PSM) Legislation. A review of the existing international FFS standards by the members of the MPC JlP was undertaken in 199 1 as the starting point for the development of a new FFS standard. Based on the resu lts of this review, it was detenn ined that a comprehensive FFS standard covering many of the typical ftaw types and damage mechanis ms found in the refining and petrochemical industry did not ex ist. In addition, the existence of many company-based FFS methods, the complexity of the tech nology that no single company c;m solve on its own, and the need to gain acceptance by local jurisdicti ons in the US further indicated the need for a new standard. Therefore, the JJP decided to start the development of the required FFS technology that would be needed to write a comprehensive FFS standard for the refining and petrochemical indus oy. The results of this work were docu-

mented in a MPC FFS TIP Consul tant's Report [6), and this document was subsequently turned over to the API Committee on Refinery Equ ipment (CRE) FFS Task Force charged with development of the FFS standard. In terms adopted by the API CRE FFS Task Group developing APT 579, an FFS assessment is an engineering analysis of equipment to determine whether it ~s fit for continued service. The equipment may contain flaws, may not meet current design standards, or may be subjected to more severe operating condi tions than the original or current design. The product of a FFS assessment is a decision to operate the equipment as is , alter, repa ir , monitor, or replace; guidance on an inspection interval is also provided. FFS assessments consist of analytical methods to assess flaws and damage and usually require an interdisciplinary approach consisting of the following: • Knowledge of damage mechanisms/material behavior. • Knowledge of past and future operating conditions and interaction with operations personnel. • NDE (flaw location and sizing). • Material properties (environmenta l effeCertain Lhe likely cause of the damage. Once the naw type is idcntilicd, the appropriate section of Lhis document t:an be selen 1 and a den whether 10 proceed with an assessment can be made Data requin•mems - The data required for FF·s assessments depend on Lhe naw t)'pc or damage mechanism being c\•aluated. Dma requirements may include: original equipment design data~ information pcnaining to maintenance and operational history; expected fu1Urc service~ and data specific to the

FFS as.sessmem such as llaw size. s1a1e of stress in lhe componem ar lhe loca1ion of 1be Oaw. and material properties. Da1a requiremen1s common 10 all

FFS assessm_e nt procedures are covet'ed in Sectio1t J. Data reqWrements specific 4

lO;;. damage

mechanism or flaw type. are covered in lhe seclion

comai.ning the con·esponding assessmem p.1·ocedU1'es Asse,n~me.nt teclmiques and acceptance trittria - Assessment techniqu-es and acceptance criteria al'e provided in each $ection. If multiple damage mechanisms al'e p1·e sem. more than one ~ Lion may have to he used for the evalua1.ion

5

6 7

8

An es1ima1e of 1he 1·emaining life or limi1ing Oaw size should be made. The remaining life is eslablished using !he PFS

Remainillg life evaluurioll -

assessmem procedures with an eslima1e of furore damage nne (i.e. con·osion allowance). T he remaining life can be used in conjunction with nn inspection code to establish an inspec1ion interval Remedimion - Remediation 1nerhods are provided in each sec1ion based on the damage mechanjsm or naw type.. _In some cases. remediation techniques may be used 10 control fu ture damage associated with naw growth and/or material degradat ion In-service monitoring - M.e Lhocts fo r in-service monitoring Hre provide d in each sectic.)n based on the damage mechanism or tlaw type . hH;ervice monitoring may be U.""-d for Lhosc case5 where, a remaining life and inspeclion interval cannot be adequately established because of the complexilies associated damage mechanis m and service environment Dnrwnenration - The documentation of an FFS asse5Stnenl s hould incl ude a record of all data and decisions made in e ach of the previous steps to qualify lbe component for continued operation . Documcnlat ion requircmenL~ t•ommon to all FFS assessment procedures arc given in Section 2 of API 579. Spcdfk Pt"l>pct·tic< Council. Ocwlx:r, 1995. British Energy. Assessment of the integrity of . t93J. l'alo Aho. CA: EPRI. 1981. Ainsworth RA. Sharples JK. Smith SO. EfTccts of rc:'l