developments in post construction vessel codes usa

7/22/2019 Developments in Post Construction Vessel Codes Usa

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EMAS Publishing 2006 1

DEVELOPMENTS IN POST CONSTRUCTION CODESAND STANDARDS IN THE UNITED STATES

C. Becht IV, J. R. Sims*

Significant activity in preparation of new codes, standards andrecommended practices that deal with equipment after it has been

placed in service has taken place within the United States. Theseactivities have been driven by the aging of facilities, and by a need tomitigate the increasing numbers of severe losses in process plants. Thenew codes and standards provide recognized and generally acceptedgood engineering practice to guide the owner in the inspection,evaluation and repair of existing equipment. This paper describes thecurrent status of many of these activities.

WHY POST CONSTRUCTION CODES AND STANDARDS

The aging of our infrastructure has led to increasing numbers of severe incidents (e.g.,>$10 million US) as the decades have passed. Recognizing that steel pipe was not inuse at the turn of the 20th century, and arc welding was not commonly used until afterWorld War II, one can readily understand that most industrial facilities have been

built during the last 50 years. They were initially constructed with finite economiclives in mind. Yet, we cannot afford to replace them. Thus, there has been anincreasing need for good post construction standards for the inspection, evaluation andrepair of existing equipment including pressure vessels, piping, and storage tanks.

Increasing incidents, including several very large and highly publicized ones, alsoled, within the United States, to regulatory action. Perhaps the most well known isOSHA 29 CFR 1910.119 Process Safety Management [1]. This regulation requires

that recognized and generally accepted good engineering practice (RAGAGEP) befollowed. This also created the desirable objective for industry to document whatRAGAGEP was. Otherwise, the standard is very subjective. Many AmericanPetroleum Institute (API) standards were developed after this new OSHA regulationwas created.

POST CONSTRUCTION CODES

There are a number of post construction codes dealing with inspection, alteration andrepair of existing pressure equipment. Post construction codes in the US include thefollowing, listed in order of their original publication dates.

* Becht Engineering Co., Inc., 22 Church Street, Liberty Corner, NJ 07938


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API 510 Pressure Vessel Inspection Code[2]

NB-23 National Board Inspection Code[3]

API 653 Tank Inspection, Repair, Alteration, and Reconstruction[4]

API 570 Piping Inspection Code[5]

The last of these documents to be published, API 570, has been in place since1993. Thus, none of these are new, they are simply listed for reference and context.

A joint ASME and API committee is being formed to create a new jointAPI/ASME document that combines the elements included in API 570 and API 510.The scope of the new inspection code will be the same as the existing ones, the

petroleum refining and chemical process industry. This Code, as with the API codes,will be for sophisticated owners that have their own, owner-user inspectionorganization.

The National Board Inspection Code (NBIC, NB-23) is a post construction codeadopted for use by jurisdictions for inspection and repairs/alterations to pressureretaining items (boilers, pressure vessels and piping) containing internal or external

pressure. Use of the NBIC is not limited to specific codes of construction but definesadministrative and technical requirements needed to inspect, repair or alter pressureretaining items fabricated to any acceptable code of construction.

The NBIC has recently incorporated fitness for service assessment criteria andexpanded sections for inspection and repairs to Fiber Reinforced Vessels, graphitevessels, installation requirements for pressure items and incorporated additionalinspection information related to specific types of pressure items such as YankeeDryers (Appendix K). The NBIC continues to be revised on an annual basis with issuedates of December 31

stfor every year.

The NBIC Committee continues to seek input from industries and organizationsinvolved with pressure equipment to address their needs and concerns and facilitatecooperation and communication to improve and unify safety requirements. Forexample, the NBIC Committee is working closely with ASME Post ConstructionCommittee to utilize their efforts in developing specific guidelines and standards forrepairs to pressure items. The NBIC Committee is also looking to expand on various

methods of repairs that are consistently utilized by repair organizations that involvewelding, bonding or mechanical assembly.

Revisions to the NBIC are posted on the National Board web site(www.nationalboard.org ) for public review and comment. Interested individuals areencouraged to submit comments to assist in improving the NBIC and facilitate its useinternationally. The NBIC is presently being used in over 50 different countries andwill continue to expand appropriate information that can be utilized worldwide.


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POST CONSTRUCTION INSPECTION STANDARDS

Traditional in-service inspection codes for pressure equipment have focused primarilyon establishing fixed intervals for internal and external visual examination based onexperience and engineering judgement. More recent guidelines and standards thathave been published or are in preparation use a risk-based approach to optimise bothinspection intervals and the type of non-destructive examination to be used (UT, RT,MT, PT, VT, etc.). These standards generally specify the following steps for eachequipment item or piping circuit:

Determine the deterioration mechanisms that are credible considering thematerials of construction, operating conditions and fluid service. Guidance onover 100 deterioration mechanisms that have been identified in the refiningindustry are provided in API-571 [6]. Similar documents have been preparedfor the pulp and paper industry and fossil electric power industry and are

published in WRC Bulletins 488 and 490 [7, 8].

Determine the probability that the deterioration mechanism will lead to afailure, and determine the failure mode. This is generally done either using a

program with built in assumptions, or by a multi-disciplinary team, including

an experienced materials engineer. Determine the consequences of the failure(s) identified. This should be done

by developing one or more failure scenarios, then determining the potentialsafety, health, environmental, and economic consequences.

Determine the base case or unmitigated risk. Risk is the probability of anadverse event occurring (e.g. corrosion under insulation leading to a leak) timesits consequence.

If the risk is not acceptable, develop an inspection program that addresses thespecific deterioration mechanisms of concern. Combinations of on-stream andoff-stream examination strategies are considered to reduce the risk to anacceptable level with the lowest economic impact.

The concepts of risk-based inspection have been developed and are beingimplemented. The intent of risk based inspection is to utilize finite resources forinspection to the greatest benefit, by allocating these resources in a manner thatachieves the greatest overall reduction in risk. The following standards have been

developed and/or are in the process of being developed.API RP 581Base Resource Document-Risk Based Inspection [9]. This document

provides one method for risk based inspections.

API RP 580Risk Based Inspection [10]. This document was published in 2002.It provides more general requirements for risk based inspection thatenable the user to implement one of a number of possible methods. It iswritten for the process industry, although it is applicable in the generalsense to all industries.


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ASME Inspection Planning. This document is in draft form. Publication willprobably be in one to two years. It provides general requirements forqualitative, semi-quantitative, and fully quantitative risk based inspection.It is intended to apply to all industries. It has been deliberately drafted tolargely parallel API RP 580, to maintain consistency in the industry.Where improvements have been made to the text, API will considerincorporation of the different text into the next edition of API 580. Themost significant difference is that the ASME document will cover fullyquantitative risk based inspection. This was not included in API 580

because fully quantitative risk based inspection planning is not generallyused in the process industry.

FITNESS FOR SERVICE

During inspection, flaws that exceed the limits permitted by new construction codesmay be found. For example, a degree of corrosion that exceeds the original corrosionallowance may be found. Yet, the equipment or piping may actually be fit forcontinued service. One example is a local thin area. An area of local corrosion may

yet have a high margin to failure, provided there is sufficient remaining metal aroundthat local area (consider, for example, a nozzle, which has no remaining thickness in alocal area). ASME Section XI [11], for nuclear power plants, contains methods forevaluating such flaws. Existing non-nuclear post construction codes provide somevery limited methods of evaluation (e.g., for evaluating local corrosion or pitting).There was a need in the non-nuclear industry for a document to providecomprehensive methods, to document RAGAGEP.

API 579, Fitness-for-Service [12], published in 2000, provides methods forevaluating flaws, with the intent that it be referenced by post construction codes, suchas API 510, API 570 and NB-23. It is now referenced in the API documents.

API 579 covers a number of types of damage, including assessment of equipmentfor brittle fracture, general metal loss, local metal loss, pitting corrosion, blisters andlaminations, weld misalignment and shell distortions, crack-like flaws, and firedamage.

It provides comprehensive flaw evaluation methods for the process industry. It is

structured to provide three levels of evaluation for each flaw, from very simple, tohighly complex. Specific requirements are not provided for Level 3, the most detailedassessment. Rather, Level 3 provides for current best practice, using sophisticatedtechniques (e.g., finite element analysis), by experts.

ASME and API have formed a joint committee to create a new fitness-for-servicedocument based on API 579, but more generally applicable to all industries, such asutilities. The committee was formed in 2002 and is nearing completion of the newdocument, which should be published in 2006. Some of the changes to the existingAPI 579 standard are listed below.


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(1) The Sections are now called Parts. Most parts have extensiverevisions.

(2) Part 3 on brittle fracture has several "fine tuning" modifications and asignificant change to the definition of shock cooling, which nowincludes calculations based on heat transfer coefficient.

(3) Parts 4 and 5 include many significant changes that modify the way theLTA analysis must be done. It will be necessary to calculate a MAWPfor the component and to consider the extent of the thin area to beanything less than the thickness used to calculate the MAWP. Inaddition, the Level 2 rules for determining the circumferential extent ofthe thin area have been rewritten using a "design by analysis" approach.

New Level 1 rules for the circumferential extent will include screeningcurves.

(4) Part 6 on pitting will have pictures for determining the RSF for a fieldof pits at Level 1. The Level 2 rules have been modified to requirecalculation of a MAWP.

(5) Part 7 on H2 blisters and laminations has been rewritten entirely, andnow includes an "LTA-like" assessment and requirements to evaluatecracks.

(6) Part 8 on shell distortions and weld misalignment has been revised toaccommodate new approaches.

(7) Part 9 on crack-like flaws has been updated without major revisions.However, Appendix C, which provides the stress intensity solutions,has been extensively revised to correct errors in the tables and tomodify the calculation approach. The primary emphasis is now onweight function methods rather than the polynomial curve fits.

(8) Part 10 on creep damage is completely new.

(9) Parts 11 and 12 have been extensively revised.

(10) Appendix B on Design by Analysis has been divided into four parts and

totally rewritten to incorporate the approach being developed for theASME B&PV, Section VIII, Div. 2 rewrite.

(11) Other appendices and parts have extensive, but relatively minor,changes.


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REPAIR

After a defect is found that is not acceptable via a flaw evaluation/fitness-for-serviceanalysis, a repair or replacement is required for continued operation. A few repairmethods are provided in Section XI and in existing post construction codes. However,these are quite limited in scope. Also, there are many repair methods in common use,including those for nuclear power plants per Section XI, that are not recognized inother post construction codes.

Recognizing the need in this area, ASME has prepared a new standard, Repair ofPressure Equipment and Piping, PCC-2. It provides methods for repair of equipmentand piping within the scope of ASME Pressure Technology Codes and Standards afterit has been placed in service. These repair methods include relevant design,fabrication, examination and testing practices. The repairs may be either temporary or

permanent, depending on the circumstances. Equipment and piping within the scopeof ASME Pressure Technology Codes and Standards includes piping (including

pipelines) and piping components (such as valves), boilers, pressure vessels (includingheat exchangers) and storage tanks. While this standard covers repair of equipmentwithin the scope of ASME Pressure Technology Codes and Standards, it may be used

on equipment constructed in accordance with other codes and standards.

The standard is being written in modular form. Each repair article is essentiallystand alone, with the exception that one section on general requirements applies to all.The first edition of this new standard is approved for publication and will be publishedin 2006.

There is often some interest in permanent versus temporary repairs.Many of the repair techniques included in this new standard are considered to be

permanent, intended to remain in place for the life of the repaired component. Othersmay only be suitable for short term service, and should be replaced with a more

permanent repair at the appropriate opportunity. The anticipated life of the repairdepends on many circumstances, and could include consideration of risk. As such, thestandard does not classify repair methods as permanent or temporary. Rather,technical considerations that affect the expected life of the repair are stated in theindividual articles.

The articles that are approved for inclusion in the first edition include the

following. Note that many other repair articles are in preparation or various stages ofapproval. As a result, the intent is to publish a first edition in 2006 and a secondedition, a year later, in 2007.

Repair Method for Butt Welded Insert Plates in Pressure Components

External Weld Overlay Repair Methods for Internal Thinning

Seal Welded Threaded Connections and Seal Weld Repairs

Welded Leak Repair Box

Full Encirclement Steel Sleeves for Piping


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Replacement of Pressure Components

Freeze Plugs Repair of Damaged Threads in Tapped Holes

Flaw Excavation and Weld Repair

Flange Refinishing

Mechanical Clamps

Pipe Straightening

Repair Guidelines for Damaged Anchors in Concrete

Non-Metallic Composite Wrap Systems for Piping and Pipework: High RiskApplications

Non-Metallic Composite Wrap Systems for Pipe: Low Risk Metal Pipe

Non-Metallic Internal Lining for Pipe-Sprayed Form for Buried Piping

Pressure and Tightness Testing of Piping and Equipment

PIPELINE DEVELOPMENTS

As a result of recent accidents and driven by impending legislation, significantdevelopments have occurred in the preparation of post construction standardsspecifically directed at pipeline safety. After an intensive one-year effort, ASMEB31.8S, Managing System Integrity of Gas Pipelines[13] was published in 2002. TheStandard is specifically designed to provide pipeline operators with the informationnecessary to develop and implement an effective integrity management program. Thedocument focuses on risk-based methods. Methods of integrity assessment include in-line inspections, pressure testing and direct assessment. The contents of the documentinclude chapters addressing Consequences; Gathering, Reviewing, and IntegratingData; Risk Assessment; Integrity Assessment; Responses to Integrity Assessmentsand Mitigation (Repair and Prevention); Integrity Management Plan; PerformancePlan; Communications Plan; Management of Change; and Quality Control Plan.

API Standard 1160, Managing System Integrity for Hazardous Liquids Pipelines[14] provides similar guidance for liquid transmission pipelines.

BOLTED JOINTS

While the various considerations associated with the design of flange joints arecovered in great detail in the ASME Pressure Vessel Code and in the literature, muchless attention has been given to the elements that comprise recognized and generallyaccepted good joint assembly practices. Yet, analyses of flange leak events have timeand time again identified the assembly practice employed as the root cause of poorleak-tightness performance, clearly identifying joint assembly as being critical to joint

performance and strongly suggesting the need for an industry document coveringproven assembly practices. The ASME Post Construction Committee prepared PCC-


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1, entitled Guidelines for Pressure Boundary Bolted Flange Joint Assembly, [15] toaddress this need.

As noted in the title, PCC-1 is a guidelines document that covers the assemblyelements essential for leak-tight performance of otherwise properly designed andconstructed bolted flange joints for which the torquing method of bolt tightening will

be used. Accordingly, these guidelines allow preparation of written procedures foruse by joint assemblers that incorporate the proven features deemed suitable for thespecific applications under consideration.

PCC-1 covers the following proven practices:

The basic requirements for qualifying joint assemblers and the joint assemblyprocedure to be used.

Examination of working surfaces, including recommended gasket contactsurface finish for various gasket types. Also advice regarding the flatnesstolerance for flange contact surface is given.

Alignment of mating surfaces.

Installation of gaskets.

Lubrication of working surfaces. Installation of bolts.

Numbering of bolts.

Tightening of bolts, including tightening methods/load control techniques.

Tightening sequence, including group tightening when the number of bolts is 36or greater.

Measurement of gaps.

Target torques based on test-verified torque/tension results for both non-coatedand coated bolts of nominal diameters from inch to 4 inch.

Joint leak-tightness test.

Joint disassembly

Records.

A task force has been formed to develop additional details for PCC-1 with respectto the qualification of flanged joint assemblers. The intent is to provide a program forassembler qualification. This qualification program can then be adopted, if desired,

by owner-users, code book sections, or others that are looking to improve the qualityof the flanged joint assembly process.

A follow-on effort to PCC-1 was funded by the Materials Technology Institute,Inc. (MTI) to develop, based on the PCC-1 guidelines, an essentially generic boltedflange joint procedure with the focus being mainly on ASME B16.5 [16] standard

pipe flanges. This document fleshes out the details of the PCC-1 topics outlinedabove in a format that can, with modest supplementation, be quickly transformed intoa working written procedure for specific service applications. Additionally, a single-

page bolted joint pretightening check list is provided, as are six, single-page bolttightening worksheets, one for each of the six bolting patterns for ASME B16.5


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flanges. These worksheets include the bolt numbering and tightening sequence for thebolt pattern under consideration, such that, with the addition of the appropriate torqueinformation, they serve as a work-efficient field reference.

To train joint assemblers in the proper application of this PCC-1-derived boltedflange joint procedure, MTI also arranged for the design of a joint assembly test rig,supplemented by a joint assembler instruction and qualification test using the test rig.

MAINTENANCE

Risk is also being used as a tool to improve maintenance and turnaround decisionmaking. Often one is faced with alternative maintenance strategies, with varied costsand benefits. Sometimes, spending money on maintenance can actually have anunintended effect of increasing risk. This can be the case in refurbishing spared

pumps. Other examples are the effect of inspector damage to protective coatings, andremoval of protective oxide films to perform inspections. Risk analysis is a powerfultool to rationalize the decision making process.

In risk based maintenance planning, the deterioration mechanisms are identified

for each piece of critical equipment. Probabilities of failure, on an annual basis, andthe consequences, are identified. These consequences can be economic, and can behealth safety and environment related. While health safety and environmentalconsequences can be characterized in dollars, it is common practice to evaluate thesequalitatively using a risk matrix. The net present value of the economic risk iscalculated, and alternative maintenance strategies to mitigate this risk are evaluated.Alternative strategies can include inspection, walk by inspection, replacement,coating, changing operating parameters, etc. Optimally, the stakeholders from theoperating facility are involved, including maintenance, operations and inspection. Themaintenance strategy that achieves an appropriate return on investment, in terms ofreduced risk, while at the same time accomplishing health safety and environmentalobjectives, is selected.

SUMMARY

There is a great deal of effort in industry to develop and document inspection,evaluation and repair methods for pressure equipment and piping. Excellent

documents that are very useful to industry are being prepared. These will continue tobe developed as technology develops.

REFERENCE LIST

[1] OSHA 29 CFR 190.119 Process Safety Management. United States Code ofFederal Regulations.

[2] API 510 Pressure Vessel Inspection Code. Washington, DC: AmericanPetroleum Institute.


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[3] NB-23 National Board Inspection Code. Columbus, Ohio: The National Boardof Boiler and Pressure Vessel Inspectors.

[4] API 653 Tank Inspection, Repair, Alteration, and Reconstruction. Washington,DC: American Petroleum Institute.

[5] API 570 Piping Inspection Code. Washington, DC: American PetroleumInstitute.

[6] API 571, Damage Mechanisms Affecting Fixed Equipment in the RefiningIndustry, American Petroleum Institute, Washington, DC.

[7] Damage Mechanisms Affecting Fixed Equipment in the Pulp and PaperIndustry, WRC Bulletin 488, Welding Research Council, 2004

[8] Damage Mechanisms Affecting Fixed Equipment in the Fossil Electric PowerIndustry, WRC Bulletin 490, Welding Research Council, 2004.

[9] API RP 581 Base Resource Document-Risk Based Inspection. Washington,DC: American Petroleum Institute.

[10] API RP 580 Risk Based Inspection. Washington, DC: American PetroleumInstitute.

[11] ASME Boiler and Pressure Vessel Code, Section XI, Rules for InserviceInspection of Nuclear Power Plant Components, The American Society ofMechanical Engineers.

[12] API 579 Fitness-for-Service. Washington, DC: American Petroleum Institute.

[13] ASME B31.8S, Managing System Integrity of Gas Pipelines, The AmericanSociety of Mechanical Engineers.

[14] API Standard 1160, Managing System Integrity for Hazardous LiquidsPipelines. Washington, DC: American Petroleum Institute.

[15] ASME PCC-1 Guidelines for Pressure Boundary Bolted Flange JointAssembly. New York: American Society of Mechanical Engineers.

[16] ASME B16.5, Pipe Flanges and Flanged Fittings NPS Through NPS 24

Metric/Inch Standard, The American Society of Mechanical Engineers.

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