Application of API579-1 / ASME FFS in carrying out Fitness For Service assessments of damaged pressure equipment HERA Pressure Equipment Cover page title Workshop 2016 year
Application of API579-1 for FFS Assessments Background I have worked at ITL for about 5 years overseen over 50 assessments in the past 3 years for 15 clients and saved $manymillions WHY, WHAT, WHEN and Cover page title HOW year
Application of API579-1 for FFS Assessments WHY? If a piece of pressure equipment no longer meets the design it can be evaluated to ensure safe continued operation. An FFS assessment will enable asset owner to make informed decision whether to Run as is Repair Rerate Cover page title Replace year
Application of API579-1 for FFS Assessments WHAT? Components primarily pressure equipment Typically: Pressure Vessel shells, heads, nozzles Cooler Header box plates Heat Exchanger tubes Pipelines and piping Also: the principles can be applied to structural and other mechanical components Cover page title year
Application of API579-1 for FFS Assessments WHEN? When a component no longer meets the basis of it’s design. Due to defects associated with in-service operation: Generalised or localised metal loss Pitting corrosion Cracks Laminations Hydrogen Damage Dents and gouges Due to changes to design conditions: Creep Brittle failure Fire damage Due to defects associated with manufacture: Cover page title Weld misalignments year
Application of API579-1 for FFS Assessments HOW? AS/NZS 3788 – Pressure Equipment -In Service Inspection has some basic assessments calc complexity Level 1 API 579-1/ASME FFS conservatism Covers a wide range of defects Level 2 Formalises methodology of assessment Consistent repeatable results Level 3 Cover page title year
Application of API579-1 for FFS Assessments Example 1 Local Metal Loss • Corrosion was found of a nozzle of a vessel. • Measurements taken and 3D CAD model created • Level 3 (FEA) assessment demonstrated fit for service with a FCA of 2mm Cover page title year
Application of API579-1 for FFS Assessments Example 1 Concepts • API579-1 Required data Rubbish in rubbish out. API often defines what measurements are recommended. • Typically corrosion but also grinding Surface defects may be removed by grinding – leaving a local thin area • Level 3 typically requires FE Analysis Cover page title year
Application of API579-1 for FFS Assessments Example 2 General Metal Loss • Corrosion was found under insulation of a nozzle of a vessel. • 3D laser scan and UT • Level 2 assessment demonstrated fit for service with a FCA of 2mm Cover page title year
Application of API579-1 for FFS Assessments Example 2 Concepts • Know the cause of defect In order to Eliminate, minimise or control the mechanism • FCA – Future Corrosion Allowance • Remaining Life The FFS assessment applies to the component as found possible plus FCA Cover page title year
Application of API579-1 for FFS Assessments Example 3 Pitting Corrosion • Pitting corrosion found on bath heater tube during routine inspection. • Photos and pit depth readings taken • Level 2 assessment found fit for service but with 1 year remaining life Cover page title year
Application of API579-1 for FFS Assessments Example 3 Concepts • RSF Remaining Strength Factor typically allowable is 0.9 • Level of assessment API sets out criteria for each level of assessment Cover page title year
Application of API579-1 for FFS Assessments Example 4 Cracks • Defects observed during phased array UT inspection of heat exchanger nozzle • Calculated crack parameters • FE Analysis predicted stresses • Level 3 assessment demonstrated crack was Cover page title safe year
Application of API579-1 for FFS Assessments Example 4 Concepts FAD (Failure Assessment Diagram ) 1.2 • Non-growing crack 1 Fail (Know what caused the defect). A crack which is suspected to be growing will be 0.8 assessed differently. Pass 0.6 Kr • FAD Failure Assessment 0.4 Diagram 0.2 A crack like flaw can be characterised on FAD 0 • Leak before rupture 0 0.2 0.4 0.6 0.8 1 Lr Similar to predicting a remaining life Cover page title year
Application of API579-1 for FFS Assessments Example 5 - Dent • Pigging found a dent in a pipeline • Site measurements and UT • Level 3 FE Analysis demonstrated that the pipeline was still safe for a restricted number of cycles Cover page title year
Application of API579-1 for FFS Assessments Example 5 – Concepts • Replicate the dent process Different cases require defend types of FE analysis Cover page title year
Application of API579-1 for FFS Assessments Example 6 – Creep • An anomaly was seen in a spun cast Incoloy tee operating at 790°C • Worst case assumed to be a crack • Level 3 assessment FEA and calculations demonstrated a remaining life of more than 6 years Cover page title year
Application of API579-1 for FFS Assessments Example 6 – Concepts • Often assumptions are required. These assumptions will tend to be conservative or 2 extreme cases. • Less common material properties addressed in API579 Methodologies for calculating creep or facture toughness properties. • Other useful tools. Cover page title year
Application of API579-1 for FFS Assessments Example 7 – Brittle failure • A risk of exceeding the minimum design temperature highlighted from Safety case • Level 2 assessment relating stress to temperature showed vessel to be fit for service provided start up is managed Cover page title year
Application of API579-1 for FFS Assessments Example 7 – Concepts • The less conservative 40 and more detailed 20 assessments often need 0 more controls 3 2.5 2 1.5 1 0.5 0 -20 MAT (C) MAT of Head More frequent inspections -40 NH3 cooling In service monitoring -60 Leak detection -80 -100 -120 Internal Pressure (MPa) Cover page title year
Application of API579-1 for FFS Assessments Example 8 – Laminations • A detailed inspection of a vessel for rerate showed areas of layers of defects. • A level 2 assessment combining a Part 9 (cracks) and Part 13 (Laminations) assessment showed that the vessel was fit for service at it’s rerated conditions. Cover page title year
Application of API579-1 for FFS Assessments Example 8 – Concepts • May need to consider combinations of defects Examples: Lamination and crack like flaw Dents and local metal loss General metal loss and pitting Creep and crack like flaw Cover page title year
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