Application of API579-1 / ASME FFS in carrying out Fitness For - - PowerPoint PPT Presentation

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HERA Pressure Equipment Workshop 2016

Application of API579-1 / ASME FFS in carrying out Fitness For Service assessments

• f damaged pressure equipment

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I have worked at ITL for about 5 years

• verseen over 50 assessments in the past 3 years

for 15 clients and saved $manymillions

WHY, WHAT, WHEN and HOW

Background Application of API579-1 for FFS Assessments

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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 Replace

WHY? Application of API579-1 for FFS Assessments

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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

WHAT? Application of API579-1 for FFS Assessments

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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:

Weld misalignments

WHEN? Application of API579-1 for FFS Assessments

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AS/NZS 3788 – Pressure Equipment -In Service Inspection

has some basic assessments

API 579-1/ASME FFS

Covers a wide range of defects Formalises methodology of assessment Consistent repeatable results HOW?

conservatism calc complexity Level 1 Level 2 Level 3

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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Example 3 Concepts

• RSF

Remaining Strength Factor typically allowable is 0.9

• Level of assessment

API sets out criteria for each level of assessment

Application of API579-1 for FFS Assessments

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Example 4 Cracks

• Defects observed during

phased array UT inspection

• f heat exchanger nozzle
• Calculated crack parameters
• FE Analysis predicted

stresses

• Level 3 assessment

demonstrated crack was safe

Application of API579-1 for FFS Assessments

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Example 4 Concepts

• Non-growing crack

(Know what caused the defect). A crack which is suspected to be growing will be assessed differently.

• FAD Failure Assessment

Diagram

A crack like flaw can be characterised on FAD

• Leak before rupture

Similar to predicting a remaining life

0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 Kr Lr

FAD (Failure Assessment Diagram)

Pass Fail

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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Example 5 – Concepts

• Replicate the dent

process

Different cases require defend types of FE analysis

Application of API579-1 for FFS Assessments

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Example 6 – Creep

• An anomaly was seen in a

spun cast Incoloy tee

• perating 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

Application of API579-1 for FFS Assessments

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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.

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments

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Example 7 – Concepts

• The less conservative

and more detailed assessments often need more controls

More frequent inspections In service monitoring Leak detection

Application of API579-1 for FFS Assessments

• 120
• 100
• 80
• 60
• 40
• 20

20 40 0.5 1 1.5 2 2.5 3 MAT (C) Internal Pressure (MPa) MAT of Head NH3 cooling

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Example 8 – Laminations

• A detailed inspection of a

vessel for rerate showed areas

• f 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.

Application of API579-1 for FFS Assessments

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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

Application of API579-1 for FFS Assessments