Application of API579-1 / ASME FFS in carrying out Fitness ... · API 579-1/ASME FFS Covers a wide...

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HERA Pressure Equipment

Workshop 2016

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

of damaged pressure equipment

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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

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?


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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?


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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?


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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?

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serv

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calc com

plexity

Level 1

Level 2

Level 3


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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


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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


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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


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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


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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


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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


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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 safe


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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

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1

Kr

Lr

FAD (Failure Assessment Diagram)

Pass

Fail


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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


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Example 5 – Concepts

• Replicate the dent process

Different cases require defend types of FE analysis


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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


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• 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.


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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


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• The less conservative and more detailed assessments often need more controls

More frequent inspections

In service monitoring

Leak detection


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00.511.522.53

MA

T (

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 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.


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• 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 / ASME FFS in carrying out Fitness ... · API 579-1/ASME FFS Covers a wide...

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