application of api579-1 / asme ffs in carrying out fitness for
TRANSCRIPT
Cover page title
year
HERA Pressure Equipment
Workshop 2016
Application of API579-1 / ASME FFS in carrying out Fitness For Service assessments
of damaged pressure equipment
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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?
con
serv
atis
m
calc com
plexity
Level 1
Level 2
Level 3
Application of API579-1 for FFS Assessments
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
Application of API579-1 for FFS Assessments
Cover page title
year
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
Application of API579-1 for FFS Assessments
Cover page title
year
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
Cover page title
year
Example 5 – Concepts
• Replicate the dent process
Different cases require defend types of FE analysis
Application of API579-1 for FFS Assessments
Cover page title
year
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
Application of API579-1 for FFS Assessments
Cover page title
year
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
Cover page title
year
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
Cover page title
year
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
0
20
40
00.511.522.53
MA
T (
C)
Internal Pressure (MPa)
MAT of Head
NH3 cooling
Cover page title
year
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.
Application of API579-1 for FFS Assessments
Cover page title
year
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