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Mahmood ShafieeLecturer in Engineering Risk, Reliability & Maintenance
Cranfield University, [email protected]
EERA DeepWind'2016, 13th Deep Sea Offshore
Wind R&D Conference
1
Motivation of research
Risk-Based Inspection (RBI)
RBI Planning
Methodology
Presentation outline
Conclusion
M Shafiee 2
Conclusion
Testing the
Model
Wind Jacket
Foundations
M Shafiee
NREL , EWEAOffshore wind energy hasexperienced an exponential growthworldwide over the past decade
The installed offshore wind energycapacity continues to rise
2004: 622 MW 2014: 8 GW (annualgrowth rate of around %30)
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Motivation
Cumulative installed capacity of offshore wind power in the European Union (EU)
M Shafiee 4
Cost reduction is of increasingimportance for all offshore windenergy players
• To make the electricity generated byoffshore wind turbines more price-competitive
The cost per kilowatt hour ofelectricity generated by offshore windturbines is approximately 22 cents,but it should reduce to 7 ȼ/kwh by2030
Motivation
22 ȼ/kwh 7 ȼ/kwh ?
M Shafiee 5
Motivation
operation and maintenance (O&M) costsaccount for about 25 to 40% of the overallenergy generation cost
A significant portion of annual maintenancebudget is wasted due to insufficient orinefficient maintenance activities
• One of the most effective ways to minimizethe inspection & repair costs is to apply risk-based inspection methods and tools
Cost drivers of a typical 5MW offshore wind turbine
M Shafiee
• Risk-based Inspection technique has been appliedto a wide range of industries
• Many institutes and organizations (like HSE, API,DNVGL, ABB, TWI) have developed risk-basedinspection solutions for different structures by takinginto account the regulatory requirements andguidelines (e.g. API RP 580 ; DNVGL-RP-C210)
• The main aim of RBI tool is to achieve safeoperating conditions at minimum inspection cost,and protect human life and the environment fromany possible damage during operation
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Risk-Based Inspection (RBI)
Risk
Likelihood (Probability) of failure
Magnitude (Severity) of failure
Risk is a combination oflikelihood and magnitude
Risk-Based Inspection (RBI)
How could risk assessment informationbe used in making more cost-effectiveinspection decisions?
Is this cost-effective to choose sameinspection strategy for high / medium /low risk assets?
M Shafiee
8
• RBI is a technique which prioritises inspection tasks according to theinformation provided by risk assessment procedure
• RBI is a technique which determines the frequency of inspection fordifferent assets based on their criticality levels
• RBI is a technique which assists inspectors to find the mostappropriate inspection method for assets
Risk-Based Inspection (RBI)
9
IDENTIFY THREATS/
HAZARDS
to EQUIPMENT
(Pipework, Vessels etc)
SUSCEPTIBILITY to
THREAT
MITIGATION
MEASURES to
REDUCE
SUSCEPTIBILITY
LIKELIHOOD of
FAILURE
FAILURE MODE
CONSEQUENCES of
FAILURE
ASSESS
INSPECTION
HISTORY
REMAINING LIFE or
INSPECTION GRADE
IDENTIFY THREATS/
HAZARDS
to EQUIPMENT
(Pipework, Vessels etc)
SUSCEPTIBILITY to
THREAT
MITIGATION
MEASURES to
REDUCE
SUSCEPTIBILITY
LIKELIHOOD of
FAILURE
FAILURE MODE
CONSEQUENCES of
FAILURE
ASSESS
INSPECTION
HISTORY
REMAINING LIFE or
INSPECTION GRADERISK FACTOR
INSPECTION
SCHEMERef: API RP 580 (2002) Risk Based Inspection (RBI). First Edition, American Petroleum Institute (API), Washington, USA.
API RP 580 Methodology
M Shafiee
There are several RBI methodologiesavailable in energy industries
Topside facilitiesOnshore TerminalsSubsea Pipeline
The larger the risk level, the more the focus on inspection
10
RBI Applications to Wind Energy Structures
RBI policy for an offshore wind turbine consisting of a single critical component
RBI for offshore windturbines based onAPI methodology inoil and gas
2008 2009
Bayesian decisionmodel to optimizerisk-based planning ofinspection for offshorewind turbines
2012risk-based approachto asset integritymanagement ofoffshore windturbines
2011
To the best of authors’ knowledge, there have been few attempts made byresearchers on developing RBI optimization methodologies for offshore windjacket structures
M Shafiee
• Jacket structures are one of themost common fixed structures usedin the offshore oil and gas and windenergy industries. The number ofinstallations is steadily increasingevery year as the offshore energymarket continues to rise
• A jacket support structure is awelded tubular space frameconsisting of three or more near-vertical legs supported by a lateralbracing system
Offshore Wind Jacket Structures
M Shafiee
Wind turbine substructures (jackets)
• The function of a jacket structure is to support the topside facilities or wind turbines and toserve as a template for the foundation system. These structures can transfer the loads fromthe topside to the seabed through the driven piles
• The offshore jacket structures should be designed with sufficient strength and stiffness towithstand the wind and wave forces, forces due to current acting on the sea, tides,temperature forces, ice forces, earthquakes, etc.
Offshore Wind Jacket Structures
M Shafiee
To review the RBI methodologies available in the Offshore Wind Energyindustries
To propose a generic RBI framework to apply to Offshore WindFoundations
To propose an Analytical framework to compare RBI performance withcurrently used constant-interval inspections
To test and validate the proposed model on various foundationtopologies
M Shafiee 13
Aims and Objectives
A generic RBI planning methodology for Offshore Wind Jacket StructuresM Shafiee
1
23
5
4
RBI MethodologyThe condition assessment data (e.g.,sea-state data, deterioration modesand causes, damage propagation,etc.) are collected from differentcondition monitoring solutions
Different damage mechanismsare identified and the associatedroot causes are investigated
The risk of potential damage tofoundation is evaluated by combiningthe likelihood of structural damageand the magnitude of consequences
The level of risk of failure forwind foundations is used toschedule appropriate inspectionand preventative repair tasksM Shafiee
Dr. Mahmood Shafiee
RBI MethodologyData collection & review
Collect data and populate the RBI document to include:
• Technical Specification – Type of Jacket, Design codes, etc.
• Operating Conditions – Temperature, pressure, weather conditions
• Construction – Material Specification, Thickness, Corrosion Allowance.
• Inspection History – Previous Reports, Repairs, Modifications.
Discussion and review of the data to agree, add and amend as necessary to form anaccurate record of the jacket condition and operating parameters
Dr. Mahmood Shafiee
RBI MethodologyIdentification of Damage Mechanisms and Root Causes
Dr. Mahmood Shafiee
RBI MethodologyRisk (Or PoF) Analysis
0)(
0)(
0
taTTP
tAaPtTP
crG
crf
Time of
failure
Time for
crack growth
to critical depth
Time for
crack
initiation
Critical
crack
depth
Crack depth
at time t
Specified
time
0T
cra
-6
-5
-4
-3
-2
-1
0
0.0 5.0 10.0 15.0 20.0
Service time (yr)
Lo
g(P
rob
. fa
ilu
re)
No insp.
Insp.at 4.5
Insp.at 9.2
Insp.at 13.4
Target
RBI MethodologyRisk (Or PoF) Analysis
Dr. Mahmood Shafiee
RBI MethodologyFailure Cost Analysis
Three cost factors are considered for this purpose:
CI: cost of inspection
CR: cost of imperfect repair
CF: cost of failure
CT = Σ[CI(t) + CR(t) + CF(t)] × (1+r)t
Dr. Mahmood Shafiee
RBI MethodologyOptimal Inspection Planning
Determine an Optimum Inspection Plan:
Min CT
S.t. R ≥ R0
• Focus effort on high risk assets
• Choose appropriate inspection techniques for each identified deteriorationmechanism
• Identify appropriate periodicities
• Consider ways to reduce risk (Inspection does not reduce consequence!)
22M Shafiee
Application
The proposed RBI planning methodology is being applied to two welded
tubular joints of a steel jacket structure
23
Likelihood of failure for
joint 9 using MCS technique
Inspection plan on the basis
of likelihood of failure
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The existing RBI methodologies in the wind energy industry werereviewed
A generic RBI methodology for offshore wind jacket structures wasproposed
The performance of the proposed RBI methodology (in terms of cost) wascompared with constant-interval inspections suggested by API
Conclusion
![API RP 580-2002 Inspección Basada en Riesgo Rev1[1]](https://img.dokumen.tips/doc/110x75/577c78531a28abe0548f9707/api-rp-580-2002-inspeccion-basada-en-riesgo-rev11.jpg)
