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1
Fatigue Performance of High Strength Riser Materials
RPSEA Project No. DW 1403
TAC Quarterly MeetingSeptember 8, 2009
Houston, Texas
Presented byStephen J. Hudak, Jr.
Materials Engineering DepartmentSouthwest Research Institute
Research Partnership to Secure Energy for America
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Project Objective
Assess the fatigue resistance of new high strength HPHT riser materials in representative environments
• Fatigue Crack Growth Rates (FCGR)• Classical S-N fatigue life
• EnvironmentsAir (baseline)Sour brineSeawater
3
MaterialsMaterial YS Sour Status
1 114 ksi yes Specimens machined; frequency-scan tests complete;Fatigue testing underway
2 131 ksi yes Specimens machined; frequency-scan tests completeFatigue testing underway
3 ~125 ksi yes Received material this quarter;Specimen machining complete
4 132 ksi no Specimens machined; frequency-scan tests complete;Fatigue testing underway.
5 156 ksi no Specimens machined;Frequency-scan tests complete;Fatigue testing underway
6 ~120 ksi yes Received material this quarter:S-N specs. machined
K, ksiin
1 10 100
da/
dN
, in
./cy
cle
10-10
10-9
10-8
10-7
10-6
10-5
10-4
YS = 131 ksiYS = 114 ksiYS = 132 ksiYS = 151 ksi
Lab AirKmax = 44 ksiin
C = -6 in-1
two tests per strength
FCGR in Lab Air
• FCGR testing in air complete for four steels initially acquired
• FCGR increases slightly with increase material YS
• FCGRs may also be influenced by material microstructure
• Air data provide baseline for comparison with FCGRs in seawater and sour brine
Frequency Response vs. YS
5
Cyclic Frequency, Hz
0.01 0.1 1 10
Ave
rag
e d
a/d
N, i
n./c
ycle
10-6
10-5
10-4
10-3
10-2
Sour BrineK = 20 ksiinR=0.5
green: YS = 131 ksiblue: YS = 114 ksi
Sour Brine
Air Baseline
Cyclic Frequency, Hz
0.01 0.1 1 10
Ave
rag
e d
a/d
N, i
n./c
ycle
10-6
10-5
10-4
10-3
10-2
SeawaterK = 20 ksiinR=0.5
green: YS = 131 ksiblue: YS = 114 ksi
Seawater
Air Baseline
K, ksiin
1 10 100
da/
dN
, in
./cy
cle
10-9
10-8
10-7
10-6
10-5
10-4
10-3
SeawaterLab Air (2 tests)
YS = 114 ksiSeawater and Lab AirKmax = 44 ksiin
C = -6 in-10.01 Hz
0.17 Hz
1 Hz
FCGRs in SW+CP vs. Lab Air
K, ksiin
1 10 100
da/
dN
, in
./cy
cle
10-9
10-8
10-7
10-6
10-5
10-4
10-3
SeawaterLab Air (2 tests)
YS = 131 ksiSeawater and Lab AirKmax = 44 ksiin
C = -6 in-10.01 Hz
0.17 Hz
1 Hz
FCGRs in SW+CP vs. Lab Air
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Background: Freq. Dependence Complex at Low DK
Region IIClassicalFreq. Effect
Region IInverseFreq Effect
Mod 4130 Steel: YS=98ksiSour Environment
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Inverse Freq. Effect at Low DK Due to Corrosion-Product Wedging
d=1/p (Kmax/E sys)2
FCGR Testing Summary
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Material # Yield StrengthAir Tests Seawater + CP Tests Sour Brine Tests
Constant-Kmax Freq-scan Constant-Kmax Freq-scan Constant-Kmax
1 114 ksi
2 131 ksi
3 ~125 ksi
4 132 ksi not required
5 156 ksi not required
6 ~120 ksi not required not required
Complete Total tests 37
In progress Comp. + Progress 21
Untested % complete 57
S-N Testing Summary
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Material # YS Air Tests Seawater + CP Tests Sour Tests1 114 ksi
2 131 ksi
3 ~125 ksi Not required
4 132 ksi Not required
5 156 ksi Not required
6 ~120 ksi Not required Not required
Percent running and complete of each task 13% 8% 17%
Complete Total Tests 104
In progress Comp + Prog 12
Untested % complete 11
Not required
Initial S-N Results:114 ksi YS Material in Sour Brine
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X65 Weldment in sour brine
trend line
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Last-Quarter Progress Procured remaining two test materials Completed all S-N specimen machining Completed frequency-scan tests on four steels
initially acquired Met with PWC to select optimum test frequencies Completed air S-N testing at SwRI to assess inter-
laboratory reproducibility with NETL Initiated air S-N testing at NETL Initiated seawater S-N testing Initiated sour brine S-N testing Initiated seawater FCGR testing Initiated sour brine FCGR testing
Machine several Ti-alloy FCGR specimens (CT geometry) and assess their viability in view of propensity for out-of-plane cracking in Ti alloys.
Perform frequency-scan tests on Ti-alloy in sour brine environment.
Assess effectiveness of variable-frequency S-N and FCGR testing strategy in terms of technical objectives and project schedule.
Assess inter-laboratory reproducibility of S-N air data generated at SwRI vs. NETL-Albany, Oregon.
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Next-Quarter Plans
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Schedule in Months
Task Activity 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
D J F M A M J J A S O N D J F M A M J J A S O N
0. Spec Design/Prep Mat Proc+Spec Prep
1. FCGR Testing Freq Scan
Air
SW+CP
Sour
2. S-N Fatigue Air
SW+CP
Sour
3. Phase 2 Plan
4. Program Mgt.
Schedule
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Costs
RPSEA Contract Amt$800KBP Cost Share $200KTotal Contracted Amt $1,000KCosts to Date $430KBalance $570K
Question & Comments Are Always Welcome
SwRI’s RPSEA DW 1403 Project Manager
Steve Hudak(210) [email protected]
RPSEA’s DW 1403 Project Manager
Jim Chitwood(713) [email protected]
PWC Co-ChairmenHimanshu Gupta Steven Shademan(281) 366-3235 (281) [email protected] [email protected]
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Backup Slides
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Environments Lab air (baseline): 70-75°F, 40-60% RH
Seawater: ASTM D1141 substitute ocean water open to the air with cathodic protection: - 1050mv vs. Saturated Calomel Electrode
Sour Brine: Production brine with oxygen below 10 ppb and 35% H2S + 65% CO2
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FCGR Specimen
Crack Length, in.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
da/
dN
, in
./cy
cle
10-6
10-5
10-4
10-3
10-2
10 Hz - air10 Hz - seawater1Hz - seawater0.33 Hz - seawater0.1 Hz - seawater0.01 Hz - seawater
YS = 132 ksiSeawaterK=20 ksiinR=0.5
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Frequency Scan Testing
Corrosion fatigue performance sensitive to loading frequency
Fatigue crack growth rates at constant-DK used to characterize frequency effect in frequency scan (FS) tests
13x
Seawater
Seawater vs. Sour Brine
22
Crack Length, in.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
da/
dN
, in
./cy
cle
10-6
10-5
10-4
10-3
10-2
10 Hz - air10 Hz - seawater1Hz - seawater0.33 Hz - seawater0.1 Hz - seawater0.01 Hz - seawater
YS = 114 ksiSeawaterK=20 ksiinR=0.5
6X
Seawater
Crack Length, in.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
da/
dN
, in
./cy
cle
10-6
10-5
10-4
10-3
10-2
10 Hz - air10 Hz - sour brine1Hz - sour brine0.33 Hz - sour brine0.1 Hz - sour brine0.01 Hz - sour brine
YS = 114 ksiSour BrineK=20 ksiinR=0.5
24X
Sour Brine
YS = 114 ksi
Seawater vs. Sour Brine
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YS = 131 ksi
Crack Length, in.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
da/
dN
, in
./cy
cle
10-6
10-5
10-4
10-3
10-2
10 Hz - air10 Hz - seawater1Hz - seawater0.33 Hz - seawater0.1 Hz - seawater0.01 Hz - seawater
YS = 131 ksiSeawaterK=20 ksiinR=0.5
Seawater
15X
Crack Length, in.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
da/
dN
, in
./cy
cle
10-6
10-5
10-4
10-3
10-2
10 Hz - air10 Hz - sour brine1Hz - sour brine0.33 Hz - sour brine0.1 Hz - sour brine0.01 Hz - sour brine
YS = 131 ksiSour BrineK=20 ksiinR=0.5
250X
Sour Brine
Yield Strength, ksi
114 131 132
Material-Environment Interactions
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Environment:
Sour Brine
Seawater
24X 250X ---
6X 15X 15X
Corrosion-Fatigue Acceleration* vs. Air Baseline
* At DK= 20 ksi√in. R=0.5 and Frequency = 0.01 Hz
