joint industry project buttsveis (girth weld jip ... 2014/konstruksjonsdagen...dnv gl © 2014 27....
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DNV GL © 2014 27. august 2014 SAFER, SMARTER, GREENER DNV GL © 2014 Utmatting av buttsveiser i rør – utfordringer og status
27. august 2014
Agnes Marie Horn
Joint Industry Project buttsveis (Girth Weld JIP) - problemstillingen og status
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DNV GL © 2014 27. august 2014
Challenges for deep water
Harsh environment
– severe fatigue loading from waves
– high-cycle fatigue damage due to Vortex Induced
Vibrations (VIV) from water currents at free spans
Large floater motions
Metallic risers for deep Water riser applications
Special concerns: Interface to floater, seafloor
interaction
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DNV GL © 2014 27. august 2014 3
Todays challenge
Riser solutions
Design standards for risers, tendons and pipelines
Overview of JIP FATIGUE OF GIRTH WELDS (PHASE 1)
Summing up
Content
DNV GL © 2014 27. august 2014 4
Steel Catenary Riser (SCR) - Deep water riser concept
Steel pipes can be arranged in free-
hanging configuration for deep water.
Denoted Steel Catenary Risers
Special joints may be applied in touch-
down area to improve fatigue
performance.
Optimization of weight distribution along
riser pipe may be considered to improve
fatigue performance.
Well suited for benign conditions
TLP, Spar or DDF required for large
diameter SCR in harsh environmental
conditions
Fatigue life in
Touch-down
critical design
issue
Flex-joint/
titanium stress-
joint to limit
bending stress
DNV GL © 2014 27. august 2014
Todays challenge; S-N fatigue versus weld acceptance criteria derived from engineering critical assessment (ECA)
.
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Need for high S-N fatigue life: e.g. high quality welds
recent fatigue test results of full scale pipes, seem to indicate that the common S-N curve classification may be unnecessary conservative for some modern high quality weldments
Weld defect acceptance criteria for girth welds are today often determined based on Fracture Mechanics assessment (ECA);
height of the order of 2-4 mm with 25-100 mm in length
predicted fatigue life is usually much shorter than predicted by standard S-N curves, and this is generally believed to be unnecessarily conservative
DNV GL © 2014 27. august 2014
Comparison of S-N and Paris from a case study
01/09
/2014
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DNV GL © 2014 27. august 2014
Objective of the Girth Weld JIP
There is a definite need to better align S-N type analyses, weld
quality/defect acceptance criteria and ECA’s in order to have a
consistent and reliable way of assessing the fatigue life of girth
welded tubulars both at the design stage, when determining
inspection programs and after inspection.
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DNV GL © 2014 27. august 2014
FATIGUE OF RISERS, TENDONS and PIPELINES
Design standards
– DNV-OS-F201 (2010) ‘Dynamic Risers’,
– DNV-RP-F204 (2010) ‘Riser Fatigue’ with ref. to DNV RP-C203
– DNV-OS-F101 (2010) ‘Submarine Pipelines’ 2012
– API RP2RD ‘Design of Risers for Floating Production Systems (FPSs)
and Tension-Leg Platforms (TLPs) ’ (to be harmonized with ISO13628-
12).
– Fatigue lives can either be estimated by S-N or fracture mechanics
approaches
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DNV GL © 2014 27. august 2014
Influencing fatigue factors
Uncertainties occur from both the loading and the resistance assessments.
Weld quality: effect of workmanship, complete joint penetration, internal defects
and welding procedure.
Depending on the welding procedure and quality, S-N curves ranging from F3 up
to C are used in design of girth welds.
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DNV GL © 2014 27. august 2014
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Fatigue of Girth Welds Phase 1
RELATION BETWEEN WELD QUALITY / DEFECT ACCEPTANCE CRITERIA AND
FATIGUE LIFE IN TENDONS, RISERS AND PIPELINES
Cooperation between DNV, Sintef/ NTNU and Stress Engineering Services
Started in 2011 ended in 2012
Phase 1a; Chevron, ExxonMobil, Total, Petrobras, Subsea 7, Tenaris, Woodside, JFE
Steel and Sumitomo
Phase 1b; Chevron, ExxonMobil, Total, Petrobras, Tenaris, Woodside, Statoil and Ptil
DNV GL © 2014 27. august 2014
Fatigue of Girth Welds Phase 1a
To identify the features of girth welds in pipes that on the one hand
influence the fatigue performance and on the other hand can be
controlled and checked to ensure that they are consistent with the
required fatigue performance.
To develop a consistent and reliable methodology for ECAs of girth
welds, quantitatively including the significant fatigue critical features,
with the particular aim of achieving better alignment of the ECA and S-N
curve based approaches for assessing the fatigue performance.
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RE-ASSESSMENT OF
FATIGUE DATA
METHODS FOR CONTROL AND
INSPECTION OF FATIGUE CRITICAL
FEATURES OF GIRTH WELDS.
FATIGUE ASSESSMENT METHODS INCLUDING
INITIATION AND EARLY GROWTH
To develop Design Guidelines for Fatigue Design of Girth Welds,
including calibrated Safety Factors.
DNV GL © 2014 27. august 2014 27. august 2014
01/09/2014 12
0
50
100
150
200
250
300
350
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 23 24 28 29 32 35
OD/WT
Co
un
t
e.g. 4.5x0.65 inch, 6-5/8x0.9 inch,
8-5/8x1.3 inch
e.g. 6-5/8x0.72 inch, 8-5/8x0.95
inch, 10.75x1.2 inch
Phase 1a Data from just under 1200 weld tests.
1084 full scale tests 109 strip sample tests
DNV GL © 2014 27. august 2014
Fatigue Girth weld database phase 1a
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DNV GL © 2014 27. august 2014
Phase 1a: OD crack failure
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1,20
1,30
1,40
1,50
1,60
1,70
1,80
1,90
2,00
2,10
2,20
2,30
2,40
2,50
2,60
2,70
4,0E+00 4,5E+00 5,0E+00 5,5E+00 6,0E+00 6,5E+00 7,0E+00 7,5E+00
Lo
g(S
)
Log(N)
S-N data
S-N Mean curve
S-N DesigncurveD curve air
E curve air
F1 curve air
m = 3
E[Log10(a)] =12,636
StD[Log10(N)] =0,424
DNV GL © 2014 27. august 2014
Phase 1a: ID crack failure
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1,20
1,30
1,40
1,50
1,60
1,70
1,80
1,90
2,00
2,10
2,20
2,30
2,40
2,50
2,60
2,70
5,0E+00 5,5E+00 6,0E+00 6,5E+00 7,0E+00 7,5E+00 8,0E+00
Lo
g(S
)
Log(N)
S-N data
S-N Mean curve
D curve air
F1 curve air
E curve air
S-N design
m =
E[Log10(a)] =
StD[Log10(N)] =
3,000
12,524
0,274
DNV GL © 2014 27. august 2014
OD failure ID failure
ID failure CASE-1 CASE-2
m = 3,000 2,583
E(log10(a)) 12,524 11,698
F curve
E(log10(a))
11,855
StD(log10(N)) 0,274 0,270
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Od failure CASE-1 CASE-2
m = 3,000 3,039
E(log10(a)) 12,636 12,724
D curve
E(log10(a))
12,164
StD(log10(N)) 0,424 0,424
Most of the OD ‘s were ground
Several were reeled
~½ of OD ground
ID/OD ground As-welded
Several were reeled
DNV GL © 2014 27. august 2014
Failed X-70 specimen
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0
5
10
15
20
25
30
35
0 0,2 0,4 0,6 0,8 1 1,2
cra
ck
de
pth
(m
m)
cycles 1=2193704 cycles
surface flaw, X-70
ai=0,09 mm(mean +2stv air)
ai=0.16mm(mean curve air)
Final flaw size from fatigue test measured; 33mmx81,3 mm after 2,19x10^6 cycles Crack growth curve for air according to BS7910 in order to assess the initiation life
Fracture mechanics evaluation
DNV GL © 2014 27. august 2014
Phase 1 b: Quantitative and qualitative safety studies
Alignment and mismatch
Weld quality, weld process, and
backing information
Base and weld metal material
strength
Weld cap and root profiles
Base and weld material chemistry
Residual stresses
Presence of flaws
Effect of reeling
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DNV GL © 2014 27. august 2014
Status of phase 1b
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Phase 1b Data from just under 1869 weld tests.
1760 full scale tests 109 strip sample tests 250 ID failure 70 OD failure 130 reeled samples
0
50
100
150
200
250
300
350
400
1,00E+05 1,00E+06 1,00E+07 1,00E+08
Str
ess r
an
ge (
Mp
a)
Cycles (N)
Database phase 1b
All fullscale
OD Crack-DNV SCF OD
Stress
ID Crack-Nominal ID Stress
DNV GL © 2014 27. august 2014
Summery
Need for high quality welds in order to meet design
fatigue requirements.
It is necessary to assure that weld quality/defect
acceptance criteria and process control, inspection and
NDT match such that it is possible to reliably assure the
weld features, e.g. weld toe geometry, weld defect
distribution, etc, that will control the fatigue performance.
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