SCC Management
16” Camas to Eugene26” Sumas to Washougal
Outline• 16” Camas to Eugene
– Background /Issues– Integrity Strategy Execution– Current Status
• 26” Sumner to Washougal– Background / Issues– Segment by Segment Strategy
• SCC strategy
NWP I-5 Corridor
16” Camas to Eugene16” Camas to Eugene16” Camas - Eugene
16” Background / Issues• Oregon City Requalification in 1994
– 22 hydrostatic test failures» Most of these 6 miles downstream at
1000 to 1100 psi– 16” x 0.250” wall; X52; Bitumastic
coating; ERW Lonestar steel– MAOP 896 psig– Cracking is SCC (classical high??;
near–neutral pH??)• Continued SCC Management (1994-
2001)– Through excavations– SCC coupons– Strategy to build & apply ILI
• 16” UT Crack Detection (Sept. 2001) – Liquid slug; no fun in a gas pipeline,
max elevation 300+ feet– Ensure longer term integrity (where are
the subcritical cracks)
16” UT ILI C-Scan16” UT ILI C-Scan
16” Short term Integrity Strategy• Identified couple of hundred
– Depth 25-40%wt: 9 features– 12.5-25%wt: – <12.5%wt:
• 2002 digs validated ILI accuracy– Length and Depth range
(grinding)
FAD, API 579 Level 2
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Lr
Kr
Kr Curve ValueMAOP1.39 MAOP
Acceptable
Un-acceptable
• API 579/BS7910; Level II and III; Well established
• JIC = 257lbs/in; SMYS=52 ksi; SMUTS=66 ksi
• Pressure 1.39 MAOP (1245 psi)
• Crack size = upper bound value from ILI + 10%wt
• Immediate Repairs
– Nine of several hundred features un-acceptable
• Elastic-Plastic Fracture Mechanics Type
• Industry Standards: API 579, BS7910:1999
• Level 2 Assessment– Low bound FAD Equation
– Very conservative
• Level 3 Assessment–Based on measured stress-strain curve –Based on measured R-curve
–Accurate and less conservative
16” Future Integrity & Current Status• Based on 2001 ILI and 2003 Field
– Establish growth rate using linear assumption
» Excavation data from the field
– Growth Rate = 0.03 in/year
– Excavation and Re-inspection driven» 22.5 to 35% requires action in 4-6 yrs
• NO INCIDENT• Validates Strategy
• ILI identify sub critical• Fracture mechanics evaluation
• Continued monitoring & repairs 2004+
No Incident since Integrity strategy implemented; Continuous Improvement
Level 2 FAD SMYS = 52.0 ksi, SMUTS = 66.0 ksiAfter Repairs, MAOP
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Lr
Kr
Kr-Lr Failure Curve
MAOP
1.39 MAOP
35% wt (0.0875")
52% wt (0.130 in)
35% wt (0.0875")
Acceptable Region
Un-AcceptableRegion
37% wt (0.0931")
26” Snohomish to Washougal
• Primarily 26” O.D. , 0.281” wt• DSAW pipe, X-52• Field applied bitumastic asphalt• Installed in 1956• Regular Corrosion Inspection• Only Snohomish to Sumner SCC
susceptible• One Incident (at MAOP 674 psi – 59%
SMYS)– SCC in 2003
» Lake Tapps
Segment (north to south)
Sumas to Mt Vernon44 miles
Mt Vernon to Snohomish46 miles
Snohomish to Sumner42 miles
Sumner to Ft. Lewis17 miles
Ft. Lewis to Chehalis46 miles
Chehalis to Washougal73 miles
Segment specific Integrity StrategySegment specific Integrity Strategy
26” Critical Size & Crack Growth Rate• Maximum survived flaw size is a function of (FAD Level II):
» length and depth,& Pressure applied (Class Location)» Actual yield, tensile, and toughness properties (upper bound value used)
• Crack growth rates (literature & field)» Re-hydro re-inspection was 2 years» Re-inspection was 6 – 9 years
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5 6 7 8 9 10
2c, (in)
a, (i
n)
USCD Threshold = 1.18" x 14% wt
At HydrostaticPressure = 1.39 x MAOP Psig
At MAOP = 674 psig
Sub critical crack size defines integrity strategy
26” Segments of the System
Segment (north to south)
Sumas to Mt Vernon44 miles
Mt Vernon to Snohomish46 miles
Snohomish to Sumner42 miles
Sumner to Ft. Lewis17 miles
Ft. Lewis to Chehalis46 miles
Chehalis to Washougal73 miles
•2003 SCC failure•Crack detection completed•DA model being developed
No SCC failure3 insignificant SCC identifiedDA model being applied
No SCC ever foundDA model being applied
•No SCC susceptibility•DA Model being developed
SCC susceptible – ILI driven; No SCC – DA to establish susceptibility
SCC Integrity Strategy
• Susceptibility– DA driven– Extent of susceptibility defines IMP
• Life Cycle Modeling– Fracture mechanics driven– Crack growth rate driven
• Mitigation strategy (data and analyses driven)
– ILI or Hydro– Repair, grind out, or replace
SYSTEMATIC, DATA & MECHANISM-DRIVEN STRATEGY CRITICALSYSTEMATIC, DATA & MECHANISM-DRIVEN STRATEGY CRITICAL
Life Cycle ModelingLife Cycle Modeling
Confirmatory ExcavationsConfirmatory Excavations
SCC Susceptibility ModelSCC Susceptibility Model
Ongoing SCC MonitoringOngoing SCC Monitoring
Sampling Model
Existing Defect Size DistributionExisting Defect Size Distribution Cyclic
Pressure History
Future Integrity ModelFuture Integrity Model
Integrity ActionsIntegrity Actions
Applicable SCC Rate
Studies
• ILI DataILI Data• Soils, Terrain, Topo Soils, Terrain, Topo ModelModel
• Coating DisbondmentCoating Disbondment• Corrosion Linearity Corrosion Linearity (MFL)(MFL)
• Pipe DesignPipe Design• Material PropertiesMaterial Properties• CP DataCP Data