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

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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

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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

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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