Stress Corrosion CrackingOverview & Introduction

David Johnson

December 2, 2003

SCC History

• Not a recent phenomenon

• Not exclusive to pipelines

• Not confined to underground environment

• Not geographically limited

• Ammonia cracking of cartridge brass

• Chloride cracking of stainless steel

Requirements for SCC

Environment

StressMetallurgy

SCC Characteristics

Factor High pH Neutral pH Location CS discharges

Wet-dry soils Aggressive soil

Anywhere Wet-dry soils Aggressive soil

Temperature Exponential temperature impact

Little apparent effect

SCC Characteristics

Factor High pH Neutral pH

Electrolyte Carbonate-bicarbonate pH > 9.3

Dilute bicarbonate 5.5 < pH <7.5 Higher CO2

Potential -600 to –750 mV Free potential

Cracks Intergranular Narrow Not corroded

Transgranular Wider May be corroded

SCC near Seam Weld

Metallography of SCC

ASME Causes of Gas Transmission Incidents

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Vandalism

Stress Corrosion Cracking

Malfunction

Prev. Damgd Pipe

Mfr

Constr/Instal

Other Failures

Unknown

Incorrect Operation

Misc

Natural Forces

Internal Corrosion

External Corrosion

Third Party Damage

Non-Pipe

Pipe

Summary of Incident Causes

Summary of Significance

• Natural gas transmission(1985-2002)– 15 of 1415 total reported incidents

• Liquid transmission (PPTS)– 5 of 472 in database

• NEB (Canada) (1992-2002)– 3 of 23– None since 1995

• Overall - about 1% of incidents

Why Today’s Interest?

• Other, higher significance threats also being addressed

Other Threats (B31.8S)• External Corrosion• Internal Corrosion• Manufacturing Defects• Welding & Fabrication Defects• Equipment Failure• Third Party / Mechanical Damage• Incorrect Operations• Weather & Outside Force

External & Internal Corrosion

• CP systems

• Gas quality standards and monitoring

• Relatively mature ILI capability

• Correlated to hydro-test capability

• Rapidly maturing DA capabilities

Manufacturing & Construction

• Specifications - materials & construction

• Advances in materials technology

• Mill inspections

• Construction inspections

• Proof testing

Third Party Damage

• Dig Safety

• Common Ground Alliance

• One Call enforcement

• Enhanced public awareness

Incorrect Operation

• Operator Qualification programs

• Qualification of controllers

• OQ-2

• B31Q

Equipment Failure

• Gaskets, Seals, Valves, Pumps, etc.

• Generally not pipe

• Generally confined

• Specifications, testing, maintenance

Weather & Outside Forces

• Design & Construction

• Forecasting

• Monitoring

• Better understanding of material responses

Why Today’s Interest?

• Other, higher significance threats also being addressed

• Less apparent understanding

• Small, but widespread, occurrence

• Methods of addressing not as mature– Inspection, characterization, assessment,

management

Today’s Workshop

• Share available information

• Understand application of current management techniques

• Update on R&D

• Future Needs– Technology development– Regulatory approach

Managing SCC

• Operators have found & managed SCC• Tools as prescribed in PLSIA of 2002

– In-Line Inspection– Hydrostatic Testing– Direct Assessment – Other

• All have specific capabilities & limitations• Gas - Liquid Pipeline Differences

Major Challenges

• Finding SCC– Shallow cracks initially– May not be visible to unaided eye

• Gas - Liquid technology differences• Service disruptions• Water disposal• Assessing what is found• Mitigation and Management

Research & Development

• Multi-faceted approach

• Environmental factors

• Surface preparation & coatings

• CP system operation

• Operational factors

• Material behavior

• Detection & sizing

Regulatory Response

• Determining reasonable response

• Setting investigation protocols

• Communication needs

Upcoming Panels

• Operator Experience with Finding and Managing SCC

1. TransCanada

2. Enbridge

3. Kinder Morgan

4. Duke

5. Williams

6. Colonial

Upcoming Panels

• R & D– What’s been done– Current work– Future needs– PRCI– ILIA– NACE

Upcoming Panels

• Regulators– Concerns & Needs– NEB– EUB– MNOPS– USDOT-OPS

Dave.L.Johnson@Enron.com

KLeewis@PRCI.org

Contacts