Stress Corrosion Cracking in Pipelines

Although stress-corrosion cracking (SCC) is thought to be responsible for a relatively small percentage of pipeline failures each year, it continues to be a safety concern to pipeline operators and government regulatory agencies, and it must be addressed in integrity management plans.

This course will provide a detailed description of what is known about the appearance and causes of SCC, and it will discuss various approaches to mitigating and managing the problem. Practical information on recognizing and dealing with SCC will be presented along with descriptions of research results that have led to our current understanding of causes and methods of management.

Who Should Attend

• Pipeline engineers, designers, and service professionals who are involved with the maintenance, inspection, and repair of pipelines
• Researchers and regulatory personnel who want to be aware of the current understanding of SCC in pipelines

Documentation

Included with the course fee are detailed course notes including an extensive list of references as well as a CD containing the comprhensive 200-page Stress Corrosion Cracking Study produced in January 2005 for the US Office of Pipeline Safety.

Lecturers

Dr. Raymond R. Fessler worked on the Pipeline Research Committee project on SCC since its inception in 1965. He personally conducted most of the early field investigations of SCC, from which he identified the major factors that cause high-pH SCC in pipelines. He also managed the laboratory portion of that program from 1965 to 1982, which added significantly to an understanding of the phenomenon and explored a number of possible solutions to the problem. For the past several years, he has been the SCC consultant for GRI and PRCI. He recently completed a comprehensive gap analysis on SCC, and he actively participated in drafting the NACE Recommended Practice on SCC Direct Assessment.

John Mackenzie is a senior pipeline specialist with Kiefner & Associates, focusing on the areas of Integrity Management Plans and Stress Corrosion Cracking. John was previously with TransCanada Pipelines for 25 years, where he was responsible for the company’s original investigation into SCC (1986-1990). This work led to the discovery of near-neutral pH SCC and identified the conditions under which it occurs. He also served as Chair of the PRCI’s SCC Subcommittee for two years.

Continuing Education Units (CEUs)

On completion of the course, participants will be awarded 1.2 CEUs.

Course Program

Description of SCC

• Definition
• Causes
• Appearance
• Other forms of environmental-assisted cracking

History of SCC in pipelines

• High-pH SCC
• Near-neutral-pH SCC
• Internal SCC

Stages of SCC

• Pre-initiation
• Initiation
• Growth models
• Early growth
• Dormancy and re-initiation
• Late growth
• Final fracture

Test techniques to study SCC

• Accelerated testing
• Electrochemical tests
• Cracking tests
• Measuring crack growth

Environmental factors

• Field observations
• Liquid composition and concentration
• Electrochemical potential
• Temperature

Stress factors

• Field observations
• Importance of strain rate
• Cyclic loading
• Sources of stress

Metallurgical factors

• Pipe grade
• Steel composition
• Mechanical properties
• Microstructure
• Manufacturer

Mechanisms of SCC

• High-pH SCC
• Near-neutral-pH SCC

Likely locations for SCC

• Geographical
• Proximity to compressor or pump stations
• Proximity to other SCC
• Soil, terrain, moisture level
• Gas versus liquid pipelines
• Coating types and conditions
• Pressure history
• Corrosion history
• Pipe manufacturer

SCC detection and integrity assurance

• B31.8S
• Hydrostatic testing
• In-line inspection
• Direct assessment

Mitigating SCC

• Operating existing pipelines
• Designing new pipelines
• Repair methods

Integrity management plans

• Regulations
• Approaches