Detecting the undetectable

April 18, 2005
One thing is apparent in the world’s energy sector these days, and that is how fast things are changing.

One thing is apparent in the world’s energy sector these days, and that is how fast things are changing. In just a few short years natural gas demand has increased dramatically. Despite unbelievable price increases, crude oil demand likewise continues to rise-especially in countries not previously known for enormous hydrocarbon demand, such as China and India. And that puts more pressure on all industries to trim costs and improve efficiency. That includes pipelines.

The pipeline industry has been under scutiny for years. An ageing pipeline infrastructure, along with increasing public demands, is straining parts of the system. Environmental problems from worn-out pipe and third-party damage, among other things, have been held up widely by critics.

Throughput capacity in areas once thought to be more than adequate are suddenly found to be lacking. Pipeline integrity has become an important area of concern.

What is SCC

The special report on pipeline integrity in this issue addresses important work in the areas of pipeline design and maintenance, specifically involving stress corrosion cracking (p. 53). SCC is the cracking resulting from tensile stress and corrosion. SCC can be almost invisible. It occurs in welds, in areas near the welds, and in the pipe’s base materials. Quite often, SCC is strongly affected by alloy composition, specific types of corrosion, and the intensity of the stress. Failure can occur without significant or obvious deformation. It is a complex problem.

OPS study

The lead article in the special report covers a study, by the Pipeline and Hazardous Materials Safety Administration’s Office of Pipeline Safety, that details the threat of SCC to pipeline integrity. The recently released study explains SCC, how it occurs, and conditions that contribute to it. The study covers detection, causes of leaks, how to manage the SCC threat, and design and construction methods to avoid SCC.

State-of-the-art equipment can detect such things as stress corrosion and other types of cracking, metal loss, corrosion, and axial defects. Photo from GE Energy Pipeline Solutions.
Click here to enlarge image

The second article covers SCC detection based on high-resolution inline inspection tools. The article describes Enbridge Pipeline Inc.’s program for SCC management, its monitoring and mitigation methods, and results from inline inspection.

More than ever before, papers at pipeline conferences are concentrating on the SCC problem. The long-term security of pipeline systems depends on finding solutions.