Leak Detection

= Pipeline Leak Detection Using Non-Destructive & Non-Invasive Testing Techniques =

Most pipelines, regardless of what they contain, are designed with a typical life span of 25 years. When they do begin to fail, they do so slowly beginning with leaks at poor construction joints, corrosion points and small structural material cracks, and gradually progress to a catastrophic ending. This disastrous failure can be expensive in terms of both dollars and lives; but planned maintenance can extend the life of almost all types of pipelines almost indefinitely and disastrous scenarios can be avoided. [“Infrared Thermography-Based Pipeline Leak Detection Systems for Pipeline Rehabilitation Programs,” SPIE, Oakland, California, June 1995]

Non-invasive systems have become the standard for many sewer testing and repair programs because they are capable of locating sewer pipeline leaks and exterior erosion voids in active and inactive refinery systems. These systems characterize anomalous areas by composition, size, depth and plume spread; and provide a system to repair and remediate these subsurface areas with no inconvenience to the facility, its processes or personnel. [“Infrared Thermography Based Pipeline Leak Detection Systems,” SPIE-Thermosense XIII, Orlando, Florida, April 1991]

Infrared Radiometric Pipeline Testing

Infrared Thermographic Pipeline testing has shown itself to be both accurate and efficient in locating subsurface pipeline leaks, voids caused by erosion, deteriorated pipeline insulation and poor backfill. When a pipeline leak has allowed a fluid, such as water, to form a plume near a pipeline, the fluid has a thermal conductance different from the dry soil or backfill. This will be reflected in different surface temperature patterns above the leak location. A high resolution infrared radiometer allows entire areas to be scanned and the resulting data to be displayed as pictures with areas of differing temperatures designated by differing gray tones on a black & white image or by various colors on a color image. This system measures surface energy patterns only, but the patterns that are measured on the surface of the ground above a buried pipeline can help show where pipeline leaks and resulting erosion voids are forming; detecting problems as deep as 30 meters below the ground surface. [ Jackson, C.N. and C.N. Sherlock, 1998, Nondestructive Testing Handbook: Leak Testing, page 519, Library of Congress Cataloging-in-Publication Data, 2008]

Application

In November 1990, infrared radiometric testing was used to inspect a 7.3 km section of subsurface oil supply pipeline for a large Illinois refinery. The purpose of the investigation was to locate the cause of a drop in line pressure. The investigation was performed from a helicopter with the aid of telephoto and wide angle optics. The 7.25 km section of pipeline was inspected in less than 30 minutes. The results of the inspection included several small oil line leaks and one substantial pipeline leak estimated at 65 gallons a minute. The investigation also helped determine how much soil had been contaminated and what the rate of contamination spread was over time. [ Jackson, C.N. and C.N. Sherlock, 1998, Nondestructive Testing Handbook: Leak Testing, page 519, Library of Congress Cataloging-In-Publication Data, 2008] In 1983, an infrared radiometric leak and erosion void investigation was performed in St. Louis because street pavement was observed to be sinking up to 150 mm along a 183 m section of a downtown street. During the radiometric investigation an area was located perpendicular to the buried water pipeline. It began at the water line and spread outward toward the sewer line. It was determined that the area was caused by heat sinking ability of the water plume as it spread out from the water line leak and flowed down the outside of the nearby sewer pipeline. Some of the fresh water was entering the sewer line through the three dime sized holes that the crawl crew had located previously. In addition to the water leak, the investigation also located an erosion area above the water line. [ “Nondestructive Testing of Buried Water Pipelines Using Infrared Thermography,” ASCE Conference on Water Management, Seattle, Washington, May 1993]

References

# Weil, Gary J. “Infrared Thermography-Based Pipeline Leak Detection Systems for Pipeline Rehabilitation Programs,” SPIE, Oakland, California, June 1995
# Weil, Gary J. “Infrared Thermography Based Pipeline Leak Detection Systems,” SPIE-Thermosense XIII, Orlando, Florida, April 1991
# Jackson, C.N. and C.N. Sherlock, 1998, Nondestructive Testing Handbook: Leak Testing, page 519, Library of Congress Cataloging-In-Publication Data, 2008
# Weil, Gary J. “Nondestructive Testing of Buried Water Pipelines Using Infrared Thermography,” ASCE Conference on Water Management, Seattle, Washington